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Next restoration: Yamaha PC2602M

amr2

amr2

Well-Known Member
Hello

I will start with this tank the next week. The amplifier is in good shape, it needs a general cleaning and some minor restorations. This model uses a (noisy) rear fan to force air when it gets hot (TH >60ºC). I will change it for a quieter model.

Now the bad part...it has a weak channel. Three output transistor and one driver are shorted. I’m thinking about using these replacements:

2SA968B/2SC2238B -> 2SA1837/2SC4793
2SA1516R/2SC3907R-> 2SA1492/2SC3856 or 2SA1962/2SC5242

I will have to change all the output transistors (5+5 per channel), I don’t like to mix old parts with subs, and although they measure fine, they can be stressed.

If anyone has used other closer replacements please post it...

I will upload photos!
 
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That is one really nice amp. Waiting for photos.

"2SA968b-PNP-200V-1,5A-25W-100MHz--equivalents 2SA1133 -2SB861.


2SC2238B-NPN-220V-1,5A-25W-100MHz--equi.2SC2660-2SD760-2SD1138"

From DIY forum
 
Thanks!

I think I'm going to use these, they are close to the originals and are available (mouser):

2SA968B / 2SC2238B -> 2SA1837 / 2SC4793
2SA1516 / 2SC3907 -> 2SA1962 / 2SC5242
 
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I'm looking forward to the resto thread. I've got one that I need to go through some day. It works fine but I'd like to set the bias and give it a general look inside.
Did you find the proper service manual for it? I have only been able to find the same copy from a few sources online that is missing a few needed pages that include bias adjustment.
I haven't made it a priority as it's not in use at the moment but I'd like to integrate it into the main system some time in the future though after running it for a while I'm thinking about either disconnecting the meters or finding the non metered version.
 
OMGCat! said:
I'm looking forward to the resto thread. I've got one that I need to go through some day. It works fine but I'd like to set the bias and give it a general look inside.
Did you find the proper service manual for it? I have only been able to find the same copy from a few sources online that is missing a few needed pages that include bias adjustment.
I haven't made it a priority as it's not in use at the moment but I'd like to integrate it into the main system some time in the future though after running it for a while I'm thinking about either disconnecting the meters or finding the non metered version.
Click to expand...

C'm on, you gotta have big meters.
 
I would like to include the predrivers (2SA1142/2SC2682) in the order (mouser). Fairchild KSA1142/KSC2682 are a good option, but the KSC is also obsolete. Any other sugestion?
(bdent is not an option)
 
The manuals Ive downloaded are missing about 7 pages total (if you go by page numbers) so the procedure is probably in there. I guess I'll need to track a real copy down somehow.

As far as the big meters, I end up staring at the rather than paying attention to the music. I might be a little ADD or someth...oh look, shiny!
 
I have the SM with no missing pages (1 to 33) and there is no info about the procedure....
 
OMGCat! said:
The manuals Ive downloaded are missing about 7 pages total (if you go by page numbers) so the procedure is probably in there. I guess I'll need to track a real copy down somehow.

As far as the big meters, I end up staring at the rather than paying attention to the music. I might be a little ADD or someth...oh look, shiny!
Click to expand...
I have a quick solution for your problem; just give me the amp, I can multi-task :D
 
amr2 said:
I have the SM with no missing pages (1 to 33) and there is no info about the procedure....
Click to expand...

Looking through the last manual I downloaded it seems that I do actually have all the pages and you're right about it not showing any adjustment procedures. There are a few pots in there IIRC and it would be nice to know how to adjust them. The PC2002 has good info as do the rest of the manuals I've got for Yamaha gear. I wonder why they left it out of this one.

rottalpha said:
I have a quick solution for your problem; just give me the amp, I can multi-task :D
Click to expand...

If I manage to find a 2602 plain version I'll definitely let you know :)
 
Will be watching this thread. I've been using a 2602m as my main power amp for almost two years coupled with a C50 pre amp and the combo has blown anyway everything I compared it to. Mine also has a very noisy fan ands runs VERY hot so comes on quite often. It also keeps blowing the LED's I fitted behind the meters but keeps on making sweet sounds.
 
Dazaa said:
Will be watching this thread. I've been using a 2602m as my main power amp for almost two years coupled with a C50 pre amp and the combo has blown anyway everything I compared it to. Mine also has a very noisy fan ands runs VERY hot so comes on quite often. It also keeps blowing the LED's I fitted behind the meters but keeps on making sweet sounds.
Click to expand...

Fan noise was never a concern when building a commercial grade amp, but when the commercial amp is used for more civil duties, it make sense to either turn the fan off or replace it wit a modern and silent kind. These amps were build to live their lives packed inside racks and a full blasting levels. It is most likely that you almost never turn that thing all the way up and it is most likely that you do not keep it in a rack / closed space. Turning off the fan is what I wold do (keep it in there, but put a manual switch ). If the idea of having the fan turned off bothers you, just look for a low noise fan. Good Luck!
 
It's very easy to change the fan, It's a standard 120mm 12VDC unit. There are a lot of options, I'm going to re-use a pc case fan, with only 15.7 dB(A) of noise level. The rotation speed is less than the original (3100 vs 1500). The air flow is also less (88,3 CFM vs 50.5 CFM). Perfect for home use, it's virtually inaudible.

On the other hand, "the beast" is already at home..

IMG_8384.JPG
 
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Congratulations! I've been using my meterless PC2602 to drive a pair of NS-1000M's the last thee years, and couldn't be happier. Great under-the-radar amplifier!

Dazaa said:
Mine also has a very noisy fan ands runs VERY hot so comes on quite often. It also keeps blowing the LED's I fitted behind the meters but keeps on making sweet sounds.
Click to expand...
Maybe you should check your amp. The fan starts at 60°C, so it shouldn't be triggered unless you play very, very loud.
 
I agree. Mine has never gotten more than slightly warm even when playing music fairly loud. It sounds like your amp might be running warmer than it should be. Unless of course you're running it as a pro amp and using all of its watts continuously.
 
Dazaa said:
Will be watching this thread. I've been using a 2602m as my main power amp for almost two years coupled with a C50 pre amp and the combo has blown anyway everything I compared it to. Mine also has a very noisy fan ands runs VERY hot so comes on quite often. It also keeps blowing the LED's I fitted behind the meters but keeps on making sweet sounds.
Click to expand...

Probably means your filters need cleaning (clogged = less air flow, more work on the fan), and the fan needs to be taken apart, cleaned, and re-lube the bearing, or replace the fan. If for some reason it has been running continuously AND the amp runs hot, you should be checking and adjusting the DC offset, Bias, and check that all outputs on the hot channel (or both) are conducting equally.

rottalpha said:
Fan noise was never a concern when building a commercial grade amp, but when the commercial amp is used for more civil duties, it make sense to either turn the fan off or replace it wit a modern and silent kind. These amps were build to live their lives packed inside racks and a full blasting levels. It is most likely that you almost never turn that thing all the way up and it is most likely that you do not keep it in a rack / closed space. Turning off the fan is what I wold do (keep it in there, but put a manual switch ). If the idea of having the fan turned off bothers you, just look for a low noise fan. Good Luck!
Click to expand...

True, poorly ventilated spaces like in a close quarters cabinet with doors, could restrict airflow a lot. Or the fan needs repair/replacement, or problem with fan or heat management. But personally, I'd never solely disconnect the fan, its there for a reason, and fan dependent heat management designs with relatively restricted convection airflow would be a time bomb just waiting for a problem to occur - Even with a stout Yamaha design as this one.
 
There was a lot of dust inside due to the airflow from the fan. I have just disassembled the chassis waiting for a new powder coating.

IMG_8395.JPG
 
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I'm going to recap the amp. I normally use Panasonic FM series for power supply and bypass. The problem with this amp is that several capacitors are rated to 100VDC, and these values are not available.
 
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