Hello,

I am currently reversing a simmons claptrap schematic as it is really interesting but it has no information on what the IC's are. I have guessed most of them (a 555, 3080 etc ) bar one which is mysterious. I think it is some kind of logic as it has minimal resistors and it has 1M feedback resistors (linearisation? ) it also seems to be inverting as when the switch is on it turns of a part of the circuit and turns off LED's . I have looked through all the 4000 series and some 74 series but no luck. It seems to have the same output as most dual gates (13 & 1 ) but would you drilve an LED off an input of say a 4002 2 input NOR? doesn't seem right.

this is my drawing, numbers with question marks are illegible but guessed.

https://www.dropbox.com/s/ozr9ekankpi6hmv/2013-01-29 08.11.23.jpg

am I barking up the wrong tree? its a circuit from the early 80's maybe late 70's so I cant imagine it is something particularly exotic.

 

Hello,

Could you post a picture of the top and bottom of the PCB?
You can upload the pictures to this forum, instead of posting them on dropbox.
Here are the instructions from the FAQ:
Attachments and Images

Bertus

 

thanks for your reply, ok no problem uploaded it as an attachment.

I do not have the PCB, I am trying to recreate an old schematic (simmoms analog claptrap ) . I guess its a non standard part but to me it really looks like a standard logic chip.

I was just trying to see if anyone recognised the configuration, I guessed a 3080, 555 and a lm301 using the same trick.

back to trawling though datasheets!

 

Hello,

Do you refer to this instrument?
http://www.simmonsmuseum.com/?area=devices&view=details&id=19

The schematics seems to be sold by this company:
http://www.musicparts.com/products.asp?Company=Simmons

You might also be interested in this thread:
http://forum.allaboutcircuits.com/showthread.php?t=79815

Bertus

 

yep thats the schematic I am working from (its scandalous they charge that much for work that is not their own without a proper parts list ) I am hoping to publish a clean re-drawn proven version.

as for that thread you actually list my site in your reply! my site is a sort of archive of the designs of synth drums. This section I am currently doing is on Clap designs ( Roland, EHX, simmons, Tama ) they are all quite similar, but the simmons has a really interesting 'humanizer' section

I attached the small section I am trying to guess, just for interest. See that this IC switches off the LFO (yellow) and the 'humanizer' effect (green). I was just wondering if anyone had a clue, but its cool I will just keep looking around at datasheets.

 

Hello,

The following site might be of interest in the look for your "mysterious" IC:
http://www.kingswood-consulting.co.uk/giicm/

Bertus

 

Looking at your drawing my guess is possibly it's a CD4013

 

meixner! I think you are right, the feedback resistor is to flip and flop the flip flop! I think I had 3 and 5 mixed up because of the clarity of the scan. it could also be an SN7474 as I can see other simmons circuits used TTL.

Bertus: Thanks for the IC listings I was looking for something like that!