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asr still not working

2006-03-04 by keith sterling

OK, all these resistors and caps all over the place, it's a mess. And
still the same problems. The TL074 gets slightly warm to the touch.
The scaling at the outputs is about a semitone short over 4 octaves and
is influenced by the counter. I am assuming that others have
succesfully built asr's with this board? There are no revision numbers
on it but it's red and was purchased a few months ago.

I would like to verify that the input buffer is working correctly. I
read these voltages at the input to the ASR and the output of the
'input buffer' Could someone please verify these voltages? (much
appreciated)

Input voltage Voltage at TL074 pin 14

0V (C0) 6.64V
4V (C3) 4.83V

Also, what is the purpose of the 22k resistors to -15V on all buffer
inverting inputs?

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> Cut the power rails to the TL074. Add 100 ohm in series between the
> power
> rails and the power pins. Add decoupling capacitors between the power
> pins
> and earth, and each other. Use 100n AND low ESR electros.
>
>> I've been staring at this asr for a few days now and I can't figure
>> out
>> its problem. I get very small (on the order of millivolts)
>> fluctuations in all outputs relative to the counter state. I replaced
>> the 10uF caps with 100uF. Power supply is ample and stable.
>> Resistors
>> are all hand precision matched. The other symptom is that the scale
>> factor is compressed- when driven by a keyboard the outputs are
>> slightly less than 1V/oct.

Re: asr still not working

2006-03-04 by sasami@hotkey.net.au

1) I would not expect the TL074 to get warm.
2) if the extra trimming resistors in the buffers failed to change the gain,
look elsewhere - like at what you are driving.
3) I can't check voltages because I sent my unit to some one else who
buggered up theirs by using the wriogn type of capacitors.
4) There is only one revision of the board. The layout changed slightly a
few runs ago, but the circuit didn't.
5) One person after doing a few minor changes, such as replacing the 356
with LM3140 said it's behavior was as good as the MOTM sample and hold.
6) Is it really the counter or is it the clock that is causing change? The
counter would cause various levels. The clock, two. The rate would also be
twice as long as the clock if it is the counter that is having the effect.
Look for other places the clock signal could be leaking in, perhaps at the
clock processor at the input.
7) I have no idea why yours doesn't work. From the feedback I've had, they
are usually successful. The only other failur I remember was when a MC4024
was used. With motorola, the correct part is MC14024.

Anyone else have any ideas?

Ken

Show quoted textHide quoted text

>OK, all these resistors and caps all over the place, it's a mess. And
>still the same problems. The TL074 gets slightly warm to the touch.
>The scaling at the outputs is about a semitone short over 4 octaves and
>is influenced by the counter. I am assuming that others have
>succesfully built asr's with this board? There are no revision numbers
>on it but it's red and was purchased a few months ago.
>
>I would like to verify that the input buffer is working correctly. I
>read these voltages at the input to the ASR and the output of the
>'input buffer' Could someone please verify these voltages? (much
>appreciated)
>
> Input voltage Voltage at TL074 pin 14
>
> 0V (C0) 6.64V
> 4V (C3) 4.83V
>
>Also, what is the purpose of the 22k resistors to -15V on all buffer
>inverting inputs?
>
>> Cut the power rails to the TL074. Add 100 ohm in series between the
>> power
>> rails and the power pins. Add decoupling capacitors between the power
>> pins
>> and earth, and each other. Use 100n AND low ESR electros.
>>
>>> I've been staring at this asr for a few days now and I can't figure
>>> out
>>> its problem. I get very small (on the order of millivolts)
>>> fluctuations in all outputs relative to the counter state. I replaced
>>> the 10uF caps with 100uF. Power supply is ample and stable.
>>> Resistors
>>> are all hand precision matched. The other symptom is that the scale
>>> factor is compressed- when driven by a keyboard the outputs are
>>> slightly less than 1V/oct.
>
>
>
>The CGS Modular Synth home page: http://www.cgs.synth.net/
>
>Yahoo! Groups Links
>
>
>
>
>
>
>

_______________________________________________________________________
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: asr still not working

2006-03-05 by c10h14no2i

I finished my asr today, and it works perfectly! It didn't at first,
but the tl074 was bad.. I had a 084 on hand, so put it in its place.
The bad 074 was getting warm.

I can test the voltages for you tomorrow, if you still need them. I
dont have a keyboard hooked to the synth right now.

asr still not working

2006-03-06 by keith sterling

>
> I can test the voltages for you tomorrow, if you still need them. I
> dont have a keyboard hooked to the synth right now.
>

Thanks c10h14no2i, I would really appreciate it. If I can't get it to
work in the next few days I am going to toss out this board and order
another and start again. But knowing those voltages will help me focus
my efforts...

Cgs synth

asr still not working

asr still not working

Re: asr still not working

Re: asr still not working

asr still not working

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