Motor/TG goes unstable after 10 minutes (Porta B - L Series)

[HammondRye]

I recently picked up a Porta B that's been well maintained with no issues except one I just discovered. After it's been running for 10-15 minutes there's suddenly a mechanical noise inside followed by the tone generator oscillating between slow & normal. The pitch goes about a whole step down then back up, then down, etc, at which point I shut it off for fear of permanent damage.

If I let it cool off a few minutes, it's fine again until the whole thing happens again.

The guy who sold it to me said it was recently oiled (and I see the cups are indeed wet). He didn't mention anything about the problem and I trust him. Either he wasn't aware, or possibly something happened while moving it to my place. Does anyone know what it could be and where I should start troubleshooting?

[Logan]

I recently picked up a Porta B that's been well maintained with no issues except one I just discovered. After it's been running for 10-15 minutes there's suddenly a mechanical noise inside followed by the tone generator oscillating between slow & normal. The pitch goes about a whole step down then back up, then down, etc, at which point I shut it off for fear of permanent damage.

If I let it cool off a few minutes, it's fine again until the whole thing happens again.

The guy who sold it to me said it was recently oiled (and I see the cups are indeed wet). He didn't mention anything about the problem and I trust him. Either he wasn't aware, or possibly something happened while moving it to my place. Does anyone know what it could be and where I should start troubleshooting?

That's a doozy of a pickle!

Every Hammond dealer I've met personally has been very knowledgeable and honest when it comes to the organs they sell.

I'd say go with your gut at first, but at the end of the day listen to your Hammond guy

[HammondRye]

Hey Logan, Yup it's a real puzzler. I should've clarified I bought this used from a studio close-out. The guy I bought it from, while knowledgeable, wasn't an official Hammond rep or technician, so it was a "what you see is what you get" kinda deal.

I've worked on spinets before in a limited capacity, so I'm not totally lost in there. But I've never had a motor or tone generator problem so this new to me!

[Logan]

Hey Logan, Yup it's a real puzzler. I should've clarified I bought this used from a studio close-out. The guy I bought it from, while knowledgeable, wasn't an official Hammond rep or technician, so it was a "what you see is what you get" kinda deal.

I've worked on spinets before in a limited capacity, so I'm not totally lost in there. But I've never had a motor or tone generator problem so this new to me!

I see. Many "renegade" Hammond dealers will pretend to be professionals and keep secrets so that you can't tell if they're lying or joking. It's sad to see.

If you ask your tech directly about the problem, I'm confident he will help. He's worked on the same spinets that you have, after all!

Edit
Have the Hammond guy take a look at the oil cups to check for dryness. I know Hammond techs who will shove their finger down there just to make sure they oiled it properly!

[sfp1954]

Sounds like the motor capacitor could be on the way out.

[Jorgen]

The guy who sold it to me said it was recently oiled

Hmm... wonder the previous time it was oiled....
When I bought my B3 it hadn't been oiled for, maybe, a decade, took SEVERAL weeks to get the bearings wet
and TG spinning......so try add some more oil and "standby" for some week.

[HammondRye]

Sounds like the motor capacitor could be on the way out.

There's something I hadn't thought of. The schematics in the Porta B Service Manual seem to omit the motor/capacitor assembly entirely. Is there a way to test the capacitor or visually see if it's dead?

- - - Updated - - -

Hmm... wonder the previous time it was oiled....
When I bought my B3 it hadn't been oiled for, maybe, a decade, took SEVERAL weeks to get the bearings wet
and TG spinning......so try add some more oil and "standby" for some week.

Aha good point. If it was just oiled before he sold it, you're right it could take a while to get through. I'll try your suggestion and see what happens!

[Wes]

No puzzle. Definitely the cap. Get a new one before the old one explodes and gets PCBs everywhere, including your lungs.

[BlueOliveB3]

No puzzle. Definitely the cap. Get a new one before the old one explodes and gets PCBs everywhere, including your lungs.

^^^^^ THIS. Do not run the organ until you replace that cap. It's an easy and cheap fix. They're available from the usual suspects.

TP

[David Anderson]

No puzzle. Definitely the cap. Get a new one before the old one explodes and gets PCBs everywhere, including your lungs.

Many older motor-run capacitors were made with a paper dielectric. Modern ones are metallized polypropylene and will last indefinitely.

[Juan]

No puzzle. Definitely the cap. Get a new one before the old one explodes and gets PCBs everywhere, including your lungs.

Which cap is this? Where is it? I'm wondering if I need to replace it in my M3. I can hear a slight oscillation. I have also noticed an odd slight quavering in some of the notes. I wonder if this is related?

[David Anderson]

Which cap is this? Where is it? I'm wondering if I need to replace it in my M3. I can hear a slight oscillation. I have also noticed an odd slight quavering in some of the notes. I wonder if this is related?

Your M3 does not have a motor-run capacitor, so it's not related.

See "flutter" for unwanted quavering of individual tones.

[Logan]

Your M3 does not have a motor-run capacitor, so it's not related.

At one point, I was worried about that same cap in my M100. But after talking with a couple Hammond guys, I realize it's just my own paranoid obsession. I totally don't need to replace that cap until it's dead. And I've been really happy with it since I've stopped thinking about it a few weeks ago

Edit
Can someone please give this thread a one star rating? Everyone hates posting in five star threads

[Sweet Pete]

Please let us all know when you locate the 'run motor cap' on your 'M100' there Logan.
And if you have an old VW Beetle,make sure and check the radiator while you're at it........

[Logan]

Please let us all know when you locate the 'run motor cap' on your 'M100' there Logan.
And if you have an old VW Beetle,make sure and check the radiator while you're at it........

Now you're speaking my language!
I'm interested in caps and radiators but I never formally learned how to check them to see if they exist or not

There is one Hammond guy who got me to think about them right away. I can't name names due to contractual obligations, but I'll call him "Mr. Pete" to avoid confusion. "Mr. Pete" can definitely tell if cap exists or not.