M3 Missing Tone, Bad Pickup Coil?

[theseacowexists]

Hey all, so I successfully installed poor man's foldback and tapering on my M3. Totally worth the backache! Now I must suppress the desire to taper my fully folded-back M101!:devil:

Unfortunately, when I put it all back together, tone #55 was missing from everywhere. Well, not exactly missing, but faint enough that it might as well be missing. Now I've narrowed it down to something wrong at the TG. Using the headphone trick, the output (going to the terminal strip) is as quiet as the tone is on the manuals. However, when I tap the headphone off of the wire coming up out of the bin (I'm assuming that's the one coming from the pickup rod), the tone comes in loud and clear. So I'm assuming that the problem is somewhere in that filter coil? Everything looks like it's connected on there. Can the coil and capacitor just be bypassed? I have no experience in this area yet, that's why I'm asking!

PS - Just to clarify, this was not a problem before I took apart the organ for the foldback and tapering.

[KC9UDX]

Coils don't normally fail, especially without cause. But I don't think there's anything wrong with the coil. Either way I suspect that you've introduced a short circuit somewhere.

[theseacowexists]

I think I misspoke - by coil I mean the filter transformer (the winding on top of the TG). Would the short be somewhere in there, since the signal is strong before it?

[KC9UDX]

A transformer is one or two coils. The short is almost certainly after the transformer.

[theseacowexists]

So in one of those tiny wires from the transformer to the output?

Is there a chance that the cap could have gone bad?

[enor]

When M-series notes go quiet, it's most often a bad solder joint in the filter. Start by reflowing all of them. Step 2 - check the capacitor.

[theseacowexists]

No joy from reflowing the solder or swapping the capacitor. :o

[tpappano]

Try disconnecting the wire that goes to the manuals from the filter's output terminal. Is the tone now present on the output terminal? If it is you may have a short in the manual wiring somewhere.

[theseacowexists]

I tried that, and it seemed like the tone was a more present. About as present as other tones from the output terminals on other filters. Hooking the wire back up to the terminal, the note was still faint as it was before. How would that indicate a short in the manual wiring?

[KC9UDX]

The signal is being shunted, bypassing the audio preamp. The definition of a short circuit: the intended load is being bypassed.

And since you altered the manual wiring, that's the most likely place to look for a fault.

[theseacowexists]

That makes sense. Of course, I'm trying to avoid opening up the manual again, unless I can figure out a way to get into it without taking it completely out of the organ again - that was probably the hardest part of this whole thing! Maybe I'll check at the terminal strip first, I can at least get to that without taking too much apart.

Tomorrow I will go back and do that same test again, and listen a bit better to make sure that there really was a difference with the wire unhooked, before I start unhooking everything else.

[theseacowexists]

Tested again with the same results - the tone was fine when unhooked from the manuals. So I checked the upper manual terminal strip - no problems there. So I figured what the heck, wife's out of town, nothing else to do, might as well dive back into the manual. Especially since I could see that the solder on one of the tapered wires I added looked bad.

I immediately saw two things when I opened the manual. First, I had forgotten to replace the sheet of paper that lays inside the bottom cover of the manual. Second, there were several taper wires that weren't long enough when I was working initially, so I had to solder an extension on in order to reach the terminal strip. Tone 55 was one such wire, and of course I had not put on a long enough piece of heat shrink, and part of the wire was exposed. The short must have been where this exposed piece of wire was touching the manual cover. I didn't want to mess with heat shrink so close to the manual, so I put a tight little piece of electrical tape on there and closed it up (with the paper cover this time). Indeed, once I got everything back together, tone 55 was back, loud and clear!

Thanks guys for pointing me in the right direction! Every time I work on a Hammond, I learn a few new things, and this time was no exception. For one thing, getting an M3 manual out is easier after you've done it a couple times. This thing really does scream now, can't wait to start gigging with it!

[tpappano]

Super! I'm still trying to work up the courage to rip into my M3 and add foldback 8)

[theseacowexists]

If you're gonna do full foldback, make sure you've got the right shaped busbars. My replacements were square, the M3 needed flat ones. I didn't know that until I got the manual open. That's what prevented me from doing full foldback, and switching gears to doing poor man's foldback and tapering instead. Wasn't planning on the tapering, but boy am I glad I did it - along with the 1' foldback, I don't even miss the other missing harmonics.

[tpappano]

Am I correct in understanding that to do a 'proper' M3 foldback mod, some of the busbars (3?) need to be swapped out because they do not extend all they way to the 'high' end of the manual? (and all the missing key contacts and resistance wires need to be added as well)

Thanks!