[R-390] PTO Massive Deaths

[Flowertime01 at wmconnect.com]

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