Help me diagnose this wacky problem (tone generator)...

[Guest]

I can't imagine what could be causing this... On my Porta B (a.k.a. L100P or P100) there are 2 tones that make no sound. These are C#4 (wheel 50) and C#5 (wheel 62). Both wheels are on the same shaft, so it would be logical to assume that the shaft isn't spinning, right? Well, here's where it gets weird.</P>


When I play both notes together, C#4 (50)+ C#5 (62), I get a healthy C#6 (74) tone. According to the schematics, wheel 74 is on a different shaft, although it is close to the shaft in question.</P>


Does anyone have a possible explanation? More importantly, how would you fix it? [:^)]</P>

[geoelectro]

Re: Help me diagnose this wacky problem (tone generator)...



Are you playing only one drawbar? Do these tones show up missing on all drawbars (when and where they should) on both manuals? Are those wheels in fact spinning? Does the C#6 sound you get played with two keys sound exactly like C#6 played normally?</p>

George
</p>

[Guest]

Re: Help me diagnose this wacky problem (tone generator)...



Hi Geo, I'll try to answer these questions as best I can before I lose my mind. The reason being: the "symptoms" keep changing. IfI didn't know better, I'd say my Hammond is haunted.</P>


Now suddenly C#5 (62) is working fine.</P>


When I play C#4 &amp; C#5 together, I still get the C#6 ghost tone in addition toC#5 which is working now.</P>


Also I just noticed that when I add F#4 to the above 2 notes, I also get a G#6 ghost tone.</P>


Go figure that</P>


Now to answer the questions...</P>


Are you playing only one drawbar?
Yes. Upper manual 8'.</P>


Do these tones show up missing on all drawbars (when and where they should) on both manuals?
Yes, although when played on the lower manual, theghost tones are much quieter.</P>


Are those wheels in fact spinning?
Good question. I haven't figured out how to check. The L100 service manual says to peel back the bottom pad under the tone generator and feel around with your finger. The problem iswith a Porta B everything is packed so tightly in there, you can't get to the underside of the tone generator without dismantling the entire organ. But I guess I'll have to do it sooner or later......</P>


Does the C#6 sound you get played with two keys sound exactly like C#6 played normally?
It's a little bit quieter, and there's no keyclick. But other than that, it sounds the same as a normal C#6.</P>


I think I should add one bit of info... I just got this organ recently, and I don't know the last time it was oiled or serviced. I just oiled it 2 days ago. Could that account for the erratic tonewheel behaviour (like C#5 suddenly working tonight)?</P>

[geoelectro]

Re: Help me diagnose this wacky problem (tone generator)...



I think first you need to make sure all wheels are spinning. Remember, oiling takes a week or more before it gets to all the bearings. In some cases, oiling through the normal means won't free up a really stuck wheel and some manual oiling and spinning may be necessary. Also, you may want to check the wiring harness from the generatore to the manuals. These wires can break easily, especially in an instrument that gets moved a lot.</p>

There's an easy way to test the generator output terminals. Take a clip lead and clip one end to the back of a drawbar. Adjust for volume. Clip the other end to each terminal of the generator and listen for a tone. Every terminal with a wire attached (not the grounds of course) should have a tone. This test can separate the generator from the wiring as having the problem.
</p>

George
</p>

[Guest]

Re: Help me diagnose this wacky problem (tone generator)...



George, as always, thanks for your great advice. You're spot on!</P>


I wanted to post back and let everyone know the problem is solved. Like George said, the first thing with any tone generator problem is to determine if the wheels are spinning. In my case they were. So I proceeded down the signal path, testing different nodes with the clip-lead-on-the-drawbar method geo described above.</P>


On C#4 the capacitor was broken clean off its terminal.A little drop of solder fixed that right up. C#5 had a hairier problem. The microscopic copper filament that's wound around that thingy (condenser?) was broken. I guess the proper procedure, according to the manual, is to replace the whole filter. But since I don't know where to find one, I tried to re-solder it. The results are far from perfect (the tone is slightly weaker than the rest and now carries a strange, faintharmonic), but it works.</P>


What was causing the C#6 and G# ghost tones I have no idea. And why they only occured when certain pairs of notes were played is another mystery. Oh well, I'm just happy to have all my tones back.</P>


Except for one, that is... I didn't mention it before, but my F5 is silent. The wheel is spinning, but there's no signal at either end of the filter. I guess this means the pickup must be dead?</P>