C4S board Problems

Mordicai · 3158

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Offline Mordicai

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Reply #15 on: March 19, 2017, 04:45:56 PM
Paul, I tried three times to get that reading. Seems when I turn the sex upside down it want to play on both channels. And when I turn it right side it wants to play on the right channel only. I just barely got that 0 volt reading in on the OB before it strted playing both channel again. I played it for  about fifteen minutes and couldn't get it to drop a channel, and started getting concerned about the heat from the tubes. Do you think playing it upside down for a long time hurt anything from the heat. I will try again tomorrow.
« Last Edit: March 19, 2017, 04:47:45 PM by Mordicai »



Offline kgoss

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Reply #16 on: March 20, 2017, 03:19:41 AM
Hmmmmm.  If it works upside down but not right side up then gravity is completing a broken connection with the amp upside down. And since your amp has worked for over a year I would suspect a wire that was not soldered or more likely a wire that is broken under the insulation which usually happen when you nick a wire while stripping the insulation.  If I were you I'd do the chopstick test with the amp playing using cheap speakers or headphones. Concentrate on moving wires looking for one that makes the channel drop.

Ken Goss


Offline Paul Birkeland

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Reply #17 on: March 20, 2017, 07:38:34 AM
Ken is spot on!

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Mordicai

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Reply #18 on: March 20, 2017, 09:18:07 AM
When this upside down magic started a few days ago, I of course felt the same way and started poking everything. My feeling was its a broken wire as Ive been over the amp many times without finding a bad connection. I was hoping to narrow down the search area a bit. What broken wires would cause the C4S resistors to burn like that? Back at it!! Thank god for the Stereomour. At least I can poke about to the Stones.



Offline Paul Birkeland

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Reply #19 on: March 21, 2017, 06:32:44 AM
When this upside down magic started a few days ago, I of course felt the same way and started poking everything. My feeling was its a broken wire as Ive been over the amp many times without finding a bad connection. I was hoping to narrow down the search area a bit. What broken wires would cause the C4S resistors to burn like that?
You're going to have to post a photo of what you're seeing.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Mordicai

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Reply #20 on: March 27, 2017, 12:20:35 PM



Offline Mordicai

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Reply #21 on: March 27, 2017, 12:22:55 PM
As you can see Paul both 150 are blackened. Only the 499 on the B side is blackened. The A side is shiny.



Offline Paul Birkeland

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Reply #22 on: April 13, 2017, 12:17:09 PM
Just for a point of reference, for how long do you generally leave your SEX amp on, and what's the approximate ambient temperature in the room? (Celsius is OK)


Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline proud indian

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Reply #23 on: April 14, 2017, 09:51:49 PM
Well, since we have the same problem, my room is air conditioned @ around 26°.

system 1. oppo, quickie,SEX 2.1 ( V cap), Decware DFR8 in ZOB cabs
System 2. Tascam cd200, Terra Dac,Zbox,Decware Zen amp(V cap) Lowther PM6A in Acousta horns.
Maple rack, Brass footers,Power conditioner, dedicated treated room, iso pads, plenty of tubes. All cables DIY.


Offline Mordicai

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Reply #24 on: April 15, 2017, 09:03:21 AM
Paul, My amp goes on about 5 AM,and off about 9 PM. Temperature in the winter about 50-68 F. I live in the high desert so summer temps can be about 65- 90. If it gets hotter then that I turn on the air.  Could the poor connection to the MJE5731A, cause the heat?? That has now been fixed and seems like everything is ok



Offline Paul Birkeland

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Reply #25 on: April 20, 2017, 06:38:10 AM
summer temps can be about 65- 90.
If your room is 90F then there is a potential for problems.  Your cell phone and computer will also not last nearly as long as they should while operating at these temperatures.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man