Grundig Partyboy 210 stuck tuning knob

[kingkong]

Dear all,

I opened up the case, tried to lubricate the spindle (shaft?). The spindle seems to go into the body of the tuning capacitor, and I can't see a bearing or anything. I saw some brown stuff, which I thought could be grease, but turned out to be rust. The spindle has rusted right where it enters the capacitor, and the body of the capacitor in that location seems to have rusted too.

I tried Servisol, WD40, then Servisol, then a drop of silicone lubricant. The spindle rotates but very very stiff. It's so stiff that I use pliers to tune to the required stations.

Was anybody lucky enough to sort this?

Thanks.

[Mike Noble]

I remember a thread about siezed tuning on these radios. The grease goes hard and heating with a hair dryer will melt the grease and free the tuning. Anyone remember more details?

[SteveJones]

Did you manage to solve this problem? Or does anyone have any further info about this? I have the same problem with a Grundrig Music Boy 210E, which must be very similar to the Party Boy 210. The tuning dial is more or less locked in position. It was always fairly stiff to tune from when I got it from my Dad, but now after some months unused in the loft, it has seized up.

Where abouts should I direct the hairdryer heat? (If that is the recommended treatment). What else could cause this?

[Restoration73]

That is the bearing. The spindle is aluminium and the body is diecast. You may find if you
actually remove the cap to avoid damage to the pcb/parts, you can heat the body near the spindle with a heat gun or large soldering iron (I use an old 100W Solon but a butane gas type is ok) it may well move - try spraying the spindle only with an aerosol freezer.
Fit a knob to the spindle, after a few turns it should be free. All the tuning caps made
by Hopt seem capable of showing the problem (including in UK sets)

[60 oldjohn]

I have a set that I treated years ago, it has seized again. I think the solution is to get every drop of the grease out before re lubricating or it will seize again in the future.
John.

[emeritus]

Traditional lighter fuel (petrol) is very penetrating, and may get a rusted joint moving where the other solvents that have been mentioned will not, but you have to be careful not to get it on plastic parts. Rocking the shaft to and fro, and flushing away any rusty solvent that emerges, can be effective in "pumping" rust out of a completely siezed joint before it becomes possible to actually rotate it. Considerable patience may be required.

[SteveJones]

Thanks for the quick responses - that gives me quite a lot to try out. It sounds like I have to dismantle it to try to get it working. Fortunately I left it tuned to Radio 4 LW for the cricket so I'll catch the 5th test before I try anything, in case I mess it up. I'll report back on progress.

[Julesomega]

I didn't see this thread when it was current, but this has exercised me too, in a Music Boy and in the Arena series of hifi receivers. These Hopf* variables are commendably engineered but invariably seize due to the polymerisation of the grease. Dismantling the unit is easy, the real challenge is to remove the tuner from the receiver which will invariably involve the tuning cord mechanism and some very heavy duty soldering. The attached photo from my Arena page shows how the grease solidifies.
* They were made by Hopf Elektronik GMBH

So far I have put my faith in the ubiquitous lithium grease but I would be interested in recommendations for a grease which can be confidently expected not to polymerise in the course of the next 100 years.

[Leon Crampin]

Aeroshell 16 is pretty good (and expensive).

Leon.

[marconi_pete]

I second Aeroshell 16. Have used it on many a radio restoration and although it may be a bit steep price wise does the job nicely and won't solidify over time.

[Julesomega]

Thanks, interesting suggestion, Aeroshell 16 would be good if you had a little bit lying about. I see the specification mentions long life along with high water resistance, suitable for heavy loading and high rotation speed, with an operating temperature range of -60 to +200° C; now superseded by Aeroshell 33, the most expensive of the Aeroshell range at about £13 for 400g