1959 M3 - Percussion sound VERY low

[proche3]

Hi,
Over the last year, the organ's percussion circuit would sometimes take awhile to "warm up" and the percussion sound would work just fine after about 10 minutes from when I turned it on, now it is just "stuck" at a very low volume, even after waiting awhile. Every key makes a percussion sound (except for the last 6) but it's just barely noticeable, certainly too quiet to be of use. Any thoughts on what needs fixed? I received this from my father a few years back and have enjoyed it a lot. I noticed when I got it that the tubes are all black, but I haven't done any service to it except annual oiling around X-mas time. Other than this minor issue, it's worked perfectly. Thanks for your time.

-Pat

[Tonewheel]

Sounds like tubes.

[bourniplus]

Hi, if you have spare tubes, you might try replacing the percussion tube.
However, the most common source of problems with percussion seems to be dendrite in the manual. A possible "fix" is to zap the dendrite with one or two 9v battery(ies). Dendrite can also be present in the percussion switch assembly, which could be cleaned.

[Tonewheel]

Good thought. I did this with my A100. Here's one reference: https://www.hammondx66.com/wp-conten...n-on-B3-C3.pdf

I was too much of a chicken to go further than the batteries!

[proche3]

Thanks for the replies! I don't have a schematic to tell which tube is the percussion tube, but I've attached a photo if you can point me in the right direction. I do have some used but still working JJ guitar amp tubes, 6L6GC (power tubes) and some ECC83S (preamp tubes) will either of these work? Do you recommend a full tube swap at this point based on that photo? Best place to get them for a fair price? As far as zapping the dendrite, I've seen this done on videos before, but also don't know where the manual location(s) are to do so. Any forums or photos are helpful. What other maintenance can/should I do this winter? I feel I owe her a little time and money to keep in shape before something else goes wrong.

[Tonewheel]

Pat, I am not an electronics guy, but I am slowly learning. The pros here will jump in and help you. But here are some items:

This might help: https://organforum.com/forums/forum/...rite-zapping-q

We have a 90 year old retired Hammond tech in town, and nobody as qualified for 120 miles. He has stories to tell about how he used to zap dendrites, and frankly it was scary. I believe it was way more than 200 volts that he used, producing a lot of smoke, and when I think of old organs with dust and wood, I was surprised to hear that he had not burned down an entire church by accident.

So the very idea of a 9 volt battery or two replacing the "old" way seemed inadequate. Years ago I performed an experiment. I placed my tongue over the two 9 volt battery terminals. That was an education. Not deadly, not as bad as tongue on frozen pipe, but very unpleasant. I have never tried an 18 volt taste test because I value comfort and the ability to speak. I do admit that, if I am too far from my tester, I have done this again to see if a 9 volt battery is dead or not. B-) Poor form...

And the 18V did fix my percussion.

You can dive in and buy a tube tester and learn how to use it.

Or you can use a voltage tester and learn how to test tubes in a rudimentary way.

This video's music drives me crazy but you will learn something.

https://www.youtube.com/watch?v=r4FNP5rVnTw

The first part of this one will get you a little further

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

Tonewheel General Hospital has a good selection of tubes. http://www.tonewheelgeneral.com/buil...subcat=Hammond

It never ceases to amaze me how these very old beasts just keep going!

Dave

[proche3]

Thanks for the video links, Dave! Man, that sounds pretty intense! My dad knew a lot, but he never taught me much on these. I've got a multimeter and your videos so I will dig in and see what I can find. That pdf above is a lot of info, but I'm working through it. Thanks for the help!

[proche3]

OK, There is very little info on how to find which tube I'm going for here. I have the M series manual from Hammond and it says a lot but doesn't show me which tubes are which. It says:

"REPLACING TUBES (a) The vacuum tubes are all standard radio types and can be tested in the usual way. (b) If the 6BA6 tube is replaced, check the pedal cutoff adjustment as explained under "Pedal note sounds faintly when organ is not being played", (c) If tube V9 is replaced, check percussion cutoff adjustment as explained under "Percussion notes weak, do not play, or do not decay properly". (Hmm, so is it V7 or V9?? read on..)

PERCUSSION NOTES WEAK DO NOT PLAY OR DO NOT DECAY PROPERLY (a) Adjust percussion cutoff control; with expression pedal wide open, "Volume Soft" tab up, upper "Drawbars" tab down, all drawbars pushed in, press "Third Harmonic" and "Fast Decay" tabs. Hold down first C key on upper manual and adjust percussion cutoff control to the exact point of cutoff or silence, (b) Check tubes V7, V8, V9- (c) Always adjust percussion cutoff control after replacing V9 C12AU7). - (So now I'm more confused)

"PERCUSSION SECTION OF AMPLIFIER - The 2nd or 3rd harmonic signal (M-3) or both (M-lOO) (depending on position of the harmonic selector tabs) is conducted through the percussion matching transformer and amplified by tube V7."

So now I'm just scared to swap all the tubes and I'm more confused about numbering: V7 - Does this mean the 7th tube from the left, like "Valve "7"? There are literally no diagrams of the physical amp that show the tube numbers assigned in the manual. Sorry to be a N00B here but... HELP?

[David Anderson]

The three tubes involved with Percussion are the three tubes at the right-hand side of the amp looking in from the back. The right-most tube is a 12AU7 that acts as an audio gate and second Percussion gain stage. The next tube over is a 6C4 that acts as the initial Percussion signal gain stage. Proceeding left, the next tube is also a 6C4 that's involved with the triggering of the percussion effect. No, you cannot substitute other tube types other than known variants of the 12AU7 and 6C4. The ECC83 will not work. Unless tubes have lost their vacuum or have suffered other catastrophic damage, you usually can't tell visually if they're good or not. You have to test them.

There are diagrams that show the tube types and locations in the main spinet service manual. You should be able to find it online via a document titled M100Mm2m3SvcMan_text.pdf.

Calm down, take a deep breath, and proceed methodically. When you write, "There are literally no diagrams of the physical amp that show the tube numbers," you have not done your homework. Hammond Organs are very well-documented. The organ is not going anywhere. Spend some time familiarizing yourself with it.

[proche3]

Ahh, page 54 of the link you shared shows the tube socket numbers. I see now that V7 would be the likely culprit since you were able to spell that out for me. I was too quick to dismiss that, you're right, but I will check V7, V8 and V9 and report back. Appreciate your time to explain "which tubes are which"!

[proche3]

Appears that the V7 tube is dead. I tested between pin 4 and 5 according to that video you shared above. Ordering a set from ToneWheel general now..

[proche3]

Photo of the one I pulled out. I'm assuming it said Hammond at one time. The numbers appear to say P28Gr...maybe?

[proche3]

however, there is continuity between pin 1 and 4.. I pulled both of the 6C4's out and tested them and they are both ringing the same.. Did the video teach me to measure them correctly? Thoughts on next steps?

[proche3]

OK, the 3rd from the right, as you say the one that is "involved with the triggering of the percussion effect" does not produce a glow or heat while powered on, but all the others do. So back to my original plan to order a 6C4, but to replace the V8 tube. Standby.

[proche3]

There we have it, V8 tube was shot. Replacing it solved the issue. Thank you for your help everyone!