[KoumparosJ]

Hello,

Here are a few pictures i took with my mobile phone, so the quality is not perfect. I did not yet put tire-ups to make it look pretty and tidy, as i wanted to make it work properly first, so it looks kinda ugly right now.

[KoumparosJ]

Continued (max data size restriction)

[KoumparosJ]

Last two:

[KoumparosJ]

The blue capacitor is a temporary replacement, as the original F&T was marginally within voltage rating and i wanted to make sure it didn't burn

[Stone]

Hi

Maybe I got it, but that would be a shot in the dark: referring to the first picture taken there is a red wire at the edge of the board which seems to be B+ - it looks like it is touched by the screw holding the board. Even it is not touched by the screw you need a minimum spacing of around 2,5 mm in order to make sure voltage will not "jump over".

I had a pretty similar failure a while ago within an amp - as you switched it on it was quite for a few seconds, than it started to "pop" and "crackle" and after a tubes had been warmed up it started to make "shooting noise" because of the crossover of the B+ voltage.

Same seem to apply to screw near 1k5 catode resistor in the top left corner. If it shortens the resistor to ground you have the so called "mu"-Amp which might overload the next stages beside ground hum (because the catode will be referenced to another point than all the other).

Fuse must not blow necessarily but voltage drop may occur.

Regards, Stone

[KoumparosJ]

The screws definitely don't touch the respective turrets, although i didn't know this about the 2.5 mm spacing. However the situation is the same even without the nuts, in which case the spacing from the screws is around 4-5mm. On the other hand, there might be a similar issue at the last large filter capacitors ( left top corner capacitor at the second picture, power supply board), where the ground turret ( the one with the black cable leaving, is ~1mm from the B+ coming from the choke and going to the preamp board ( purple cable). This one is really close, bad design by me i guess....

[Stone]

Hi

I am not sure about the spacing but if I refer to PCBs then it should be 2,5 mm or even more ... 1 mm might be too close - as of the spacing itself there is not much current flowing, but voltage is going across it if it is high enough.

Maybe another one can give a second opinion concerning the spacing to prove if I am wrong or right.

Is there any chance to disable the ground turret for testing purposes?

Regards, Stone

[mordpol]

Hey!

I know the thread grew old already, but did you try to go out of the effect send into a different amp to locate where the problem is actually happening? Did you also try to give the whole chassis some hits, or parts of the turret board etc. to hear if there's some mechanical problem (could solder joint)?

The turret board layout looks really nice by the way 

Best regards
Mathias

[KoumparosJ]

Hello everyone! I wish a happy new year to you and your beloved ones.
After quite some time now, i finally finished moving back to my homecountry, and  back to building, so i need to solve these issues with my sloclone, with your kind help.

Following Stone's suggestion, i made sure all the B+ voltages are well separated from neighbouring ground turrets, and the situation is improved by a lot.

However i have the following issue. The overdrive channel is leaking into the Normal channel in some way. When the amp is on the normal channel and the gain of the overdrive channel is crancked above 4-5, the "clean" sound also has some distorted signal into it ( the more the overdrive gain the more the distorted signal). I suspected this might be because of the non-infinite resistance of the LDR2 when off, but even if i completely disconnect it from the board, the leaking is there at the same level as before. Can someone please give his/her insight on this?

[Stone]

Hi

Good to hear that the amp became more stable by separating B+ and ground lugs.

The effect you are noticing appeared two or three times within my 19" preamps - as I am using B+ filtering and PCB from the Anvil preamp kit and the Anvil itself is pretty quiet I assume some other failure, but I never could figure out what it caused.

I shorted the gain wipers of the gain potientiometers of the distortion channels to ground and that fixed the issue (but did not solve it in a a way). Also I could only hear distorted sound at very low clean gain settings.

Could you prove if you are hearing a distorted sound while shortening overdrive gain wiper to ground?

And the Vactec LDRs often are leaking or are broken - this can be proved by various problems within Mesa amps, especially channel switching is not working as expected (and clean channel does have a certain amount of distortion).

Regards, Stone

[KoumparosJ]

Greetings,

Well, Stone, when the gain wiper of the overdrive channel is shorted to ground, there is no overdriven sound leaking, but this is the same as having that pot to zero. What really baffles me is that with LDR2 completely disconnected from the circuit, not only there is overdriven sound in the normal channel (depended on the gain seting of the OD channel), but also the overdrive channel works pretty much as it should. Since the LDR2 is the only gateway for the overdriven signal, i really can't understand how this is possible. I am checking everything again, but please let me know if something comes to your mind. Thanks for your time everyone.

[KoumparosJ]

Hm,

Also the normal channel plays, at low volume, with LDR5 disconnected....strange

[Stone]

Hi

Can you point me to the schematic you are referring to? I am reading Joachims SLO 0.7 schem available here, but there is no LDR5 (or I am missing that totally).

If LDR2 ("behind" V2B , C10 and R20) and you still got "normal" overdriven sound at normal volume level there must be a bridge or something like that.

I would assume as long as that problem exists, you will have overdriven sound while being in normal channel as LDR1 will not necessarily shorten grid of V2B to ground (there will be a small resistance which might be sufficiant causing the problem).

Regards, Stone

[KoumparosJ]

Hi Stone,

I am using the schematic from slocloneforums.com. LDR5 is an addition to the original, placed after the (r17//c8) combination and before the r21 resistor, essentially switching the feeding of the signal of the clean channel into the grid of V3B. This is a common mod to stop the clean signal which is  added to the overdriven in the original soldano, when in the overdrive channel.

But as i said with both LDR2 and LDR5 disconnected from the board ( in practice both paths of the normal and overdriven signal are cut), the amp still works, at somewhat lower volume. If I ground R21, there still exists some sound, but lower volume. Only when i ground the grid of V3B directly, there is no sound at all, which is strange. I have checked for bad connections/bridges, but i didn't find anything obvious... 

[Stone]

Hi

Ok, I got the scheme and had a look to it.

If you connect R21 to ground on its "left" side (opposite side to grid of V3b) you still have a small grid resistor - if you 've still got sound then I would assume there is a leakage on "B+" (connection points A and B).

But - as you said - it sounds more like a bridge somewhere before V3b as with leakage on B+ the amp should run at very low volume level (as of my experience).

At the moment I do have no idea ... if you remove LDR2 and LDR5 there should be no signal - also (more or less) even very little signal avoided by stray or something like that but no "useable" volume level at all.

What about disconnecting V2a grid?

Regards, Stone