[R-1051] diagnosing dead bands
David Wise
David_Wise at Phoenix.com
Mon Mar 31 12:24:41 EDT 2014
Posted July 31, 2012. I include it here as an attachment and as plain text.
From: r-1051-bounces at mailman.qth.net on behalf of David Wise [David_Wise at Phoenix.com]
Sent: Tuesday, July 31, 2012 4:03 PM
To: R-1051 Discussion Group
Subject: [R-1051] Update - Pretty Much Working
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
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-----Original Message-----
From: r-1051-bounces at mailman.qth.net [mailto:r-1051-bounces at mailman.qth.net] On Behalf Of Mark Richards
Sent: Monday, March 31, 2014 8:36 AM
To: R-1051 Discussion Group
Subject: Re: [R-1051] diagnosing dead bands
David,
I've looked at each month and subject line but cannot find anything that
comes close.
Any chance you might have your instructions available to re-post?
I have already gone perhaps far too deep into dis-assembly anyhow, but
perhaps a few drops of wisdom will save it from further damage :)
/m
On 03/27/2014 16:08, David Wise wrote:
> Look deeper into the archive. Two different people (one of them myself) documented how they got the motor out and back in. Slightly different methods. It can be done, and safely, but it's no cakewalk.
>
> The motor short brings a spinning motor to a quick stop, to prevent overshoot. It doesn't have any noticeable effect at hand-turn speed.
>
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