Help with Boss GE-7

DavidRavenMoon · March 23, 2009, 08:58:30 PM

Hello everyone. I have a Boss GE-7 EQ. Its fairly new. I was doing some mods on it and one of the wires from the circuit board broke. It's a gray wire coming from a spot on the board marked "P4", and it's right under IC2. It's still connected to the board, and I have no idea where the other end went. I can't seem to find any spot where a wire was soldered that is missing a wire.

I found a schematic online, but it seems to be for an older unit, and it doesn't help.

My circuit board looks like this:

Ironically in that photo the wire to the P4 pad is also disconnected. On mine it's disconnected on the other end.

Anyone have one of these?

Taylor · March 24, 2009, 01:36:18 AM

Well, I hate to respond with obvious stuff, but what does that wire connect to where it is still connected? Have you plugged it in to see what isn't working?

gigimarga · March 24, 2009, 02:16:09 AM

try to look at the schematic here: http://www.schematicheaven.com/effects/boss_ge7_eq.pdf

vondran · March 24, 2009, 02:22:20 AM

It looks like it connects to P4, right between R24 and R25, and just below the JRC4037G chip near the center of the board.

Taylor · March 24, 2009, 03:45:14 AM

Right, I can see where it is, but I was wondering what it actually connects to - sometimes physical proximity doesn't equate to actual electrical connection.

After looking at the schem again, it looks like R24 connects to the EQ slider pots. Looks pretty likely that that's where your gray wire should connect.

Mike Burgundy · March 24, 2009, 06:30:49 AM

Good possibility. Check for continuity between R24 (one of the legs) and the grey wire. Then check if there's anything connected to both ends of the slider pots collectively. One line should be the + feed for the next opamp (pin3) the other the - input (pin2). Should be the same IC. R24 should be connected to pin 3. If it's also connected to teh grey wire, that should go to one end of the sliders.
hih

DavidRavenMoon · March 24, 2009, 09:23:15 AM

Hi everyone. Thanks for the replies.

I was being lazy and the picture I posted was from the internet, and has the same wire disconnected at the circuit board, but on mine it's still connected at the board, but the other end broke from where it was connected.

QuoteAfter looking at the schem again, it looks like R24 connects to the EQ slider pots. Looks pretty likely that that's where your gray wire should connect.

That's what I figured also, but I'm not sure exactly where. The board with the sliders has a ribbon cable, and nothing there looks like a wire came off. There is no hole missing a wire, but there is a spot where the metal parts of the sliders are soldered to the board.

The schematic that's all over the 'net seems to be for an older unit that had a different circuit board layout, and uses different op amps. It could be the same circuit, but I couldn't follow it.

This is not my unit, I'm modding it for someone, and he supplied the mod kits. I haven't plugged it in yet to see what happens with the wire off. I thought I'd ask around first. I usually make note of where wires go, and even take photos. This was the last of three pedals I was doing for the guy, and was all finished when I saw the wire!

Here's two photos of the pedal showing the disconnected wire. The wire does come from the pad marked "P4". I may have to use an eye loupe and a bright light and look at the slider board again.

Mike Burgundy · March 24, 2009, 10:24:58 AM

Can you get a pic of the underside of the pcbs, plus the other side of the slider pcb now hidden by the flat ribbon cable?

Mike Burgundy · March 24, 2009, 10:45:25 AM

Here's a hunch: first, check visually if there's a ground connection made from the pcb to the input jack. That jack should have, if I see this correctly on your pics and some other info, a wire to the pcb from the tip (that's the input, I believe that's white to P1), one to the battery/adapter -pole and the pcb(for the protection diode) from the ring (black, probably), and, here it comes, one ground connection to the pcb.
No idea if this is the case, BUT looking at other pcb's and schems, and the layout of the other wires (purple P7 looks like it goes to the switch, P5 power, P1 input, wire cable shows 15 connections, all of which *match* this:http://web.tiscali.it/boxsmt2clone2005/_web_boss_ge7/boss_ge7.htm ) it might just be ground connection on the input jack.
You can check for continuity between the input jack sleeve and the pcb ground to verify.

Edit: ok, just saw the same answer on a different bbs. Ah well. It was still fun

liddokun · March 24, 2009, 10:56:48 AM

I had the grey wire in my GE7 once. If I remember correctly, it was attached to one of the jacks. Check the jacks to see which one is missing some sort of a connection. Sorry I'm not much more help.

fuzzo · March 24, 2009, 11:11:35 AM

it connected to the ground of input jack (I looked in mine)

gigimarga · March 24, 2009, 11:20:29 AM

What mods have you made?
It sounds better now?
I am very curious because i've just bought one and i want to mod it

DavidRavenMoon · March 24, 2009, 12:00:03 PM

Quote from: fuzzo on March 24, 2009, 11:11:35 AM
it connected to the ground of input jack (I looked in mine)

Yes, that seems to be where it goes!

Thanks

DavidRavenMoon · March 24, 2009, 12:10:55 PM

Quote from: gigimarga on March 24, 2009, 11:20:29 AM
What mods have you made?
It sounds better now?
I am very curious because i've just bought one and i want to mod it

I'm doing this for a customer and he supplied the mod kit. It's from a well known website that sells such kits.

I haven't tried it out yet, due to the broken wire, but what it did was replace the SIP JRC J213A op amp chip with a small riser board holding two Burr-Brown OPA2134PA op amps. Then the 3 JRC J241B op amps were replaced with RC4558P op amps. 4 caps were replaced with .047uF box caps, 3 other caps were replaced with 1uF tantalums, and another cap was replaced with a .1 metal film cap. A resistor was replaced with a 1.1K carbon comp... can't quite figure why they would use those, but these kits (and the two TubeScreamers I did for the same guy, a TS09DX and a TS10) used carbon comps in places. Lastly there's a new bright LED.

This is supposed to make the EQ quieter and cleaner. I didn't try it out before hand, but I will when it's done.

The two TubeScreamer kits made a huge improvement from the stock units.

DavidRavenMoon · March 24, 2009, 04:48:03 PM

OK, the pedal works! Thanks to everyone for the help!

I didn't try the pedal before the mods, but it sounds very nice. It's clean and quiet, only having some hiss when you push the high frequency sliders way up.

Kurt9099 · June 06, 2016, 06:24:34 PM

Got it, thanks anyway!

News:

Help with Boss GE-7