Flanger, debugging

[PeopleHateMe7666]

OK i dont wanna use an audio probe unless someone can help lol... umm can i just send an MXR flanger to them and you fix it? i dont care about learning from this thing i just want it FLANGING! its the dunlop one, powered by 18 v dc

[petemoore]

A digital multimeter?
 It may or may not be hard to figure out.
 Could be a power supply even.
 Does it light up?
If you want to send it to me, PM or email me, I like to figure these things out !!
 I pride myself on my "Debbuggabbillitty". Might end up with a socket under an OA etc.
 Does the board have a toasted look to it anywhere?  
 Can you read the OpAmp#'s ?

[Mark Hammer]

In what way does it "not work"?

[PeopleHateMe7666]

no flanger, bypassed its fine, but engaged, total silence

[petemoore]

I smoked a 10k pot this morning, it's legs picked up a rogue wire...actually I think it was the wire...the pot's still good.
 We can have coffee and I'll take a look at it. How hard can it be?
 Oh, got any substitute chips for it?

[petemoore]

Did you look at the Pin Voltages Yet?

[PeopleHateMe7666]

no i didnt... havent done anything but tried it out, and checked if anything looked damaged... prolly can get the chips from smallbear its a sad1024 if i remeber correctly...

[petemoore]

Check PinV's first. Battery connections etc.
 Also I like to Beep' mode test through all the offboard stuff.
 then I'd connect my thumb to all points in the circuit, one by one, starting from the output. I find probs readily and real kwik using this method...you need an amp, battery, and a pointy conductive item to 'connectouch' to 1 wire, pin, lug, etc at a time. You should [if the signal makes it that far] be able to hear 'Hummm' when you touch around the input pins and output pin of the opamps. This is often where the signal path is interuppted.
 Oa's are not usually that bad to figure, once the voltages are set so it can operate, and input is supplied, the thing has to work, or it's fried.
 A flanger is probably as good a debug test technique tester as anything...lotsa stuff in there...could be anything, once you start in there possibilities should narrow down pretty quickly. It did work once, chances are it's just one 'simple' thing.

[PeopleHateMe7666]

do i need something going thru it? like a cd player in or something or wuld ur little touch and hum check work? damn... lol you people always get me to just work it thru... no easy ways to fix things.. u sound like my teachers...

[petemoore]

Plug it in the amp, connect the battery, turn the bypass to effect on position, and touch the output pots tip connection with your body, or somehow connect to it...what do you hear throught the amp?
 Don't turn off or disconnect anything, and try that trick [connect your body to] pins 1,2,3, 5,6 and 7, of the Dual Op Amp...what do you hear now?
 Measure the voltage from ground at pins of the Opamp.
 I'm sorry, I can't provide the hate you request from me...

[Mark Hammer]

There will be two categories of things to look for: flanger-specific issues, and generic FX-pedal issues.

The most common problems with flangers will be poor biasing (the guitar signal going to the delay chip has to sit on top of a steady DC voltage in order to pass through the delay chip), or static sensitive chips that have taken on a new career as Southern-fried-epoxy (usually at least a couple of static-sensitive chips in a flanger).

If someone says "I get a signal when I engage the effect, but no flanging sound", that usually points to a biasing problem - the signal makes it up to the doorway of the delay chip but doesn't go any further.  If someone says "I get a bypass signal, but when I hit the stompswitch I get absolute silence" that can mean a bad switch, or poor connection between switch and board or some other discontinuity that does not apply in the bypass situation.

[PeopleHateMe7666]

k thanks ill try that tommorrow