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Author Topic: HQ 170 A Vernier Drive Slips  (Read 348 times)

KD1I

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HQ 170 A Vernier Drive Slips
« on: November 26, 2022, 03:39:43 PM »

The Vernier for fine tuning is apparently a planetary drive built into the variable capacitor.   The drive was slipping such that turning the knob did not always turn the capacitor or pointer.   I tried to use some tuner cleaner into the back side of the tuning cap but that seems to have made this all the worse. Now it slips full time so fine tuning is no longer possible.
Some years ago I had removed the entire front panel to replace the dial windows, a job not for the faint of heart. There's lots to go wrong and it requires unsoldering the 'S' meter, clock and more. Also the dials can be damaged in the process.
Does anyone have any experience with repairing the Vernier drive ?    Can this be done without disassembly?
If it does require removal, any advice on removing the front panel on an HQ 170 A ?    I know I have done this on 2 units now but there can always be a better way.   Many Thanks in advance.     73, Jim     KD1I
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W6MK

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Re: HQ 170 A Vernier Drive Slips
« Reply #1 on: November 26, 2022, 05:06:21 PM »

There are a few youtube videos on repair of vernier dials. One, with at least three parts, is about an old RME receiver, in which the vernier is taken completely apart.

Apparently there are several kinds of wear which can seriously affect vernier function. Ball bearings may become worn and out-of-round as may ball-shaped ends of shafts. Such worn components need
replacement or reshaping so they no longer can bind.

Actual wear of components seems to be at the heart of problems rather than simple contamination with dirt or drying out of lubricant.
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KD1I

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Re: HQ 170 A Vernier Drive Slips
« Reply #2 on: November 26, 2022, 08:36:06 PM »

Thank you for the reply.   I had thought of hardened grease in the mechanism and that's why I tried the tuner cleaner.  It only made things worse.  I'll look for you tube videos in the AM...   good idea.
I wanted to remove the entire variable capacitor as the vernier mechanism is integral to it and possibly immerse it in a solvent.
The ball type planetary reduction must make use of some internal friction to operate but I don't know enough about them.
Best 73, Jim     KD1I
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KB7TT

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Re: HQ 170 A Vernier Drive Slips
« Reply #3 on: November 27, 2022, 07:52:20 AM »

the most prevalent defect in verniers is that the grease inside dries up.  I soak the verniers in gasoline or similar liquid and the grease eventually disolves.  I then push lithium grease in through the shaft socket on the input end until I see fresh grease coming out the seams.... I use a piece of 1/4 inch shaft material to push it in like a ram. simple but it works and you do not have to disassemble the drive spilling ball bearings out all over the place. 

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KD1I

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Re: HQ 170 A Vernier Drive Slips
« Reply #4 on: November 27, 2022, 08:11:28 AM »

OK, I reviewed all three videos on you tube.   That is a very different drive assembly.  Mine is integral to the capacitor itself. It cannot be removed.   I give the maker of the videos credit for disassembly of that mechanism and its 19 tiny ball bearings.  These bearings cannot be removed and are only a fraction of that size.    I tried additional contact cleaner, spraying from the front and back of the drive end of the capacitor. It seemed to help.  Unfortunately, I ran out of this contact cleaner so I'll have to get some hopefully today.
I think KB7TT has the right idea.   I'll try to clean it further and then use a very light lube, pressing it in gently.
I noted the caps rotor was a bit difficult to move at first but the cleaner did help.   It probably has not been serviced over its long life.
Thanks again for the tips.    73, Jim
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K0RS

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Re: HQ 170 A Vernier Drive Slips
« Reply #5 on: November 27, 2022, 12:21:11 PM »


I think KB7TT has the right idea.

Except for the gasoline.  Stoddard solvent is a much safer alternative.
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KD1I

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Re: HQ 170 A Vernier Drive Slips
« Reply #6 on: November 27, 2022, 03:39:04 PM »

I'm using CRC non-residue contact cleaner with no lubricant.  I could not find any 103 Octane gasoline.  I'll post the results. Sure hope that works because taking that front panel off is no fun.  I've done it before.     
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KD1I

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Re: HQ 170 A Vernier Drive Slips
« Reply #7 on: November 27, 2022, 04:43:11 PM »

It certainly seems to have worked.   After many flushings with the CRC, it moves quite well now.   I remounted the panel screws and reassembled.   Several tests indicate success - at least until it hits my shack bench.    Thanks for all the tips.    73, Jim
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W2JJV

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Re: HQ 170 A Vernier Drive Slips
« Reply #8 on: November 27, 2022, 04:48:47 PM »

I'm sitting here looking at my 180A wondering if it's ever going to happen to me?

I do love a good ending though!
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KD1I

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Re: HQ 170 A Vernier Drive Slips
« Reply #9 on: November 28, 2022, 10:36:30 AM »

It's an even better ending if you don't try to remove the front panel.....  Using a solvent like CRC means a lot less work.  It leaves no residue and does not contain a lubricant.   You can spray in the front after removing the knob and from the rear after removing the chassis from the cabinet. That is not a big job.   I used a canned duster for computer keyboards afterward to ensure all of the solvent had evaporated..... CRC is flammable.   This is also a good time to put a small dot of a light oil on the detent of the switches.
73 All,   Jim
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WA8NVW

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Re: HQ 170 A Vernier Drive Slips
« Reply #10 on: December 06, 2022, 03:04:03 PM »

Another solvent/lubricant that is low volatility and cheap is lamp oil.  It often comes pine-scented this time of year.
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W3SLK

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Re: HQ 170 A Vernier Drive Slips
« Reply #11 on: December 07, 2022, 07:23:23 AM »

WA8NVW said:
Quote
Another solvent/lubricant that is low volatility and cheap is lamp oil.  It often comes pine-scented this time of year.
Isn't that kerosene based?
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KE0ZU

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Re: HQ 170 A Vernier Drive Slips
« Reply #12 on: December 07, 2022, 07:14:10 PM »

For de-greasing I use Acetone, and a little goes a long way in the cleaning process.   And as you've found out lubing verniers usually isn't the correct process.   Same holds true for split, zero backlash gears as well as brass gears.   Dial mechanisms that use pinch washers on the edge of a brass or steel plate also shouldn't get any lube.   In addition to eventual hardening, oils simply hold dust and other contaminants which can make the edge drive cause tuning frequency to jump as you are slowly tuning around, and is quite noticeable on CW and sideband signals.
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Regards, Mike
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