[R-390] School House bugs

[Roger Ruszkowski]

Craig,
 
The Fort Devens Mass school house had class rooms.
In each room was a weeks worth of education.
Every Monday you started in a new class room for a year to 18 months.
You had a tool box. TK105 You picked it from your old class room on Monday and brought it to your new class room.
Each room had ten seats.
Each room had benches, stools, equipment to learn this week and test equipment needed to maintain equipment to learn this week on each bench.
Ten benches five bugs two of each bug. 
Big grid on the calk board 10 names, 10 positions 1-2, 3-4, 5-6, 7-8, 9-10.
Log your start and stop time. 
You could watch the board and see how the day was going.
The front end of school was theory.
The back end of school was week after week of equipment.
In the equipment weeks you did:
Monday theory of item and play with item.
Tuesday was schematic analysis of item.
Wednesday was find 5 bugs in item on bench
Thursday was find 5 more meaner bugs.
Friday was find 5 more bugs. two from wed, two from thurs and a new one.

There were like plenty of bugs to mix up from week to week.
Bad line audio this week Bad local audio next week.
Bad fuse here. Bad fuse there.
Burnt out lamp.

We had fried tubes for every tube in the item.
We have bad  items for every thing that would plug in, relays caps, tubes, fuses crystals.
We would plug in 4 bugs and solder a fifth so you only had to solder up two units a day.
We had meg ohm resistors carefully repainted to solder in as open resistors.
We had every solder joint on a terminal board re soldered so you could not just eye ball for new solder.
We would open wires in the wire harness plugs to give you a bad wire harness.
We could mess up clamps, knobs, shafts and miss align any thing that needed adjustment.

Every student spent 6 months in common theory and test equipment.

A student spent 6 to 12 more months depending on the school
three days a week 6 hours a day at a bench trouble shooting 5 bugs a day on a piece of gear he
had never seen or heard of before Monday. 
R390 school was two weeks. One week alignment. One week bugs.
The first week you got do three alignment semi annual PM procedures.
You had to pass signal to noise on every band. As you got a part procedure done you asked for an instructor sign off
as you demonstrated the step.
An instructor could walk past an R390 on the bench with spline tool and tweaker never break stride and keep a student busy all day getting that receiver back in alignment.
 
I got more real hands on education at Fort Devens than any where else in my life.
I did four years 6 days on two days off in Viet Nam, Korea and Okinawa applying what I had learned in school.
I did two years teaching a tape recorder week after week after week.

Roger 33C4H
 
-----Original Message-----
From: Craig Heaton <hamfish at efn.org>
To: 'Ken Harpur' <igloo99nz at yahoo.co.nz>; 'Larry H' <dinlarh at att.net>; 'Roger Ruszkowski' <Flowertime01 at wmconnect.com>; bill.riches <bill.riches at verizon.net>; 'R-390 at mailman.qth.net' <r-390 at mailman.qth.net>
Sent: Mon, Jul 21, 2014 12:00 am
Subject: RE: R-390A Noisy Ant. Trim and Raspy Calibrator revisited




Ken,

If you have time try connecting a speaker to the line output. See if the
audio is loud there also. I swapped IF's, AF's, etc between a Motorola and
the Amelco, always had loud audio on both Line & Local audio.

By the way, if I didn't mention it before..................The original
audio pot for the local gain on the Amelco had 2.5K on the cover of the pot!
But when checking the pot with a VOM, it was a 5K audio taper pot. The guts
were switched, solder connections looked original. The acceptance seals were
still on the top & bottom covers, stuck to the sides of the RX. Kinda makes
you wonder. 

Anyway, the Too Loud Amelco has been playing nice for the last couple of
weeks. I have to ask the rest of the gang here on the R-390A e-mail
reflector if the mil tech schools had booby trapped receivers for students
to trouble shoot?

Craig,  

-----Original Message-----
From: Ken Harpur [mailto:igloo99nz at yahoo.co.nz] 
Sent: Sunday, July 20, 2014 2:44 AM
To: Larry H; Roger Ruszkowski; hamfish at efn.org; bill.riches at verizon.net;
R-390 at mailman.qth.net
Subject: R-390A Noisy Ant. Trim and Raspy Calibrator revisited

Hi Larry, Bill, Craig and Roger,

Firstly, I am sorry it's taken me a while to respond to all your
suggestions...it's been busy here and I haven't been working on the radios
until this weekend.

As far as the noisy Antenna Trim on the Teledyne I haven't made any progress
on this at all. No amount of exercising the trimmer seems to be cleaning up
the scratchiness...so I think the next step is to have a look inside.
Something completely unrelated came up on this radio though...While
reassembling the front panel I noticed the Local Audio pot had been changed
to 5k. I installed a correct value NOS 2.5k and now I have the "Too loud"
audio problem that Craig had. So someone in the past had tried to fix the
issue with a larger value pot. I have yet to try substituting AF
decks...that is something I will try next time I am in the shack.

As far as the Calibrator on the EAC goes. The raspiness issue was resolved
by replacing C-313. I believe the issue with the remaining distortion is the
AGC and swapping out the IF deck with two others seemed to confirmed this,
both with the calibrator signal and listening to on-air broadcasts. With the
EAC deck back in...on a strong signal it distorts heavily with the RF gain
full up (just like it does if you switch to MGC).  If I turn the RF gain
down the signal cleans up nicely.

I feel a bit stupid re trying to Scope E-208...I thought I'd see the output
from the calibrator there but of course we are talking about micro-volt
level signals so it makes perfect sense why I wouldn't see anything. While
having another look at E-209 I discovered my probe is faulty which could
explain what I was originally seeing, if I wiggle it just right, it works.
For fun I had a look at J-221 and I could see the 17 Mhz signal from the
first crystal oscillator...nice and clean sine wave. I scoped the IF out for
the calibrator signal...a sine wave but a little blurry. I also had a look
at the IF out with a normal broadcast station and same result. Unsure of how
to interpret what I was seeing, as this is the first scope I've ever owned I
went to youtube to learn. I found the blurred waveform was just the sine
wave being modulated by the signal. So still tuned to the broadcast station
I slowed the timebase way down and could see the modulated audio, just like
I was seeing in the videos.

So...I had fun, got a little side-tracked and when I get more time to get
stuck into it again I'll go hunting for the AGC problem. Thanks for the
responses, comments and advice...as always I've learned a little more about
these radios.

Very best 73
Ken Harpur 
ZL3AA