[KoumparosJ]

Hi,

well as signal from both channels is going through to the V3B, even with the LDR2 and LDR5 completely disconnected, i suspect it shouldn't be some kind of bridge, but rather B+ leaking. As i am not that experienced with this kind of stuff, could you please give me a few details on what this is, how should i check if this is the case and what might cause this? (faulty components? wirind errors and where) Thanks a lot once again

[Stone]

Hi

Normally B+ should be "free" of any signal, but due to wiring error or something like that there may some signal leaking from one stage to the other ...

There are several ways to check this.

First of all you can check the wiring and the placement of components and their values - do have the filter caps the right capacity, do they have the correct DC voltage rating, are they connected the right way and so on. And if they are connected in the same way as written in the scheme (it is important that you have the same series as in the scheme).

But I do have it only once or twice since I have started working on tube amps.

Maybe it can also be caused by a faulty filter cap or if the resistors value is too low, e.g. you did not use 15k / 10µF, but 1k5 / 10µF which will raise filter frequency from 1 Hz to 10 ... imagine using a 150 or 15 Ohm resistor by accident. But this should also be indicated by to high anode voltages.

My suggestions / thoughts ...

If LDR2 is removed, but there is still a lot of distortion sound in OD channel at a reasonable level of volume it might be that R20 is connected in a wrong way and does have a connection from C10 to R21 ...

If LDR5 is removed but there is still a good amount of clean sound in NR channel at a reasonable level of volume it might be that there is a bridge from R17 to R21.

I agree that it does not make any sense still having sound while having LDR2 and LDR5 removed.

But I think with B+ leakage you will not have a pretty loud clean or overdrive sound. Running grid wires in parallel to each other gives us various effects as well.

Regards, Stone

[Striker52]

Hi, I had a very similar issue  in an amp where I used these small switches for channel switching. It was just crosstalk because the two signals were too close together. Using a bigger switch solved the problem.

Cheers Axel

[KoumparosJ]

Hello,

Stone,

Thank you for your suggestions, i double checked everything and i can't find anything wrong...I will post some closeup photos tomorrow, maybe some fresh eyes can catch something that i missed

Axel, Thank you for your advice, but in this specific amp, the actual channel switching is performed by the LED/LDRs, so the small switches do not carry any signal. The clean/crunch switch does carry signal but this one performs perfectly.

The major issue right now is that i get sound, especially on the OD channel (but at low volume) even when the signal chain is broken. Could it be that because i am using 5W wirewound resistors for the power supply resistors R62, R63 and R64, they act somehow as transformers inducing signal from B+4(A) and B+3 (B), to the B+2 (C) supply of V3, V4 and V5??? (notation according to Joachims (sloclone) schematics respectively)

[Stone]

Hi

At the moment I am running out of ideas ... can you point me to the discussion about the wire resistors? I have no experience with them as I was always using metal and carbon types, but in general (as far as I remember from my apprenticeship) copper cores wired in circles are kind of choke, but I think with a very, very small effect.

But as I said ... I do not remember exactly and maybe Joachim has a totally different experience especially in B+ wiring / setup.

Regards, Stone

[KoumparosJ]

Hello,

well i am running out of ideas too... my thought about the wirewound resistors was exactly as you said, that maybe because of the winding of the wire in the resistor it acts somehow like an inductor... But still the large capacitors should filter any signal at that point to ground...I don't know, just guessing at the moment.

[Stone]

Hi

I was thinking about the effect you described, but at the moment I am just catching at some straws ... normally it should something like interspersal, but I do not know where - I will have a closer look to your pictures again later on.

Maybe - just another straw - it is some crosstalk between R20 and R21 if they are close together; that came into my mind as Axel mentioned the switch problem.

Regards, Stone

[KoumparosJ]

I tried removing some components, as suggested by a member of slocloneforums, mainly coupling capacitors to try and locate the problem, with the following results:

Removing C10, still sound at the same level (left out)
Removing C7 , still sound at the same level (left out)
Removing wire between R29 and R30, NO sound (reconnected afterwards)
Removing the wire from fx return to V4A pin 7, still sound at lower level (left out)
Removing R26, NO sound (reconnected afterwards)
Removing C6, still sound at same level (with all the above disconnected
Removing C2, NO sound (reconnected afterwards)


Removing V3, still sound at much lower level
Removing V4, No sound

The whole time LDR2 and LDR5 are removed. As a reminder i get sound on the OD channel and on the normal channel only if OD gain is high (same sound in both channels)

Any thoughts?

[KoumparosJ]

Greetings everyone!

Today is a good day, as i managed to fix the amp.

I had tried replacing the filtering capacitors C34 and C35 just to make sure they weren't faulty, but it hadn't made a change. Today I took a long shot, and replaced them not only with new, but with larger capacitors of 47uF and the amp works fine!!! What a monster amp and what a relief!!!!

I would like to thank all the members of the forum for maintaining this helpful community, and especially Stone  who devoted a lot of time to look into my problems and help me fix them. Thanks guys, your help is much appreciated!!!

[Stone]

Hello

Happy to read about your success.

Maybe for some reason the value of the resistors is much lower than expected and stated and therefore using 10 µF caps did not work. I would not deny that it may also happen that the 10 µF caps were labeled wrong, this may also apply to the replacement ones if they are from the same manufacturer and out of the same series.

I will keep this information in mind - maybe it does make sense to increase filter cap value to 47 µF on SLO style amps in general.

Also thanks for your kind words as I believe a lot of people have read about your problem and started analyzing it by heart.

Regards, Stone