CGS ORIGINAL sequential switch pcb question

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tragedybysyntax
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CGS ORIGINAL sequential switch pcb question

Post by tragedybysyntax » Wed Apr 09, 2014 4:47 pm

Alright... i'm about to hack this thing into pieces and throw it out into the fkn woods. lol... that's a bit harsh but I'm stumped! I have this thing 90% working... no led's lighting up, no gate outs (infact if i plug one of the gate outs into cv of a vco.. it lowers the pitch of the vco)

anyway... i've replaced all the ic's on this thing.... only thing I can possibly think is that it looks like i have a glob of solder that i cant get off the pads of P1 and also at P4 (gate outs) the other 6 gate outs have a slight hair of pcb material inbetween the 2 pads for each output but it seems like mine are joined together on 1, and 4. Can anyone tell me if those 2 stages are supposed to be that close ala... soldered together or you think that's creating a short?

Other weird thing it's doing is, reset button only works if going the one direction (forward) with the sequencer running backwards it has no effect.

ANYONE? :/

PLEAAAAAAAAASE HELP!
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Post by the bad producer » Wed Apr 09, 2014 5:29 pm

I had lots of problems with this, and then changed the LM324 for a TL074 (a mentioned)... then it was worse and I changed it back - and now it's fine! I think I also changed the logic chips for ones from another compaant at the same time...

Can't specifically say much as it just seemed to happen, whether I had a cold solder joint? The UP DOWN reset was funky before I went back the the LM324 FWIW, I could have another look, what chips you got in there?
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Post by andrewF » Wed Apr 09, 2014 5:35 pm

Is it a Vers.1 PCB? In which case read up on how fussy the 4516 is -
http://www.cgs.synth.net/modules/cgs28v ... witch.html (version 1 page)

Some brands of 4516 just do not work without some mods, I guess Ken has designed Version 2 to work with all brands as there is no mention of this issue on the updated page and there are some changes on the schematic.

The reset should work "independent of all other input conditions"

The gates shouldn't be soldered together :drinking: but it probably wouldn't stop the rest of the cct from working.
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Post by tragedybysyntax » Wed Apr 09, 2014 6:04 pm

HMMMM, i bet that's part of the problem then. Certain company of 4516....
these 2 are 4516BE and the logo is a cube with a S on each side. 8346831506

And I was thinking the 4051's were the problem... hehe. Hmmm.
As far as the pads for the 2 mentioned output gates... each gate out has 2 pads which i assume is ground, and gate. The other 6/8 have pcb material inbetween... so i just took an exacto and carved out the center of the 2 mentioned, problem is still apparent ;)
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Post by the bad producer » Wed Apr 09, 2014 6:30 pm

I had a "length" switch on mine, it was odd, so I made the mods as Ken suggests (swap LM324 for 074, cut trace etc) then I went back to the LM324, changed the logic and got rid of "length" switch, this is over a period of about 8 years! :hihi: I only actually got them (3 of them) working yesterday as a friend came round and he was like "this sequencer's shit!", I kind of agreed so finally got round to sorting it...

It looks like (looking at my PCB's and the schematic) the pads are supposed to be together - the pads are after the 820R resistor, and before the 680R resistor to ground ie both are P1 P3, P6 et
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Post by tragedybysyntax » Wed Apr 09, 2014 7:30 pm

should also mention this had gotten plugged in bkwds causing the tl072 to smoke so I then replaced all the iCs... lol. There anything else you think would of went with it?
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Post by tragedybysyntax » Thu Apr 10, 2014 7:43 pm

so...... realized that when i had this build 5 years ago, Metalbox installed all of the transistors backwards. HOW the hell this worked before i took it apart for this new panel is entirely beyond my comprehension!
SO, I have half of the stages working and the direction is working is well with the resets! Going to pick up some new transistors tomorrow and replace them at the faulty stages... i'll go from there. ;)
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Post by Liquidcolor » Fri Apr 11, 2014 7:57 pm

tragedybysyntax wrote:so...... realized that when i had this build 5 years ago, Metalbox installed all of the transistors backwards. HOW the hell this worked before i took it apart for this new panel is entirely beyond my comprehension!
SO, I have half of the stages working and the direction is working is well with the resets! Going to pick up some new transistors tomorrow and replace them at the faulty stages... i'll go from there. ;)
Please do not go making such ridiculous statements. If the Switch was working before you hacked it apart, it follows that the transistors were installed correctly.

Pinouts for the BC547 and the 2N3904 are reversed which is why you may be confused. Don't always trust silkscreening.
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