Ibanez AD-202 troubleshooting

[duck_arse]

ahh, well, you didn't mention which transistors you'd replaced, please tell me "not all of them". so, not q106 is fine, he says hopefully, we can back up a bit further to q101, q102, q103. try them. I can't fathom the fet switching arrangement as far as more/less noise to the chorus/flange at the moment, I'll have to think about that.

[beatnik]

yeah i only replaced q106. i will try with the other ones and let you know. thanks mate

[armdnrdy]

Have you tried the AD-202 with a different amplifier?

[beatnik]

yeah i tried different amps, different cables,... but that didn't matter. actually without even connecting audio input/output the noise can be seen on the led meter as the leds light up in random way as the noise does.

i tried replacing q101, 102 and 103, but guess what? still nothing...

i understand that is quite hard for you to give suggestions without having the unit on your bench, i appreciate your help very much.

if i have to do measurements, record audio or video, just tell and i'll do whatever that makes your life easier in helping me

[armdnrdy]

I listened to the noise sample and took a quick look at the schematic again...

since you replaced the power supply filter caps, and the sound is intermittent...I would imagine that DC voltage is leaking into the audio path.

It will be one (or more) of the DC blocking caps that is bad.

My earlier suggestion of audio probing the circuit should pinpoint the problem area.

[armdnrdy]

Do you hear the noise when using the "dry out" output?

[beatnik]

no noise in the dry output, and also no noise in fx out but with blend pot all the way to dry.

i will definitely try to replace these capacitors. C237 to C246 right?

[duck_arse]

well, I dunno. looking at the paths common to all sections means, if it is a dying semi, either one of the fets q104/105 (I don't know if they go bad with sound effects) or the compander ic105 or the 4558's ic102/103/104. something in the pink or orange, but there's lots of stuff there.

you'll have to go section by section, lifting caps to see if you can isolate the bad stage.

[duck_arse]

any update on progress?

[beatnik]

Hi, I am waiting to buy the replacement caps. Will keep you posted next week.

[beatnik]

hi guys finally got back working on the ad-202

i replaced the 10uF caps on the psu rail and the noise finally disappeared!

thanks again to everybody who gave help!

[duck_arse]

fantastic. I was just thinking about this today.

and I thort you said "it's not the power supply ....."

[beatnik]

after troubleshooting this unit i definitely learned something! thanks man

[armdnrdy]

Great news!

So were the caps you replaced C237 to C246 local reservoir caps for each IC power input? On the schematic the caps are depicted attached to the power rail with no detail as to location.

[beatnik]

yeah exactly it was one or more of those capacitors on the psu rail

they are spread all over the circuit, every different section has one or more

so happy i fixed this effect, the analog delay mode sounds amazing ! much better than a mn3005 memory man in my opinion

[Alban LG]

Hello everybody !
I'm posting in this old thread because I'have a "Regen" failure on my AD202 and it seems to me that there are some AD202's expert here !!
When I put Regen at min : I have 1 tap, when I put Regen to the max : I have 5 or 6 tap Maximum !! No more crazy feedback...
You know, where did these things come from ?
Lot of thx !!

[beatnik]

I suggest you to recap the unit and to check out the calibration, there should be an internal trimpot that adjust the feedback