Re: 2SC4751

[Tinco Brouwer]

Declan Moriarty wrote: Recently, Somebody Somewhere wrote these words Hi Declan, this was some new information! I found a German site, discussing the C4741-1 in a power amplifier. The conclusion was that you can replace them with Motorola MJ 15024 and MJ 15025. http://forum.electronicwerkstatt.de/phpBB/topic15491_f12_bxtopic_viewsxDESC_by1_bz0_bs0.html Your German must be better than mine, Uwe. I checked the link, and they are talking about the C4751-1, so I ignored your typo. Of course, I had "English" set as a language, because the others I have any knowledge of (Irish, and Latin) have very few web pages in them. I have a few words in French, but that's not much use. also here: http://www.diyaudio.com/forums/showthread/t-43304.html Somebody mentioned another 2sc part with a larger SOA, but I'll see what I can get locally. Thanks again folks. I'm glad the data wasn't lying on 3000 web sites anyhow, because you feel stupid when you ask then. I got MJ 15024 and MJ15025 transistors from Farnell. There are a lot of amps using those transistors, e.g. Krell, Carver Pro, Crown. In their service manuals Crown gives the commercial partno. if the normal part is a direct replacement for the crown partno. In a Krell KSA200 (total 2 x 18 of them) the only marking on the transistors was a red or a blue dot, very helpful. It is best to replace all powertransistors (both NPN/PNP) by new ones and select them on current gain. In a batch of 25 I found enough transistors with not too much difference in gain (around 45 iirc) for the Krell. Depending on how important reliability of this amp is, replacement of the emitter resistors can be advisable even if they seem to be ok. Regards, Tinco Brouwer.