Allen ADC-6000 Mystery Repair

[myorgan]

Well, y'all are on the right track. I just went to the organ today and tried John's suggestion of switching the two boards, and the problem moved from one set of stops to the other (attached photos). I believe the MA-1 board controls the tuning of the entire instrument, and not just a section, or frequencies distributed to various sections of the organ. The MA-2 may have done that, but not the MA-1.

So, I have a defective USFG-1 board without any sockets to reseat. Now what? I was hoping to get it done this week-vacation week, but I guess it's going to drag on.

Thanks, all, for your help.

Michael

[don60]

Michael, if you are feeling brave, try resoldering all of the IC pins on the bad board. I have fixed at least one of mine that way. Evidently, Allen's wave soldering was not the best during this era.

The next step would be to shotgun all of the standard TTL chips. After that, you will probably have to capitulate and buy a replacement from Allen--those puzzling S-152 chips are not going to be available anywhere else.

[circa1949]

speaking of puzzling

The next step would be to shotgun all of the standard TTL chips. After that, you will probably have to capitulate and buy a
replacement from Allen--those puzzling S-152 chips are not going to be available anywhere else.

Right, those are the chips that Walter Greenwood said "performed a few standard logic functions" or something. I bet the right outfit/individual could reverse engineer them pretty easily these days, if push came to shove. There's a whole subculture interested in doing that, they even have an open source program to help them interpret the traces.

No need to start a new thread for this...
I saw this on ebay:
http://www.ebay.com/itm/ALLEN-ORGAN-...-/380627939096
It's an ADC era TG-5. TG mean tone generator right? But this appears to have no sockets, or even EPROMS! Anyone know what this thing did? Did the very earliest ADC organs (1000,2000, 3000 etc.) actually use custom made memory ROMs? That's what those "RCA X 406" chips could be, perhaps?

DOH! I just remembered that's an alterable voice generator. Had a "still waking up moment!" It has 2 4-bit RAM chips to presumably hold the MSB & LSBs of what is on the 8 bit card, making it able to produce 1 alterable voice.

[don60]

Right you are--the TG-5 does not have EPROMS (at least my two do not).

I believe the S-152 must be used to decode the bit streams for stop and keying information that are generated by the multiplex board. The universality of the S-152 suggests that it performs a function that is needed throughout the system. Despite Walt's disingenuous remarks, I do not see any standard TTL chips on any of the boards that would perform this task--which is not as simple as one might first believe. Just look at some of the original Allen patents, where many low-level logic gates were used for the companion operation of generating the multiplexed data. And look at the multiplex board in the ADCs, which again has many low-level chips on it.

I understand that the Chinese are not above copying even cheap electronics such as network cards and graphics adapters for standard PCs. Perhaps if we marked one of these S-152 chips TOP SECRET and "accidentally" left it behind on a flight to Beijing, it would turn up on the aftermarket in a few months.

[jbird604]

I wonder if the S-152 is simply a frequency generator chip. The S-151 on a MOS2 KBA2 board is a frequency synthesizer, according to the schematic, though I don't know the function. I do know that there is a specific S-151"A" for the KBA2 board in the mixture computer of a large MOS2 organ.

[myorgan]

So, I have a defective USFG-1 board without any sockets to reseat. Now what? I was hoping to get it done this week-vacation week, but I guess it's going to drag on.

In light of recent posts about the USFG-1 board, I thought I'd update this thread.

I ended up getting the replacement board from my Allen repair person--sent through the mail, but the replacement board didn't work. I think I took pictures and will post both of them when I find them. Turns out the replacement board had one pin difference between my board and his board. I'm not sure if it was because of the generation (i.e. x000 vs x300 series) or what the problem was, but his board did not work. I ended up sending both boards to him so he could observe for himself, and he forwarded my board to Allen for repair. Of course, it was expensive, but the board came back better than it was. I ended up sitting down and playing the organ a bit while testing because it sounded so good.

Not sure if this will provide any enlightenment on the other recent thread concerning USFG-1 boards, but thought I'd update and share. I'll review the post and attach photos if/when I find them.

Michael