5F6A low volume

[vinceg]

Hi, I re-wiring my own 5F6A clone and now it has a very low volume. What could cause the problem?

[nosaj]

Hi, I re-wiring my own 5F6A clone and now it has a very low volume. What could cause the problem?

Pictures and the schematic you used would be appreciated.

nosaj

[vinceg]

You are right, sorry.

[vinceg]

I used Ceriatone and Robinette layout for mods

[Helmholtz]

You are right, sorry.

Not sure, but picture 9 might show a diode shorted by a cap's lead.

[vinceg]

Not sure, but picture 9 might show a diode shorted by a cap's lead.

Possible. Thank you for the tip. One thing to watch tomorrow with the light of day. Italy is now evening.

This could be the cause?

[nosaj]

Possible. Thank you for the tip. One thing to watch tomorrow with the light of day. Italy is now evening.

This could be the cause?

Also since you used Dale resistors, we can't tell what the values are. Sometimes a wrong resistor value in certain position can choke the volume. It will be up to you to verify each one against the schematic or layout.

nosaj

[vinceg]

Also since you used Dale resistors, we can't tell what the values are. Sometimes a wrong resistor value in certain position can choke the volume. It will be up to you to verify each one against the schematic or layout.

nosaj

I will also control the values of the resistors. Although I doubt they are wrong. Unless Mouser did not make a mistake.

Anyway, it seems strange to me that the amp does not have a back hiss. I noticed that without guitar plug in there is not classical valve hiss, even raising volume control. Could it be a problem in V1 preamp section?

[nosaj]

I will also control the values of the resistors. Although I doubt they are wrong. Unless Mouser did not make a mistake.

Anyway, it seems strange to me that the amp does not have a back hiss. I noticed that without guitar plug in there is not classical valve hiss, even raising volume control. Could it be a problem in V1 preamp section?

Anywhere in the signal chain can choke the signal, whether it is in the preamp or the poweeramp.

See this on page 47 the click test. http://theguitar-blog.com/wp-content...r-Handbook.pdf

nosaj

[Helmholtz]

Italy is now evening.

Same over here in Germany.

In winter time most of the day(s) I depend on electric lighting.

[J M Fahey]

Just curious, did it work properly before the Mods?

Personally I have found that by far the best Mod, the one which brings smiles to users, is to rip all of them off and return amp to original circuit, go figure.

Not kidding: amps become Classics for a reason: they provide better sound than others since forever, and peak sound and performance was reached after extensive , ear tested modding ... 50 years ago.

Once at the peak of the mountain, all paths lead downwards

[Enzo]

If an amp was working, then you do something to it, and it no longer works right, it is a safe bet the work you did was the cause. SO look especially at every part you changed, every joint you soldered.

[vinceg]

Just curious, did it work properly before the Mods?

Personally I have found that by far the best Mod, the one which brings smiles to users, is to rip all of them off and return amp to original circuit, go figure.

Not kidding: amps become Classics for a reason: they provide better sound than others since forever, and peak sound and performance was reached after extensive , ear tested modding ... 50 years ago.

Once at the peak of the mountain, all paths lead downwards

Yes, it worked well. I just decided to change the resistors and capacitors and improve the wiring. The mods concern only the bias circuit.
However, this night I had a flash of inspiration: I forgot to solder the feedback resistor at the output. I can not wait to run into the lab to see if this is the cause of the problem.

[vinceg]

Update
I realized I forgot to solder feedback resistor to out. Unfortunately I do not think was the problem. Now the amp has right volume but sometimes it disappears. It also seems to produce some sort of oscillation when I increase the volume control and it has background noise.
these are the values I have read:

Power transformer has 325+325 V AC than it is correct. At B+ there is 411V DC.

V5 (6L6)
pin3 400
pin4 413
pin5 -40
pin6 404

V4 (6L6)
pin3 400
pin4 400
pin5 -40
pin6 407

V3 (12ax7)
pin1 233
pin3 41
pin6 236
pin8 41.5

V2 (12ax7)
pin1 170
pin3 1.1
pin6 310
pin8 167

V1 (12ay7)
pin1 152
pin3 2.3
pin6 153
pin8 2.3

[alexradium]

Yes, it worked well. I just decided to change the resistors and capacitors and improve the wiring. The mods concern only the bias circuit.
However, this night I had a flash of inspiration: I forgot to solder the feedback resistor at the output. I can not wait to run into the lab to see if this is the cause of the problem.

feedback resistor just lowers the overall gain,assuming it is the right value and the phase is correct,hence negative.Resistor and cap change has a slight effect,for good or worse,only if your building technique is the best possible required,from what i see it's not,sorry,most probably you have some bad soldering or miswire,although voltages are looking fine,which is a good thing.