I just found a Yamaha P2200 Amplifier and purchased it. It was suppose to be working but after getting it home to clean it up I found that there is 82V on the left speaker terminals and 5.4MV on the right speaker terminals. I am NOT a technician but do know a little bit about solid state amps. Not a lot but a little. I went to the service manual I downloaded off the Internet and set the bias on both channels at the recommended 10.0 MV. This reading kept going up and up as I had power to the amp so I had to keep resetting it over and over. I then went to the two test points that are to read 0V and found 82.4V on the Left channel and 5.4MV on the right channel. I don't have any idea how I am suppose to get these readings to the 0V they are suppose to be. I then put an input into the right channel from a cassette deck and it passed sound and sounded pretty good. I could get some pretty good volume out of the right channel using this cassette deck. I was afraid to connect a speaker up to the left channel with their being 82V across the speaker lugs. The amp is not running hot nor is it blowing any fuses so I am at a loss as to what to do. Is there a VR that will zero the voltage to the speakers like there are in my Sansui BA-3000 Amp. The Sansui has VR's to set the Bias and set the voltages to 0V at the speaker lugs. HELP!!!
The right channel may very well be ok, but the left channel, with a high DC voltage at the speaker output,
is not. First check for blown internal power supply fuses, but from the manual it appears that there are none.
There may be bad output transistors (and maybe more), but that won't be something you could repair yourself.
Do NOT connect speakers to the amp, they will be damaged. I would return the amp and get your money back.
Last edited:
The purchase of the amp was AS IS and I really don't want to return it as it is well worth more than the $50.00 I paid for it. I really do want to repair this amp and feel confident that wit a little help I can. I have replaced Power transistors several times including replacement of other parts. I have been working on audio gear for about 50 years but I am NOT a technician. I have all the necessary test equipment and all the tools to work on this amp. I just don't want to start replacing parts for the sake of changing parts. I have a good bit of experience with the Sansui amps and after years of dealing with them I can identify what the problem is with them. This Yamaha is a different animal and I am smart enough to know that I don't know enough about this amp so I am asking for some help chasing down the problem. I have enough of the correct power transistors to change them all out but if there is something else wrong, which I suspect is the case, all I would be doing is damaging them. Thanks for your quick reply to my thread.
Verify that the negative supply voltage is getting to bad channel's pcb.
I would check all of the bad-channel's semiconductors in-circuit, and remove any doubtful ones
for further testing. Also check all the 0.47R emitter resistors for open circuits.
You do have the good channel to compare voltages with. https://www.hifiengine.com/manual_library/yamaha/p2200.shtml
Last edited:
I had the time today to check all of the 0.47 emitter resistors in the right channel that is giving me trouble and they all tested fine. I also decided to pull and check all of the power transistors in the right channel and they also checked good. While I had them out I went ahead and removed all the dried out heat sink compound on the heat sinks and transistors and put fresh on. To be safe not to short anything out when comparing voltages between the two channels I am going to have to lengthen some wiring so that I can lay the channels down flat. I hope to get started on this tomorrow. What is throwing me a curve with this problem with the right channel is that the Amp is not blowing fuses or Power Transistors. If I evber have to change Power Transistors in this Amp I plan on using MJ21195G and MJ21196G transistors as trying to find REAL original transistors for this amp is next to impossible unless someone out there knows where there are some of the originals laying around.
I need to say that I misspoke when I said my problem was with the Right channel because it was my Left channel that had the problems. I found the problem as to why I had the 80V at the speaker lugs of my Left channel. I found where the B+ was soldered to the wrong lug on the PCB. After I switched the Negative lead with the B+ lead on the Left channel the voltage went from 80V to 45MV. The Bias was the same and could not be turned down to the 10MV where it is suppose to be. Now the problem with the Left channel is the inability to be able to adjust the Bias AND the Left channel is getting very hot and making the thermal sensor to be lit up. I had to stop there for the day. If anyone out there has an idea where to start looking for what is causing this overheating problem, please let me Know
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.