[R-390] PTO Massive Deaths

[Bob Camp]

Hi

Actually yes I do know that quite a few PTO's wound up in strange 
places. Back when I was in High School I bought part of one of those 
piles of PTO's and spent a couple years selling them at the local 
hamfest ...

	Take Care

		Bob Camp
		KB8TQ


On Apr 8, 2005, at 8:09 PM, Flowertime01 at wmconnect.com wrote:

> The 390A's have been "eating" PTO's since the mid 60's. There are 
> documented
> stories of mountains of dead PTO's piling up out behind various depot
> locations.
>
> Strange
>
>         Bob Camp
>         KB8TQ
> --------------------------------------------------
> Yup,
>
> The PTO was an exchange item not fixed at the organization level. New 
> ones
> were to be had for exchange. So we just shipped one in and got a brand 
> new one
> back if it even looked dusty.
>
> Prior to the 70's most units did not have a frequency counter. So the 
> unit
> had no way to do an end point adjustment. If the spread got to far 
> off, (300
> Hertz) the tech just did the paper work for a replacement. The PTO 
> wound up in a
> stack at some Depot. Get a thousand stacked up and you consider a 
> contract to
> refurbish. Until they went out of production, why bother just build me 
> a new
> one please.
>
> Until the late 60's did not under stand how the crystal ovens were 
> cooking
> the receivers. It was common practice to run the receivers with the 
> ovens on
> thinking it added something useful to crystal stability. Buy 1972 even 
> sites on
> the DMZ in Korea were well heated enough that the receivers were run 
> with the
> ovens off. If you had a Van full of receivers you just turned every 
> thing on
> and let the shelter heat up until it was warm enough to work in. We 
> had a MLQ24
> van in Korea. It was a 3/4 ton truck and shelter. Some nights the Van 
> was the
> warmest place on the site and all the off duty guys would sleep on the 
> floor.
> Yup it was warmer in a Van full of tubes than in a block building with 
> space
> heater glowing as red as the filaments in the vacuum tubes. I digress, 
> back to
> PTO's.
>
> PTO's were going to depot for all kinds of reasons. Lack of counters to
> adjust them. Killed from ovens being on in summer heat. Bounced down 
> roads in Vans
> until something broke. Pulled coax connectors. The fair number of cold 
> solder
> joints that would not be explored because the unit was an exchange 
> item. You
> just trouble shot your problem down to the PTO and exchanged it. If a 
> tube swap
> did not cure a PTO problem, it went to the big pile at the depot.
>
> Once the depot sent big bunches off to a contractor to refurbish 
> because new
> ones were not coming off the assembly line any more, the problems 
> found were a
> variety of simple problems. Lucky for us so many got swapped out, 
> there are
> lots spare units around today. Do you have any idea how many PTO's 
> have been
> built into home brew VFO's? The contractor bitched that more problems 
> were from
> the poor handling than actual problems with the PTO's. The issue 
> became a good
> hour lecture on the handling of PTOs in the R390/A class room buy 1968.
>
> Most were just needing end point adjustment. The little wiper was 
> dirty and
> PTOs warbled. Some were cooked from their own oven heaters. A few had 
> broke
> cores from bad G's. Some had broken pins on the wire harness. There 
> were a number
> of cold solder joints. The upshot was, tech started to inspect PTOs 
> when
> problems occurred and frequency counters were added to the R390 
> service bench.
>
> Roger KC6TRU
>
>
>
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