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r 151 accent resistor burns

Posted: May 29th, '14, 13:15
by franzkleid
r151 esistor starts burning after powering on !
checked all 20 times !
Somebody any other sugestions :cry:

Re: r 151 accent resistor burns

Posted: May 29th, '14, 16:01
by gihaume
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.

Re: r 151 accent resistor burns

Posted: May 31st, '14, 15:32
by e-licktronic
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

Re: r 151 accent resistor burns

Posted: Jun 4th, '14, 04:24
by keen
Hello franzkleid,

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

cheers

Re: r 151 accent resistor burns

Posted: Jun 4th, '14, 15:51
by gihaume
Thank you!

The batch before the 4th did have a different 4011 than BE?

Re: r 151 accent resistor burns

Posted: Jun 4th, '14, 23:53
by zmb
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:
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Re: r 151 accent resistor burns

Posted: Jun 5th, '14, 09:56
by keen
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,

Re: r 151 accent resistor burns

Posted: Jun 5th, '14, 11:03
by krisbo
Replace your 4011. I replaced mine with a 4011BE and it's rocking now!

Re: r 151 accent resistor burns

Posted: Jun 7th, '14, 07:09
by gihaume
I also have a few yocto kits so I tried with the 4011BE of another kit (not built yet), and again the same problem!

Re: r 151 accent resistor burns

Posted: Jun 8th, '14, 13:53
by krisbo
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.