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Old 19th July 2016, 10:09 AM   #1
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Default Tueblab SE not working anymore!

Hey guys,

I need your help as I've encountered a problem with my 300b SE.

I built it roughly 2 years ago and have zero issues during the build and since. It's powered up everyday and operated beautifully.

I recently sold it and shipped it to Its new owner however its arrived not working. The rectifier tube warms up however the driver and power tubes remain cold.

We've checked all the obvious things like the source, volume, correct input etc etc and it appers something has gone south with the power to the tubes.

Now, the new owner has connected his 6 ohm speakers (he thought they were 8) to the 8 ohm output transformers, could this have damaged anything?

I've suggested purchasing a new rectifier tube but otherwise I guess it a case of going through the checkout procedure?

Can anyone suggest anything?

Cheers guys!
__________________
aka Gavin.
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Old 19th July 2016, 05:01 PM   #2
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Have the new owner post here directly. Otherwise it will take forever to figure things out.
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Old 19th July 2016, 06:22 PM   #3
CalTurk is offline CalTurk  Germany
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Quote:
Originally Posted by Evenharmonics View Post
Have the new owner post here directly. Otherwise it will take forever to figure things out.
Good idea.

So far I've tried to test things out with my one multi-meter but there's too much I don't know and people have been coming and going all day so I haven't been able to dedicate my full attention to it. Testing what I believe to be R30, (please see the attached photo) the reading I get is 400.


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Old 19th July 2016, 07:12 PM   #4
CalTurk is offline CalTurk  Germany
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Also, to be clear on everything . . .

I put the tubes in from small to large into their designated spots. Then connected speaker cables and phono. Then power cord, then powered on. Power switch lit up as it should and rectifier warmed up showing a nice mellow orange and with my ear right down to the unit, I could hear a faint buzz. Tried switching from one input selection to the next going slowly and didn't get any sound. Tried again with volume up pretty high and still nothing. Stopped the record and tried at maximum volume while brushing the stylus with stylus brush and still nothing.
I then noticed that although the rectifier tube was toasty, the other 4 tubes were dead cold. I then shut it all down and spoke with Gavin.

After that I also tried a cd player and even another turntable but still nothing.
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Old 19th July 2016, 08:22 PM   #5
zxx222 is offline zxx222  Europe
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If all heaters except rectifier do not light up, there is high probability that 6.3 v power transformer secondary is disconnected from board.
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Old 19th July 2016, 08:54 PM   #6
CalTurk is offline CalTurk  Germany
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Quote:
Originally Posted by zxx222 View Post
If all heaters except rectifier do not light up, there is high probability that 6.3 v power transformer secondary is disconnected from board.
I don't know if you misspoke but the rectifier is the only one that heats up while all the others stay cold.
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Old 19th July 2016, 11:05 PM   #7
w5jag is offline w5jag  United States
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I agree with zxx222 - first item to check is the 6.3 volt secondary where it connects to the PCB. Likely it is loose.

Thermal expansion/contraction can make them loosen up over time.

Win W5JAG
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Old 19th July 2016, 11:09 PM   #8
CalTurk is offline CalTurk  Germany
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Quote:
Originally Posted by CalTurk View Post
I don't know if you misspoke but the rectifier is the only one that heats up while all the others stay cold.
Sorry, I just reread that I see that I missread it.
Thank you. I'll look into it.
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Old 20th July 2016, 02:47 PM   #9
w5jag is offline w5jag  United States
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Sorry it's a bad pic -

This is the area you need to check; the 6.3 volt AC for the filaments connects to the circuit board immediately adjacent to the two 1N5401 diodes. My finger is placed on the connection pads to the board. I have my leads soldered directly to the board - most builders seem to use terminal blocks.

The 6.3 volt leads have probably become dislodged from the terminal blocks, or the screwed down connection to the termnal block may have become loose from thermal expansion / contraction. The blocks perform a clamping action on the wire, so it is important to make sure the wire is properly placed in the block, and is actually clamped in place when the screw is tightened.

Let us know whether or not this fixes your issue.

Win W5JAG
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Old 21st July 2016, 09:07 AM   #10
CalTurk is offline CalTurk  Germany
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Thanks for that Win.
I've set aside time to address this on Monday. I'll report nack then how it went.
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