r 151 accent resistor burns

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r 151 accent resistor burns

Postby franzkleid » May 29th, '14, 13:15

r151 esistor starts burning after powering on !
checked all 20 times !
Somebody any other sugestions :cry:
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Re: r 151 accent resistor burns

Postby gihaume » May 29th, '14, 16:01

As stated in the thread VCA accent troubles, we are 2 people to have this same problem, and at least me without any other unfindable mistake (yes only another one but I know why).

I also checked many times a lot of things, so much that with all the movements, I broke the "Cable 10Pos" linking both PCBs! I checked every component's place and way, resistors values, and transistor's proper functioning of the accent section.
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Re: r 151 accent resistor burns

Postby e-licktronic » May 31st, '14, 15:32

Dear Diyer,

R151 burned because you get a short cut between ground and +15v psu rail.
C34, Q27 or the 4011 could be the problem.

Best regards,
e-licktronic
Best regards,
e-licktronic
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Re: r 151 accent resistor burns

Postby keen » Jun 4th, '14, 04:24

Hello franzkleid,

I had same problem on 4th batch kit.
Please try unbuffered 4011UB.
I solved R151 problem by it.

cheers
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Re: r 151 accent resistor burns

Postby gihaume » Jun 4th, '14, 15:51

Thank you!

The batch before the 4th did have a different 4011 than BE?
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Re: r 151 accent resistor burns

Postby zmb » Jun 4th, '14, 23:53

keen wrote:Hello franzkleid,

I had same problem on 4th batch kit.
Please try unbuffered 4011UB.
I solved R151 problem by it.

cheers

wow is that really the issue? My local electronics retailers don't seem to differentiate, just listing "4011" without any suffix. I guess I could go in-person or call to verify the buffered vs unbuffered versions...

EDIT: I just checked the TR-808 service manual and as far as I can tell they used 4011B type NAND gates. So maybe that's not the problem?
Attached screenshot from the service manual:
Untitled.jpg
Untitled.jpg (21.15 KiB) Viewed 5026 times
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Re: r 151 accent resistor burns

Postby keen » Jun 5th, '14, 09:56

Hello.

Sorry, I'm not sure why UB version solved it.
I have 2 kits of 4th batch. Both kits had same problem. And solved it with 4011UB.
BTW, 4011UB is used for 9090 too.

regards,
keen
 
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Re: r 151 accent resistor burns

Postby krisbo » Jun 5th, '14, 11:03

Replace your 4011. I replaced mine with a 4011BE and it's rocking now!
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Re: r 151 accent resistor burns

Postby gihaume » Jun 7th, '14, 07:09

I also have a few yocto kits so I tried with the 4011BE of another kit (not built yet), and again the same problem!
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Re: r 151 accent resistor burns

Postby krisbo » Jun 8th, '14, 13:53

By the sound of it there may be some issues with the 4011 used seeing as a fewguys have had issues with them. Pick yourself up a new one from an electronics shop and see how you go.
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