I'm still working on the modding of the Harley Benton GA5. I swapped the output tranny for the hammond cse, and it works fine, so now I enter the walhalla of this modding project, the extra tube (mod II). I sincerely hope you'll help me out once more with some things. I managed to figure out most of the soldering bij looking at the scheme and pics, but I do have some questions (I don't want to blow things up now) ad not very technical:
- Anode is this the little red wire and conncected to C8?. Do I have to attach this to the - or + at the capacitor?
- Heater voltage is this the big black wire connected to C12?. Do I have to attach this to the - or + at the capacitor?
- I think I see 2 ground wires (blue ones). Is this correct?
- One of the blue ones is connected to pole 5 at the socket, is this corrrect?
- Where is the other one connected to?
- Are the poles 4, 5 (ground?) and 9 not used at the socket? I don't see anything in your schematic?
- Anode is the - symbol in your schematic?
- Heater voltage is the © symbol in your schematic?

the rest I figured out, I do have all the materials, only these questions before I can begin.....
You would help me out big time!

Hi,

the Anode needs positiv power and this comes from the positive side of the capacitor.
The heater needs to connection. One from the + and one from the -.
Just check out http://www.tube-town.net/info/datenblaetter/tubes/jj/jj12ax7.pdf there you can see which pins are used for the heater.
If you are using 12,6 V for the heater Pin 9 is not connected and if you ar eusing 6,3 V both heaters must be used parallel.

Best regards, Dirk

thanks! I must be bugging you.........

so the little red one is the anode? the big black one is the heater?

I want to perform the same mod you did, that means I have to do what?

- positieve side of the heater voltage goes to pole .... of the socket

- negative side of the heater goes to pole .... of the socket

I don't understand the pdf file.

And what about the ground wires (are there two? and to which poles are they connected)

regards lars

- positieve side of the heater voltage goes to pole .... of the socket
- negative side of the heater goes to pole .... of the socket

It is regardless. Connect the + to Pin 4 and the - to Pin 5 and try to find somebody how knows a little bit more about this stuff and who can check your amp before your power it on. It is the savest way !

And what about the ground wires (are there two? and to which poles are they connected)

Which ground wires ?

Best regards, Dirk

Thanks for your reply.

I do see some blue wires (two?) I thought those were the ground wires and one is connected to pole 5 on the socket. the other one I cannot see it going on....

grt. Lars

Hi,

Pin 5 of which tube ?

Best regards, Dirk

hi dirk,

Thanks for helping me out once more, I think I understand better now, the two blues wires are coming from C12 (heater voltage), aren't they? Connected to pin 5 and 9 on the socket of the new tube.

pin 5 to the - of the heater and connecting pin 9 to the + of the heater? Is it correct what I say above?

nb. You mentioned I should solder pin 4 also to the + of the heater. This I should still do?

Then my final question is: there is also this (big) black wire that goes under the PCB (connecting some things on top of the new tube), where does it connect to under the PCB?

regards,

lars

Hi !

I am sorry Lars, but you better try to find a good tech otherwise you will kill the amp and / or yourself too !!!! Don't do this what you wrote.

Best regards, Dirk

Hi Dirk,

Thanks for your reply and for your worries. I'll think I manage and look out for myself. I've already started soldering it up. I know about filter drainage, etc.......

Is it true that these last two questions will sort things out? Or am I mistaken. Because those three wires (2 blues and one big black one coming from under the PCB) I cannot see clearly on the pics where they come from and go to. I think the big black one is the ground wire connected to rk1/rk2 and the two 470k on the new tube. Is this correct?

The two blue ones are coming from C12, one goes to pole 5 (+ as you mentioned) on the socket and one goes to.... (I think pole 9...)

I don't know any tech-guys.....

Hi,

don't build based upon the picture - take the schematic and read it ! This is importend and will not lead to mistakes, well, if you understand it. And evyrthing should be clear. As long as you don't understand this basics you should not touch the amp !

Best regards, Dirk

thanks for your reply.

I can see everything in the schematic, so I'm using the schematic for most of the things. Only the heater questions stays. I don't see that in the schematic (I think a technician would....), so I was using the pics for that.

I imagine you won't help me any further considering you're last post?

grtz lars

I imagine you won't help me any further considering you're last post?

Well, I don't know what else I should write. Everything is in the schematic and the pin-numbers are listed on the datasheet for the 12AX7 and / or EL84 (marked with F = filament). It is absolutly simple, just like a bulb. Check it out closely again - also the datasheet !

Best regards, Dirk

thanks Dirk for your help, I figured it out already. Just drillng some holes and it should work.

Everything works properly! and it sounds nice! thanks for all the help.

connected pin 4/5 of the socket together and wired it to cap c12 and did the same with pin 9.

I still would like to perform some extra mods which I'm not certain if they can be performed after adding this extra gainstage. At this site (http://www.ultimate-guitar.com/forum/showthread.php?t=481701&page=6&pp=20) on page 6 of 15 call1800ksmyazz adds a pentatode/triode switch. He explains what he has done at his post on 1-10 at 8.55 pm (post 114). Is it possible to perform this mod having done the TTE mods?

I want the overdrive to sound a little bit more creamier/saturated) and I'm interested in doing this mod.

Any comments?

regards,

Lars

Hi,

I did not read the mentioned posting but basicly it is possible to add such a switch regardless if you modded the preamp or not.

Best regards, Dirk