Yamaha P2200 DC offset

I have that Yami for about two months and it works nicely. Nonetheless, I never could find the service manual for it. Just the owner manual, which gives no detail as how to set the DC offset.

Anyone has the instructions to set DC?

I have a multimeter and a small screwdriver ready to operate ;-)

TIA

Lee
 
Picture somebody hitting his head on a concrete wall.

Started by adjusting the right channel. Probing pods were easy to locate, so was the potentiometer. I was at 16mV and adjusted to 10mV as per specs even though it could be set to 5mV.
Went to the left channel. Connected the voltmeter, started turning the pot, then my elbow slipped, the screwdriver touched the live wire next to the potentiometer and then a simple DC offset adjustment turned into the Fourth of July. Sparks, flames, fumes. I pulled the plug immediately but damages were done. One dead channel. I slid the driver/transistor board and it is badly burned. That side is definitely toast.

Anyone has a left channel DC board for sale? I deeply apologize for being such a low life fucktard. ;-(

DSCN0085.jpg
 
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Tekko

Banned
2005-01-01 3:33 pm
**** happens you know. I miswired both the output transistors and the driver transistors in my latest build, outputs survived, but drivers went up in smoke, replaced the drivers and rewired the outputs and it worked just fine afterwards.

Your board is likely repairable if you clean off the soot and charred remains, prollem is sourcing modern equavilents for the transistors used.

Atleast you have the right channel for reference for resistor values and such.
 
I did a cosmetical clean-up. No more charcoal. I flipped the boad to see if some races have burned. Everything seems to be okay. No fuse has popped either.

I will be checking R128 and 129, as well as TR110 (which is most likely damaged from the spike.
TR110 seems to be easily available. The service manual indicates 2SC1213A, C or D. Not specifically though.
 
Seeing that this side of the amp has probably been stressed now, maybe it's time to change the driver and output transistors (on both sides). While we are there, I also have another P2200 with various brands of transistors on it that could need some TLC ;-(

By experience, what would be the ideal transistors? Anything from ONsemi?

Don't worry, I now have another P2200 and a PC2002 to listen to while the wounded ones will be fixed.
 

skybar8

Member
2011-08-16 6:22 am
Hello everyone
Please someone correct me if iam posting in a wrong way or violating the forum rules. I was searching where to post my issues but couldnt find the proper place to post. I found this thread which would match my issues.
I have p2200 amp with constant 80vdc on both channels. I checked and tested every single transistor, resistor, capacitor almost all the components on the PCB but couldnt find any faulty component.
I also checked the output transistors, the PNP and NPN but no luck, both 909 and 586 tested with positive result. Do you guys think that the output transistor would test good when you take it off the power amp, and it would do a shortcut when you put it back in. I am thinking to buy all the output transistors but i just dont waste my time if they are still in a good working condition.
I appreciate any possible help
 
"Checked everything."

There is no certainty that two amps with V+ on the output have the same problem inside.

If you have 80v on the outputs, start with the power supply, are both V+ and V- present at the output transistors? Are both +15 and -15 present at all op amps? (Unless that model uses 12v) DO both channels have the same 80v output? Or just one side? It may not be output transistors at all, your channel may be turning them on farther back.
 

Robbie44

Member
2011-06-12 3:42 am
Hello Again
i checked all resistors all transistors recapped the channels
checked all the output transistors 2sa909 and 2sc1586 i am really stumped still 77,vdc out
i checked all the wires ... can it be the VR-101? or D114 , D115 has anyone had a mystery problems like this..... any help would be appreciated Robert Denmark
 

Robbie44

Member
2011-06-12 3:42 am
"Checked everything."

There is no certainty that two amps with V+ on the output have the same problem inside.

If you have 80v on the outputs, start with the power supply, are both V+ and V- present at the output transistors? Are both +15 and -15 present at all op amps? (Unless that model uses 12v) DO both channels have the same 80v output? Or just one side? It may not be output transistors at all, your channel may be turning them on farther back.

Hello this amp has no op amps on each channel it shows 77+ on bolth channels