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Allen Printed Ciruit Boards

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  • Allen Printed Ciruit Boards

    Can anyone tell me if you have heard of the foil bubbling up on Allen printed circuit boards? I have an 80's ADC series and have noticed that many of the boards in both cages are bubbled. No apparent breaks in the clear coating over the foil, and no breaks in the foil itself that I can see, but I am having some issues and had read somewhere about this problem. Just wondering if anyone here has had any experience or knowledge of the issue. Allen is known for your quality and build all their on boards in-house, so I'm looking for insight.
    Many thanks

  • #2
    I know what you are talking about, but I believe the wrinkling is actually in the coating rather than the foil. I just looked at one of my ADC boards that has this problem, and in one of the wrinkled areas a bit of the coating has been scraped off to reveal a perfectly flat foil beneath. Allen might have dipped their boards to apply the coating and gotten a bit too much on.


    • #3
      Often the circuit board traces will appear crinkled when 1) the solder resist mask is exposed to the high heat of wave soldering; 2) solder flows under the solder resist mask.

      If the circuit trace foil is truly moved away from the substrate surface, you can tell with a magnifying glass and by touch.

      The ONLY time I know of circuit traces lifting is when repairs are done and excessive heat is used. These almost always are at a pad (soldering point), and can be repaired with small (say, 30 gauge) wire.


      • #4
        Oh great news! Thanks so much, I feel better. I need to take a closer look.

        - - - Updated - - -

        As with the other post, I feel a lot better. This is an 8000 and a total of 16 of the boards are this way. As I stated earlier, I am having other issues for which I am waiting on an opinion from an Allen rep. Allen builds such a superb product, all in house, so I was spooked by seeing this in view of the issues I am having. I have had their products that date back to the early 70's and in my opinion, there is just nothing that can compare with their quality.
        Thanks so much Toodles and Don60 for your comments. The organ has suddenly crashed. Most of the Great and Swell are gone. The pedal and Choir are functioning pretty much as before, but when you select a registration with a lot of reeds, it sounds like every key and pedal on the organ is being played. The Reeds on the Swell are also ok. Very strange. I have told to check the batteries on the A Cage, and they were low, so I will replace those. We will see what Allen folks say and who knows, one of you smart guys on the forum might give me a solution as well.


        • #5
          Your problem is almost certainly in the A cage, which produces the stops you mention as being bad. The only purpose of the batteries is to retain alterable memory through a power-off; the organ, and in fact the alterables themselves, will work just fine without them.

          As the fellow said, "It could be anything." The ADC troubleshooting chart fingers almost every board in the cage as a possibility.

          With a second cage, you can if you are adventurous swap boards between them to try to isolate the problem. Recognize that boards having EPROMS (socketed chips) will not work quite as intended in most cases unless you swap the original chips onto the test board. To avoid possible damage to the chips, you are better off just to keep them where they are and understand that the test board might not restore operation perfectly--but it should solve the major problem. To be safe, swap only like-for-like--that is, only substitute a board having exactly the same designation such as FG-1. Experienced techs know that some cross-swapping is possible, but they normally have replacement boards in their caddies and don't need to do so.

          Although the technique does not work with any other boards, you can also try removing the EG cards one at a time--the organ will play without them although the attack and release will sound abrupt because the amplitude envelopes will be gone. Allen says that you can "pop" the boards with the power on--but you should not put them back with the power on! For some reason, a single bad EG board can cause dead stops served by other EG boards, so don't overlook this simple test.

          Otherwise, given the extent of your problems, the bad board is probably one in common to the entire cage, probably a KA (key assigner) or MA (master) board. Allen says the MA is the very last to suspect since it has few problems. So a KA is the likely suspect for "crazy keying" and dead divisions.

          The other major line of inquiry will be the multiplex board that encodes stops and keys and sends serial data to the two cages. You cannot troubleshoot that board except through substitution, although you can check to see that the cables are all plugged in properly. This board is usually located on a swing-out panel at the bottom of the console--it should be marked US-CM1 (for "univeral system console multiplexer"). Given that an entire cage is apparently faulty, you could have a bad data output on this board.

          It is quite possible that all of these problems come from nothing more than a poor connection--probably in a socketed EPROM. I have had a few ominous-sounding problems in my own ADC that were cured by reseating chips. You can certainly try prying each chip partway out of the socket and then rocking it gently back into place to burnish the contacts.

          Occasionally a bad solder joint shows up on these boards as well. I have cured other issues on my organ by resoldering the suspect board.

          If all else fails, your Allen tech can probably find the problem in ten minutes if he has a full complement of replacement boards with him. The replacement will not be cheap, but it will probably be just a single board. (If you sustained a lightning strike, however, multiple boards could have failed.)

          Good luck with your troubleshooting.


          • #6
            Thanks for your great overview of the issues. I think switching boards and prying out chips is a little more than I feel comfortable in trying. I need to digest this a little. I appreciate your detailed explanation.