I recently repaired an Adcom 5802 amp. It had a blown output transistor. I replaced it and all the electrolytic caps and Zener diodes as well as any cap that I could replace with a Wima and matched input mosfets… 555 timer …relay … tested all the other transistors… tons of stuff.
This is my first time doing something like this. I’m learning a lot. I made a lamp limiter and hooked it up last night. 100w was not enough for the relay so I went to 200w. That worked. No smoke, no noise and the bulb is a faint glow after the initial power up. I set the offset to near 0 on each channel and have not messed with the bias yet, it’s still original. I let it warm up for 20 min. and so far so good.
In probing around with a meter (DC) I’m getting some high voltages on the metal tops of some of the electrolytic caps. Namely the 47uf (+100v) on the input board and the 100uf on the main amp board. (one is +170v on one channel and +70v on the other, strange that they are different…) I’m not sure if I should be looking at the back of these caps but my question is does this sound right to you? The voltage is over the rating on the cap.
My next step is to see if there is high voltage on the input XLR jack and if not try it with some signal into speakers but I need some advice from those who have seen this stuff. This could just be trepidation after all the work…
Second question: is it OK to do an audio test with the lamp limiter? (200w bulb I also have a 300w)
This is my first time doing something like this. I’m learning a lot. I made a lamp limiter and hooked it up last night. 100w was not enough for the relay so I went to 200w. That worked. No smoke, no noise and the bulb is a faint glow after the initial power up. I set the offset to near 0 on each channel and have not messed with the bias yet, it’s still original. I let it warm up for 20 min. and so far so good.
In probing around with a meter (DC) I’m getting some high voltages on the metal tops of some of the electrolytic caps. Namely the 47uf (+100v) on the input board and the 100uf on the main amp board. (one is +170v on one channel and +70v on the other, strange that they are different…) I’m not sure if I should be looking at the back of these caps but my question is does this sound right to you? The voltage is over the rating on the cap.
My next step is to see if there is high voltage on the input XLR jack and if not try it with some signal into speakers but I need some advice from those who have seen this stuff. This could just be trepidation after all the work…
Second question: is it OK to do an audio test with the lamp limiter? (200w bulb I also have a 300w)