[Milsurplus] Let's appreciate crystals

[Bob Camp]

Hi

As you “lap” the crystals, you monitor the frequencies of the batch. It’s a “lower precision” step early in the process. 

The radios used typically are “whatever we could get”. In some shops that might be a big long row of some fairly nice surplus radios. (a group of SP-600 comes to mind …). 

The problem is that they are being used in a part of the factory that is full of lapping compound. It gets everywhere. Packing your radio full of it is not a great thing. Anything that will grind down quartz will also do a fine job grinding down metal. Eventually anything that depends on mechanical precision (tuning capacitors …) in the radio is going to degrade quite a bit. 

Best to pass up any “deal” you get on one of these radios. The rebuild process is really insane.

Bob

> On Oct 28, 2025, at 3:18 PM, Hubert Miller <Kargo_cult at msn.com> wrote:
> 
> I recall a couple decades back a crystal lapping machine was being offered for sale here in the Portland OR area. It was something i felt should be saved, but not by me. I don't know where it was from or where it went. Maybe, i'm thinking, it could have been from 'Radio Specialty Company' of Portland, but that's only a guess. 
> I also recall about a decade ago, maybe a little more, there were more than one Radio Shack DX-150 receivers being offered somewhere east of the Mississippi, that came out of some unnamed crystal grinding shop. The receivers were described as being in somewhat "beat" condition, which did surprise me. Also that such a pedestrian radio was used, altho that does make sense. I suppose this was just for first  "roughing in" the crystal frequency.
> -Hue Miller
> 
> 
> 
> Sent from my Galaxy
> 
> 
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