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I cant find the "biasscrew" on my fireball, anyone know where its located?
I cant find the "biasscrew" on my fireball, anyone know where its located?
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Strictly from memory isn't there a hole in the board with a trimmer underneath? Any chance of sending a photo? I've done a couple of these, but it was a while ago... male menopause etc... -
ill run down to rehearsal and get pícs for yaComment
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No, sorry, can't see it there. But there is a bias trimmer (TR1) on the schematic I have. Is it through a hole in the top or side of the chassis? Maybe with a little popout grommet in it? Sorry to be so vague... just remember poking my screwdriver through a hole into something (or was that just a fantasy)...
The pin 5 tracks seem to run over to the right - see if you can spot where the bias feeds in via a pair of 330K resistors (R50 and 51) that connect between the coupling caps (C24 and 25) and the grid resistors (R52 and 53). C14 and 15, smallish metal cylinder caps one bigger than the other, might lead you to it, they're on the same track smoothing the bias supply. As might R86, through which the trimmer grounds.
I've got an Engl combo in at the moment, I'm going to look at it today, might be similar - I'll get back to you.Comment
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...actually I think this is it (circled on attachment). The combo I have in is a Screamer 50, different board, but it reminded me that Engl trimmers are little white things accessed through a hole in the board. Take a look at this place on the board. Should be a little tiny screw thing through the hole.Attached FilesComment
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I got the pin count on the output tubes wrong too. Pin 6 will be the missing one from the circle.Comment
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ill run down and check it out right now...thanks manComment
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