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Reviving this thread once again.
New user; first post and seeking for help with my MB33 II.
I have a strange issue with main OUT volume dropping as soon as I turn the distortion pot CW.
The volume drops a LOT as soon as I engage the pot and then goes to zero about 1/3 of the distortion pot's travel.
As I understand from the schematic there's some passive current mixing going on before the signal hits the main OUT opamp which seems like it's only a I-V converter from the sumed current  leaving the OTAs.
So far do good but I don't see any good enough reason for the volume to rapidly drop as soon as the pot is turned.
I get just a little bit of distortion before the signal vanishes.
I have a hunch that it's probably a DC bias issue at play which manages to collapse the whole 13700 but I could be wrong of course.
I haven't actually had a proper look on the circuit but thought to post here in case anyone might have any suggestions.
Possibly help others as well..
Cheers.

in the interest of posterity, and since Yahoo doesn't care about posterity.....if anyone has the information from the now-defunct Yahoo group mentioned in this thread, would you consider posting it here? (or somewhere) thank you, all!! 

Hi All,

I am new to circuit-bending.
I have an MR-16 and want to start to mod it,
I found this post http://www.groovecriminals.co.uk/2009/04/bit-of-ebay-find-no-work-today-then.html
that shows what could be done.
Before starting and try (not to fuck it up) would any of you guys share some insights ?

Cheers
Bruno.

Has anyone installed individual outputs to a Tascam portastudio? I have a couple models and I’m seeking help.

The models I have are the 488, 488 mkII, and the 414 mkII.

Schematics for all three can be found here: https://tetrakansupermonobloc.home.blog/category/manuals/service-manuals/


Thanks for any help!

Replying to my own post.  Bad crimp job on a cable was giving not so great (tm) power to the LTC.

Working like a champ now.  I'll post some info about my project once it is done.  The 4066 chip w/ the ROM bends is pure awesome when using with a modular synth.

I'm having difficulty taming this combo.  I've cut the trace on the board (and pinned it out).  I'm getting 5V from the rectifier to the LTC and hooking the LTC up as described on the site and as I have in the past for other machines (like my Yamaha RX-5, which works a treat).

But this thing just won't cooperate.  I've tried all kinds of different pots and values, shorting B/C, etc.  Everything is super low pitch and it varies as time goes buy, and by a lot.  It's almost the same kinda behavior you get when a capacitor is charging up.  I'll get a low pitched sound, and then over a little bit of time it becomes unresponsive.  The only time I get something sorta resembling normal sounds is with NO resistance attached to the pot inputs and A/B/C not shorted at all.  It's just a little lower pitched than normal in this case, but it also fluctuates (although I'd kinda expect this, as maybe the pot inputs are floating, or is the trimmer in series?).

I've also tried 2 different LTCs and the exact same behavior, so it's most likely something I'm doing wrong, and probably pretty simple that I'm overlooking.

Anyone else using these in an HR16?

Any tips would be greatly appreciated.  This thing is almost done, I have all 3 chips broken out to sockets, a 4066 for CV control of the bends, a vactrol, all kinds of goodies.  But the part I thought would be easiest is proving difficult.   

Here's a pic (I get an error w/ attachments, something about can't find attachment path)
https://www.dropbox.com/s/zcpxel267nwuaof/IMG_2417.jpg?dl=0

any news on where do we patch in with those LTC1799s ?? :0

Hi all, I wonder if anyone who knows about electronics can give a clue as to what could be wrong with my MD16R drum machine?

The display is not lit up and only displays a series of black blocks. It has had a new screen placed inside it, but the black blocks still display.
The drum machine plays sounds etc, and I cannot see any battery leakage(had a new battery put in).

Any help would be greatly appreciated.

Has there been any developments here? A pcbs would be great!

I expect this thread is going to get very busy over the next few days. I just joined a Facebook group of toy keyboard noodlers and mentioned what we had been doing with the SK samplers. Expect a barrage of new members!

https://www.facebook.com/groups/966873446990657