Put your EFM synth kit corrections here, thanks!

the19thbear · Joined: Apr 19, 2007 Posts: 151 Location: denmark

Although the EFM synth kits are cheap, and very cool, it is known that the schematics/pcbs have errors Very Happy

, so please, all of you EFM synth kits builders out there: do us all a favor and post you corrected schems/pcb layouts here.
thanks

prophei · Posted: Wed May 30, 2007 2:03 pm Post subject:

once i figure out all the problems i am having with my boards, i'll be sure to help Wink

fonik · Posted: Wed May 30, 2007 2:06 pm Post subject:

hi all,

tom gamble was recently selling off the older PCBs he had on stock. i'm talking about the 1900er series.

a fellow from the old and vanished EFM forum was so kind to mail me all the information from the old EFM forum he filed.

you'll find information on errors and modifications.

i just started to upload these old topics. more to come...

old EFM forum topics

prophei · Posted: Wed May 30, 2007 2:12 pm Post subject:

thank you!
unfortunately, i have the new boards =\ not sure how much those will help!

the19thbear · Joined: Apr 19, 2007 Posts: 151 Location: denmark

thanks you very much fonik! Very Happy

keep up the good work!

prophei · Posted: Tue Jun 05, 2007 12:08 pm Post subject:

Tom has now ignored me for over two weeks since selling me his boards. His documentation is wrong, he refuses to answer emails...

I'd say to not bother with his product.

Unless you are very skilled with electronics, his materials are too flawed to work with. Bummer! Mad

frijitz · Posted: Wed Jun 06, 2007 8:31 am Post subject:

prophei · Posted: Wed Jun 06, 2007 9:38 am Post subject:

crazeydazey · Posted: Thu Jun 07, 2007 8:22 am Post subject:

I was looking at the 4616 VCO and VCA on his 4600.

Has anyone built it and does it work, I'm a newbie and building circuits that don't work in the 1st place and finding the bugs is not my strong point yet.

I just liked the look of some of the 4600 units..

prophei · Posted: Thu Jun 07, 2007 9:33 am Post subject:

prophei · Posted: Thu Jun 07, 2007 8:31 pm Post subject:

hello all...

i know that this is for posting corrections, but i guess i am requesting some ideas as to how to make one.

i have successfully gotten tom's korg delta style filter (46212) to work, and have noticed that the cutoff could use more range. it just doesn't seem to cut deep enough. do you have any ideas as to how i might approach modifying this behavior?

much thanks in advance!

crazeydazey · Posted: Fri Jun 08, 2007 1:04 am Post subject:

cheers prophei,

I'm not going to order any PCBs from tom, I am going to make them up on solderless breadboard first, gives me more chance to just mess and see if I can fix it by shear luck.

I was thinking of doing the Korg Delta VCF, I had one and loved it (don't know why I sold it.. Crying or Very sad

)

I may be wrong (and possibly am) but would a bigger pot give you more range??

I remember on the Korg they had trims on the PCB, and if you adjusted them it turned it into a beast whilst toms doesn't.

I have the original schematic for the korg (not sure if I'd be allowed to post doe to copyright but if I can you can check the circuit against the original and see whats different..

cheers

Daz

prophei · Posted: Fri Jun 08, 2007 7:08 am Post subject:

crazeydazey · Posted: Fri Jun 08, 2007 7:28 am Post subject:

I'll risk it then..

I can see a few changes I'd like to try when I breadboard it, like the adj pot on the COF.

I'm actually thinking I should try and copy the schematic and get the values as close as and see what happens..

I did tape some stuff where I'd sync it to a roland mc202 and a korg kpr77 drum machine but I can't find it now..

Delta-filter.jpg

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prophei · Posted: Fri Jun 08, 2007 10:25 am Post subject:

being a novice, it will take me a while to look over it, but at first glance, i recognize parts of it from the EFM version, but can see that there are some different resistor values in there...

thanks for posting this!

fonik · Posted: Mon Jun 18, 2007 1:15 am Post subject:

just added old forum topic VCF 8E (MS20 style). great improvements by harry bissell himself.
http://www.modular.fonik.de/Page37.html

BTW i did not compare the old schematics and the new (3500/4600er series) in detail but i assume that they are very similiar especially those designs, which did not use obsolete ICs.

current status of old forum topics posted:
KBD 2A, LFO 5A, RMP 1B, RXCV, RXCV pro, VCA 5B, VCA 6B, VCF 1E, VCF 2E, VCF 2F, VCF 6C, VCF 7, VCF 8E, VC ADSR.

fonik · Posted: Tue Jun 19, 2007 3:48 am Post subject:

FYI:
just added old forum topics
VCF 12A (sallen-key)
VCO 3D (dual VCO, Rogue)
VCO 3D (multiwaveform, Prodigy).
http://www.modular.fonik.de/Page37.html

current status of old forum topics posted:
KBD 2A, LFO 5A, RMP 1B, RXCV, RXCV pro, VCA 5B, VCA 6B, VCF 1E, VCF 2E, VCF 2F, VCF 6C, VCF 7, VCF 8E, VCF 12A, VCO 3D, VCO 4D, VC ADSR.

fonik · Posted: Thu Jun 28, 2007 6:42 am Post subject:

FYI:
just added old forum topics
VCO 3E (dual VCO, Rogue)
WAV 1B (waveshaper/sub gen)
The WILDCAT (i just ordered the last available PCBoard of this modular midi synth! i am sentimental, i guess)
http://www.modular.fonik.de/Page37.html

current status of old forum topics posted:
KBD 2A, LFO 5A, RMP 1B, RXCV, RXCV pro, VCA 5B, VCA 6B, VCF 1E, VCF 2E, VCF 2F, VCF 6C, VCF 7, VCF 8E, VCF 12A, VCO 3D/3E, VCO 4D, VC ADSR, WAV 1B, WILDCAT.

kokoon · Joined: Jan 09, 2006 Posts: 158 Location: slovenia

great, some wildcat info at last Smile

now i need to clear my desk and start building mine.

fonik · Posted: Thu Jun 28, 2007 9:09 am Post subject:

kokoon · Joined: Jan 09, 2006 Posts: 158 Location: slovenia

yes. i have. it's excellent. but still this EFM archive makes me feel a bit less alone with the wildcat Smile

prophei · Posted: Fri Jul 06, 2007 10:11 am Post subject:

I finally have something useful to contribute here!

Last night, I was working on my EFM 46212 (Korg Delta) Filter, and noticed that the cutoff range and general sweep characteristics seemed very limited. I made the following modifications that made it work FAR better.

Please try this and see what you think!

I changed 2 resistors...

R26 was changed from the original 75k to a 27K
R31 was changed from the original 150k to a 68K

I think you will find the behavior of the filter far better, provided your results resemble mine Wink

machvingtsun · Joined: Jul 07, 2007 Posts: 11 Location: Galway

Anybody have corrections for the 4628 MS20 VCF and the 4627 Arp VCF?
Ive built both, neither work

Dave Kendall · Posted: Sun Jul 08, 2007 4:14 am Post subject:

Hi.

FWIW, EFM parts lists are notoriously iffy, often with many wrong values..... The schematics are usually right. There are sometimes a few track bugs here and there, and on a few boards the silk screen for transistors can be backwards(!) Quite a common error that....This definitely applies to the older 1900 boards, and most probably to the newer ones too.

Checking each trace and component on the board against the schemo is often the only way to find the bugs. I had to do that a few times with the older ones....

Hope you get it sorted.

and, welcome

cheers,

Dave

etaoin · Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL