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Old 9th November 2008, 11:30 PM   #1
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Question Yamaha P2500S fault

Hi to forum users, i have a Yamaha P2500S amplifier which somebody kindly plugged a speaker lead into channel 1 and the other end into channel 2...... not a good thing to do i know !!

2 output devices test out as being shorted namely 2SC3856 and 2SA1492.

Looking through past threads some have mentioned using 2SC5200 and 2SA1943 as replacements as i cannot get original output devices here in the UK. Would these be direct replacements or would i need to change any other components as well, bias setting etc ?

I do not have service manual or schematic diagram for this amp so if anyone can help me i would be very gratefull.
This amp has normal transformer type power supply, not SMPS.
Thanks.
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Old 11th November 2008, 05:17 AM   #2
Bigred is offline Bigred  Canada
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The Toshiba transistors are TO-247 case but should be fine. I have used onsemi as replacements for 2SC3856, 2SA1492 Sankens with excellent results (NJW0281G, NJW0302G) and are the same MT-100 case style as the Sankens.
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Old 11th November 2008, 07:54 PM   #3
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Default Of Course

you need to replace all and rebias the amp ....

its not a drop in replacement ....

also dont know how many trs per chanel but you need to replace all of them you cant have two of these and two of that
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Old 13th November 2008, 10:39 PM   #4
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Hey thanks for your replies Bigred and Sakis, i will replace the TR,s with originals and thanks Bigred for the offer, if i have no luck with a company i have found in UK i will contact you if that is ok

Have any readers got the scematics for this amp so i can identify the pre drivers too as a lot of people recommend replacing these as a matter of precaution ?
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Old 14th November 2008, 08:14 AM   #5
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Default by the way

i also have 2 pairs of these (original sanken ) used but otherwise in perfect condidtion so if your problem is only these i can just as well give them to you ....

since they are no use to me it would be very stupid to replace all transistors if the originals exist ....

of course there is always a chance that a company like yamaha will use factory matched transistors ( alll from same family at least )

so here is the data of my transistors to see if they can say anything to you
down under 2sc3856 it says 20Y
down under 2sa1492 it says 200

if you want them i will post them for free

regards sakis
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Old 20th November 2008, 11:31 AM   #6
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Hi Sakis,

Don't know if you got my email but could i take you up on the offer of the Sanken devices please.

Thanks, Kevin.
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Old 20th November 2008, 03:06 PM   #7
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Default i got it

but it seems that i cannot reply to this specific adress .....could you please sent me some adress to e mail you back ????
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