Allen 120C-3 Amp issues?

[Hiawatha]

Hi everyone,
I went back to the summer place and pulled the dust covers off of an Allen 120-3 that I haven't plugged in for at least 10 years. I gave up fixing it because I was in the middle of a DMA program from HELL.
There are two main issues:
1. The expression pedal does nothing, even thought I installed two Harrison Expression Pedal Isolators in the audio chain. I don't remember doing that, but here we are.
2. One of the amplifiers (the one with the giant white caps, which seems to deal mainly with Flutes, Strings, and Mixtures makes a lot of background noise. This noise includes popping, snapping, low level buzz, all encompassing buzz, etc. My iphone does not do it justice because it seems to have filtered out all of the higher spectrum.
a. This noise seems to get worse anytime I adjust the gain directly on the amplifier and
b. the brightness control knob
3. It is worse when the front tweeters are turned on with the "front projection" or whatnot switch

Am I to assume it is a simple matter of dying electrolytics? Can I just switch out the malfunctioning amplifier with the one from my old TC-3?
Is it more serious?
I'd love to get this organ going even though I'm getting a fully functioning 120-C on Wednesday. This organ has Salazional I and II, which I assume is some sort of celeste which, as far as I can tell is the only difference in the organs.
Here are video links that do a poor job of demonstrating the problem. The videos make it sound like one of those relay buzzer circuts we all made as kids, but really it doesn't sound much like that in real life, mainly just a mid to high pitched all encompassing hum with lots of crackle like listening to a baseball game play by play on AM radio when I adjust what I assume are potentiometers.
https://www.youtube.com/watch?v=yzUDvL3nDvY

https://www.youtube.com/watch?v=-EvMwPkKYys

https://www.youtube.com/watch?v=LIgbYWL4CFI

[you795a]

I am not sure about numbers 2 and 3 but number 1 could be a burned out expression lamp. It is located in the expression shoe housing.

[myorgan]

1. The expression pedal does nothing, even thought I installed two Harrison Expression Pedal Isolators in the audio chain. I don't remember doing that, but here we are.

You795a is right on the money with the expression bulb. It has either burned out, or the black dot on it has come off, thereby causing the expression to either be fully on or fully off (I can never remember which one).:embarrassed:

a. This noise seems to get worse anytime I adjust the gain directly on the amplifier and
b. the brightness control knob

Have you taken a look at the speakers? It sounds to me like it could be that the surrounds on the mid-range speakers have deteriorated. That is one additional possibility.

Can I just switch out the malfunctioning amplifier with the one from my old TC-3?

I'm not sure of the compatibility between the TC-3 amplifiers (probably T-50) and the MOS-1 amplifiers (probably S-100, Code 5, Code 10A, or Code 12). Read through this topic to see if the amps are interchangeable: https://organforum.com/forums/forum/...mplifier-codes.

I hope this helps.

Michael

[you795a]

If the bulb is not lit the volume is full. There is a shutter inside the housing and when the expression pedal is depressed the shutter blocks the light from the CDS cell causing the volume to get louder.

[John Vanderlee]

To me that sounds like bad speakers! If it sat for ten years make sure mice haven't gotten into the speakers. Most likely bad surrounds though. Pull them out and look!

have also seen where there was enough corrosion on the bulb socket, where it pops into the expression body, that it no longer makes contact with that body.

The amp with the big caps is the S-100 type.

[myorgan]

To me that sounds like bad speakers! If it sat for ten years make sure mice haven't gotten into the speakers. Most likely bad surrounds though. Pull them out and look!

Rather than pulling the speakers, you can shine a flashlight through the grill cloth, and get an idea of the condition of the speakers. If your grille cloth is the straw-type (as best as I can describe it), then you'll probably need to remove the woofer & mid-range speakers to assess any possible damage.

If the surrounds are cracked, or if there are losses, it is quite inexpensive to have the surrounds redone. If you're particularly handy you can do it yourself. There are a couple of threads here on how to do it yourself.

Michael

[Hiawatha]

But it only happens on the great, not the swell.

[John Vanderlee]

The materials cost is around $12 for a 15" woofer, considerably less for the midranges(although I find those a bit more difficult to do)
Oh yeah, plus shipping!

[John Vanderlee]

You may have more going on, but dont forget 2 amps means 2 separate channels each having its own speaker(s).

[Hiawatha]

It's been so long since I've had time to fix up my old Allens that I'm afraid that I forget how they work. I think I may have actually purchased a new computer board about ten years ago and replaced some chips (I don't remember which ones, but I do remember that when I pulled them with the chip puller it flew out and embedded itself in my left hand, that was "interesting." The organ has not changed sine I put it on mothballs. I suspect I may have even taken the amplifier to the repair shop. No matter, I guess I'll just use it for spare parts for my other MOS-1 organs.

[myorgan]

But it only happens on the great, not the swell.

That's because it is quite probable the Great and Swell are on different channels, therefore, they use different speakers. Generally the Swell is separate, and the Great and Pedal are together on smaller organs. However, with MOS-1 organs, sometimes they had "Flute" and "Main" channels rather than separation by keyboard, so it would depend on which stop you're using.

If you can identify exactly which stops on the Great are causing the issue, we can help you further.

Michael

[Hiawatha]

So here's a better recording of a run through of the stops. Telling, I think, is that the Dulciana doesn't function at all. There is also a low grade, but rather loud in person, hum. The weird distortion is especially prominent in the 1' flute stop. Any ideas? The sound today was different from all the other times as there wasn't this "ghost f minor" hum at all times. I'm suspecting something is really wrong with the amp...

This first video includes the 1' (sorry it's piercing and loud) but shows the distortion I'm talking about.
https://www.youtube.com/watch?v=pSZOf3Ns3L4

Here's the Great:
https://www.youtube.com/watch?v=N8PLTb-gBD8

Here's the Swell:
https://www.youtube.com/watch?v=gxII_rwQAc8

I didn't bother with the pedal now as the whole thing is in a tight area in my garage and didn't feel like bringing it out.

[John Vanderlee]

I have trouble following you. I think you keep starting a “new topic”. Anyhow, have you visually inspected the speakers?

[myorgan]

Sorry to be so long responding. I just returned from a week-long trip.

One of your amplifiers is obviously quite a bit louder than the other. Stops should be in order from left-to-right, loudest-to-softest in each pitch level. Yours are not. If it's in a location where the temperature fluctuates quite a bit, that could have caused the problem. Personally, I'd find two S-100 amplifiers that have been tested, and use those instead of what you have.

The hum you describe comes through on the videos. I've never heard leaking capacitors before (sometimes called "caps"), but from what I've heard, it sounds like that may be the issue creating the hum. If they are about to "give up" on your amplifiers, that could be the cause, but don't quote me on that.

I suspect if you clear up those two issues, your 1' distortion may resolve itself.

I'm not an organ tech, so please wait for those who are techs to weigh in, but I believe I'm on the right track.

Michael

[Hiawatha]

Thanks, as always, for your help. I'm sorry the postings have been a bit confused and that I've been late updating them-- I'm in the process of moving back to my summer place for a few months and it's always a big deal. They made it look so easy in "On Golden Pond."

[Hiawatha]

Well I looked and it appeared that the DAC card was out of its socket. I put that back and it sounds like it did before. I wonder if that's not the source of the problems. Perhaps a new one would fix it. Alternatively it could be the RCA connectors. They appear to be original (except the ends I put in years ago— and the organ sounded like this ten years ago too, so it's nothing I have changed that seems to be causing the problems. I checked the sorakers and there is nothing obliviously wring with them to my eyes... sigh

[myorgan]

Hiawatha,

Please stop creating new topics on this issue! I believe I now have them all merged into this one topic, but it makes it quite difficult for people to help you if you continue to create new topics on the subject.

Thank you in advance for your help.

Michael, Moderator

[John Vanderlee]

Thank you Michael, I stopped responding because I lost track of the topics.