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Pioneer SA 7500 II restoration help

While I am waiting on the capacitors to come in I am trying to work through how to get my hands on a pair of output transistors for this amp. I spent the last couple days scouring the internet for available replacements but so far absolutely zero luck sourcing anything. Even prior threads on here list ones that are all out of production and I don't want to waste my money getting scammed for counterfeit parts on ebay. Does anyone have any recommendations on where to turn for a pair of these?
 
The original style will be very hard to find. You may need to start searching for alternate case styles. You may need to drill and tap a new mounting hole after. I have seen others who use a clamping bar across the new transistors to take advantage of the original screw holes from the "bat wing" output transistors.
 
The Fuxtor said:
The original style will be very hard to find. You may need to start searching for alternate case styles. You may need to drill and tap a new mounting hole after. I have seen others who use a clamping bar across the new transistors to take advantage of the original screw holes from the "bat wing" output transistors.
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I have also seen TO3P cased transistors using one original mounting screw hole. (no drilling and tapping) The transistor leads face sideways and flexible wire leads are used to connect it to the PC board.
 
laike said:
While I am waiting on the capacitors to come in I am trying to work through how to get my hands on a pair of output transistors for this amp. I spent the last couple days scouring the internet for available replacements but so far absolutely zero luck sourcing anything. Even prior threads on here list ones that are all out of production and I don't want to waste my money getting scammed for counterfeit parts on ebay. Does anyone have any recommendations on where to turn for a pair of these?
Click to expand...
Adapting TO-220 looks like your best bet. You'll want to compare datasheet values of old and new transistors. Get reasonably close to the original bandwidth product (fT measured in MHz). If the replacement is too high, you could experience high frequency oscillation.
 
Thank you all so much for your input! The amp is fully functioning and sounds absolutely gorgeous, I couldn't have done it without all of your help.

For posterity's sake I'll list everything that I fixed in the amp and as many of the resources across the web that helped.

Full recap job done with help from This Post from dbayles here on the forum. Some of the listed components were discontinued so equivalent caps were used in place.

The obvious issue with the amp was the left channel being out which was confirmed to be a dead 2sd588A transistor. The others were working fine but I opted for MJL4302/MJL4281AG pairs which mounted beautifully with thermal pads and new holes drilled in the heatsink.

The EQ causing issues when engaged was due to a polarity swap on the silkscreening that was pointed out here at C23 & C24.

There was scorching on the pcb at R68 and the resistor was coming loose on the board, I replaced that and all surrounding resistors just to be safe. I assume this must have been due to a short from whatever had spilled.

Q11 was fully fried and corroded entirely through, replaced with a KSC2073

I will post a final update in a few months with pics included once my financial situation is back on track, but I plan to replace the power indicator light and build a new case for the unit.
 
mrk229 said:
The "kit" with the dual SMD transistor and adapter board will be great since the dual transistor package used should be very well matched giving low offset.
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i bought the adapter boards off ebay and the dual smd transistors off mouser and build some of these

the ones i used were not that closely matched and did not even give as good a result as matched ksa992s give.

the dc offset was acceptable and would be fine..... but i won't spend that money again. i'll stick to the 992s.

ymmv.
 
painttoad said:
i bought the adapter boards off ebay and the dual smd transistors off mouser and build some of these

the ones i used were not that closely matched and did not even give as good a result as matched ksa992s give.

the dc offset was acceptable and would be fine..... but i won't spend that money again. i'll stick to the 992s.

ymmv.
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What did you use?
 
tarior said:
What did you use?
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Count me in as curious as well.

I just purchased some generic adapters that I can make work with a dual SMD.

I have some Toshiba dual SMD transistors to use with them, I don't have the part # here though.

Guess I should measure a few.
 
mrk229 said:
Count me in as curious as well.

I just purchased some generic adapters that I can make work with a dual SMD.

I have some Toshiba dual SMD transistors to use with them, I don't have the part # here though.

Guess I should measure a few.
Click to expand...
For dual PNP, matched pair, common emitter, in stock at Digi-Key using those filter parameters, we have 2SA1873, 2SA1618, and HN4A06. So far, 1873 is the only one I've used. I mean to investigate the others some time in this life.

​

 
I just slapped an 1873 on my little tester. Hfe/Vbe 250/652 and 252/651. That's pretty darn close. The gain on HN4A06 is impressive. Though it's worth noting that no two testers agree with each other.
 
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