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Tubelab Discussion and support of Tubelab products, prototypes and experiments

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Old 19th June 2010, 06:51 PM   #1
kerux is offline kerux  United States
diyAudio Member
Join Date: Jul 2008
Default Simple SE - no sound on one channel

My Simple SE used to work fine. I had to store it away for a few months due to home remodeling. Currently, I am only getting a low volume out of 1 channel/speaker and no sound out of the other channel/speaker. If I switch the speaker cables, I now get low sound out of the other speaker.
It appears my volume control is no longer working either as I get the same volume regardless of turning my volume control up or down. I tried checking both the rca jacks and the speaker jacks and I didn't see anything wrong.

I saw tubelab's posting about a plan to troubleshoot and I will start on that. Any input would be appreciated.

"Assuming no board modifications were performed and there is a wiring error, or defective component, we need a plan to find it. The first attack will be divide and conquer. The board has 4 main circuits. There are 2 drivers, and 2 output stages. Lets find out which of the 4 circuits are bad.

Looking at the board from the top side with it oriented so that the "Tubelab Simple SE" printing is right side up, run a temporary jumper wire (solder a wire, or use a clip lead) from the left side of one coupling cap to the other (C11 and C21). It can be on either side of the board, but it must be on output side of the caps. This allows either driver circuit to feed both output circuits.

Connect the board up in the usual manner and test it. Is there sound from both speakers? If yes, the problem is in the input section. If there is still sound from only one channel the problem must be in the output section. Verify this by unplugging each input cable one at a time. The sound should continue from one speaker with either input connected.

If the output section is at fault, the most likely place for a failure is the wiring on the secondary (speaker) side of the output transformer. This is about the only place that won't affect the DC voltage readings. The most likely place for a short is where the speaker connectors go through the chassis.

If the input section is at fault, the usual place is the wiring from the input connections to the volume pot and input connectors. Temporarilly connect the two outer terminals of the input connector on the PC board together. If both channels work, or neither work the input wiring is at fault."

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Old 19th June 2010, 07:13 PM   #2
SGregory is offline SGregory  United States
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Join Date: Apr 2003
Location: Southern Tier NY
Break the amp into two sections first, Power Supply and then Amplifier. Make sure power supply is delivering required voltages. Once you know PS is working then break the amp down into halves. Driver Stage and Output Stage.

I would start with power supply or your ground wire as the issue seems common to both channels.
Living Life Doing the Waltz in 4/4 meter.

Last edited by SGregory; 19th June 2010 at 07:16 PM.
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