EH Graphic Fuzz

petemoore · July 21, 2004, 09:58:33 AM

Debuggin on this one...repaired the input jack wire...passes signal in both modes, Fuzz on/off switch has no effect.
The EQ's vol control works, can't tell if the EQ sliders work tho [probly not since I can't tell]..
Is there a schematic available of this unit?

petemoore · July 21, 2004, 10:37:13 AM

Found some problems.
Temp fixed the ground, which was getting to the trace, but only 'semi beeped' wehn DMM tested at the OA's...clipped another ground to one of the OA's, now ground beeps on all of them. I don't want to solder under an OA, and the trace already reads ground...I need to establish a more permanent ground to the IC's but don't want to fry them, would judicious iron application times and a heat sink on pin 4 be the way to do it?...maybe ice the chip down with metal first..frozen coin taped to it or something.
So I've established sufficient ground to determine that the OA's are showing nothing more than 2v... :idea: being as it is a transformered PS, possibly I should be checking in that area, a new area for me, I suppose look on the cct side of the tranny for ground, and the other side for 1/2v and V+ or the like, possibly try an alternate PS?
edit:
Whoops, make that -1.89V at the pin 8 of one 4558, the others are closely following suit.

petemoore · July 22, 2004, 08:25:57 AM

'Anyone ever hear of schematic or fix info on this one bump'.

petemoore · July 23, 2004, 02:01:53 AM

I found 31 some volts at the power supply, couuld new caps help the pin voltages...they're kinda low...all at like around 2v..

petemoore · July 25, 2004, 10:02:13 AM

Last try for help on this one....
Anyone have any tips or ideas for a schematic?
If I had a clue what voltages to look for at the PS or on the chips might help...
Yes I took these in and portrayed the prospect of trying to fix them for a friend of a friend...
I'm beginning to think I'll just back out, without the schematic I don't feel like I can reasonably go foreward with it , I don't really know what's what...might make a mess of it trying to fix it like it was mine..
last gasp bump hope....
Any ideas on what voltages I should look for in the PS or on the chips,...a schematic sure would help....
AnyTHing...

puretube · July 25, 2004, 11:05:45 AM

is it the vintage or the new issue?

A schematic (DIY-drawn) shows a 7812 regulator for pos. supply,
and a diode, probby zener, for neg.;
very strange schem... (dated 2003);

petemoore · July 25, 2004, 11:15:49 AM

Ill say vintage, because it looks kinda old...
Other than that I can't say for sure...

puretube · July 25, 2004, 11:26:45 AM

the schem used to be here:
http://stomper.hp.infoseek.co.jp/sakujyo.html
seems like the guy had a copyright-issue with the mfr.....

petemoore · July 25, 2004, 12:41:30 PM

Symbols I can read:
Schematic symbols: most
Chinese symbols: 0
lol...probly in there somewhere...

puretube · July 25, 2004, 01:09:52 PM

the red english letters say he had to take the schem down..
(and I know fersure it used to be there - I seen it)

it`s Japanese, btw, you could mail the guy: dig_suck@yahoo.co.jp
and ask him if that was the new or old one, and to mail a personal
copy to you...

Mark Hammer · July 26, 2004, 10:32:36 AM

Jack Orman sent me a scanned copy of a ragged, hand-drawn thing he had a couple of years ago (with a request that it not be posted; just as well given how much info there was missing in the drawing), and there were noticeable differences between what was recently linked to and that drawing. I don't know if the drawing was incorrect or just a redesign, but the two ARE different.

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EH Graphic Fuzz