MXR Micro Flanger: Flanges ok, but its quiet.....SHHHHH

[heyniceguy]

Hey guys,

I got this broken MXR Micro Flanger today at a pawn shop, and i thought maybe you guys could assist me in repairing this demon. Insides as seen here:

http://www.modezero.com/mxr-micro-flanger.htm

So i go to fix it, and i repair 2 broken wires. i check the output while giving a 1khz 200p-p input. it flanges ok. swirls ok. but the volume is very quiet (a tenth or less of the input voltage). so i trace out the signal and it stops at the very first op-amp stage. the signal goes into the (-) input strong. comes out at the output very weak. (+) input sounds like a very weak flanged signal. i dont have the schematic so i do not know the function of this stage. so i proceed to replace the signal path op amp (TL062). no change. i then.....

- replace all the transistors (4 NPN and 1 PNP). no change.
- i re-solder the whole board. no change.
- replace the LFO op amp (TL061) just because. no change.
- fiddle with the trimpot. no change at all. usually, this would cause the signal to get all effed up (lost flange sound, distorted), but the signal changed none at all.
- check the inverter ins/outs on a scope. look like they should.
- check the input of the delay chip (which is an R5106 if you look at the picture - and it's what was already in the pedal). it's a dry quiet signal.
- check the output of the delay chip. it's a quiet wet signal. sounds like a flanged signal, but very quiet. so it seems like the LFO/delay portion of the circuit is operating as it should.

what am i missing here?? im tempted to buy the schematic from schematic connection, but i just cant bring myself to give that guy money for whoring schematics that he didnt create (and mostly because he wont email me a schematic, but he will snail mail it - and im impatient - and i want to flange NOW).

[jonathan perez]

electrolytics?

caps?

[MartyMart]

Yes, first thing after checking voltages and for broken wires etc, would be to look for
suspect electro caps.
Does it look like it ever recieved a reversed/wrong voltage ?

MM

[heyniceguy]

i dont think it rec'd reverse voltage, as all the semiconductors were either replaced or checked for functionality. theres a blocking diode from the 9v supply that would have blocked a -9v input. it was fine.

there are 2 electrolytics in the LFO section, and the LFO seemed to be working fine, as i get a delayed/flanged output. there are other ceramic and "blob" type caps in the signal path. havent replaced them. i've never seen caps of that type go bad before. is that something i shouldnt overlook?

[eddie84mx]

Hi
I have a micro flanger with un-connected cables...

can you say me the order of cable from gray to violet related to this picture:
http://www.modezero.com/images/mxr-micro-flanger-Bx.jpg

I not have the schematics...and so I would first reconnect the entire pedal...

thanx a lot
max

[stephanovitch]

Hello,
try to replace tantalum cap(s) in the lfo with chemical caps.