Am i right in assuming that 2SC1904 is replaced by BF459, or even BD232? There are two on my amplifier tone board and one has green disease on it's legs. Do i need to replace both? Thanks.
MJE340 is more than adequate. The green colour is from the acid in the flux used. clean it off and it will be fine.
So this part will be fine. Do i need to replace both for an even balance. Thanks for your help everyone.
MJE340 | Magnatec MJE340 NPN High Voltage Bipolar Transistor, 0.5 A, 300 V, 3-Pin SOT-32 | Magnatec
MJE340 | Magnatec MJE340 NPN High Voltage Bipolar Transistor, 0.5 A, 300 V, 3-Pin SOT-32 | Magnatec
It would help to see the circuit before saying whether something else would be OK. The 2SC1904 is bordering on what I would call a 'video output' type (like the BF459). An MJE340 may well be OK, in fact I'd be surprised if it wasn't, but its nice to be sure.
Yes, replace both for completeness even though there should be no impact within the audio band of using a different type.
The 2SC1904 is available from Dalbani (Nikko)
Search results for: '2sc1904'
If want to use MJE340's then try the CDIL manufactured parts as I have found these to be right at the top end of the spec for these devices:
CDIL - MJE340 - TRANSISTOR, NPN, TO-126 | CPC UK
You could try doing just a snip of the appropriate part of the circuit (snipping tool in Vista, W7, W8.1 and W10) or simply Ctrl +PrtnScr and paste the result into paint. I'm assuming Windows 🙂
If part is working, I would not replace it (except by same type) , just wash legs in tap water scrubbing with some rough cloth to take green out, dry it and paint over corroded parts with nail enamel , then resolder on board.
Will work at least for 50 more years 🙂
I suspect that amp, from the Golden Era of Japanese Hi Fi , was tightly compensated to have WIDE frequency response and very low harmonic distortion (which implied tons of NFB way back then) , so a different part might give you instability headaches, why go through that unless there is no other choice?
Will work at least for 50 more years 🙂
I suspect that amp, from the Golden Era of Japanese Hi Fi , was tightly compensated to have WIDE frequency response and very low harmonic distortion (which implied tons of NFB way back then) , so a different part might give you instability headaches, why go through that unless there is no other choice?
I see your point but turning the tone controls makes very little difference to the sound and was wondering if it was related.
I recently recapped this unit with Nichicon muse es for the bipolar caps and Panasonic FR, FM for the rest. No perceived change in sound afterwards. A good thing.
But all the original and i mean all the old caps had perfect ESR, a lot were equal to the Panasonic's that replaced them? Also all the Panasonic's measured were nearly 10% lower than there rated value, but all the the Elma's were about 5% higher than rated value why?
I recently recapped this unit with Nichicon muse es for the bipolar caps and Panasonic FR, FM for the rest. No perceived change in sound afterwards. A good thing.
But all the original and i mean all the old caps had perfect ESR, a lot were equal to the Panasonic's that replaced them? Also all the Panasonic's measured were nearly 10% lower than there rated value, but all the the Elma's were about 5% higher than rated value why?
You mean X205 ?
Looking at the circuit and I think a modern production MJE340 would be fine.
As to the cap tolerance... there was a recent thread about this. If I find I post a link. The outcome was no problem though.
Looking at the circuit and I think a modern production MJE340 would be fine.
As to the cap tolerance... there was a recent thread about this. If I find I post a link. The outcome was no problem though.
Here we go, but it was film caps not electros,
http://www.diyaudio.com/forums/parts/295168-new-capacitors-out-tolerance-what-would-you-do.html
The user instruction manual (or specs in the service manual) should quote the tone control boost and cut range, written something like -/+10db @ 100Hz and -/+12@ 10kHz.
That would give an idea how much effect they have but I can't really see there being an issue (fault).
http://www.diyaudio.com/forums/parts/295168-new-capacitors-out-tolerance-what-would-you-do.html
The user instruction manual (or specs in the service manual) should quote the tone control boost and cut range, written something like -/+10db @ 100Hz and -/+12@ 10kHz.
That would give an idea how much effect they have but I can't really see there being an issue (fault).
Sorry i did mean X205, there are two X 205 and X206, X206 looks fine.
Does the HFE tell you anything? Thanks,
Does the HFE tell you anything? Thanks,
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