Allen quantum speaker/amp issues

[smp]

Hey guys

I'd like to get some opinions before I call-in one of my local tech's. By the way, the closest tech I have tends to prefer to go straight to ordering parts before even attempting to diagnose things- the other, older and more experienced tech seems to be much more on-the-ball with diagnostics but he is more expensive. I guess I just want a few opinions before calling the better guy. He is worth the money- I know that much.

So here's my issue (I have a Q345 heritage by the way)- intermittently, there will be a dead channel on either the swell or the choir manual, sometimes both. Sometimes all stops of the affected division are affected sometimes only a few stops. Weird, right? This started happening a few months ago. Sometimes everything will be perfect and I won't have issues at all until a while into practice and a choir channel might die suddenly. Also, sometimes I'll hold a chord and hear crackling from a choir channel speaker. While holding the chord, the affected channel will die then come back again. Same issues on the swell a lot less frequently though.

Heres what ive tried - exercising pots on the amplifiers for all channels. (Gently) Pulling and re-seating all inputs and outputs on the Amps. Pulling the Audio boards from the organ computer cage a little then re-inserting them. Pulling the cables from above the audio boards then re-seating them. I have not yet tried pulling and re-installing the speaker wires at the speaker ends. I am hoping this is not a power supply (nor an amplifier) replacement situation.

Any ideas? Very frustrating of course. And I also don't want to call a tech just to hear (we'll replace the amp and see if that works) when there might be a simple fix.

[jbird604]

You could have bad horn drivers in the two HR-200 cabinets (the affected channels). Just this week, we serviced a Quantum H4-79Q custom 4m where the organist had reported an occasional "static" or nasty sound quality just on certain notes of certain stops. A second person had gone up into the chamber and identified the speaker cabinet that was the source of this (even though it didn't happen all the time). We were able to quickly isolate the trouble to the tweeter in the HR-200. We replaced the driver on the horn and all was immediately made well.

There has been a bit of a history of failure with these horn drivers, for some reason. I've probably replaced a dozen of them over the past 15 years. Not that many, but enough to tell me that they do fail.

You should carefully play note by note chromatically on each stop in the affected divisions, locating the notes that sound bad. Then block one down and see which speaker cabinet it is in. You can swap the speaker cables to verify that it is the speaker that is at fault. You can even swap the horns if you're inclined to go that far on your own.

The driver is easy to change. It has spring-loaded tabs holding the signal wires, and the driver unscrews from the rear of the horn. Just order a new one online and change it out.

[smp]

Thanks so much John! You are a legend. I'll try your diagnostics and report back soon!

[John Vanderlee]

The failure is usually the element in the driver which is easily but carefully swapped out

[jbird604]

Could be something else entirely, of course. I just thought of the horn driver because it was fresh on my mind, and your mention of the "crackling" sound reminded me of exactly what we heard on this Allen.

Since the trouble is intermittent, it seems unlikely that it will be a defective board in the cage. Typically, the cage boards either work or they don't, rather than being intermittent. It's audio components that come and go.

BTW, does the sound go through an antiphonal relay on the way to the speakers? That is also a common failure point in the audio path. If there are antiphonal relays in the console, you can bypass them entirely by moving the speaker cables to the screws on the antiphonal assembly where the signal comes in from the amp, instead of having them on the actual "main" or "Ant" screws. That disables the antiphonal function, of course, but it does take the relay out of the circuit and will either confirm or rule out that it is the problem.

Trouble with relays is that the audio signal has to pass through what I would call rather flimsy and sketchy connections inside that little "ice cube" relay switch, where just a tiny bit of dust or corrosion can disrupt the good electrical contact and produce distortion or noise. Allen's antiphonal relay system is one of my pet peeves!

[smp]

John

I'm not too sure about antiphonal relays. How about I take come detailed pics and drop theme somewhere here? Thank you both gentlemen for your time and advice for which I'm super grateful!!

[jbird604]

Take pics of the assemblies and wiring in the floor of the console and the terminal strips where the speaker wires are screwed on. That will tell me whether or not you have relays installed, and I can give you detailed instructions about bypassing them, if present.

*You can simply post pics here for all to see.

[smp]

John

so i tried switching the choir channel output cables then input cables at the amplifier. No change doing either thing - still had a dead channel. Or at least greatly weakened channel. Chromatically of course - every other note was waaaaay softer. One of the choir channel speakers is definitely crackling when I hold a chord on that manual (with choir stops only drawn, nothing coupled from the swell). Again sometimes I'll turn the organ on and this issue won't be present. I wonder if this would lead you to believe the amplifier is bad...I'm sorry these pics are terrible and I will try to get better ones on Friday at some point. I hope you can make out something helpful at least!

[smp]

[smp]

[jbird604]

The pics are fine. They show that you have no antiphonal relays installed, so we can rule that possibility out.

If you switched the OUTPUT cables and the problem stayed with the same notes of the same stops, then your speakers are ok.

If you switched the INPUT cables and the problem still stayed with the same notes of the same stops, then your amps are ok. (Had the problem moved to the OTHER notes of the scale, then I'd think the amp was bad.)

So make sure that the exact same notes in the chromatic scale on the exact same stops are still weak or absent regardless of which way you swap either the input or the output cables on the amps. If that is the case, then the trouble MUST be upstream from the amps, which points to the cage, of course.

Just last fall we had to change out the audio processor board (JCF-4) on a Quantum organ because one audio channel was dead. I believe in that cage it was the board in the far right-hand slot, the one with the audio output cables attached on top, running to the amps. (Some larger models have two JCF-4 boards; if yours has two, it could be either one.)

Be sure to have the organ turned off and UNPLUGGED FROM THE WALL before you pull anything out of the cage, as there is power to the cage even when the organ is off. Be sure that you have discharged yourself to ground so you won't be carrying any static electricity before touching anything inside the organ.

Pull out the JCF-4 board (after carefully disconnecting any cables attached to it at the top. Then look to see if there are any socketed components (such as a SIMM or DIMM module) that you could carefully remove and re-seat. Then re-insert it into the cage "firmly but gently" to make sure it is properly seated into its socket. Re-attach the audio output cables, also with that "firm but gentle" pressure, and make sure they are seated into their output jacks.

Speaking of audio output jacks, take a very close look at those plastic Molex plugs and sockets on the top of the audio processor board. Make sure the wires are securely crimped into the pins and that the pins match up squarely with the mating parts in the socket.

While you're working on the cage, you should also gently pull and re-seat each of the other cards in the cage after removing any cables that attach on the top of the cage. There's always a chance that some card is not making solid contact with the backplane of the cage. Some cards may have socketed components on them, which need to be firmly pressed down to make sure they are tight.

Beyond these measures, there isn't anything that you or even a tech can do besides getting the JCF-4 factory exchanged. It costs several hundred dollars for the swap, but in the case of the organ we worked on last fall, it was the solution. That was the first time I ever had to change out a board in a Quantum cage, so they must be very reliable and have a very low failure rate.

[smp]

Hey John
So tomorrow I will switch input then output cables again and detail the differences so I can tell as you're saying if the speaker is the issue or the amp. I do have 2 JCF-4 boards and I have tried re-seating those gently only once each and re-seating the audio wires from above again only once gently. Thank you so much for your guidance. I do hope I don't need a board - especially now that my one-year dealer warranty has probably lapsed.

[smp]

Hey

Reporting back! So I sat at the organ today with a pen and paper to properly take notes. Here's what happened -

1) Turned the organ on. No issues at all - everything sounding as it should.
2) Left the organ ON, walked away. Came back to the organ after about 10-15 minutes and sure enough - dead/greatly weakened choir channel.
3) Opened the organ and switched output cables for the two choir channels - no difference.
4) Switched the input cables for the two choir channels - problem immediately solved.
5) Left the organ ON, walked away and came back to it after about 10-15 minutes to check if anything changes - no changes - everything sounding perfectly as it should.

Questions - are we thinking bad speaker, bad amp, poor wiring, or still problems on the JCF board(s)? Is it safe and wise for me to leave the input wires switched as they are right now, even just to see if it solves my issue permanently over the next few days? I feel like leaving things as they are for a few days would help me give better details to you for further diagnostics.

[jbird604]

Step #3 seems to prove that the speaker is NOT the problem. But that is about all you can say at this point. Had the problem moved to a different set of notes, we could say that it was the amp, but since it didn't do that, we still don't know.

I'd leave it like it is for a while just to see what happens. Could be something peculiar such as the input connector itself not seating properly on the pins of one of the amplifier inputs due to one of the plugs having a mis-shapen pin or ring inside. Or could be the crimp where one of the wires attaches to the metal pin or ring inside the plug. Or even a bad solder joint inside the amp where the jack attaches to the circuit board.

At this point, you won't really know unless it recurs and you can swap inputs again to see if the problem moves.

Your choir division probably has a C-C# split scheme of some kind. As you play chromatically up the scale, the notes of an individual stop should move back and forth between the two channels. So you could put on a single stop such as an 8' flute in the choir and play chromatically to see how this works. You will find that it is not a strictly C-C# arrangement, and at certain points you will have two adjacent notes in the same channel as the scheme reverses.

Anyway, if the problem recurs, put on that single stop and play chromatically to see which notes in the center octave are affected. Then reverse the choir input connectors again and see if the problem moves to the OTHER notes in the same octave. That would be the proof that the trouble is inside the amp itself.

[smp]

Hey John

So today here's what happened -

turned the organ on, practiced solid for a good 30-45 minutes with no issues at all (kept the choir input cables switched from yesterday).
Turned the organ off to take the dog a walk, came back around 20 mins later, turned the organ on and the issues are on both the swell and choir manuals (I wouldn't say DEAD channel, just greatly weakened channel...maybe it's the same thing?). Definitely hear what you're saying ie the C-C# split. Very frustrating. Switching choir inputs and outputs again does nothing - doesn't move the affected notes, doesn't bring weakened channel back to 100%. Haven't tried anything for the swell channels yet.