[R-1051] Update - Pretty Much Working

[David Wise]

I found a procedure for removing the 1MC motor in
NAVSHIPS 0967-034-2000 (Technical Manual for Repair of
AN/WRC-1 and R-1051/URR 2N Modules), which I got from
Al Parker's boatanchors site after discovering the
link in the mail archive.  It's paragraph 3-5.

I did not have to do all that to get the motor out.
The only wires I had to unsolder were the motor wires
themselves, and one coax.  Then it was possible to
separate and flex and rotate just enough to free it.
The brushes were okay.  I just cleaned the commutator,
and added oil to the motor end bearings.  As caution
overcame excitement, I decided not to open up the
reduction gear assembly.  I got it all back together,
and the 1MC was happy.  I still have to make sure it's
putting out as clean and loud a signal as it's supposed
to, but at least it doesn't sound scary anymore when
the motor runs.

I have run into various other troubles and fixed them.
I'll list them in case someone else can benefit.

- Hard to describe the symptoms, but I highly recommend
  that you touch up the various trim-pots in the Spectrum
  Generator, and, for 1051-plain, the 500cps Lock pot.
  All of mine were at or over the edge, resulting in
  ragged, intermittent, or off-frequency injection signals.

- I traced an intermittent blank-out to loss of 10kHz spectrum
  at the 1&10kc synth.  It turned out to be a bad SMB connector
  on the board.
  It looked like a lot of work to replace it, so I tried
  rerouting the cable so the plug mated at a different
  angle.  Seems okay for now.

- My radio is a patchwork of various age modules.  One IF
  looks original (NAVSHIPS 98481A or NAVELEX 0967-LP-970-9010),
  with a 9-transistor A1 board, while the other has a
  13-transistor A1 like the R-1051H (EE125-AF-OMI-010/E110-R1051H),
  which would support MGC/FAST/SLOW if my front panel did.
  (It might have been introduced in a lower model, but I
  don't have any other manuals.)  Someone inadvertently
  stuck an early shield can on it, so the silkscreened
  board layout is wrong.  Does anyone have a spare late can?

  Someone put the old IF's AGC Threshold trim-pot
  at full-CCW like he started to adjust it.  I think I
  got it straightened out, but the three procedures I
  have available to me (four, if you count the
  test-fixture-only one in R1051H) are pretty different
  from one another.  Does anyone have a favorite?

  My RF module doesn't match any manual I have.  Unlike
  NAVSHIPS, NAVELEX, and R-1051H, it puts full AGC on the
  6BZ6 and reduced (85%) on the 6AN5.  The 6AN5 is too hot
  to touch, but the voltages indicate it's within design
  maximum in the tube manual.

  My Frequency Standard is another module that appears
  to have been introduced in the middle models between
  plain and H.  Its mode switch has INT, EXT(NORMAL),
  and EXT(OVEN STBY) like the H, but it's discrete
  transistors and does not include the automatic
  switchover on loss of external input.  I can't find
  any reference to its part number except the robot
  sites that are eager to sell me one for a couple
  thousand dollars.

- When I last wrote about it, I had gotten my thermistor
  sort of working.  It has become more stable, and I may go
  on using it.  I got Bourns type 3006P and 3296 trim-pots,
  and the 3296 is not feasible.  The 3006P drops right in.
  The crystal had a clearly-distinguishable frequency
  turnaround near 85C.

  I still want to try an NTC since they're so cheap and
  available.  I got a pack of 5 for a few bucks.  Anybody
  want one?  10k at 25C, about 1.1k at 85C.  I'll epoxy it
  inside the oven at the bottom, and for testing, bring the
  wires out to an external breadboard that replicates the
  oven control circuit from A1.  It looks like an easy fix
  if your thermistor has gone pfft.  Just remove P2-3
  (the pin connecting A1 to the original thermistor),
  wire a 7.5k resistor from the pad to ground (8.2k if
  R16 is 4.3k), and replace R13 with the new thermistor
  plus 6.8k in series.  No trace-cutting.

  I also got an SMD PTC thermistor from Mouser, but I have
  second thoughts about mounting it.  It's more of a challenge
  than the epoxy-dipped leaded NTC part.  Maybe solder it onto
  a chip of copper-clad FR4 that's been scribed and manipulated
  so copper extends past the laminate so it can be wrapped around
  to the other side for wire attachment.  And it still would
  have to be insulated from the oven can.  If I can make NTC
  work, it will be the way to go.

- I traced low sensitivity in the 12MHz band to a manufacturing
  defect, a dry solder joint on the RF module's A2 turret strip.
  Putting the turret back together is a pretty tense experience!

  My spectrum analyzer and tracking generator made checking this easy.
  (141T/8553B/8552A/8443A.)

- Is it normal for 2MHz to be weak?  As in, 6uV for 10dB S/N
  vs 2uV or less elsewhere?  I may be doing the turret dance
  again.

- By adjusting detents and sprockets, I have the chain drives
  all synced up.  The MC code generator wafers are marginal,
  but there doesn't seem to be much room for adjustment, as
  some are on the CW edge, some CCW.

- On the late models, the gain control mode is selected by
  a switch on the front panel.  It seems to me that this makes
  FSK aka RATT superfluous, because it's just USB+FAST.  Right?

It has a ways to go, but it's definitely firing on all cylinders.

Dave Wise

>-----Original Message-----
>From: David Wise 
>Sent: Tuesday, July 03, 2012 6:11 PM
>To: 'R-1051 Discussion Group'
>Subject: RE: [R-1051] Tools, and first assessment
>
>I bench-tested the motors in the RF module and the 1MC module. 
> The former seems okay, but the little gearmotor in the 1MC 
>needs attention - the brushes are worn down and the bearings 
>are squealing.  It appears to me that with some soldering and 
>finagling, I might be able to remove the baseplate, and then 
>get at the motor.  Is this the best way?  Is there a modern 
>substitute for the brushes?
>
>Thanks,
>Dave Wise