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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Wed 07, 2018 1:29 am 
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Joined: Jun Sun 23, 2013 9:03 pm
Posts: 358
Location: Canandaigua, NY
In that photo above, doesn't the long set screw that acts as a stop also hold the whole shebang to the shaft? Can you slip something in from the side to loosen it or is the dial too close to the panel?


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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Wed 07, 2018 1:42 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Albuquerque, NM 87123
Your toggle switch is probably open. Set the equipment on its back and dribble several drops of Deoxit down the round opening at the base of the toggle, then actuate the switch several dozen times. I have brought hundreds of switches back to life this way.


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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Wed 07, 2018 3:50 pm 
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Freeze-it component cooler or a can of compressed "dust-air" turned upside down applied to the set screw. Use an Allen wrench and "tap" on it numerous times using a small hammer with just enough force to cause light mechanical shock. Try loosening it with the wrench and if still stuck, repeat the process again a few times more.

I've done similar tricks on vehicle chassis' by heating up a frozen nut/bolt threads, then apply cold water to the bolt threads themselves which then contract, leaving the nut still hot for easier removal, thereby saving the threads. In your situation you can't risk damagine surrounding plastic, etc.

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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Fri 09, 2018 11:09 pm 
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Joined: Apr Wed 13, 2016 1:23 am
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Location: Independence, MO
Kinda off topic ---but does anyone know where I could find the aluminum dial piece?? Mine is all corroded and hard to read

Thanks in advance,
Jim


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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Fri 09, 2018 11:55 pm 
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Location: Albuquerque, NM 87123
rja, you can buff those dials. I use 0000 steel wool (gently) then use an aluminum polish that you can find at any automotive parts store. It will make the dial look like chrome. You will probably want to use nitrile gloves.


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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Sat 10, 2018 9:09 pm 
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Joined: Apr Wed 13, 2016 1:23 am
Posts: 84
Location: Independence, MO
Johnnysan,
Yes I tried that but it looked like it was removing the lettering? I'm going to try that soon. maybe a little more elbow grease.

Thank you for your response,
Jim


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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Sat 10, 2018 9:38 pm 
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Location: Albuquerque, NM 87123
Isn't the dial plate lettering stamped into the metal? I have never had a problem with buffing the dial plates.


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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Sun 11, 2018 2:01 am 
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Joined: Jun Sun 23, 2013 9:03 pm
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Location: Canandaigua, NY
AFAIK, there have been a variety of different styles and finishes used on those dials. Some might shine up and some might be ruined by abrasive cleaning. My 200CDR has an anodized dial with deep engraving, so the lettering wouldn't go anywhere, but the anodize could certainly be messed up. I remember having an older one that was shiny, so probably not anodized.


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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Sun 11, 2018 5:04 am 
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Conrad Hoffman wrote:
My 200CDR has an anodized dial with deep engraving, so the lettering wouldn't go anywhere, but the anodize could certainly be messed up. I remember having an older one that was shiny, so probably not anodized.

Are you sure is it anodized and not alkaline-etched? All the post-200A,B,C,D audio oscillators I've seen have what looks to me to be an alkaline-etched dial. They can get badly water-stained, which I don't think could happen with an anodized finish.

Once they get stained, the only cure seems to be polishing them up. (I used a buffing wheel on my bench grinder --- I've forgotten what buffing compound I used.) You can then fill the dial markings with black lacquer stick.

If you want to restore the satin finish after polishing, use an alkaline dip. Household lye (plain old drain cleaner with no additives) will do. I overdid mine by leaving it in too long, but this finishing.com forum post says start with a 5 minute etch, and to add a bit of sodium fluoride to the sodium hydroxide:
Quote:
The most popular method of getting satin finish in our industry is to alkaline etch in Sodium or Potassium Hydroxide with additives. Sodium Fluoride at about 1.5 oz/gal on top of about 6 oz/gal of Sodium Hydroxide at 140 F for 5 minutes should get close to what you want. Then experiment from there.

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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Sun 11, 2018 8:12 pm 
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Location: Canandaigua, NY
Not positive, but I'd expect an etched finish to be quite fragile in terms of scratches and mars. I can't get at it, but a way to tell might be to pull the dial and lightly scratch the back. Anodize will be hard and tough. It also won't buff easily!


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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Sun 11, 2018 11:11 pm 
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Joined: Apr Wed 13, 2016 1:23 am
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Location: Independence, MO
Johnnysan and all others,

Yes, the letters are deep enough to not worry. I did again the steel wool and then car polish and WOW!. What a difference. I still have some marks that just won't come out but over all I can read it and my set screw comes out :cry: -yes I only have the one.

Jim


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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Wed 14, 2018 3:11 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2423
Location: Potomac, Md.
Johnnysan was right. The on-off switch was bad, and no combination of D-5 and flipping the handle back and forth until I thought I'd develop carpal tunnel problems was able to cure it. So I replaced it with a close copy in my junkbox. But at least the power transformer is good.

So now I've fixed 1) the switch and 2) the hard-to-turn dial, by giving up on taking the big tuning knob off and instead adding a drop or two of sewing machine oil to the drive every few days and giving it a good workout.

One of the two 6CW5 tubes is dead. The other one, the two 6AU6s and the two lamps in the bridge are good.

I don't know whether I want to do a whole restore on this unit, though. Other projects are calling.

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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Sat 17, 2018 1:25 am 
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Hmm. Maybe I should go ahead and part out my "junker".


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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Tue 20, 2018 8:45 am 
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Are the setscrews Bristol? Or spline maybe? Just a thought.

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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Tue 20, 2018 9:33 am 
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Location: Lincoln City, OR
Greetings to Avery and the Forum:

Avery writes:
Quote:
One of the two 6CW5 tubes is dead.


Gee.... you have a nice late 200 CD. Mine uses 6AU5 octals.

Regards,

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Jim T.
KB6GM


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 Post subject: Re: Ideas, please, for loosening setscrews on HP-200CD main
PostPosted: Feb Tue 20, 2018 3:12 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2423
Location: Potomac, Md.
Radiosmoker wrote:
Are the setscrews Bristol? Or spline maybe? Just a thought.


Per previous post(s), getting a good fit with the wrench was not the problem, and I'm done trying. It's clear that removing the knob would not be a solution, and I've pretty much fixed the dial drive (and replaced the power switch). It's headed for a new owner

Per my observation that one of the two 6CW5 tubes is dead, Jim writes:

Quote:
Gee.... you have a nice late 200 CD. Mine uses 6AU5 octals.

Regards,
_________________
Jim T.
KB6GM


I knew there had been a change. I'm feeling lazy...want to tell me whether it was a pin for pin replacement or involved reworking the circuit?

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Avery W3AVE


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