Tube Amps / Music Electronics
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|2/25/2004 3:46 AM|
|Dave||Re: Mesa Studio Pre|
Thanks that mod sounds perfect!!!! I can't wait to de-fizz it.
The Twinmaster is made by Budda.
I plugged the guitar into the return of the loop and that got rid of the nasty sound(s). So it's in the preamp. It looks to me like the way this thing is wired the the loop is inbetween the two 12ax7 tubes, thus making it tube one that is the culprit. There are five orange drops on the turret board, the middle one wasn't holding a charge like the others. All of them held 12vdc but that middle one wouldn't. I wired up a capacitance tester and it just dropped straight to zilch.
BTW I decided not to mod the 74 JMP. The touch response on it is too good to give up.
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|2/25/2004 1:39 PM|
I've only worked on one Budda but your cap test method is sorta shakey - you can only hold a charge on a cap is it's not connected to anything that will dischard it - and most meters will given enough time. But if we assume that you've disconnected at least one lead of the cap and it won't hold a charge that means that that it is internally shorted to some extent. And if it is internally shorted then you can measure resistance between the leads with your DMM. If you can't read resistance then the other possibility is that there is an internal break in the cap and it's not taking a charge - instead of not holding one. Either way seems easier to just replace it but this isn't a test method I'd recommend nor use.
Generally caps pass AC and block DC - if there is DC on the "downstream" side of a cap it's shorted and if there is no signal it's open.
|2/25/2004 3:30 PM|
Well I spoke to Jeff Bober @ Budda and he said that wouldn't be thhe problem anyways, so I have back up and try something else.
|2/26/2004 3:06 PM|
Back to the studio pre..
This is a bad week for me with amps now the studio pre is acting up. No matter how high you turn up the drive on the lead channel the massive amounts of gain this preamp shiould have doesn't show up. Maxed out it's just louder. Somethings not right.
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