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Transistor Cross Reference help - Yamaha DX7S switching power supply

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grantb5:
I'm pretty far out of my element here, but got a deal on a dead Yamaha DX7S synthesizer (USA version) and would like to at least try and fix it. I'm in the US, so I'm not converting, just fixing hopefully.

It has a switching power supply from about the late 80's. I've located some dead components and there is one transistor here that I can't find. It's a 2SC3570. The original is in a plastic TO-220 package.  On another synth that uses the same power supply (DX7II) the service manual says 2SC3570 or 2SC2929. They are similar, but to my untrained eyes, definite differences. I'll start by showing the schematic and parts list:

The part in question is Q1 to the left of J4.


Layout (US and Canadian versions, very similar):




Schematic:
http://yates.ca/dx7/Schematics%20&%20PCBs/DX7IIFD%20Schematic.jpg

I can't find the original anywhere (2SC3570), at least on this side of the pond. The NTE cross for this and the alternate come up with completely difference numbers, so I'm not 100% confident that the alternate (2SC2929) is a good idea.

I'll post the transistor info in a followup message. Let me know what you think. Or what parameters I should focus on.








jmelson:
Well, this doesn't look very exotic.  I think just about any 250 V 5A transistor likely would work fine.  Seems the spec is a 5A, 400 V transistor, so that gives plenty of margin.  You ought to be able to use any number of 2N type switching power transistors with similar ratings to substitute.

Jon

grantb5:
Here is a link to info on the 2SC3570:

https://alltransistors.com/transistor.php?transistor=14906

And the 2SC2929:

https://alltransistors.com/transistor.php?transistor=13897

Comparing:

--- Code: ---Type Designator:                              2SC3570        2SC2929
Material of Transistor:                       Si             Si
Polarity:                                     NPN            NPN
Maximum Collector Power Dissipation (Pc):     25 W           40 W
Maximum Collector-Base Voltage |Vcb|:         500 V          450 V
Maximum Collector-Emitter Voltage |Vce|:      400 V
Maximum Emitter-Base Voltage |Veb|:           6 V            7 V
Maximum Collector Current |Ic max|:           5 A            3 A
Max. Operating Junction Temperature (Tj):     125 °C         150 °C
Forward Current Transfer Ratio (hFE), MIN:    40             20
Package:                                      TO220            TO220

--- End code ---

I can find the 2SC2929 but the case might be metal tab instead of plastic ... eBay sellers are a bit vague in the descriptions. Do you think this cross is acceptable? Or should I try and find something closer to the original 2SC3570?

Thanks.

grantb5:
You're going by the fuse and the maximum collector current? Is it true that since this is a switching application, the different hfe isn't a concern?

Here is what NTE comes up with ( http://www.nteinc.com/search.php ). I know they are not universally loved. Curiously that they are not the same NTE cross:

2SC3570    NTE2337  http://www.nteinc.com/specs/2300to2399/pdf/nte2337.pdf
2SC2929    NTE51      http://www.nteinc.com/specs/10to99/pdf/nte51.pdf

I can break out the specs for these too. People are saying that NTE isn't really great at adhering to their specs though. I'm certainly not one to say.

Actually I can't break out the specs. The two NTE pages have different abbreviations for almost everything and I have no confidence of transposing the correct numbers.

Jr460:
Just wondering did you find any of R2,  R3, R9 open?

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