[sdiy] TMS3617 pinout and bizarre size note.

[Bob Weigel]

I've been trying to get this Crumar Composer worked down that has been 
over here for a while.  I got it all working and a chip stopped 
working.  I found a guy on ebay who had them for 21.00 in china.  
Ordered three because I thought I might have a couple more but turned 
out to be a bad cap taking out the High C.  Anyway i get the chips 
and...surrrrprrrrrissssseeeee... they are smaller!  28 pin .1" spacing 
on the TMS3617NS in the machine.  These smaller chips with closer pin 
spacing have EXACTLY the same number!  TMS3617NS.  I've never seen a 
mfg. do that.  Anyone?

Now I do have this same chip package in a TMS3615NS .  So....it would 
make one think maybe.  On the other hand, it's very possible someone 
simply remarked those chips to make a bunch of money too.  THE EBAY 
SUPPLIERS SEEMS TO HAVE AMPLE QUANTITIES OF THINGS LIKE UA726 
chips...for cheap.

Hmm.  The sad reality is..there is big money in running  a business 
where you remark chips and the few who complain you simply give a 
refund.   The *others* rest peacefully thinking the have a cache of rare 
chips at a good price.  THEN..years later when they actually NEED one 
and find out it doesn't perform at spec.... what do they do?  Nooo 
warrrannttyyyyyyy....  I hope it's not one of those deals anyway...

Meanwhile here's the pinout from my measurements:

1- 1 Mhz Clock roughly it appears.  4V to 11V or so trough to peak.
2- nc
3- C trigger (These lines dive to .7V or so then gradually rise when 
*that* key is pressed.  If OTHER keys are pressed the voltage goes back 
up to 11.5Vish)
4-C# "" ""
5-D  "" ""
6-D# "" ""
7-E  "" ""
8-F  "" ""
9-F# "" ""
10- Can't figure.  Line sets at a voltage set by a transistor/resistor 
circuit.  No matter what I do it doesn't move from 4.8V or about there.  
Perhaps it's a Chip enable that has a power up circuit.  No time to 
check now.
11-Pull down 100K to -12v.
12-  2 2/3' output to transistor buffer
13-  2' "" ""
14-  8'
15-  5 1/3'
16-  4'
17-  16'
18- Gate.  9V until key pressed.where it dips to near ground.
19- 12V with 10ohm fuse resistor
20- G trigger "" ""
21- G# "" ""
22- A  "" ""
23- A# "" ""
24- B  "" ""
25- HIGH C "" "" (When used.  Otherwise wired to +12V supply)
26- nc
27- 2 mhz clock
28- Ground

I haven't checked yet where the clocks are sourcing.  It may be there is 
an internal dividers for the 2Mhz clock..I dunno.  -Bob

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