Posts: 14
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Joined: Mar 2009
Hi all:
I bought a heath IG-102 signal generator from ebay. Works fine, calibrated the bands, and even set trimmer to make the dial accurate. It has one annoying feature I didn't pay for, though - when the vernier knob is turned at a medium-fast rate, all is fine, but when it is turned slowly to zero in on a frequency, it slips. It would seem as if there is wear in the ball-bearing vernier drive, or maybe too much friction in the capacitor rotor shaft. I removed the cap and washed it in solvent, thinking old grease might have got gummy - didn't help. As for wear, the unit appears to have been used very little - not quite mint condx, but nice. Can the vernier shaft come out, and be replaced with a separate reduction drive? Can the frame of the cap be tweaked to reduce friction or apply more force to the drive ball bearings? All suggestions welcome, and thanks in advance!
73, Stirling.
Until next time,
Stirling KC0NXM.
Posts: 892
Threads: 9
Joined: Mar 2008
City: Vieques, PR USA
State, Province, Country: PR
Is this the 'standard' Jackson Bros. 6:1 vernier drive that was used in so many things?
4511DAF for instance?
http://jlkolb.cts.com/site/vernier.htm
[Image:
http://jlkolb.cts.com/site/fotos/vdjb1fw.jpg]
If so, then like the author of that site says you might have some luck with a thorough cleaning and tightening the tabs. I see new ones around for sale and they fetch about 13 US$. I've got a bunch of old ones here but I'd hate to guarantee any of them for very scrutinous tuning.
The tuning cap should be very 'free' turning. Not loose, mind you, but not enough to cause any drag on the drive. If thats ok and the vernier still slips then it may just be worn.
Next option if its not one of the Jackson drives. If its the shaft-in-a-shaft type as used in old radios they almost always respond to a good disassembly and cleaning. There's tricks to getting them apart. Maybe a photo of yours would help make a determination?
Posts: 14
Threads: 4
Joined: Mar 2009
First, thanks for your consideration! I really thought this might be a kind of dead-end. I don't have a picture of it handy, but it's the shaft-in-shaft type (not much to see) - built into the cap itself, with a twist. The main shaft is 3/8" and the vernier is 1/4" instead of 1/4" and 1/8" as many are. You mention there are ways to disassemble it, but I'm running low on dynamite - are there other ways?
Until next time,
Stirling KC0NXM.
Posts: 14
Threads: 4
Joined: Mar 2009
OK, here are some pix of the unit. Not great quality, but it's a video cam.
Until next time,
Stirling KC0NXM.
Posts: 892
Threads: 9
Joined: Mar 2008
City: Vieques, PR USA
State, Province, Country: PR
Ugh, I see what you mean. Report back if the dynamite doesn't work
FWIW, I've had my best luck with caps like that using copious amounts of carb cleaner worked in between the shafts. You'll have to remove it from the chassis of course. I''d bet a good ultrasonic cleaner could deal with it if you have that option. The thing looks brand new so I'd guess that dried grease inside is the culprit rather than wear.
I'll be standing by for other ideas...
Posts: 14
Threads: 4
Joined: Mar 2009
Strange you should mention carb & choke cleaner, which is exactly what I used to clean it, a by-product of my other hobby! I did remove it first, too. Just before hitting the hay last night, I thought I'd try packing the bearings with some new grease - what could it hurt? In the worst case, I have plenty of carb cleaner... But it worked! Evidently, this unit depends on some amount of 'tackiness' delivered by the grease. There is only a tiny amount of play now, which I think is caused by the tolerance between the drive balls and the holes drilled in the outer shaft. I really don't think wear is an issue. Again, Thanks for your help!
Until next time,
Stirling KC0NXM.
Posts: 892
Threads: 9
Joined: Mar 2008
City: Vieques, PR USA
State, Province, Country: PR
Glad to hear you got it going.
-Bill
