I am the end of my rope...I ordered the c1625, it arrived today and I installed it...the meters remained full left...so I measured the voltages...they were totally incorrect across the board...not only the new c1625 but also the new sa815....removed both from the circuit...now I have nothing at the base and collector holes of both and a ridiculous 6.49 volts at the emitter...wtf??
With those two transistors removed you should:
1/ Check that both 750 ohm resistors that feed the collector are intact. Measure them.
2/ With the amp on you should see +22 volts across D421 and -22 volts across D452.
I worry over how genuine any 2SC and 2SA parts actually are (unless bought from authorised suppliers) and wouldn't (myself) even think of sourcing the original type numbers for a repair.
So check the above carefully and lets see where it is at.
1/ Check that both 750 ohm resistors that feed the collector are intact. Measure them.
2/ With the amp on you should see +22 volts across D421 and -22 volts across D452.
I worry over how genuine any 2SC and 2SA parts actually are (unless bought from authorised suppliers) and wouldn't (myself) even think of sourcing the original type numbers for a repair.
So check the above carefully and lets see where it is at.
Attachments
after my blood pressure returned to normal and the blood drained from my eyes, I reasoned that the events I described to you made no sense...I turned the amp over and measured for any power in that section of the main board...there was none except for 13 volts across 4 diodes...there is a gaggle of wiring on that board that comes from the rectifier board...red, blue and yellow...directed to each channel, left and right...they are the old style wire wrapped around a post...i checked each one...wiggled them a bit...and like magic the voltage reappeared in the transistor holes...as well as from the various resistors on that board...somewhere a connection is spurious and evil...question...if not the original numbers, then what...and where can I find viable substitutes? Yeah...I know it's a PITA...I wil repay the favor some way...maybe write you an ad...or a book..or give you a flying lesson...I am almost as good at piloting as I am at electronics...ha..
well, after wiggling and diddling with the wires, and resoldering the 'new' sc1625, all is well...meters are rocking like they should...but now your comments about the old sc's and sa's have me concerned...there are a dozen substitutes listed for each of those transistors...so how do I choose the best? Thank you once again...it's been a long trip...
jim
jim
its all good fun though, and I'm really pleased to hear you have it working again. OK, so the likes of eBay have become well known for fake and remarked parts, particularly semiconductors (IC's and transistors). If an authorised distributor (Digikey, Radio Spares, Farnell and so on) are supplying the part then its almost certainly 100% genuine. Anyone else and its a judgment call.
Have you come across this thread which is running from 2006 to present:
My Transistors, original or copy?
For general purpose applications (like your regulators) there are common parts that make up a 'go to' list. TIP41C for NPN and TIP42C for PNP type in the T0220 package outline, BD139 and BD140 for T0126 style...… there are quite a few.
Yours need to withstand around 70 volts worst case and the TIP41C and TIP42C (must be the C type) are 100 volt rated. Current and power handling are far in excess of what you need here. As this is a simple series pass regulator there are no worries on dynamic performance such as high frequency performance and so on.
https://www.fairchildsemi.com/datasheets/TI/TIP41C.pdf
You're the one who has it working..I just follow directions...however, once the op amp indicated 3.9 volts coming in and not 21.5 and the related transistor indicated it was outputting 3.9 volts and not 21.5...it was pretty clear cut, right? Tempted to swap out the sc's and sa's...but if it's not broke, don't fix it etc etc...you agree with that?
Now to jump on my pioneer sg 9800 eq and figure why it explodes with a loud pop through the speakers after it's been on about 20 minutes...you have created a monster
Now to jump on my pioneer sg 9800 eq and figure why it explodes with a loud pop through the speakers after it's been on about 20 minutes...you have created a monster
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