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Old 21st February 2006, 07:24 AM   #1
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Default Proton D940 schematic ?

Hi all

A workmate of mine has asked me to repair his Proton D940 receiver (blown output). Has anyone got a schematic diagram of this one ?

Regards

Charles
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Old 25th August 2007, 05:25 PM   #2
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I'm also looking for a schematic for a D940, pretty shure my output transistors are shot too. I just picked this reciever up, would have payed WAY less if the seller indicated it was fried . When the unit is powered up with a source connected (CD player) the overload protection clicks immediately (no speakers attatched). The crazy...and I mean crazy thing is if you turn the volume up enough you can actually hear music eminating from the bread board (shakes head)!!! The output transistors do not seem to get very hot, there are a total of 8 of them . I'm going to put he VOM on them and see what I get for resistance, any advice would be greatly appreciated.
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Old 26th August 2007, 03:35 AM   #3
anatech is offline anatech  Canada
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Hi Guys,
I put in a request at ShareFx for you. Let's hope someone out there can help you out. I'll try to post if I can get it.

-Chris

Edit: Charles, do you still need these?
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Old 26th August 2007, 08:50 AM   #4
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Hi Chris

No, I don't need it anymore but thanks anyway !

Regards

Charles
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Old 26th August 2007, 11:08 AM   #5
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Thanks Chris! I found some ultra hot power transistors , I could use all the help I can get.
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Old 26th August 2007, 12:35 PM   #6
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I'm pretty sure Proton and NAD are the same thing. Try and figure out what the equivalent NAD model is to yours - since NAD's are more common you may have more luck in getting the schematic that way.
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Old 26th August 2007, 01:29 PM   #7
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Yep, I have been looking at a few NAD schematics and nude pics folks have posted on the net but so far I see the same weird heat sink but totaly different output transistors and breadboard. The proton uses SanKen A1186,A1386A, A1386 and C3519A, C2837, C3519. Things are not looking up for the Proton, board is slightly brown over by the safety relays and power transistors (all are HOT) .Still wondering how my breadboard is making music?!
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Old 26th August 2007, 10:22 PM   #8
anatech is offline anatech  Canada
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Hi S.Speilbergo,
No response yet. I requested again.

-Chris
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Old 27th August 2007, 02:20 AM   #9
Maniac is offline Maniac  Taiwan
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I have a Proton AM-300 that looks as if it got the same power amp stage as D940, and I have a copy of the ORIGINAL service manual of it too.

If you guys still needs it, please let me know, I'll scan the pages of the service manual's circuit and post it.

However, I'd really be happy if someone could post a high res pic of both the overhead shot and underside shot of D940, as I'm thinking about getting one myself :P


However, if D940 is what I think it is, then you will have to match the output transistor VERY CLOSELY, since they do not have any resistors connected to the emitter of the transistor, just straight wire. But you only need two pairs to be matched, the other two pair are for DPD power boost, and they don't need to be matched at all, just make sure they work well, that's all :P
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Old 27th August 2007, 02:31 AM   #10
Maniac is offline Maniac  Taiwan
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Forgot to mention, from my own AM-300, it seems as if the really good engineer only designed the REALLY hard part of the amp, the power amp stage. The rest seems to be left to junior engineers...

The result is fairly bad power supply attention on the pre, and rather lousy wiring performance for the speaker output.

#1. The pre/tone control section can really benefit from some power rail bypassing, and the stupid coupling cap can be removed for much better clarity. As for me, I bypassed the entire tone control section, which I don't really use at all anyways.

Please do note that it seems to be a 2.5V potential at the input of the power stage, the coupling between pre and power stage must be kept.

#2. The speaker wiring on mine is a disaster, not only the wiring is too long on lousy wires, it went through some rather lousy mechanical switches. Just tore it out, replace the speaker binding post, and use short, direct wires had made most difference I have ever heard while modding this amp. None of the resistor mod, capacitor bypass, better coupling caps, and the like can even hold a candle to this.


Ah well, that's all I can say now, I'll go and do some scanning when I get home.
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