Yamaha emx 640 output devices.

[fireman]

Hi all,

I have been given a non working emx 640 mixer/ amp, originally blowing the fuse on power up, traced the problem to a shorted power amp section by using a light bulb limiter and multimeter.

The poweramp uses SK D2560 and SK B1647, I have looked on Mauser and RS and google but cannot find these devices on sale, I presume there are obsolete as this unit seems to be around ten to fifteen years old.

Do any of you Yamaha gurus know if they are skill available or can suggest a working alternative, I would think that they would need to be matched sets.

I think that I may have a data sheet somewhere for at least one of these but it is several months since I last looked at this project, again the internet seems not to know of these devices.

Looking forward to any info, cheers.

[g1]

Search for 2SD2560 and 2SB1647.

[Enzo]

Agree^^^

The SK denotes the brand, and on Asian transistor types there is an unerstood "2S" ahead of the numbers.

If you have the service manual or the parts list, I suspect the full number will be on the listing.

[fireman]

Thanks guys, I know electronics components go out of fashion quickly but it did seem strange that there was no reference to these on the net.
I do have the schematic and layout for this somewhere but I have just found a pic on my phone of the Darlington pairs that has spurred me on to get this working again.
I do remember powering it up with the blown outputs removed and one of the SIL 4558 got really hot, I thought it may have been shorted by something on the table under the circuit board, but now I think it was probably due to the missing parts.

[Enzo]

No reference? I just googled 2SD2560, and first hit was the data sheet, and second hit was Digikey telling me they had 1600 of themin stock at $3.50 or less.

I used to buy my Sanken parts from B&D Enterprises, never got any fakes from them. I just looked, and they have that pair at $3 and some each.

digikey.com

bdent.com

If you only searched the abbreviated number from the part, then I am not surprised at slim findings. Always use the eitire part number.

[fireman]

Yes, I feel very foolish now, I searched again using the 2s prefix and got loads of stuff I quickly checked eBay and loads of these available, ( would not be my preferred place to buy these) will look on Rs, etc now I'm looking for the right part numbers, I hadn't realised that SK was the manufacturer.

I'm presuming the blown outputs where the result of a shorted speaker lead, I have no other information about what happened to stop it working, are there any other common causes of blown outputs that relate to the emx 640?

When powered through the light bulb limiter it should only glow briefly then settle down to being very dim if the shorts are gone, yes?

Thanks for your time and knowledge.

[Enzo]

SK is Sanken.

[oc disorder]

Hi er um fireman.. I have repaired a couple here in Aust. Yamaha still supplied me with the spares, they sold them only as matched pairs.
Here the part number from the parts list has been superseded but give them a minute and they can translate.
Of course the UK version may work differently.

Old part number ? VV081700 Pair Transistor B1647/D2560

You could try contacting them via the technical support number and inquire where you can buy spare parts...

https://uk.yamaha.com/en/support/contacts/

Thought it worth a try.

Check the diodes near to the edge of the board too. I recall those often short in the destruction process.
Sorry I can't be more explicit.

[fireman]

Ok, thanks for the heads up, I'll check those diodes too, it may have been one of those that caused the 4558 opamp to get hot.
I've found a sanken distributer in wales so will give them a call and see if
They do small orders.

Thanks