Tube-Town Forum
Technik => Tech-Talk Soldano => Thema gestartet von: Guile am 10.10.2016 20:00
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Cloners!
I'm in desperate need of help to save my SLO50 clone project. I don't speak enough German, so I hope English is okay.
I bought a SLO100 clone a while back that is based on the Tube Town pcb and transformers set. It sounds AWESOME. Downside is that it was put together very poorly. It failed on me several times. But still, it sounds BRUTAL \m/ I absolutely LOVE it.
So I decided to build a SLO50 and bought the pcb's from [ADMIN]Werbung entfernt[/ADMIN] and bought the 50 watts transformers [ADMIN]Links entfernt[/ADMIN]
I'm fairly new to making cloned amps (only made a Fender Reverb Deluxe) so it took a long time to make it work. It works now but it sounds bad: flat, shrill, harsh and unforgiving. Not at all like the badly made SLO100 which sounds radically different: very transparent, sparkly with tons of bass without being shrill but with great bite. It sound already great with all the pots at noon. I can't dial in ANY acceptable sound with the newly build SLO.. The middle pot is the most useful for more body, but still no match for the poorly built SLO100.
I checked all the parts and their values and all voltages but can't find an error.
Swapped tubes many times and always biased correctly.
I also compared everying with the SLO100.
Could it be the difference in transformers?
Would love to hear suggestions
Thanks
https://www.flickr.com/photos/115176149@N03/
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Hi Guile
Sad to hear about your build … :-(
I am using InMadOut transformers, too, and never ever had any trouble with them and also in my opinion the OTs are sounding pretty good. And at least I think Dirks transformers are also IMO or based on them.
The only thing I get in mind is about the colour code of wiring of the transformers, which change in the past as I had to notice on a MA100 set.
It is hard to guess, what you mean by "harsh" and "shrill" - is there no bottom end (bass) at all? Have you checked the amp by plugging the guitar directly into the FX return? How is it sounding then?
If the sound has kind of "crackles" I would assume there is a broken or bad soldering point; also the VTL are a source of problems - have you checked their resistance within the different channel switching positions? Maybe you have crossover distortion and something is out of phase which will lead to a harsh sound (think of out of phase pickups in a guitar e.g.)?
I know about the C3 boards (I have bought one in the past) but I do not have a scheme for the C3 board - maybe you can post the scheme here? I am not sure, but I can imagine, the numbering of the different parts does not match the scheme of Joachim (which the TT pcbs are based on).
Can you post some more detailed pictures? I had a look to them on Flickr, but some more in higher resolution would be nice.
Regards, Stone
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Thanks for your reply Stone.
I will do my best to give you information.
The amp has almost no bottom end and is very trebly and midrangy, not smooth, unfriendly to the ears..
I put a guitar in 'return' and got weak sound (not loud) with humm.
Please explain how I could test the octocouplers.
I used several sources to build the amp (see attached). This led to confusion, but I compared it to the poorly build TT SLO.
I will take more closeups and post them on flickr asap
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I added more pictures to: https://www.flickr.com/photos/115176149@N03/?
I also attached the colourcodes of the transformers. Could I have made a mistake? Please check if you can.
Thank you!
[ADMIN]Anhänge entfernt. Für Produktsupport von Fremdanbietern bitte diese Anbieter kontaktieren oder deren Foren verwenden[/ADMIN]
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Hi
I am not sure, if the schemes match the C3 board, but I know them all - more or less by heart ;) Especially the one drawn by Joachim, which is the basis for the TT boards (as I said before).
If you plugin the guitar to the fx return you should have low volume, but I think it should not produce any hum. If it does and it sounds like mains voltage hum (50 or 60 Hz) then I think there is a wrong ground connection on the fx return - you could check the preamp by connecting fx send to a separate power amp (or connect it to fx return of the SLO100 you got); how does the preamp sound?
The optocouplers can be checked pretty easy with a multimeter - if you refer to the layout the connectors on the "tube" side of the board are the resistance part of the couplers as the opposite side of them is the voltage connection.
If you switch to clean then VR1 (according to SLO 0.7 scheme of Joachim) and VR4 should measure only a few ohms (I do not have the data sheet at hand, but Vactec should measure around less then 100 ohms), VR2 and VR3 should be around 50 meg ohms I think.
If you switch to lead the other way round: VR1 and VR4 are of high resistance as V2 and VR3 are of low resistance.
Everything around a few kilo ohms when switched will be too much (also check the voltages at the optos … not sure about the Vactec, but they need 1,5 to 2,0 volts in order to switch correctly I think).
If the preamp is working correctly (as mentioned you could check this by using fx send) the power amp may be wired wrong - how is it sounding if you adjust presence and (if installed) depth?
I still assume that there is a mismatch in the parts labeling of the C3 board and the schemes you used - I will check it tomorrow as I have got a board, too (as mentioned).
I will have a look at the pictures ;)
Regards, Stone
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Hi
First guess as it is hard to follow the traces / wires in the pictures: you did not set up a PE wire from the mains connector to chassis, but you connected "black" (CT of the secondary side of the power transformer) to the mains connectors "middle" eye?
If so ...
You need to / must set up PE connection (!) - a green/yellow wire from "middle eye" of the mains connector to chassis and to connect "black" (CT) to chassis ground connection (you set up a lug with several ground wire connection near the plastic clamp).
Not sure, but I think I misunderstood the use of the C3 board - you have used the TT boards and transformers for your 50 watt model? If so, the scheme of Joachim (SLO 0.7) is valid.
Regards, Stone
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Hi
Hard to follow the wires of PT … do me a favor and check them again.
As far as I can see there is a brown wire running from PE tap of mains connector to chassis star ground next to plastic clamp, right? Should be green/yellow wire and must be placed with a separate screw and lug near mains connector to chassis (afaik).
CT (Black) of heater connection goes to? Is it connected to ground / chassis?
What about BIAS voltage?
Hm …
I would recommend to clean it up a little bit concerning wire layout, length and wire color code (PE is a must in green/yellow with separate connection).
After that I would try to run the preamp by using FX send of the SLO50 into the power amp by using FX return of the SLO100 and have a "look" if it is still not sounding.
If it does sound the right way there must be a fault from FX return into power amp section of the SLO50.
Regards, Stone
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Thanks Stone.
I added a new picture: https://www.flickr.com/photos/115176149@N03/?
I believe the PE is wired correctly? If not tell me.
You are right about the colourcodes
Bias voltage= 45
CT (Black) heater connection is connected to ground / chassis. could you please check TASLO5.pdf and TUSLO50.pdf I have doubts if I have interpreted the different wires/colours correctly!
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Hi,
at a first glance your cable laying is horrible! :o
Most cables are too long: especially the red cables - which go to the pre-stage tubes.
As a beginner you should use different colors for the cables, which makes the error search considerably easier.
Please remember, this is a high voltage device!
There is no room for interpretation:
CT (Black) heater connection is connected to ground / chassis. could you please check TASLO5.pdf and TUSLO50.pdf I have doubts if I have interpreted the different wires/colours correctly!
You have to know what you are doing!
It's better if you rebuild the AMP step by step.
Ask before you do something that you do not know if it is right.
This is the best solution.
At the end you will have a functioning AMP which is also great to watch. ;)
Regards
Jürgen
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Hi Guile
PE must be connected to a separate screw on chassis; it will work this way, but afaik it is not allowed to connect PE to ground lug together with other ground wires any longer.
The wiring seem to be ok - the new photo clears it up a bit to me.
According the datasheet you should have purple-grey-black-purple as 0,5 mm2 wires which is HT and BIAS tap, wires with 1,5 mm2 and brown-black-brown which is heater with 6 amperes and pink-black-pink for heater number 2 (with 3 amperes).
Primary side is white-blue-grey-brown - I think with 0,5 mm2.
Heater centre taps (black) can be connected to ground directly.
According the last pictures it looks connected in the right way (I can guess from the other pictures where the black ones are connected to).
I went through your posts: the 50 one has been build with the C3 boards. I would recommend to check the preamp the way I described (connect fx send of the 50 one to another fx return, e.g. of the 100 SLO) in order to see if it is a power amp related problem.
Also it would be interesting to check voltages before and after anode resistors of the preamp tubes; same to cathode resistors - I remember mixing up resistor two or three years ago and my amp had nearly no volume at all (mixed up 2M2 with 2k2 ...).
Again, how is the amp sound if you turn presence and depth controls?
Regards, Stone
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Hi,
at a first glance your cable laying is horrible! :o
Most cables are too long: especially the red cables - which go to the pre-stage tubes.
As a beginner you should use different colors for the cables, which makes the error search considerably easier.
Please remember, this is a high voltage device!
There is no room for interpretation:You have to know what you are doing!
It's better if you rebuild the AMP step by step.
Ask before you do something that you do not know if it is right.
This is the best solution.
At the end you will have a functioning AMP which is also great to watch. ;)
Regards
Jürgen
+1
Jürgen is right - a re-wiring of the power transformer stage would clean up a lot ... and most of the times the fault is erased, too.
Regards, Stone
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by the way ... are those boards the actual ones of C3? I have got a green silked one and it is about 2,4 mm thick with a very accurate labeling of the parts on it
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Hi, many thanks for taking interest in my project.
Have to admit that I did not expect this amp to be so complicated. I took great care in sourcing the parts and took my time to put it all together..
In my defense, the wiring looks messy but since it sounds so bad I did not yet tidy things up. I like it to look good too (within reason, electrons don't care if they wear a tie).
I ran the SLO50 (+ guitar) send into return of the SLO100. I have to open up the master and preamp of the SLO100 to have audible sound. Volume is very weak and thin with a hum.
Can you see from the picture if Send/Return is correctly wired? Jacks are well isolated from the chassis btw.
The pcb's are 100% C3 amps.
I will take care of the PE wire (separate screw on chassis).
The presence and depth controls work, but presence gives even more highs and depth does almost nothing.
Rebuilding the amp sounds like a good idea. Please tell me how to proceed re-wiring the power transformer stage.
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I compared the voltages of the two amplifiers on both PA and TS and I see no major abnormalities. What I did notice is that the new SLO has +/- structurally 10% lower voltages. I also noticed that the standby switch of the SLO50 is 470V and 375Von the SLO 100.
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I made a couple of quick samples of the the two Slo's. The first riff is the SlO100, the second is the SLO50.
All pots are dialed in at 12:00.
https://soundcloud.com/guilese/comparison-slo-clones
To my ears the SLO50 sounds like a Behringer amp...
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I made a couple of quick samples of the the two Slo's. The first riff is the SlO100, the second is the SLO50.
All pots are dialed in at 12:00.
https://soundcloud.com/guilese/comparison-slo-clones
To my ears the SLO50 sounds like a Behringer amp...
When it sounds like a Behringer, i think you build a Behringer.... :devil:
Your Link is dead:
We can’t find that track.
Did you try to access a private track while not being signed in?
Maybe the track has been removed.
The reason for the bad sound is not the power supply.
Please do what I have recommended:
Rebuild (= rewire) the AMP step by step.
Shorten the Cables to the Tube sockets
use different colors for cables
don´t tie Signal cables together
Regards
Jürgen
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Does this link work: https://soundcloud.com/guilese/comparison-slo-clones/s-Iq8dW
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Hi
I agree to Jürgen.
Why re-wiring and cleaning it up? It is hard to follow the wires within the pictures; also it might be hard to follow them with the amp opened up on the workbench - this is one of the major faults people do and have got in their amps.
Using different and correct color codes ensures that people are reading the same out of schemes and pictures of wiring - it is hard to tell about the "thin black wire to the left" and the "a bit more meaty wire across the thin left black wire running to the right side" ;) You get me?
Do answer your question concerning FX loop.
As far as I can see there is a 1k resistor soldered from signal tip to ground, which has to be 1 Meg (I cannot read the color code of it, so I might be wrong).
At second I cannot see how you made a ground connection for FX send jack and FX return jack. Are both jacks of switching type? I assume … check the wiring and if there is no ground connection you will not have any reference for the signal to be fed into another amp / fx return.
Do not use the shield as ground connection, as you will create a hum loop by using it in most cases (and I think so in this one).
The SLO is not the most complex and complicated amp, but it is also not a beginners DIY project … again, re-wiring will help to sort out things.
And if it comes to several amperes it seems current will always flow straight forward - but that 's another story ;)
Regards, Stone
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I ran the SLO50 (+ guitar) send into return of the SLO100. I have to open up the master and preamp of the SLO100 to have audible sound. Volume is very weak and thin with a hum.
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I ran the SLO50 (+ guitar) send into return of the SLO100. I have to open up the master and preamp of the SLO100 to have audible sound. Volume is very weak and thin with a hum.
Yes - which is quite normal to my opinion if there is no correct ground connection of the fx send and fx return jack of the SLO50 (this could cause the weak sound internally of the SLO50).
Regards, Stone
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Thanks for both replies.
Please tell me how to correct this. Would you have a comprehensible picture of the send/return?
Only the upper jack has a switch btw
could this be the cause of the bad sound?
nb I already reflowed all the solder points. I'm not sure that changing the wire of the entire amp and making the same connections will make the amp work though..
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I'm not sure that changing the wire of the entire amp and making the same connections will make the amp work though..
Currently your AMP looks like if someone had done spaghetti in the chassis.... :o
The cables at the Tube sockets and many other are much too long - shorten the cables.
If you do not know how, look at the attached Picture....
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I understand you don't like the way the amp looks, message received. But is there any proof that shortening the wires will change the way it sounds?
Thanks for the pic of Mike's work, true piece of art.
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But is there any proof that shortening the wires will change the way it sounds?
Yes, the Signal .... :o
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Hi,
I understand you don't like the way the amp looks, message received. But is there any proof that shortening the wires will change the way it sounds?
Thanks for the pic of Mike's work, true piece of art.
there are multiple reasons why you need to tidy up the amp. First, it's nearly impossible to debug an amp with a chaotic wiring, even if you have the amp in front of you and do know what to look for, much more so from pictures alone.
Moreover, loose wiring can cause all sorts of problems especially in a high gain amp such as the SLO. There will very likely be a lot of crosstalk in your amp, which can lead to multiple problems, including frequencies being canceled out and oscillation. Both problems are very likely to occur in your build.
There's a reason amps like the SLO are built the way they are, and those reasons are not purely esthetically.
Cheers Nils
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Hi
For a short check it will be satisfying to draw a wire from fx loop jacks ground connection to speaker jacks ground connection - a detailed picture of the fx jacks can be found in Joachims "SLO 100 Schritt für Schritt" Thread at this point: http://www.tube-town.de/ttforum/index.php/topic,3292.msg31779.html#msg31779
There is also a pretty well working ground scheme http://www.tube-town.de/ttforum/index.php/topic,3292.msg36124.html#msg36124
To have the fx ground connected to speaker jacks ground is just for testing and may cause hum. But from my point of view it will not work without any ground connection.
If you are using a switched jack for fx send it will do (more or less if you are not using fx return with another preamp or so), but having both ones of switched type is the better choice (and ... which one is the upper one? Chassis top over on the desk or ... ;-) ).
Nils nailed it - shortening the wires leads to better overview and therefore analysis of problems is much easier. Some people build there amps in a very "esthetic" way if it comes to wiring, but the nice view is a plus beneath the elimination of all kind of unwanted noise.
Regards, Stone
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Hi guys, thanks for the information and explanation, makes a lot of sense. I will get to it.
But the SLO100 clone which I bought a while back looks like this:
https://www.flickr.com/photos/115176149@N03/?
(Jurgen try not to vomit ;) )
It sounds great though.. And as far as I can determine it is the same as the SLO50. Same part-values and voltages.
I tried the fx loop instructions, but no result..
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But the SLO100 clone which I bought a while back looks like this:
https://www.flickr.com/photos/115176149@N03/?
(Jurgen try not to vomit ;) )
Well, it does have shorter cables. ;D
At least where it counts.
Gruß, Peter
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Hope this link works (grrrr): https://soundcloud.com/guilese/slos
All pots at noon
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Hi
I agree to Jürgen.
Why re-wiring and cleaning it up? It is hard to follow the wires within the pictures; also it might be hard to follow them with the amp opened up on the workbench - this is one of the major faults people do and have got in their amps.
Using different and correct color codes ensures that people are reading the same out of schemes and pictures of wiring - it is hard to tell about the "thin black wire to the left" and the "a bit more meaty wire across the thin left black wire running to the right side" ;) You get me?
Do answer your question concerning FX loop.
As far as I can see there is a 1k resistor soldered from signal tip to ground, which has to be 1 Meg (I cannot read the color code of it, so I might be wrong).
At second I cannot see how you made a ground connection for FX send jack and FX return jack. Are both jacks of switching type? I assume … check the wiring and if there is no ground connection you will not have any reference for the signal to be fed into another amp / fx return.
Do not use the shield as ground connection, as you will create a hum loop by using it in most cases (and I think so in this one).
The SLO is not the most complex and complicated amp, but it is also not a beginners DIY project … again, re-wiring will help to sort out things.
And if it comes to several amperes it seems current will always flow straight forward - but that 's another story ;)
Regards, Stone
Stone, the fx/send is in ordnung. Can you please tell me which setup to make?
Both amps on Normal channel
Send SLO50 to return SLO100
Guitar in SLO50
And then?
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Hi
If the grounding of the fx loop does not change anything and the resistor tied to fx return is 1 Meg and not 1k, then I would assume a problem within preamp.
Stone, the fx/send is in ordnung. Can you please tell me which setup to make?
Both amps on Normal channel
Send SLO50 to return SLO100
Guitar in SLO50
And then?
Speaker connected to SLO100 - I think this is obligatory to say, but ... ;-) If you play your guitar then it should sound like "normal" (clean more or less) channel with standard volume.
Is there any change in sound if you switch to lead channel on the SLO50?
If I should judge by the soundfile then I would assume you have a problem with the amount of distortion - sounds like a Marshall SLP ... which has only 2 stages of distortion generation - and it has e.g. a 2n2 coupling cap.
So we are left with check of VTL optos, checking resistor values and capacitor values - and more important - checking right connection of cathodes and anodes etc., does the preamp really switch from normal to lead (or are we hearing the normal channel boosted?), etc.
Regards, Stone
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Hi,
you said the voltages are ok - which voltages did you mesure? Could you post them, please?
If you are right and the amps dc path and the tubes are ok then you shold check the ac path,
which means especially capacitor values and the circuitry after the coupling caps of each stage.
But please go step by step and report the results so you don't generate unnecessary work for
yourself and us. That is, check the value of said resistor at the fx return and follow the divide
and conquer strategy as Stone pointed out (from one amps fx loop into the other ones and
vice versa).
Cheers, Peter
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Hi
I listened to the sample again because I needed to be at home to have a better pair of speakers available; the second half is not that much different to the first one, except of missing bottom end (as far as I can hear through the speakers available).
It sounds like bass potentiometer turned to zero, so I would suggest beside all the other checks to have a look to the bass cap and potentiometer values.
Regards, Stone
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Hi
If the grounding of the fx loop does not change anything and the resistor tied to fx return is 1 Meg and not 1k, then I would assume a problem within preamp.
Speaker connected to SLO100 - I think this is obligatory to say, but ... ;-) If you play your guitar then it should sound like "normal" (clean more or less) channel with standard volume.
Is there any change in sound if you switch to lead channel on the SLO50?
If I should judge by the soundfile then I would assume you have a problem with the amount of distortion - sounds like a Marshall SLP ... which has only 2 stages of distortion generation - and it has e.g. a 2n2 coupling cap.
So we are left with check of VTL optos, checking resistor values and capacitor values - and more important - checking right connection of cathodes and anodes etc., does the preamp really switch from normal to lead (or are we hearing the normal channel boosted?), etc.
Regards, Stone
Signal is clean, but as I said, very low volume (not standard).
I think the amount of distortion is not the problem. The recording is every pot at 12:00 (not preamp and master). It switches normally from clean to lead.
I checked every resistor and cap visually and tested resistors with multimeter and (unfortunately) all is according schematic/layout.
I'm beginning tot get tired of this amp. I rewired most of the spaghetti and believe it or not, it sounds even more shrill then before.
Anyone wants to buy this piece of shit?
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Dude,
you need to operate more systematicly when troubleshooting.
How about the voltages - are they still in place? What are they? If you don't give us the necessary information
we're just guessing. Looking at the burnt resistor on the power amp board I start to believe that it's more than
an error in the singal path. Something is drawing too much current or the resistor is weak.
Cheers, Peter
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[...]
Anyone wants to buy this piece of shit?
It depends on the price you try to get.
Basically I am interested.
If you have checked all resistors, caps, etc. there must be a problem with the wiring - if you have shortened some wires and the problem increased I guess the error / fault is located somewhere next to the changed cabling.
On the other hand side - and I am far away from being a wiring and layout expert - it is important e.g. to have heater wires installed accurately otherwise you will get all sort of noise, first of hum, keep wires to grids and anodes as short as possible, some people recommend to tie them together, shielded cable for input, fx loop, first stages grids, correct connection of shield and so on.
Sometimes - to get away a little bit of the wiring - it is a pretty little error you have overseen or an effect you did not think about in any way and most times their reason is pretty simple.
What I remember if it comes to low volume and less bottom is a Marshall 2210 I got some years ago for repair - one of the B+ resistor (10k) was faulty. After 2 or 3 minutes the amp became quiet, the sound was close to your sound sample. It turned out that the resistance of the faulty resistor increased during operating time - took around 10 minutes to find it, because I started measuring voltages.
I will have a look to the pictures again - maybe I can find some things more; updated pics would be fine. But if you like, you can make me an offer for the 50 one.
Regards, Stone
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Dude,
you need to operate more systematically when troubleshooting.
How about the voltages - are they still in place? What are they? If you don't give us the necessary information
we're just guessing. Looking at the burnt resistor on the power amp board I start to believe that it's more than
an error in the signal path. Something is drawing too much current or the resistor is weak.
Cheers, Peter
I appreciate the comments guys.
Resistor is not burnt. What you see is the residue of my capacitor discharger that got burnt when I forgot to take it out. The amp sounded already bad when that happened.
These are the voltages:
V1
1 228
2
3 2
4
5
6 159
7
8 1.4
9
V2
1 228
2
3 1.9
4
5
6 300
7
8 4.4
9
V3
1 360
2 173
3 193
4
5
6 174
7
8
9
V4
1 360
2 153
3 158
4
5
6 141
7
8 2.4
9
V5
1 227
2 13
3 40
4
5
6 237
7 12.3
8
9
In general the tone stack acts weird:
Bass: does not add bass but adds mids
Middle: adds more fullness and bass
Treble: adds highs
Presence: adds (earpiercing) highs but only after 15:00
Depth: adds depth, but not much.
I will now measure all of the resistors of the SLO100 and compare with the SLO50 (again)
Hopefully this information helps to find something!
Thanks in advance.
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Hi
Check the resistor and ground connection of that at V3b, pin 8. You wrote down any value, but you should have something around 1,5 volts and 2,0 volts. There must be current flowing through the triode, because you have a voltage on pin 6, which is lower than B+, but no value indicates a rather high value (and multimeter was set to low) or another fault.
Also have a closer look to V4b - pin 6 and pin 8. Measured value for pin 6 is a little bit low, also value for pin 8 seems to be a little bit.
If the tonestack is not behaving the way we expected it to do, check the wiring of the potentiometers and also their values and type (mixing up linear and log type is a common fault).
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[...]
I will now measure all of the resistors of the SLO100 and compare with the SLO50 (again)
[...]
This must be more detailed ... if you are measuring cathode resistors, e.g., you need to measure resistor to ground (chassis) because this will tell if the resistor has a ground reference.
What I cannot figure out on the pictures: how are the speaker jacks connected to ground? (<= and this is pretty important!)
Regards, Stone
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Hi,
Resistor is not burnt. What you see is the residue of my capacitor discharger that got burnt when I forgot to take it out. The amp sounded already bad when that happened.
ok, I understand.
There is a 20V difference between the grid and the cathode of V3A -> there must be something wrong
or the measurement is incorrect.
At V4 you measured 153 at the cathode followers grid but 141 at the feeding anode. ???
Are your voltages jumping up and down during measuring?
Cheers, Peter
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[...]
At V4 you measured 153 at the cathode followers grid but 141 at the feeding anode. ???
[...]
That 's what I had in mind ... thanks for clarifying.
Regards, Stone
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Hi
Check the resistor and ground connection of that at V3b, pin 8. You wrote down any value, but you should have something around 1,5 volts and 2,0 volts. There must be current flowing through the triode, because you have a voltage on pin 6, which is lower than B+, but no value indicates a rather high value (and multimeter was set to low) or another fault.
Also have a closer look to V4b - pin 6 and pin 8. Measured value for pin 6 is a little bit low, also value for pin 8 seems to be a little bit.
If the tonestack is not behaving the way we expected it to do, check the wiring of the potentiometers and also their values and type (mixing up linear and log type is a common fault).
You are correct
V3b - pin 8: 1.4
V4b - pin 6: 252
V4b - pin 8: 1.4
I checked the wiring of pots and their values and did not find errors.
The speaker jacks are connected to ground on the chassis.
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V4 looks problematic:
1: 352
2: 184 to 177 to 172
3: 208 to 198 to 194
4/5:
6: fluctuated a lot 222, 214, 189 and 130 so I put a new tube in. Started at 170 then 188 then 173. Standby switched off and on 209
7:
8: 1.5
9:
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Do the dc voltages at V3 and V4 change when you toggle the fx bypass switch?
(Then you have a faulty capacitor in the tone stack.)
Cheers, Peter
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They definitely do, all of them drop to zero when bypass is to 'off'
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What? Are we talking about the same thing? I don't mean the standby switch.
Maybe you didn't built in a fx bypass switch. I attached a schematic where you
can find it before the tone stack. If you don't have it, disconnect the the tone
from V4s cathode follower.
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Sorry, my bad
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please explain what to disconnect exactly
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Hi
Peter is thinking of disconnecting the whole tone stack from V4 - therefore you need to disconnect the 47k slope resistor of the tone stack and the 470pF of the tone stack as the connection between V4a cathode (pin 3) and the tone stack is hard wired on the PCB.
This will sort out if there is a broken capacitor in the tone stack which causes kind of short cut under some circumstances to V4a cathode.
Again … if we should sort out things we need some updated pictures and still the amp needs to be cleaned up a lot more - as far as I see we have a lot of faults on wiring - maybe some don't exist, but it is hard to figure out.
I will sum up, what I think I can see by the pictures:
- mains and standby switch "should" (must) be changed; you need to switch both "poles" of mains and of B+ … currently you are switching only one phase of mains and standby switch seems to be located after the rectifier
- Xicon resistors on the power tube sockets seem to touch one of the power tube sockets' screws (each one on each side) with one of the resistors lugs
- it is still not clear to me if fx jacks are grounded correctly and which one of the jacks is of switching type and how it is connected
- I am not able to see how (and if) the input jack is grounded (seems to be grounded by one of the lugs of one of the switches on front)
- there seems to be a white wire running from the 10µF 450 volts caps on the preamp pcb to one of the fuse holders which does not make much sense to me (if so)
- I am not sure about the wiring of the impedance switch and the OT, because it cannot be seen clearly
Overall I think the amp can be fixed within half an hour while being at the desk of Jürgen, Peter or me or nearly anyone else, because that 's the only chance to figure out where wires are running from and going to.
And I think we do have two mistakes / faults: one within preamp circuit and maybe one within the power amp circuit.
At least it can be a pretty simple fault in nearly everything … e.g. if fx send is not wired properly you won't get any good signal with any power amp connected to it, if a cathode resistors value is too high you won't have any gain at that point (every triode stage got its own gain … gain is not only the pot in front of many amps), if something is shortening or doing a crossover you won't get any useable signal, etc. etc.
Again - if you like to sell it, make an offer.
I am pretty sure it can be "healed", but it needs to be built a bit more properly.
Regards, Stone
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Damn,
Stone is faster than me. I'll post it like this anyway:
Let's start over,
- the voltages at V3, as you posted them, make no sence - like this the cf would be biased at -20V in total cut off
- this may be
-> a measuring error
-> a faulty tube
-> faulty component
-> wrong values/wiring, unintended connections underneath the board
-> because the voltages are jumping as you saw on V4; if so, why?
* is the supply voltage jumping too? please let the amp warm up before measuring
* is the stage oscillating? test: short the grid to ground via a capacitor (e.g. 47n 630V)
* is the stage loaded with some failing circuitry? test: disconnect anything that follows
- as you don't have the fx bypass switch, the tone stack is never attached to V3 so it can't be responsible for V3 (as i thought first)
- regarding V4: now that the jumping stopped - did it? - what are the voltages now?
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Do the dc voltages at V3 and V4 change when you toggle the fx bypass switch?
(Then you have a faulty capacitor in the tone stack.)
Cheers, Peter
Thanks for your patience so far.
I made a new picture of the FX send return. As you can see there is a switch (based on C3amps layout).
The voltages change in V4; They all increase about 10% when switched
No movement in V3
Please tell me if this is helpful or not before I proceed to the other suggestions.
Vielen dank
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- mains and standby switch "should" (must) be changed; you need to switch both "poles" of mains and of B+ … currently you are switching only one phase of mains and standby switch seems to be located after the rectifier
OK
- Xicon resistors on the power tube sockets seem to touch one of the power tube sockets' screws (each one on each side) with one of the resistors lugs
IT'S NOT TOUCHING THE SCREW
- it is still not clear to me if fx jacks are grounded correctly and which one of the jacks is of switching type and how it is connected
FX JACKS ARE NOT GROUNDED BY THE CHASSIS (https://www.flickr.com/photos/115176149@N03/)
- I am not able to see how (and if) the input jack is grounded (seems to be grounded by one of the lugs of one of the switches on front)
INPUT JACK IS NOT GROUNDED BY THE CHASSIS BUT PER PREAMP PCB
- there seems to be a white wire running from the 10µF 450 volts caps on the preamp pcb to one of the fuse holders which does not make much sense to me (if so)
THAT'S THE CT
- I am not sure about the wiring of the impedance switch and the OT, because it cannot be seen clearly
I WILL CHECK
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Hi
The fx jacks need to be grounded.
At least to ground of preamp PCB or directly to chassis. I would suggest to connect fx jacks ground to speaker jacks ground for testing purposes.
Regards, Stone
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I did; but no difference
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I made a new picture of the FX send return. As you can see there is a switch (based on C3amps layout).
The voltages change in V4; They all increase about 10% when switched
No movement in V3
I don't see no switch. If you mean the switching contact of the return jack... I posted the schematic some
posts ago and explained why - if it where there - it might help to find the problem. If you are unable to
distinguish between what the one in the schematic does and what the switching contanct of the return
jack does, I can't help you. You shouldn't be working on tube amps then.
The dc voltages shouldn't change when plugging sth. into the fx return.
And for gods sake, clean that jack. It's corroded like hell.
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- there seems to be a white wire running from the 10µF 450 volts caps on the preamp pcb to one of the fuse holders which does not make much sense to me (if so)
THAT'S THE CT
Sorry to say, but that makes no sense … are speaking of HT? The high voltage wire? If so, it is more or less wrong wired. And I repeat Jürgen and Peter and myself: in order to sort things out it is mandatory to have a clear overview and also to make sure the wiring is correct - to me it sounds the wiring is incorrect.
I cannot follow how B+ is wired - standby needs to be BEFORE rectifier diodes, not after them; at the moment it is a one pole type and as the purple wires are connected to rectifier directly it seems to be installed somewhere after rectification … if there is a wire from HT fuse to preamp board (b2 or b4 labeled connection), how are the plates of the power tubes are sourced? How is choke wired? And so on ...
Sorry, but I started an explanation twice now and deleted it after a few sentences - you need to be familiar with wiring of PSU of an tube amp and a lot more; at the moment I am not sure, if you are able to follow the PSU schematic as it is provided by Joachim e.g. (slo-100_psu_0_9) and on the other hand side this does not help for all questions as the C3 PSU board is different in some things.
So, it is essential to have the schematics for the C3 boards at hand - if C3 did not send you any schematics, please ask them to send …
Without a deep knowledge you will not only get misbehavior and bad sound, but a lot of security risks which can cause serious injury by high voltages.
Regards, Stone
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Thanks for your replies. They're not helpfull though.
Should I make some more pictures or should we call it quits?
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It is completely built like the attached layout
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Hi
I had a look to the layout - maybe I am wrong, but I have never noticed this wiring before … the layout shows OT and speaker jack connection labeled the right way, but not shown in the right way: impedance switch is connected (as labeled) to tip of speaker jacks, whereas sleeve must be connected to ground.
At least there is no ground connection drawn in the layout for speaker jacks - all what can be seen is a black or purple wire running from sleeves to OT. If it comes to the TT output transformer it must be wired "black" to ground and grey, brown, pink to impedance switch.
From the layout is becomes clear, why the white wire is running from fuse to the end of the board and I am now aware of what you meant by CT … the layout is different to those I know about (mostly the SLO clone layouts and that one Joachim described here at TT forum).
Is the OT's black wire tied to ground? Cannot see it on the pictures.
But at least I have run out of ideas … I am pretty sure, that the problem can be solved, but not "remotely" by me; there are too many possibilities which cause the unwanted sound, like e.g. the switch of the fx return may give no proper connection for the signal, etc.
Regards, Stone
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Hi
I had a look to the layout - maybe I am wrong, but I have never noticed this wiring before … the layout shows OT and speaker jack connection labeled the right way, but not shown in the right way: impedance switch is connected (as labeled) to tip of speaker jacks, whereas sleeve must be connected to ground.
At least there is no ground connection drawn in the layout for speaker jacks - all what can be seen is a black or purple wire running from sleeves to OT. If it comes to the TT output transformer it must be wired "black" to ground and grey, brown, pink to impedance switch.
From the layout is becomes clear, why the white wire is running from fuse to the end of the board and I am now aware of what you meant by CT … the layout is different to those I know about (mostly the SLO clone layouts and that one Joachim described here at TT forum).
Is the OT's black wire tied to ground? Cannot see it on the pictures.
But at least I have run out of ideas … I am pretty sure, that the problem can be solved, but not "remotely" by me; there are too many possibilities which cause the unwanted sound, like e.g. the switch of the fx return may give no proper connection for the signal, etc.
Regards, Stone
- What is wrong with the impedance? Or is it fine the way it is?
- speakerjacks are grounded to the chassis
- what fx switch are we talking about? The jack switch? Is the picture clear enough?
- 'CT' is what is written on the notice with the output transformer (see attached)
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- What is wrong with the impedance? Or is it fine the way it is?
I cannot see, if the OT is wired with its black wire to ground, too.
- speakerjacks are grounded to the chassis
Ok, but the OT needs to be grounded, too.
- what fx switch are we talking about? The jack switch? Is the picture clear enough?
The jack switch, yes - but as Peter said, it is pretty much corroded and may not give any proper connection - I think the same could be the case with the send jack.
- 'CT' is what is written on the notice with the output transformer (see attached)
As the layout I am used to use is different in various points I was not aware that CT wire is running that way through the chassis.
As I said - at the moment I have no idea and from my point of view I would change all the things which have been mentioned in order to track the fault.
You could change tone stacks caps as Peter mentioned some posts earlier, as they might be faulty - voltages should be stable at all points after the amp has been warmed up for around 1 or 2 minutes and not "floating" for a few volts anywhere (if the multimeter toggles between - lets say - 191 and 192 it is ok, but it should not show 172 changing to 184 changing to 177 or so ... just an example).
And the VTL have been unchecked until now, I think, which is also a possibility to give no sound (or less).
Regards, Stone
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Hi,
Since a couple of days I see the progress of this thread. I notice a deep involvement of the 'core team' but to be honest I get the feeling that even with that support, you are fighting with your amp.
Wouldn't it be better to check to find somebody to troubleshoot your build? You could learn from this person.
My fear is that through your own troubleshooting, that your amp will become even more dangerous and unstable... The wiring for a SLO or any High gain amp needs to be clean. What I saw on the pictures is not really compiling to that.
Please do not understand me wrong but you enter the phase of disappointment, where finding the mistake (I think there are probably several issues actually) will bring you to put the amp aside for a whike or even to disassemble it.
Just take a moment to think about it.
Cheers,
Laurent
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Hi thank you.
don't worry, I'm way beyond disappointed >:D
I get too much suggestions and frankly all the criticism coming in sideways is not helping.
The fact of the matter is that the amp is there, I made it and it works but sounds thin and without bottom end.
I have absolutely no clue where to begin. Before I start performing a made suggestion there are three new posts that suggest other options.
If you still want to help me out, let one person respond with one topic at a time. If you don't, I will not be offended. I appreciate everybody's time and patience!
Oh yes and... THE PROBLEM OF THIS AMP IS NOT THE WAY THE WIRING IS LAID OUT. If that were the case half of all the tube amps in the world would sound like crap (especially Italian ones).
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THE PROBLEM OF THIS AMP IS NOT THE WAY THE WIRING IS LAID OUT.
I think ist is!
You have no idea at all ...
I´m out.
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http://www.geofex.com/article_folders/lead_dress/lead_dress_in_tube_amps.htm (http://www.geofex.com/article_folders/lead_dress/lead_dress_in_tube_amps.htm)
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Hi,
Please don't take me wrong. I just notice that as you said you don't know where to start with. That indicates me the need to have somebody with more experience at your side to help. Remote troubleshooting is always a difficult matter.
BTW my first action would be to print out the schematic and the layout and to cross check everything one by one again (values, wiring ends, contacts...) and to mark it on paper. Then I would measure the voltages. In such situations, you need to go very very systematic to be able to move forward. This what the others try to help you with.
Anyway, good luck and stay tough.
Cheers,
Laurent
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I think ist is!
You have no idea at all ...
I´m out.
You were never in :devil: