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Cyrus Two power transistor PT7 BUV28

H

hifienthusiast

Vintage by heart
I plan to repair a Cyrus Two amplifier which need new power transistors. It is the earliest version Issue 06 which uses four NPN transistors per channel. They are marked PT7,TO220 package according to the service manual. The equilvalent transistor is BUV28. It seems that BUV28 has been discontinued.

1. Is there any equilvalent to BUV28?
2. Should I take the risk of buying some used or "brand new" transistors from ebay or Taobao?
 
I would see if somebody like Cricklewood or Dalbani has some stock left first, before trying ebay or substitutes.
 
Cricklewood doesn't have any in stock. I will try Nikko.

May I ask why one should not buy from ebay? Are there fake transistors around?
 
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demotivated said:
Jabdog is a largish well known UK supplier. 3055 is bread and butter stuff, so I can't see money in fakes. And homoepitaxial - 'H' - do cost a bit more, as they are more robust. I think the 3055 was designed for car battery regulators initially, but I can't remember where that's from, so maybe wrong.
Click to expand...

Thank you, most helpful, I was thinking of using them in a Quad 303 to replace the odd Motorola RCA 38494 transistors. I have a vague recollection that the 2N3055H was on their circuit diagram as an alternative.
 
hifienthusiast said:
BUV28 are plastic TO220 package, is there still fake ones?
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If its rare and obsolete, there is a good chance it will be fake on eBay, unless you know and trust the supplier. I had some 2SJ77 and 2SK214 lateral FETs that were just some irf depletion mode devices, the drain and source were the wrong way round! Just badged and that's it. Its better to buy from the big distis like farnell/RS/avnet etc unless you know someone trustworthy, there are a few.
 
Also I am sure a cyrus 2 uses an output device which is physically larger than a to220 so buv28 could be the wrong part . to220 size is used in cyrus 1.
 
Early plastic case Cyrus 2 amps used doubled up buv28 parts, later metal cased Cyrus 2 used the larger buv48

Ian
 
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