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KWM2-A Disassembly Advice Needed

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KWM2-A Disassembly Advice Needed

Postby w0ab » Sun Aug 10, 2008 2:13 pm

Just about to start on a very clean KWM2-a project, absent any rust or corrosion. Need advice on the initial steps of getting behind the face plate of the rig. I have a Collins manual, but it is sorely lacking in the things that would normally be in a repair manual, i.e., exploded parts pictures of sub-assembly for dial mechanism.

The first issue is that the dial spinner knob shaft - the PTO?-seems to bind, or slip - one can turn the knob, but the dial will not move more than 2 khz in either direction- and knob seems to be slipping on the shaft. There seems to be no mechanical action within the pto itself that would cause binding, and so, am looking at the dial gear drive mechanism and/or a stuck dial cord. Any surprises? - hidden springs, parts that jump, dial cords that are impossible to re-install if taken off a wheel, etc.?

Thanks,

Gary,

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Postby N9LCD » Sun Aug 10, 2008 7:28 pm

I had an R-388 that developed similar symptoms. It turned-out that the PTO was jammed. The set had taken a direct hit on the KHz tuning knob, pushing everything back into the PTO.

No visible signs of damage but the -388 went back to the seller for a refund.

I would suggest using a hex key and checking to see if the tuning knob set screw is reasonably tight. Also check if all set screws on the PTO shaft coupling(s) are tight.

Careful!! It's awfully easy to strip the head of a set screw and AWFULLY HARD to get a stripped one out!

73's!

Jerry

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Postby k9yli » Thu Aug 14, 2008 2:07 pm

LCD
Tricks on allen set screws..

First off happiness is a 4 flute Bristol set screw.
you can't round them out and you cant roundoff the wrench.
I have 4 flute and 6 flute with more than 360 degree twists in the wrench.

That said.
To remove a rounded out set screw, us a small rat tail file. the file is very hard material.. Size of file depends on size of screw.

I have used either end but try the square end ( handle) first.
Tap the handle down into the rounded hole providing you have a file that will
not slip right in.. whap it with a heavy pliers a few times to cause its edges to cut into the set screw, take the pliers and grab the file and give a quick twist.

I have also driven the cutting end into the set screw, edges of the file grip the screw head, as the file is tapered. The big thing is get a sharp twist to snap the screw loose. Like a one shot impact wrench.
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kwm2 maint

Postby WA5DTY » Wed Aug 27, 2008 3:13 pm

You are in for a surprise.....believe me. I've been there. Try to get the tuning
mech freed up before you go any further. Behind the knob (behind the cabinet) there is a hole about 1/2 inch in diameter. Get some rubber revitalizer and use a q-tip to apply the liquid to the rubber tire that you can see (if you look hard) let it set for a min or so, then attempt to turn the dial.
That thing is a mess to disassemble and even harder to re-install it.
Unless absolutely necessary, STAY OUT OF THE THING.....
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Postby W5INC » Sat Nov 08, 2008 1:32 am

I have to go a little father then what WA5DTY mentioned. The PTOs are a very hard if not close to impossible to re-calibrate once broken or taken apart incorrectly. Collins at the factory had a special jig setup just to calibrate the PTOs. From what I remember in a conversation from a very astute Collins guy it had a couple of frequency readouts on the jig. This was the only way to calibrate them correctly when they were first made. This Collins guy knows how to take them apart mark them correctly so he could put them back together correctly. If the PTO was broken he would find another PTO from a parts rig and use that one. This Collins guy has been working on them for over 30 years and he has done all of my Collins gear so I tend to believe what he says. Maybe your best bet is to find a PTO on the Collins reflector or a parts rig where you can, 73s DE W5INC
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All lis not what it seems../

Postby K4ICL » Sun Nov 09, 2008 11:50 am

The slipping situation you describe is quite common and is easily fixed.

When you turn the "big" knob on a KWM-2 you are actually turning a small "satellite" friction driver knob that contacts a larger inner ring of the main tuning dial. This satellite knob's shaft can be adjusted to engage the ring tighter or less tighter by removing the large main tuning knob from the front of the panel and loosening its concentric locking sleeve, holding the the tuning knob shaft.

After you get the large knob off, you will notice a hole in the front panel showing a "slotted screw head". This is the actual end of the PTO shaft. Using a screw driver you should be able to gently turn this to change the PTO frequency. If the PTO is working, all you will need to do to correct the slipping satellite shaft is to adjust the concentric sleeve to make it engage the ring better and then tighten the shaft lock nut.

Don't loosten any thing else, getting the main dial to read if is "unsynced" with the dial mechanism is a bear of a job entailing a lot of extra time, much cursing, and crankiness.

Good luck on the project.

AL K4ICL
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