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Post by tjstrat on Apr 3, 2018 18:31:49 GMT -7
I have something that was characterized to me as a TW Express clone. It's running way too hot and I want to pull the chassis and VERY CAREFULLY see what I can do to set the bias with the help on the Eurotubes bias pro. Aside from being extremely careful, is there a pot in those circuits that anyone knows of or any way to fix that bias without taking it to a tech (which I will do if it looks like I'll just end up smoking myself)? Is there even a bias pot in clones of those circuits?
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Post by purpletele on Apr 3, 2018 18:59:42 GMT -7
I have something that was characterized to me as a TW Express clone. It's running way too hot and I want to pull the chassis and VERY CAREFULLY see what I can do to set the bias with the help on the Eurotubes bias pro. Aside from being extremely careful, is there a pot in those circuits that anyone knows of or any way to fix that bias without taking it to a tech (which I will do if it looks like I'll just end up smoking myself)? Is there even a bias pot in clones of those circuits? I can help you at least figure out what you have. i sent you a pm
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bradm
Junior Member
Posts: 74
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Post by bradm on Apr 3, 2018 20:42:23 GMT -7
Let's say you have the Ceriatone clone, that one does have an adjustment pot on the board. If you peek here, www.ceriatone.com/tw-clone-expression/ , you'll see a part labelled 22KL on the right of the documentation (schematic layout). I have the Eurotubes adapter. What I like about it is...it reads the current (in mA) right at the plate pin so you don't have to guesstimate a screen current to subtract. Peek at the diagram I referenced. If indeed a TW clone, look at pin 5 on the EL34 sockets and you should trace those wires back to a coupe of 220K resistors that join together and are wired to the bias voltage circuit (follow the purple wire to the right). There you see a 47K resistor in series with a 22K pot. That pot varies the bias voltage. Make sure your meter is measuring mA. However, if this is something someone just said,"It's a Trainwreck clone.", it may not have what you see in the diagram I referenced. The bottom line is, if you aren't sure...take it to a tech that will know all the safety precaution to follow. It's very dangerous inside these things.
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