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A-188-1 (1024) problem

2019-07-02 by zoog_angelspit@yahoo.co.uk

I fear my A-188-1 is faulty. What's embarrassing it that I think it's been busted the entire time I've had it (I bought it brand-new years ago).

Symptoms:

the CV inputs do nothing.

I can not hear the delay effect

I can hear a "phasing movement" sound when I turn the Delay Clock.

The feedback works

The CV OUT does not output CV.

There is no "clock noise" when I use it.

...so I can't figure out if the VCO is dead of the BBD chip is dead...or both.

Any ideas?

Where can I get replacement parts?

Thank you!

KARL.

AW: [Doepfer_a100] A-188-1 (1024) problem

2019-07-05 by yahoo@doepfer.de

Hello Karl,

I'm sorry about the problems with the module. From the distance it's difficult ti find out what's wrong. If the CV inputs have no effect and even the CV out does not work I suppose that the quad operational amplifier IC2 (LM324 or TL084 below the OFFSET trimming potentiometer) is defective and has to be replaced. It's a standard electronic part and should available locally without problems. If you cannot fix the please follow the repair notes on the FAQ page of our website:

www.doepfer.com > English > FAQ > General > Repair procedure

Or send the module to our address in Germany provided that you stay within the EU.

Best wishes
Dieter Doepfer

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> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Gesendet: Dienstag, 2. Juli 2019 23:18
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] A-188-1 (1024) problem
> 
> I fear my A-188-1 is faulty. What's embarrassing it that I think it's been
> busted the entire time I've had it (I bought it brand-new years ago).
> 
> Symptoms:
> the CV inputs do nothing.
> I can not hear the delay effect
> I can hear a "phasing movement"  sound when I turn the Delay Clock.
> The feedback works
> The CV OUT does not output CV.
> There is no "clock noise" when I use it.
> 
> ...so I can't figure out if the VCO is dead of the BBD chip is dead...or
> both.
> 
> Any ideas?
> Where can I get replacement parts?
> 
> Thank you!
> KARL.

Re: A-188-1 (1024) problem

2019-07-11 by zoog_angelspit@yahoo.co.uk

Thank you Dieter!

I replaced the LM324 and the CV input works!

the delay is still very slight. its a 1024, yet the delay sounds tiny.

Q: if the delay chip is fried, can I replace it?

THANK YOU AGAIN!

KARL.

AW: [Doepfer_a100] Re: A-188-1 (1024) problem

2019-07-12 by yahoo@doepfer.de

Hello Karl,

before you replace the BBD chip I'd recommend to measure the clock output (center top socket). It should output a rectangle in the frequency range about 10 kHz ... 200 kHz when the delay clock control is operated from 0 to 10. It could be also another range (e.g. about 15 kHz to 300 kHz) but about 1:20 frequency relation. If that's not the case probably the high speed VCO is defective (built around CA3096/LM13700). In this case I'd recommend to replace the CA3096 and LM1700. If the clock output is OK probably the BBD chip has to be replaced.

Best wishes
Dieter Doepfer

Show quoted textHide quoted text

> -----Ursprüngliche Nachricht-----
> Von: Doepfer_a100@yahoogroups.com [mailto:Doepfer_a100@yahoogroups.com]
> Gesendet: Donnerstag, 11. Juli 2019 22:03
> An: Doepfer_a100@yahoogroups.com
> Betreff: [Doepfer_a100] Re: A-188-1 (1024) problem
> 
> Thank you Dieter!
> I replaced the LM324 and the CV input works!
> the delay is still very slight. its a 1024, yet the delay sounds tiny.
> Q: if the delay chip is fried, can I replace it?
> THANK YOU AGAIN!
> KARL.