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nathanscribe
Silver Member
United Kingdom
376 Posts |
 Posted - 03/19/2009 : 21:59:38
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Anybody have schematics/service notes/internal pics? My searches so far have been fruitless...
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/20/2009 : 15:39:26
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quote:
Originally posted by nathanscribe
Anybody have schematics/service notes/internal pics? My searches so far have been fruitless...
Hi nathanscribe
What seems to be the issue-problem with your GE-10?
Or is it just for your data archive?
Regards Dr. Bob  |
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nathanscribe
Silver Member
United Kingdom
376 Posts |
Posted - 03/20/2009 : 16:51:28
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quote:
Originally posted by Dr. Bob
Or is it just for your data archive?
Yep, just for info. I've got stacks of schematics, likely the same ones as everybody else, downloaded from the web - but some are hard to find. This is one of them.
Partly, I'm interested to know what ICs were used. I have a couple of old Boss mixers (KM-6 and 60) that use a load of TA7136 single op-amps, and looking at the GE-6 pics, I see it uses a couple of RC3403 quad op-amps. The GE-10 is from the same era so wondered if there was an op-amp for each band, or dual/quad devices had been used.
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Edited by - nathanscribe on 03/20/2009 16:56:20 |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 03/20/2009 : 18:14:04
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So pull the back off and show us some pics 
(please) |
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nathanscribe
Silver Member
United Kingdom
376 Posts |
Posted - 03/20/2009 : 18:16:59
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quote:
Originally posted by Laurie
So pull the back off and show us some pics
(please)
I haven't got one! I was hoping someone else would... |
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princeton
Copper Member
5 Posts |
Posted - 03/08/2010 : 10:00:10
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Hi, sorry to hijack your thread nathanscribe (my first post here) but I didn't want to start a new thread just for asking if someone could help me solve issue that I have with my GE-10. My Boss GE-10 is hissing and crackling badly no matter how much gain I add. I checked faders and they seam to be OK. Anybody have some idea? I'm also in need of schematics/service notes. THX
P.S. Sorry for my english, I hope you'll understand what I wrote. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/08/2010 : 10:32:46
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Hi princeton
Welcome to the forum from Australia.
Has your GE-10 just recently stated to be noisy?
Or has it been that way all the time?
Sometimes it's the inter-stage/coupling capacitors
Boss tended to use electrolytic for this function,
& they have been causing problems on various pedals.
Your English is fine.
Regards Dr. Bob |
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princeton
Copper Member
5 Posts |
Posted - 03/08/2010 : 12:14:39
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| Thank you for a warm welcome. I bought GE-10 few days ago and it already was noisy. So you're proposing to check elcos. I'll try and report back. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/08/2010 : 13:59:45
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Hi princeton
You didn't mention it so,
I'm not sure of your Technical or Electronic skills.
Or what equipment & tooling you have but.
Check all the usual stuff like
Possible noisy or unregulated power supply.
Try running it with good NEW batteries.
Check the input & output sockets for dirt & grime.
Check for dry or bad solder joints.
Check the wiring.
Check the condition of the sockets to the chassis ground for corrosion.
Look for leaky caps.
Compare it to another known good GE-10.
Do a general visual inspection.
With the electrolytic capacitors, it's is difficult to measure them with a capacitance meter.
What you really need ( other than replacing them with new ones)
is a piece of test gear called an ESR meter.
ESR = (Equivalent Series Resistance).
This measures the change in the capacitor internal ESR, which changes with time.
An electro cap can & will measure correctly on a standard capacitance meter, but will fail an ESR Test.
I have been telling people about these for a few years now.
I have owned on for about 10 years, it's amazing what you can find with one of these.
They cost about the price of a decent Digital Multimeter, and pay for themselves in the first few repairs.
If possible, please upload a few pictures of both sides of the board.
Good luck
Regards Dr. Bob |
Edited by - Dr. Bob on 03/08/2010 14:01:58 |
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princeton
Copper Member
5 Posts |
Posted - 03/08/2010 : 17:36:54
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So hear we go. The pictures...First, I'll recap all the electrolytics then we'll see.
Download Attachment:  IMG_0007.JPG
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Download Attachment: IMG_0008.JPG
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Download Attachment: IMG_0011.JPG
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Download Attachment: IMG_0012.JPG
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Download Attachment: IMG_0019.JPG
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ChristoMephisto
Platinum Member
Canada
1288 Posts |
Posted - 03/08/2010 : 22:58:57
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Like the old school transformer in it |
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princeton
Copper Member
5 Posts |
Posted - 03/10/2010 : 17:45:32
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OK. Problem solved. It was one of the opamps (nec 4558).  I also changed all electrolytics. No noise at all. Thanks for your suggestions. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 03/11/2010 : 08:55:25
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Hi princeton
That's good news.
How did you deduce it was one of the 4558 opamps.
And do you mind telling us which one went noisy/faulty.
Regards Dr. Bob |
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princeton
Copper Member
5 Posts |
Posted - 03/11/2010 : 14:03:28
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After I changed electrolytics but not solved the problem, I started tracing signal. Someone changed one of the resistors near the 1. opamp and pcb looked slightly darker in that area. So I thought too high of temperature could have easily demaged opamp. I removed the opamp, soldered IC socket and put new opamp in socket.
Bingo!
I marked faulty opamp in attached photo.
Download Attachment: faulty-opamp.jpg
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GE-10 graphic EQ
IMG_0007.JPG
IMG_0008.JPG
IMG_0011.JPG
IMG_0012.JPG
IMG_0019.JPG
faulty-opamp.jpg