Replacement transistors for a Yamaha P-2200

Do you have a correlation between measured gain difference and resulting offset?

Not questioning that it causes it, just curious if you have noted a consistent relationship. For example, 2 point different in gain causes 10mv offset or whatever?

No. Not really. I just try to match'm up with identicle gain numbers.Even then you still may be off a few millivolts. But it usually gets it pretty close -- +/- 10mv.
 
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Replacing TR101 and 102 in both channels with closely matched (Hfe) transistor may get you closer to 0.00 mv of DC offset. The higher the gains the better, matched of course. Might have to get 20 or more.

512-KSA992FBU

I get them in the TA packaged. Then check each one and write the gain numbers right on the tape.

BTW these are not A992's

I changed TR101 and TR102 to the KSA992's as recommended. Here's the results and details:

Offset in left channel went from 23mV to 13mV :banana:

Offset in right channel went from 43mV to 16mV :banana::banana:

Left channel, old transistors:
TR101: 345 hFE
TR102: 331 hFE

Left channel, new transistors:
TR101: 398 hFE
TR102: 396 hFE

Right channel, old transistors:
TR101: 281 hFE :eek:
TR102: 348 hFE

Right channel, new transistors:
TR101: 410 hFE
TR102: 410 hFE

Thanks again, avionic, for this excellent advice!

The repair of this amp (maybe I could also call it a refurbishment) was a awesome success and it turned out to be a fun project :yes:

After completion, I connected the amp to my ADS L880's, and I have probably close to 8 hours of listening. The sound is fantastic! Tall, wide, and deep soundstage. Very clear and detailed. There's a sense of space between instruments. It powers the L880's with authority :guitar:

If there are any other improvements or mods that could be done, I would be interested in hearing about them. :yes:
 
I changed TR101 and TR102 to the KSA992's as recommended. Here's the results and details:

Offset in left channel went from 23mV to 13mV :banana:

Offset in right channel went from 43mV to 16mV :banana::banana:

Left channel, old transistors:
TR101: 345 hFE
TR102: 331 hFE

Left channel, new transistors:
TR101: 398 hFE
TR102: 396 hFE

Right channel, old transistors:
TR101: 281 hFE :eek:
TR102: 348 hFE

Right channel, new transistors:
TR101: 410 hFE
TR102: 410 hFE

Thanks again, avionic, for this excellent advice!

The repair of this amp (maybe I could also call it a refurbishment) was a awesome success and it turned out to be a fun project :yes:

After completion, I connected the amp to my ADS L880's, and I have probably close to 8 hours of listening. The sound is fantastic! Tall, wide, and deep soundstage. Very clear and detailed. There's a sense of space between instruments. It powers the L880's with authority :guitar:

If there are any other improvements or mods that could be done, I would be interested in hearing about them. :yes:


Just wanna say I did exactly as you did, without reading this thread. I put in sockets inplace of tr102 and 101 and put A992s in there untiI got 3mV, since I buy A992s in bulk. I'd say transistor replacement for better performance is modding. Slew rates aren't published for this amp but I'm sure they're good enough for 37.417V at 20khz, top rated power and audio frequency.

I bet slewing rate can be improved for lower TIM distortion. I also added a resistor in series with one channel to get rid of channel imbalance.

Damping factor and frequency response is good for this amp, but I bet a higher value (film) input coupling cap would help with bass. Maybe some Romex wire and ring terminals from 22mF caps to external 10mF or 6.8mF 100V caps would also help, maybe with an inductor in series with the bridge rectifier. Or relay to bypass the coil after charge up. Perhaps an external capacitor and DC protection box with all this fanciness.

I know I have some high current coils and a 12A relay and 4 15mF caps sitting around. Like always, the box is the hard part.
 
Just wanna say I did exactly as you did, without reading this thread. I put in sockets inplace of tr102 and 101 and put A992s in there untiI got 3mV, since I buy A992s in bulk. I'd say transistor replacement for better performance is modding. Slew rates aren't published for this amp but I'm sure they're good enough for 37.417V at 20khz, top rated power and audio frequency.

I bet slewing rate can be improved for lower TIM distortion. I also added a resistor in series with one channel to get rid of channel imbalance.

Damping factor and frequency response is good for this amp, but I bet a higher value (film) input coupling cap would help with bass. Maybe some Romex wire and ring terminals from 22mF caps to external 10mF or 6.8mF 100V caps would also help, maybe with an inductor in series with the bridge rectifier. Or relay to bypass the coil after charge up. Perhaps an external capacitor and DC protection box with all this fanciness.

I know I have some high current coils and a 12A relay and 4 15mF caps sitting around. Like always, the box is the hard part.

Excellent, happy modding!
 
Reviving this thread; Finally got around to doing something about the too-warm left side of my P2200 (~10 years??). Ordered the appropriate capacitors, from suggestions cadged here, and suitable transistors. [if this works] You can see in the (001 jpg) what the left side looked like to start, obviously been repaired in the past, r128 had been replaced, soot on the heatsinks, DSBG here and there.

When I got TR109 and TR111 out and tested them, their hfe's were only 34 and 19 (!!!!). The expected values for 2SD381 k/l is (k 180/3250) or (l 80/160), so totally out of spec. I replaced them MJE15032G's with hfe's of 84 & 85. Also scrubbed up the heatsinks and put down new thermal paste.

The 2SB536 was within spec, had an hfe of ~130, so went back in with a cleaned heatsink and new paste too. Installed the new capacitors on the left side now too (002 jpg)
At this point the left side did not run hot anymore, so I put it back together and checked it was working. DC offset on left was ~25mv and on the right ~30mv on the right.

I must say listening to an amp with only one side re-capped can really demonstrate whether it was worth it or not. Felt like the right side basically had lost definition and sharpness, and I had thought it sounded good before.

Next day, I replaced the TR101, TR102, TR201, and TR202 capacitors, the ones people have suggested would drop the DC offsets if they were well matched. I had bought 12 KSA992FATA (they seems to have the tightest spec for hfe's) and measured them still in the tape. I was lucking in finding two pairs with high and matching hfe's (003 jpg).

The service manual only shows the left driver board, and I had to be very careful because on the right driver board TR201 & TR202 are oriented the opposite way to the diagram.
Left side old hfe's --> 315 & 300
Right side old hfe's --> 284 & 330

Left side new hfe's --> 338 & 338
Right side new hfe's --> 336 & 336

The new DC offset's are ~20.6mV and ~19.6mV

Now I recapped the left side and checked it still worked. (004 jpg)
Wish I hadn't waited so long, but things got busy.
 

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Hi Everyone and thank you for taking the time to read my comment.

I need to replace 4 fuse resistors - the Yamaha parts list PDF tells me they are as follow (see attached photos - they are the little white resistors):




Fuse Resistors:

- 100mA 68 Ω
- 30mA 470 Ω
- 45mA 220 Ω
- 150mA 22 Ω

I have searched on Mouser.com and RS Components, have googled them etc... and can't seem to find the exact same ones anywhere. Is there anyone here who can help me in locating these please? I am not sure what these are called? Ceramic Resistors? Through Hole Resistors? I can't find them anywhere :(

Kind regards,
Henry
 
Many use 1/4 watt flame proof resistors when this go bad. The lowe mA might need 1/8th watt.

The electronic experts here will go into more detail, I never remember the formulas for figuring these out.....or I'm just lazy to do so ;)

Nashou
 
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