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Old 18th August 2012, 03:30 AM   #1
diyAudio Member
Join Date: Aug 2012
Default Music angel el34b problem

Hi guys,

I've got one of these chinese thingys:

Bought off a well known auction site...

It was working brilliantly... until i decided to fit magic eye vu meters to the sucker. I proceeded to burn out 2x resistors on the tube socket side of the board. Does anyone here have a picture of that side? I can find plenty of the underside of the board, just not the top.

How it blew: I hooked up the magic eye board as it should be (or how i thought it should be) and turned it on. no input connected & volume at minimum. after about... 6 seconds one resistor caught fire (yes. fire.) and the second followed shortly after. as a result i am unable to identify the values to replace them.
It turns out the magic eye tube socket was on the wrong side of the board - me= stupid for doing that. and a short circuit resulted. I have since removed the magic eye stuff so i can focus on getting the amp back to normal.

(i suppose this is what i get for assembling a kit without instructions) It would have been nice if the guy i got the kits off supplied me with them, but the damage is done. Now it's fixing time!

I'll see if i can rustle up a pic of the board soon
Thanks in advance...
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Old 18th August 2012, 04:07 AM   #2
diyAudio Member
Join Date: Aug 2012
Here's the board...
Not in it's original case. I butchered a bamboo cutting board & glued some hardwood to it.

The pics might not be too clear, but l/h channel went from pin 4 of the two el34s to a 220UF cap (big sucker)
the r/h did similar, but the cap is a 180.

Without the resistors it sounds like a boss DS1 distortion pedal maxed out. and really quiet. not exactly the sound i was after...

When i guestimated the values (1k for L/H & 4.7k for r/h - from what colours i could make out), it made an almighty squeal/bassy rumble that terrified the neighbours dogs

The other possibility is when i blew the resistors i may have damaged the tubes, but i'll start with replacing these 20c parts first.
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Old 18th August 2012, 10:07 AM   #3
Cookj is offline Cookj  Belgium
diyAudio Member
Join Date: Aug 2004
Location: Bruxelles
Pin4 on EL34 is Screen Grid, there should be 4 resistors all same value. Try 100ohm 2 Watt


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