Frac envelope generators

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Tubeampguy
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Re: MOTM 1800 Looping EG

Post by Tubeampguy » Sat Feb 23, 2019 10:58 pm

davedatt wrote:
Tubeampguy wrote:
davedatt wrote:Hi, I have 2 FRAC MOTM Looping Envelope Generator PCB's stuffed but no front panels and no Pots. Could someone take pictures of the rear of their 1800 and if possible note the values of the pots. The schematics are unavailable from Paul (HD crash).

Thanks in advance.
dave
I have (over many years) found several MOTM-1800 ADSR's
My first one had been modified with banana jacks. I still haven't figured out how I'm going to fix that one. Here are some of the pictures I have on my computer. The pictures show the lower circuit board for the jacks and the ribbon cable jumper to the main circuit board. Sorry no pot pictures. Hope it helps you?
Thanks, these are helpful, but unfortunately do not answer the Pot question.

There were only a small amount sold unfortunately.
I will likely have to make an educated guess then observe the results then fine tune.
dave
Dave, Working around my work schedule and the bad weather, I can take more pictures and get you the values on the pots. Also some views from the main circuit board & panel details. The 1800's are the best around, They are comparable mostly to the Bananalogue VCS But those are really rare too.
dave
:tu::blacet: :tu:

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werock
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Post by werock » Sun Feb 24, 2019 10:55 am

I wonder how similar circuit wise this was to the MOTM-800 ADSR.

That used 1M log pots for the A, D & R pots and 10k lin for the sustain pot. Might be a good starting point?

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Synthnerd
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Post by Synthnerd » Wed Feb 27, 2019 8:31 pm

I have a MOTM1800. All 4 pots appear to be the same, stamped "DI YA 05 43". I'm frustrated that I can't find my multimeter at the moment to measure values, but I'll take the module into work tomorrow, as we have one there. I read elsewhere that Doepfer and Carvin Amps use DIYA pots and they are usually custom made in large order quantities. Here's a picture:
Image[/img]

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diophantine
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Post by diophantine » Wed Feb 27, 2019 9:54 pm

A multimeter may not tell you the answer, if there is any sort of resistance in the circuit that is in parallel with the two ends of the pot.

A lot of times pots only have the value written on the front, in which case you'd have to pop off the knobs & remove the nuts...

If I had one I'd be happy to do that, but I don't...

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Synthnerd
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Post by Synthnerd » Wed Feb 27, 2019 11:58 pm

Thanks for passing on the knowledge. It was easy to take the front panel off. The pots are marked B50K. I think this means 50K ohms, linear taper. Here's another picture to show how the pots are mounted:

Image

davedatt
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Post by davedatt » Thu Feb 28, 2019 8:17 pm

Synthnerd wrote:Thanks for passing on the knowledge. It was easy to take the front panel off. The pots are marked B50K. I think this means 50K ohms, linear taper. Here's another picture to show how the pots are mounted:

Image
Thank you guys! 50K Linear!

I will assemble will let you know!

dave

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