Transistors for Yamaha C-80

[ebk231]

Hello
I need help making sure I get the right parts. I usually can find what I need by using the search but no such luck this time. I am doing a restoration on my C-80 and a buddies C-85. Both of these preamps are pretty cooked inside and are ready for some new parts.
The transistors I want to replace are:

d1275
b949
d1260
b937

 

[avionic]

B+D Enterprise has them all.

http://www.bdent.com/nsearch.html?#...ze=15&storeid=yhst-864421581610834172249761/1

 

[avionic]

d1260

2SD1260A will sub nicely for and 2SD1260. Same goes for the 2SB937A.. The " A " indicates a little higher Vcbo and Vceo voltages.
http://www.datasheetarchive.com/pdf...ff6562dfacffcdaa99aed431&type=M&query=2SD1260

 

[avionic]

Whatever new ones you select. They are still going to run just as hot.

 

[avionic]

Did you find any corroded 4.7KΩ 1/4 watt resistors that sit just in front of those two pass transistor/heatsinks ? Glue damage.

 

[slimecity]

All of your transistors that you have pictured are definitely testing as dead?

 

[ebk231]

All of your transistors that you have pictured are definitely testing as dead?

I didn't even test them I'd just like the piece of mind of some new ones 30 years of the temps seems like long enough.

 

[slimecity]

If they aint broke........

 

[ebk231]

Did you find any corroded 4.7KΩ 1/4 watt resistors that sit just in front of those two pass transistor/heatsinks ? Glue damage.

I just looked, sure enough they are corroded. More partrs for the parts list.
Do you have any other things I should look at? I have been reading a couple threads that I can find on them. I am doing a recap and replacing the rca jacks. I thought I read about some troubling diodes do you know anything about that? I also have some resistors in the moving coil section I would like to address and get both channels matching.

 

[OMGCat!]

Look at the film cap by the corroded resistor as well. I had a C-80 where the leg was corroded right off.
Other than that I always use small machine screws with plastic washers to hold down those heat sinks so they have some mechanical strength. The sinks are already tapped and the boards have holes in the proper spots.
There are also a few transistors in the front left (knobs facing you) that run really hot. Those are likely wiggling around in their sockets by now. Actually, looking at your picture they are the ones you have removed without heat sinks on them. I don't have one open in front of me but if the new parts come with tabs I'd try to mount some sort of heat sinking on them.

I've always wondered why Yamaha used carbon comp resistors in the phono section of these preamps. My B2x has some giant carbon comps in it too. They must be there for a reason and they sound great so I haven't messed with replacing anything.

 

[ebk231]

Thank you so much for the input. I would like to try and do a heat sink on those transistors. Thats what I need help with though getting a newer device that is the correct part.

 

[ebk231]

I do need to replace the one of the transistors and I thought for a few bucks I will do them all. Would anyone be willing to help me find substitutes from mouser? I got a cart ready from them and it gets annoying to pay shipping for 8 transistors but if I got to get the originals linked above, I will.

 

[restorer-john]

A heat-sink isn't going to do a thing except for a few minutes until the transistors reach the same temperature again. Without air circulation they will continue to cook.

If the Matsushita original transistors are fine- leave them alone other than removing the crusty cooked solder and resoldering them.

The bottom line is Yamaha went cheap on the PCB material in the C80, provided absolutely zero ventilation and the design is poor. There were far too many non-ventilated preamps pushed out by Yamaha (and other brands) which ran far too hot.

The irony is, the matching Yamaha power-amps at the time were generously ventilated and full of fresh air.

 

[pdm4606]

Looks like time for a fan. I installed a fan on my C-50 and it works fine. I put an 80 MM and power it from an old wall wart that puts out 12V DC.

 

[restorer-john]

Just run it with the case off, installed in a rack with a shelf 6 inches above it to keep the dust off.

A fan used in a preamp is just ridiculous.

 

[ebk231]

Well mine would be exposed so I kinda want to keep the cover. I have been tossing around the idea of a fan.

 

[restorer-john]

Perhaps have a completely perforated steel top cover fabricated (bent up) and painted black?

Keep the old case if you ever want to sell it.

I've had C-80s and sold them The CX-1000 doesn't run as hot and has a much bigger case. The little CX-600 runs cool.

 

[avionic]

I also have some resistors in the moving coil section I would like to address and get both channels matching.

R149 - R152 --> 12 Ω / 1 watt
R121 - R124 --> 560 Ω / 1 watt

Both are listed as " carbon resistors " .. IMO .. I think the OEM's look like carbon composite. May want to go with carbon or metal film . Flamproof/resist coating probably be a plus.

 

[avionic]

R149 - R152 --> 12 Ω / 1 watt
R121 - R124 --> 560 Ω / 1 watt

Both are listed as " carbon resistors " .. IMO .. I think the OEM's look like carbon composite. May want to go with carbon or metal film . Flamproof/resist coating probably be a plus.

I'd be checking all the transistors , diodes and e-cap's on that MC pre-amp circuit before powering up that circuit..... Resistors don't just overheat on there own.

 

[avionic]

The little resistors are 4.7 Ω / 1/4 watt Flameproof carbon film. Carbon film or metal film " flameproof / resist coating for sure. Probably had a shorted final in the MC pre-amp circuit at one time or another in its past.