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Author Topic: TR626 WAVEFORM ROM  (Read 6852 times)

C M O S

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TR626 WAVEFORM ROM
« on: December 05, 2009, 07:51:03 PM »
I  have the datasheet for the 2 mbit waveform rom used in the 626 drum machine. Does anyone know if there is anyway of getting a spare?? I think that my original has become corrupt. I have some service data for the 626 and i am going to do some diagnostics around the ics. The display seems to work fine, when the start button is pressed there is no activity from the tempo led. It would seem that the tempo ocillator is constructed around a cmos 4069 of which i believe is ocillating but it's output is gated. The gating action is controlled by the fsk chip BU3904S. I have only spent a short time trying to comprehend the circuit and i am still trying to understand what the fsk chip is actually doing in the circuit. The DAC circuits in this thing are quite primitive and i can understand now why this thing is so highly bendable!! ;D I have read on the web that someone has used a copier to copy the data from the rom chip, if so does anyone know what reader was used to achieve this. I am beginning to understand the data structure of this ic but i still have quite away to go. I always try to understand how the system functions before bending any piece of kit, this usually prevents catastrophic damage. I will when finished post some of my own circuits including a DR55 i have completely built from scratch.
« Last Edit: December 05, 2009, 09:38:49 PM by C M O S »
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C M O S

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Re: TR626 WAVEFORM ROM
« Reply #1 on: December 05, 2009, 08:45:24 PM »
Got the tempo working, a 4069 replacement sorted this out.
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Gordonjcp

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Re: TR626 WAVEFORM ROM
« Reply #2 on: December 06, 2009, 04:57:59 PM »
The ROM is a plain ordinary 2Mbit ROM, like a 27C2001.  The samples are in a fairly scrambled order though.  I wrote a bit of software to descramble the ROM, but I can't find it at the moment.  It *is* possible though.

If you want a dump of the ROM, I can stick it up somewhere.  The ROMs rarely fail, though - the chips that drive it are fragile and do cause trouble.
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If at first you don't succeed, stick it through a fuzzbox.

C M O S

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Re: TR626 WAVEFORM ROM
« Reply #3 on: December 08, 2009, 12:16:03 AM »
The gate array has been fried in this one (63H). Custom roland chip?? nothing around on the web. Could not see any activity using a scope. I suppose you have to ask yourself...is it worth repairing?? Thankyou for the offer  for a dump of the rom data, That coulld prove interesting. I did say that i would post a schematic and service data for the 626 From MR McGINSKY. It has his stamp all over it and it is a secure PDF. I  did pay a little money for it and i am  still considering a post when i get round to it. Could you maybe put a link on the forum for the ROM DUMP?? I will let you know if mine has the same data.
THANKS GORDON
p.s Nice site by the way!! 8)
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