1991 GK 800RB
my effects loop isn't working - when I first got it a year ago, it would shriek when any 9v pedal was run through the loop and it would clip both of my 18v EQs. I finally opened it up today to compare it to schematics. apparently, a previous owner rewired it at the loop jacks. anyways, I tested it out, again:
1: effects loop jacks left empty = good signal with no issues (maybe a little more hissing/noise than I think it should have).
2: patch cable between send and return = no change in signal; no issues (still has hiss).
3: Boss Super Chorus pedal = original/dry signal good; no effect applied to signal when pedal engaged (no shriek, but still has hiss).
4: MXR M108 or M108S EQ pedal = with no instrument jacked into the front input, the EQ's level and gain sliders flash (set at +/-0), indicating the pedal is clipping from too much signal. when i turn the volume up (the knob near the input) enough to pass a signal, the speakers move violently and make what sounds like a robot vomiting ...very loudly. the same occurs with an instrument jacked into the front input.
the 1991 schematic does not match my current wiring. looking at a post from 2012, I can see that my loop wiring is definitely not the same: mainly the grey and brown wires coming off the main board. I can't be sure of exactly what is going on at the return jack's switch terminal in that thread due to it being out of focus. here is my wiring:
notes for pic above: effects loop jacks are just below the circular, black direct out; the left/return jack has 3 terminals (one is a switch connected to the hot connection that disengages when a plug is inserted) while the right/send jack has the standard 2 terminals; the brown wire was not completely stripped away by a previous owner and then fed through adjacent terminals on the return jack.
this is the color scheme coming off of my main board at P2:
- on my 800RB, the grey wire (from input) and brown wire (to amp EQ) are both connected to the joined positive terminals of both jacks as well as the return jack's switch. I believe the way mine is wired, the signal is looping/doubling at the return jack when the effects loop is utilized. my guess is someone did this because the jack switch corroded just enough to break up the signal.
TL;DR: I think I need to remove the jumper wire between the send hot and return hot, then move the P2 brown wire to the joined terminals (send hot, return hot switch). I'd like to verify this before I dive in, so...
Could someone open their 800RB up and take a good photo or two of their loop jacks as I have above?
much thanks!
my effects loop isn't working - when I first got it a year ago, it would shriek when any 9v pedal was run through the loop and it would clip both of my 18v EQs. I finally opened it up today to compare it to schematics. apparently, a previous owner rewired it at the loop jacks. anyways, I tested it out, again:
1: effects loop jacks left empty = good signal with no issues (maybe a little more hissing/noise than I think it should have).
2: patch cable between send and return = no change in signal; no issues (still has hiss).
3: Boss Super Chorus pedal = original/dry signal good; no effect applied to signal when pedal engaged (no shriek, but still has hiss).
4: MXR M108 or M108S EQ pedal = with no instrument jacked into the front input, the EQ's level and gain sliders flash (set at +/-0), indicating the pedal is clipping from too much signal. when i turn the volume up (the knob near the input) enough to pass a signal, the speakers move violently and make what sounds like a robot vomiting ...very loudly. the same occurs with an instrument jacked into the front input.
the 1991 schematic does not match my current wiring. looking at a post from 2012, I can see that my loop wiring is definitely not the same: mainly the grey and brown wires coming off the main board. I can't be sure of exactly what is going on at the return jack's switch terminal in that thread due to it being out of focus. here is my wiring:
notes for pic above: effects loop jacks are just below the circular, black direct out; the left/return jack has 3 terminals (one is a switch connected to the hot connection that disengages when a plug is inserted) while the right/send jack has the standard 2 terminals; the brown wire was not completely stripped away by a previous owner and then fed through adjacent terminals on the return jack.
this is the color scheme coming off of my main board at P2:
- on my 800RB, the grey wire (from input) and brown wire (to amp EQ) are both connected to the joined positive terminals of both jacks as well as the return jack's switch. I believe the way mine is wired, the signal is looping/doubling at the return jack when the effects loop is utilized. my guess is someone did this because the jack switch corroded just enough to break up the signal.
TL;DR: I think I need to remove the jumper wire between the send hot and return hot, then move the P2 brown wire to the joined terminals (send hot, return hot switch). I'd like to verify this before I dive in, so...
Could someone open their 800RB up and take a good photo or two of their loop jacks as I have above?
much thanks!
