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Re: New EH Small Stone

3/12/2000 4:09 PM
Mark Hammer Re: New EH Small Stone
Yeah, I got that one too. I got what appeared to be another one from someone else's site that was a 2-parter, but I forget where. If it helps jog anyone's memory, one gif containing a (neat) handdrawn schematic of a 1975 issue, and the other contains a rough (i.e., not press-n-peel ready) PC mask and parts-layout/wiring diagram. It doesn't seem to be the same issue as the one at the U of A archive. The mod article is from DEVICE, and none of the PC board pads referred to in the article seem to jive with the board depicted in the gif described above.  
I put together a board from the gif and populated it, but I'll be damned if I can get it to work. Getting the CA3094's was another entirely! (Although I owe Mike Irwin a debt of gratitude for the last 2 needed to stock the board.)  
Rather than try to keep track of who I still owe e-mail to (and I am sure there are many against whom I have committed this crime), is there one person with a web-site who would volunteer to post my scan of the mods article?
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3/12/2000 9:25 PM

i'm also having a hard time tracking down  
the ca3094 chip. trying to fix a microsynth  
any ideas on where to find some???  
thanks sk
3/12/2000 10:08 PM

If you only need one or two give me an e mail and I send you a couple.  
3/16/2000 8:04 AM
Joe Fuzz

Okay, Mark, finally found time to pop the top off. There are 5 chips labeled with a capital H (I'm guessing Holtek). They are indeed CA3094E chips. I can also spot 4 transistors (I think -- they're three-legged TO-92 package labeled 3107E), couple dozen or so resistors, and around a dozen caps -- 4 of them electrolytic. It's a single-sided board, however: there are also jumper wires on the trace side along with a resistor and cap tack-soldered to the back of the board. The labeling is in Russian.  
It looks to be wave-soldered.  
Having built a few stompboxes myself, this one is one of the more complicated circuits I've seen. I suspected as much, that's why I bought one instead of built one.  
I'll leave the cover off overnight in case you have any other questions, either here or in the chat room. If you want to meet in the chat room, give me a time in the afternoon or evening tomorrow along w/ your time zone.  
It really appears to be a well-built, sturdy box. And it sure sounds great!
3/16/2000 3:41 PM
H would be for Harris, Hassis bought RCA semis awile ago if I remember correctly. CA was a RCA prefix
3/16/2000 5:02 PM
Mark Hammer

Thanks for the info. It would seem that the design is pretty much the same one as before. Given the difficulty most people seem to have in locating 3094's, I was wondering if they had started using LM13700's or something. Apparently not. The cap tacked on the back is likely the biggest one there, right? 470uf or thereabouts?  
If my hunch and the info you offer line up, then the mods article should be pertinent.  
Steve, did you get the scan? Is it up yet? And what would the URL be for the curious folks?  
If anyone wants to repay the favour, look at the posted schematic of the J issue Small Stone, and let me know (by posting here) where the mod goes. As mentioned earlier, the mods article refers to pads, not to a schematic, so I can't tell where they would go on a homebrew.
3/16/2000 5:24 PM
Joe Fuzz

"The cap tacked on the back is likely the biggest one there, right? 470uf or thereabouts?"
No, not at all. Marked 104 = 100000pF = .1uF.  
"...look at the posted schematic of the J issue Small Stone..."
I looked over the schematic last night after I posted and it appears that one of the transistors on the schematic is an NPN and the other 3 are PNP. I just wanted to confirm that this is possible -- I can only read 3 of the transistors. The fourth one may be an NPN.

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