It's NOT the amp :-(

[buzzyreed]

So after driving my amp off to the fix it shop I came back today and installed my reverb. The Harrison Labs 'thing' did the trick. I then hooked both Flute and Main divisions up to one set of amps and hooked the speakers together... somehow....

Anyway.. I found out it's not the amp that has caused the popping and crackling as it still happens. It is something with the flute division. I reseated every board and put new RCA cables in where they were clearly needed.

For a few minutes, it worked and I had no popping or cracking, then it came back and I've run out of ideas.

Is it something big and scary like needing new boards or something?
I suppose it's just as well as I'll have to Midify this thing soon anyway...

[jbird604]

DAC board perhaps. That's about the only analog audio part beside the amps. Now and then they come up on ebay and sell very cheaply. I thought you'd already disconnected everything from the amp and it still popped, thus proving a problem with the amp.... Of course there can be more than one problem.

Look at the DAC board and see if it has some socketed chips. If so, pull them out, wipe legs with Vaseline and re-insert. Also look at the underneath of the DAC board and see if there might be bad soldering. Very unlikely but a possibility.

[buzzyreed]

So, I'm driving to my parents farm this weekend and I am wondering if the DAC board from my Allen Sys 600 or 601 or whatnot would work. They hardly ever use the organ and if I can get that one in there and replace the Sys 600 one at a future date when they become available on e-bay....

I added the Alesis reverb and honestly, it's a good little organ, fantastic by the standards of 1981 technology. I assumed it had all the same 'stuff' as my SYS 600 which I am sure was an early model MOS 1 organ, but I'm wondering if they didn't change a few things and tweak a few sounds because this 1981 organ sounds better than the 1973 organ...

[jbird604]

Many parts from the 600 will work in a later MOS, though there were changes over time. DAC boards were revised several times over the MOS era, so unless the DACs in your 600 have been updated at some point, they may be the old-style DAC1 or DAC2, while the 1981 organ will probably have DAC3, DAC3A, or even DAC4. It is possible to plug an older DAC into the socket instead of a newer DAC, and it might work. I say "might" because the early DAC boards got power through the socket, while later DACs get it through the piggy-back connector on top. Some newer MOS organs still have live power in the socket, some do not, depending on the serial number. (When subbing an older DAC for a DAC3 or 4, just leave off the piggy-back plug.) There is no harm in trying. It will either work or it won't.

So yes, get the DAC boards out of the 600, whatever type it has, and try them in the newer organ. If the problem goes away, you will know that your DAC board is at fault. If the problem remains, well.... I am puzzled. The DAC and the amp are the only audio parts, other than the sound relay and the "voicing" knob.

[thadfield]

I believe I have a spare DAC 2 and a spare DAC 3 or 4. If you want to try swapping it and you want to pay for the shipping costs (which I'm sure would be pretty minimal), I can send you one to try. If it fixes the problem, I'd be happy to sell it to you for what I paid for it. If not, you could ship it back. Your board will say on it what DAC it is (original, 2, 3 or 4) and I can see if I have one that matches. Contact me off list if you want to check one out. You'll get to your parents, though, before you'd get this... but at least then you don't have to rip into two instruments.

[buzzyreed]

That'd be wonderful. I tried to prvt you but wasn't sure if it worked.