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Old 24th Oct 2019, 2:36 pm   #1
AlistairC
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Default Albany House AM-208 Power Transistor Replacement

I have a 1970's era Albany House AM-208 amp not used for decades but I wish to get running again.
One of the channels is silent.
I replaced all the electrolytic capacitors with new modern equivalents but
that didn't fix it. I looked next at the 4 power transistors and found one
of them is shorting between the base and the collector.
I will replace all 4 then, but am a bit puzzled wonder if anyone could
help as follows:-
1) The original power transistor is labelled with C1398 on the top line
then P 2F below
It has a logo I guess its made by Matsushita/Panasonic but the logo
resembles Mitsubishi three triangle logo.
Looking the schematic, it is shown as 2SD330-D "or" 2SD234-0 (not sure what "or" means in this context - does it mean you could use either or ...or does it mean some models with this schematic had one, some had the other but we're not going to tell you which).

I am a bit confused - is a C1398 P 2F the same as a 2SD330-D or a 2SD234-0?
What does P 2F refer to?
What should I buy as a replacement?

The other component I was checking were the two MV-13 bias diodes. On the
schematic it shows them coloured BRACK(sic)/GREEN but mine are BLACK/RED.
Is the colour change of any significance?

Hope someone can help as the amp was really good.

Thanks
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Old 24th Oct 2019, 3:21 pm   #2
paulsherwin
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Default Re: Albany House AM-208 Power Transistor Replacement

The 2SC1398 is a TO-220 power transistor: https://alltransistors.com/transisto...ansistor=11852
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Old 24th Oct 2019, 3:46 pm   #3
WME_bill
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Default Re: Albany House AM-208 Power Transistor Replacement

Audio amplifier replacement transistors.
The number C1398 is the usual shortened form for 2SC1398. The P2F will probably be a manufacturing date or batch code.
The parts list you say quotes 2SD330 or 2SD234. These are possible alternatives to the 2SC1398. So you have plenty of choice, and the part is clearly not critical as negative feedback will take up any small differences.

The letter at the end of a transistor part number usually indicates either a gain selection, or particular pin out arrangement or voltage rating. In this case, apparently a medium gain close selection - hfe 60 to 120. Necessary to help matching the pair.

So I suggest replace both the failed one and its pair. All npn silicon, 50v,3A ratings, TO220 style case, central collector.
Similar to BD241, TIP31, BD589, 2N6123, and lots of others possible. Just get two of the same sort and alpha coding. No need to replace those in the other channel.
The diodes are probably for temperature compensation. Quite uncritical apart from current rating. The different colour coding is probably because from a different supplier.
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Old 24th Oct 2019, 4:20 pm   #4
Edward Huggins
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Default Re: Albany House AM-208 Power Transistor Replacement

Wow! Who remembers Albany House. Sadly, I do - they were a second brand of Teleton.
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Old 25th Oct 2019, 11:00 am   #5
AlistairC
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Default Re: Albany House AM-208 Power Transistor Replacement

Thanks everyone. That's a great help.
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