I have a sweet peach amp (FU-50) and it has been working fine. I started having two issues...
1-getting popping sounds
2-the right channel started going out.
As for 1...i noticed i could clear it up if i tapped on the center tube. I took it apart and found that the center tube socket was pulling out of the circuit board...ie the pins of the socket were pulling out of the solder joints. So i cleaned up and re soldered the socket and that solved that issue.
As for 2...i did not see anything unusual but did notice that i would hear audio out of the right channel when i first turned it on for a second or two and when i switched it off...also if i left it running for a while it might pop in. I did try swapping the two large tubes and also some other ones i had. It did seem to follow some tubes. When i had a pair that seemed to work, i notices that the right channel tube was nuclear hot...visible glowing red significantly more than the left side...also if i swapped two working tubes...what ever i put in the right side would glow like rudolfs nose. (see photos of the two sides compared)...i also noiticed that the two circuit boards used for the two large tubes were populated differently....the right one, (the one am having trouble with) is missing R2, R3 and has no ground wire soldered to it....is this normal? (see photos).. Any help would be appreciated...i am afraid to use this now.
1-getting popping sounds
2-the right channel started going out.
As for 1...i noticed i could clear it up if i tapped on the center tube. I took it apart and found that the center tube socket was pulling out of the circuit board...ie the pins of the socket were pulling out of the solder joints. So i cleaned up and re soldered the socket and that solved that issue.
As for 2...i did not see anything unusual but did notice that i would hear audio out of the right channel when i first turned it on for a second or two and when i switched it off...also if i left it running for a while it might pop in. I did try swapping the two large tubes and also some other ones i had. It did seem to follow some tubes. When i had a pair that seemed to work, i notices that the right channel tube was nuclear hot...visible glowing red significantly more than the left side...also if i swapped two working tubes...what ever i put in the right side would glow like rudolfs nose. (see photos of the two sides compared)...i also noiticed that the two circuit boards used for the two large tubes were populated differently....the right one, (the one am having trouble with) is missing R2, R3 and has no ground wire soldered to it....is this normal? (see photos).. Any help would be appreciated...i am afraid to use this now.
Attachments
Do not run the amp with the red plating tube for more than 30-60 seconds at a time if at all possible.
You'll have to source a schematic for this or start drawing one. You could also post the DC voltage measurements at each tube pin for each output tube. They are going to be very different just based on that red plating.
You'll have to source a schematic for this or start drawing one. You could also post the DC voltage measurements at each tube pin for each output tube. They are going to be very different just based on that red plating.
The 'missing' R2 and R3 (each 100 Ohm) connect the two heater pins to ground (to eliminate/reduce possible hum). If the heater of the tube on the circuit board which misses R2 and R3 is being fed by the same transformer tap as the tube on the circuit board that has R2 and R3 soldered in, you will be fine without them (than they are meant to be missing).
Edit: After a quick search on the internet, i think your amplifier runs the two FU50's (one per channel) in triode mode and with fixed bias. So you should check if the (right) bias voltage is there. It could offcourse also be that one of the FU50's died on you.
Edit: After a quick search on the internet, i think your amplifier runs the two FU50's (one per channel) in triode mode and with fixed bias. So you should check if the (right) bias voltage is there. It could offcourse also be that one of the FU50's died on you.
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Addition:
http://bilder.hifi-forum.de/max/782567/sweet-peach-fu50a_434185.gif
If this is basically the schematic (looks like there are some modifications noted in this schematic), than the two FU50's each have a separate tap for their heater supply. If this is also the case in your amplifier, than the two 100 Ohm resistors should be installed where they are missing now, unless one of the heaterpins is connected straight to ground.
I do not know if this possible omission explaines the problems you are facing. The amplifier was working ok for some time anyway. But it is surely not good practice to let a heater supply floating when a tube is used like it is being used in your amplifier. You only really see floating heater supplies in some stabilized power supplies.
http://bilder.hifi-forum.de/max/782567/sweet-peach-fu50a_434185.gif
If this is basically the schematic (looks like there are some modifications noted in this schematic), than the two FU50's each have a separate tap for their heater supply. If this is also the case in your amplifier, than the two 100 Ohm resistors should be installed where they are missing now, unless one of the heaterpins is connected straight to ground.
I do not know if this possible omission explaines the problems you are facing. The amplifier was working ok for some time anyway. But it is surely not good practice to let a heater supply floating when a tube is used like it is being used in your amplifier. You only really see floating heater supplies in some stabilized power supplies.
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First...thank you all for your responses...and the time you took. I figured it out. I went to start measuring the voltages across the tubes and comparing left to right. V- was at 0....i traced the wire feeding it and found a short to ground...fixed that and all seems good. Both channels working...sounds good, i now have an amplifier again and not a whole house heater! Thanks again...little by little i am learning more about all this.