I’m devastated!

[Vebo]

Suddenly tonight, I lost 90% of the volume on all my Tibias on my ADC 3500, on all manuals and in the pedal. It's unplayable like this. HELP!?!? I already had an issue with my Tibias on ACC being half volume of the Tibias on SOLO. I'm in a Tibia mess. My organ is sooo hard to move for maintenance. *sigh*

[AllenAnalog]

I can't help with the technical issue but have resigned myself to the fact that my older instruments can no longer be situated so they cannot be moved easily for service. It is especially annoying when you spend 3x the time moving the console than you do fixing what turns out to be a trivial problem that is solved by exercising a pot or re-seating a cage board.

My 3-manual analog theater organ is especially difficult to move since the pedalboard is hard wired with multiple connectors rather than being magnetic.

[myorgan]

Vebo,

Are all the Tibias that lost volume on one channel? If so, follow the sound from cage, to amplifier to speakers. You might find the issue there.

Another possible cause could be that the LDR light for the Tibia expression pedal has burnt out, or alternately has lost the dot on the bulb the LDR uses. There are a few threads on the Forum about how to fix that issue.

Personally, all my larger organs are on rolling platforms for ease of movement, as well as for maintenance purposes. Alternately, you can place the organ with one side against the wall, but I'm sure that defeats the purpose for having it in your house in the first place (looks).

Hope this helps a ltitle.

Michael

[Admin]

A burnt out lamp in the expression pedal will cause the sound to go to maximum loudness, not minimum.

[myorgan]

Thank you, Admin. I couldn't remember which way it would go. However, with the loss of a dot, would that make it go to the softest level? I've read about them flaking off before.

Michael

[Admin]

The dot prevents the lamp's filament from shining directly on the LDR. Without the dot there could be sudden decrease or increase in level when the mechanical shutter allows the hot spot to shine on the LDR or hides it. If the spot falls off, the level could decrease somewhat when the shoe was all the way closed, but the maximum level when the shoe was open, and the light totally blocked by the shutter, would remain unchanged.

[Vebo]

This morning, some of the volume returned, but it sounds like it's coming from down a long hallway (that could be the NanoVerb working overtime with what signal it's getting). As far as channel, I don't know, I'm using the internal speakers. Just as a test, I tried my Tibias available on Alternate Voice tone card. As expected, they are fine. I have a busy day, but look forward to thoughts and suggestions, will tackle the issue as soon as I can.

[AllenAnalog]

With my morning coffee now in hand I'll contradict my post (#2 above) and try to be more helpful.

For troubleshooting any ADC era instrument, if the issues are impacting the overall tone generation and not individual keys, pistons, transposer, etc. you must become intimately familiar with the cage chart for your organ. It is the key to understanding how a sound goes from the digital data in the EPROMS on the tone generator cards to the amps and then to the speakers.

Once you understand how Allen formatted the information on that chart, you can be very logical in your troubleshooting. There is a copy of the 3500 cage chart in the information I sent to you via email.

Of course checking cage voltages, exercising pots (after noting their current position) and re-seating boards in the cage after cleaning the edge connector traces are always good practice when an instrument has not been serviced in a while or if you are experiencing problems. Moving on to re-seating EPROMS in their sockets is a further step you can take if necessary.

The one thing about your problem that puzzles me is that you only lost the tibias - on both manuals and the pedal. The tibias do not have their own separate tone generators. All of the voices for the pedal, the accompaniment and the solo manuals come from a tone generator specific to that keyboard. Likewise, the orchestral voices have a separate TG board so you have those four TG boards plus the one for the alterable voice.

******************************
EDITED TO ADD:

A tone generator (TG) board does not act independently. It's operation is connected to the cage master card (MA), the key assigner card (KA), the frequency generator (FG) card and envelope generator (EG) cards associated with it. The MA and KA cards are for the entire cage. The FG and EG cards are assigned to specific TG cards in the cage and that connection is shown in the cage chart.

Since a theater organ is unified, the spec for your organ says "42 stops from 16 equivalent ranks." Obviously there is some clever switching going on with the system to give you multiple pitches from the same tone generator data. I suspect that happens through the console multiplexer board and perhaps also the FG-1 frequency generator card in slot 4 of the cage.

HOWEVER, you also have an envelope generator (EG) card in slot 6 that affects the output of the tone generator cards. After looking at the cage chart I see that one IS common to the pedal, accompaniment and solo.

Other people on here ("myorgan" comes to mind) have had problems with the EG cards in the past so right now that is my favorite potential culprit for you problem since it might just affect the tibia voices at all pitches. There is a second EG card just for the orchestral division and alterable voice. The fact that your orchestral voices and alterable voice are working OK leads credence to this suspicion.

This is one of the few cards you can temporarily remove from an ADC organ cage and still have the organ work. It just won't have the proper "attack" envelope when a key is depressed. However if it malfunctions it can keep tone generator outputs from sounding at the correct level.

I'd suggest removing it (with the power off) to see if your problem goes away. If it does, try cleaning the edge connector traces and re-seating the EPROM on the board. Put it back in (again with the power off) to see if the problem stays cleared or if it returns. (Note: Allen says you can pull this board with the power on but I prefer not to do that. NEVER put a board back in with the power on.)

**********************************
Back to my original post since this is still good troubleshooting infomation:

What they have in common is that four of the cage outputs go through a mixer board and two of those cage outputs also go through Trem3 boards before hitting the mixer input. Both of those boards have pots that may need exercising and the trem boards are also potential points of failure.

Sometimes when there are multiple devices between the cage output and the amplifier input, it makes sense to run a temporary RCA cable directly between the cage output jack and the input jack of a known good amplifier channel. That way, by removing any potential problem device from the audio chain you can eliminate suspects.

Of course testing the amplifier channel with an external signal from a CD player or something similar is important so you have confidence that the amp is not your problem. Following a logical troubleshooting path and making notes about what you find (not trusting your memory) are highly recommended. But that also applies to defining the symptoms. I would test each stop on each keyboard and note your findings before pulling the instrument away from the wall. That may turn up additional clues for your troubleshooting.

[Vebo]

This information is PURE GOLD. I feel bad I declared tibias were alone the problem, I've been working on a simple piece, and trying to learn constraint in registration. With the panic that something seemed/is wrong with my new baby, I panicked rather than doing a proper check. I feel bad about wasting your energy with incorrect information, but: you managed to see beyond the misinformation, and in doing that, helped me start to understand how the system works. Thank you so much for patiently sharing your knowledge and time!

[Vebo]

Had a busy day, no time to work on diagnostics, nevertheless developed a plan for moving heavy furniture near organ and storing elsewhere while I bring my baby back to good health.

[Vebo]

I think there may be some clue as to why all my Tibias are tied to each other in this post:

https://organforum.com/forums/forum/...e-my-self-test

[AllenAnalog]

No matter how your stops line out in your mind, the tone generator listing in the cage chart is the final word on what is happening inside the organ.

The tibias are not all tied together from a TG board perspective, originating in four different sections on three different TG cards. The same envelope generator feeds all three of those TG cards. That's why I'm suggesting you check that first.

[Vebo]

Thanks for the info, Larry! I have a plan for moving (and storing) some of the furniture while I work on the organ. It will take me a while to implement it, meanwhile I'll do more testing/diagnosing/praying and studying up on exercising the pots, etc.

[Vebo]

Ok, today's diagnostics...the failures are more than just tibias, it's spread across 21 different stops across PED, ACC, and SOLO, including the percussion. No floating ORCH voices are affected. Looking at that chart, this means either 3/4 of the TG cards were affected at once, with only some voices on each TG affected, or maybe the problem is elsewhere. The sleuthing continues.

[Vebo]

Mulling over today's diagnostic tests, and somewhere back in there the plethora of other possible issues mentioned here... I am wondering. I have two very curious cats. The ADC 3500 is before Allen started “caging in/out” the expression pedals. I wonder if the skinnier of my two cats went exploring...he gets devious around 4:30 am.

[Vebo]

Ok, Y'all are gonna think this Munchausen syndrome, but as another test, I left the organ powered up all evening. All the voices are back (right now). Next test, what happens after powering down and up again.

[AllenAnalog]

Presuming your card cage has its front cover on and the cat did not pee on the vented top of the card cage, this continues to point to the EG card in slot 6. Once you can access the back of the organ the first thing I would do after taking off the cage cover is to pull the EG card in slot 6.

[DaveADC6500]

Hello All,
I have joined the group and can already see by Larry's post that this is a worthy investment.
Larry's right. You have to stick with following the data that you have.
I only have some block diagrams but it's been enough to get me through some times when I've lost half of the organ.

I worry about the next time when I may need an IC instead of a bulb or pot exercise.
Now that will be a real problem. But so far my ADC6500 is still going. Good luck Vebo
Dave

[AllenAnalog]

Dave, welcome to the Forum and thanks for posting. Based on reading the specs, your ADC-6500 looks like quite the nice instrument.

While the "golden age" of Allen ADC-era instrument technical discussions on here seems to be winding down (witness the lack of responses to a more technical thread of mine on here) the availability of cage and external boards on ebay, Daffer, etc. is still quite good for these instruments.

If a problem does not stem from a defective EPROM but some other component failure, you can still buy a used board and transfer your existing EPROM on the problem board to the replacement board. Some of the cage boards do not have EPROMs so that makes the exchange even easier.

Worst case, dollar-wise, you can still get an exchange board from Allen through your dealer.

Fortunately, some percentage of problems just come from pots that need exercise (don't we all?) and boards that are no longer making good contact with the cage edge connectors.

[Vebo]

Today, the problem voices are back to low volume upon switching organ on. Am going to leave on for a while and see if I get my voices back again after it has thoroughly “warmed up.” Three more clues though:

1. There is just enough volume on the affected voices that I can hear (I think) the attack in the sound envelope is markedly slow. Important because of what Larry said regarding the EGs above.

2. This all started when the arctic blast hit (and the back of the organ is near a drafty window). You know, that Arctic Blast that's in the news right now. Maybe that's why it came back after being on all evening - it overcame being too cool (just guessing, it's around probably 60F near that window when heat goes lower during the workday and we are experiencing very cold conditions).

3. I matched up the affected stops/voices with the cage chart. Note that the percussion stops on the ACC aren't listed on the chart, so I had nothing to mark for them but they are also affected, but LOOK, a PATTERN! (DATA!) I'm still figuring out the chart, but all the affected stops are in the A row.

Finally, I've resigned myself that I need to do the basic service and voicing jbird outlined in another post I found (https://organforum.com/forums/forum/...en-adc-voicing), but I'm going to make that a different thread, because regardless of what happens with this issue, that just needs to be a thread on its own.

[myorgan]

Vebo,

That cage chart makes me believe the EG-1 card in Slot #6 is the culprit. Try removing it and see what happens to the voices then. It turns out Larry may actually know what he's talking about-go figure!;-)

FYI, sometimes service people will use cold to diagnose solder intermittent issues. Your window may be doing the diagnosis for you. Let us know what the result is.

Michael

[myorgan]

P.S. Make sure the organ is OFF before you reinsert the cage card. Sorry, forgot to mention that.

Michael

[Vebo]

Ok, I pulled eg1 in slot 6. The affected voices were just barely hearable, just like before I pulled the card. I cleaned the contacts with alcohol, and reinserted it, still no change.

What else might all these voices/stops have in common? I guess I'll proceed with pulling each card, cleaning contacts, and start exercising pots after noting position

[Vebo]

I think the temperature thing may be a red herring. Approximations: at power up, 30% volume of affected voices, 3 hours later, 50% volume, 4 hours later, 15% volume, 5 hours later, less than 10% volume. It's been toasty in here since +1 hour.