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Old 11th June 2019, 07:52 PM   #1
randytsuch is online now randytsuch
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Default TSE: what did I blow up?

One channel of my TSE is sick

I moved it from breadboard to case, and while I was doing this, somehow one pin of the DHT socket came loose. Pretty sure it was the filament pin, so I powered up the amp with the filament pin floating with no connection to the output tx.
I powered up the amp a few times in this condition, but only for a short time.

I fixed that, but now when I apply power the bias voltage on that side shoots up, so I shut it down.

I tried different driver tubes and DHT's, so pretty sure those are OK.

I still need to inspect the passives, but assuming I don't find a charred resistor my guess is that Q1 blew, and needs to be replaced.

There's not much here that could have broke.

Any advice to get my TSE back up and running would be appreciated.

Randy
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Old 13th June 2019, 02:40 PM   #2
w5jag is offline w5jag  United States
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Quote:
Originally Posted by randytsuch View Post

I fixed that, but now when I apply power the bias voltage on that side shoots up, so I shut it down. ...
If by "shooting up" you mean becoming increasingly negative, it should just cut the power tube off, so should not damage anything while you troubleshoot.

My WAG is the MOSFET on that side, OR a bad solder connection in that area that got boogered up when you moved the board to the case.
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Old 13th June 2019, 04:38 PM   #3
Tubelab_com is offline Tubelab_com  United States
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First off, remove the output tubes to avoid the possibility of damage. If the grid voltage is highly positive and does not adjust, the associated mosfet is likely shorted. Even a microsecond momentary short on the grid of the output tube will blow the fet.

After replacing the fet the voltage should adjust through a range of negative voltages. Once that's working, then reinstall the output tubes and set bias.
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Old 13th June 2019, 05:20 PM   #4
randytsuch is online now randytsuch
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Thanks for the replies.

I needed to place a Mouser order for some other stuff, so also bought the CCS's and Mosfets to replace if required.
Had to buy a different Mosfet from what I have installed because it's obsolete, so will likely replace both of them.

Randy
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