P-2200 repair?
- Thread starter whoaru99
- Start date
What he said. Awesome amp, just start by pulling the output transistors and testing them and look for overheated parts along the way.
In an amp like this that is older and gets hot, a recap really would be good to do, as well as replacing potentiometer with sealed multiturn types. Not many of them either which is nice. For the outputs I would recommend MJ15025/24G.
In an amp like this that is older and gets hot, a recap really would be good to do, as well as replacing potentiometer with sealed multiturn types. Not many of them either which is nice. For the outputs I would recommend MJ15025/24G.
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whoaru99
Epic Member
Interestingly, all 12 outputs test OK using the diode check of my meter (don't have a transistor tester). Haven't disassembled it other than top and bottom covers and the output covers but don't see anything burnt peering in and around with a light.
Disconnected the main caps and tested them as best I can, again using the multimeter and time to charge calculation in the Fluke 87 manual. The caps are supposed to be 22,000uf, one indicated roughly 21,000 and the other roughly 23,000 by that method.
Checked the rectifier bridge and it seems like it's shorted on two adjacent legs (the two legs from AC > + < AC ). Pretty uncommon, isn't it, for just the bridge to fail?
Disconnected the main caps and tested them as best I can, again using the multimeter and time to charge calculation in the Fluke 87 manual. The caps are supposed to be 22,000uf, one indicated roughly 21,000 and the other roughly 23,000 by that method.
Checked the rectifier bridge and it seems like it's shorted on two adjacent legs (the two legs from AC > + < AC ). Pretty uncommon, isn't it, for just the bridge to fail?
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25A 400V
This should do the trick..
http://www.mouser.com/ProductDetail...=sGAEpiMZZMtQ8nqTKtFS/MRt2/0z7Bct866kwxpWb6Q=
This should do the trick..
http://www.mouser.com/ProductDetail...=sGAEpiMZZMtQ8nqTKtFS/MRt2/0z7Bct866kwxpWb6Q=
whoaru99
Epic Member
I don't repair too much stuff so I need y'all opinion.
None of the internal fuses are blown, just the two external "user serviceable" fuses.
One of the main caps appears to have a very slight whitish deposit around the screw terminal. I don't know if it's just oxidation from the aluminum or the start of leakage. As mentioned before, both caps check very close to rated....at least in capacity. I don't have means to test ESR.
Should I just replace the bridge rectifier (confirmed one leg is bad with it out of circuit) and give it a try before doing further refurbishment?
I'd really like to get it fired up to see if both meters and stuff work before deciding to put any real $$ into it. It's not trashed but by no stretch of imagination is it a garage queen. Definitely been in a rack with some miles on it. Not too dirty inside though, mainly just a bit of dust.
None of the internal fuses are blown, just the two external "user serviceable" fuses.
One of the main caps appears to have a very slight whitish deposit around the screw terminal. I don't know if it's just oxidation from the aluminum or the start of leakage. As mentioned before, both caps check very close to rated....at least in capacity. I don't have means to test ESR.
Should I just replace the bridge rectifier (confirmed one leg is bad with it out of circuit) and give it a try before doing further refurbishment?
I'd really like to get it fired up to see if both meters and stuff work before deciding to put any real $$ into it. It's not trashed but by no stretch of imagination is it a garage queen. Definitely been in a rack with some miles on it. Not too dirty inside though, mainly just a bit of dust.
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See if some vinegar will take the white stuff off. If the main caps are ok capacity-wise they're probably fine but ESR is very nice to know.
For sure replace the bridge and fire it up first to make sure nothing else is wrong before refurbishing.
Yeah it should. I wouldn't know what wattage however, I always use a 60.
whoaru99
Epic Member
It's alive.
Replaced the bridge and it fires up fine. Passes a normal-looking sine wave on both channels and both meters register equally for the same signal input and gain settings.
Some of the meter lights are not working, and got the bias voltage set to 10mV per channel. DC offset is a little higher than I'd like to see though, 20-25mV.
Doesn't seem to be any DC offset adjustment so if wanting to bring that down what does one look at?
PS: I'm very disappointed with the rectifier bridge from Vishay. The terminals must be nickel plated...I should have known from the bright, shiny finish. They didn't take solder worth a damn. Will be the last one of those I buy.
EDIT: Apparently nickel-plated terminals are all the rage now. Looked at other options and where listed they said nickel too, for the Faston terminals. I guess they all suck.
LOL.
Replaced the bridge and it fires up fine. Passes a normal-looking sine wave on both channels and both meters register equally for the same signal input and gain settings.
Some of the meter lights are not working, and got the bias voltage set to 10mV per channel. DC offset is a little higher than I'd like to see though, 20-25mV.
Doesn't seem to be any DC offset adjustment so if wanting to bring that down what does one look at?
PS: I'm very disappointed with the rectifier bridge from Vishay. The terminals must be nickel plated...I should have known from the bright, shiny finish. They didn't take solder worth a damn. Will be the last one of those I buy.
EDIT: Apparently nickel-plated terminals are all the rage now. Looked at other options and where listed they said nickel too, for the Faston terminals. I guess they all suck.
LOL.
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It's alive.
Replaced the bridge and it fires up fine. Passes a normal-looking sine wave on both channels and both meters register equally for the same signal input and gain settings.
Some of the meter lights are not working, and got the bias voltage set to 10mV per channel. DC offset is a little higher than I'd like to see though, 20-25mV.
Doesn't seem to be any DC offset adjustment so if wanting to bring that down what does one look at?
PS: I'm very disappointed with the rectifier bridge from Vishay. The terminals must be nickel plated...I should have known from the bright, shiny finish. They didn't take solder worth a damn. Will be the last one of those I buy.
EDIT: Apparently nickel-plated terminals are all the rage now. Looked at other options and where listed they said nickel too, for the Faston terminals. I guess they all suck.
Looks like the bias is the only pot on there, so I'd saw that's as good as it gets. Does it lower after 20 minutes or so? It could improve after a recap and such.
