Tweet
Hello all, and happy father's day to you dads in here.
I'm working on a friend's amp that had some problems. This is an early 90s Rivera 55-12 that had some blown out filter caps and other assorted leaky electrolytics. The amp had so many leaky caps we just shotgunned them all. 23 in total. The good folks at Rivera like to use roofing tar to glue their caps to the board and solder from the top and bottom so that was a fun afternoon. Normally with changing this many caps I'd do a little at a time and test as I go, but this amp required total board removal so I did them all at once. Blah.
The amp works very well now, sounds great, low noise floor, nice and stable. It still needs new tubes, but the amp works fine. We brought the caps up slowly on a variac through a light bulb limiter. No problems. I'm seeing expected voltages where you'd expect to see them...and some where I didn't expect it.
The issues:
1) I'm getting DC voltage on the outside of a few caps. 200vdc to be exact on one of them. I wasn't expecting this. The caps are installed cleanly and oriented correctly. Why would there be that much voltage on the outside shell of a cap? And if there is a problem with it why is the amp working so nicely?
2) With the tone controls all the way off there is no signal. I didn't test this before we dug in but it seems odd to me. Same situation on both channels. With the tone controls all the way off there is no sound. Crack any one of the tone controls open a little and the sound shows up. Maybe that is just a feature of this amp, I'm not sure. Doesn't seem right though. I also found two pot-to-PCB solder connections that were left unsoldered at the factory. I soldered them because they had traces on the board. Maybe I inadvertently made a connection that aint supposed to be there?
Here's the only schematics I could find and they're pretty hard to read.
Rivera_r_series.pdf
I'm working on a friend's amp that had some problems. This is an early 90s Rivera 55-12 that had some blown out filter caps and other assorted leaky electrolytics. The amp had so many leaky caps we just shotgunned them all. 23 in total. The good folks at Rivera like to use roofing tar to glue their caps to the board and solder from the top and bottom so that was a fun afternoon. Normally with changing this many caps I'd do a little at a time and test as I go, but this amp required total board removal so I did them all at once. Blah.
The amp works very well now, sounds great, low noise floor, nice and stable. It still needs new tubes, but the amp works fine. We brought the caps up slowly on a variac through a light bulb limiter. No problems. I'm seeing expected voltages where you'd expect to see them...and some where I didn't expect it.
The issues:
1) I'm getting DC voltage on the outside of a few caps. 200vdc to be exact on one of them. I wasn't expecting this. The caps are installed cleanly and oriented correctly. Why would there be that much voltage on the outside shell of a cap? And if there is a problem with it why is the amp working so nicely?
2) With the tone controls all the way off there is no signal. I didn't test this before we dug in but it seems odd to me. Same situation on both channels. With the tone controls all the way off there is no sound. Crack any one of the tone controls open a little and the sound shows up. Maybe that is just a feature of this amp, I'm not sure. Doesn't seem right though. I also found two pot-to-PCB solder connections that were left unsoldered at the factory. I soldered them because they had traces on the board. Maybe I inadvertently made a connection that aint supposed to be there?
Here's the only schematics I could find and they're pretty hard to read.
Rivera_r_series.pdf
Comment