EV 3000 amp fault...

[Jazz P Bass]

That schematic made my eyes cross
What is this thing?
Grounded bridge?
And just what is cold & hot bias?

[plec.22]

yep I agree there Jazz p Bass..it took me a lot of time reading this one over...part of the o/p is grounded..wtf.. but it does power fine and the collector rails read ok..

Hot and cold bias setting is done via placing meter's over r11 and r109 for the hot side..next place meter over r41 and r 134.. power up and set to 15 mv per setting let the unit warm up and re adjust the setting once that is done the float rails have to be balanced up to 67+/- volt's...did you see the float ht line's in the power supply lines... and the long tail in put circuit..it's a beast of amp to work on...

now you can see how the set should be done from the file's dc offset at 10mv per side and reading more on the setting up I did not care to under take the short circuit test where the o/p is shorted out in order for the protection to kick in...no way on that one watching them o/p trannies pop all at once!

did you see in the ref voltage's -11 ....7v5...float 67volt's per rail and all them mj340's mj350's etc...

it does make your eye's crossed...I've gone over this thing for many hour's now and that the schematic is printed in my head!

Here's the pain in the butt..you have to refit all the board's in order to power up and carry out checks..my next step its to do current compare via metering the + supply line and see how much is being drawn from side to side... there's no fuse line's here just straight linked in to each block...at each power off I drain the ht feeds via bulbs..

[plec.22]

This many not be the answer to sorting these monster's out but after speaking with a few company's for advice some said it was the pc breaking down!!

one tech even said it's the zobel circuit change the cap's...been there done that still the same!

how odd, still one tech said he refitted parts to a used board and worked fine...surly this can't be the answer?? to me the board is in good order now burnt/damaged tracks...still on wards must get this tank of an amp to correct working order..the price for a new board is £700 from ev Germany no way keep it...

I have a few day's rest from it now and will take a fresh look at things...thanks to all you who have added comments..