[R-1051] Several Broken Radios (was Re: R-1051 Digest, Vol 50, Issue 6)
David Wise
David_Wise at Phoenix.com
Wed Oct 31 13:16:08 EDT 2012
All my experience is with the plain, which uses the six-pack, but
I have also studied the H manual (flat-top).
The Frequency Standard has several locked-oscillator dividers that
will put out the wrong frequency if misadjusted. The same goes for
the Spectrum Generator sub-module in the six-pack. Check your
injection frequencies. This is easy if you remove the RF Amp and
the cover of the RF Translator. Get a manual. There are free scans
of the plain, B, and H out on the internet. One page is especially
useful for evaluating injection. For the plain, it's in
NAVELEX 0967-LP-970-9010, available at www.jamminpower.com ,
Figure 3-3, page 3-9, pdf page 34.
This will probably narrow it down to one or two sub-modules. Report
your results here, and maybe I can help you.
Six-pack: First injection comes from the 1MC synth, which is
independent of the rest of the six-pack, using only the Frequency Standard.
It's a PLL with a crystal-based VCO. It should be spot-on. (The other
injections will be merely almost right; their errors are supposed to cancel
out.) If it fails to lock, its output will only be nearly right: off by
however much that MC's crystal is off. Second injection comes from the
100KC synth, but it depends on the 500cps or 100cps synth and
the 1&10KC synth. Third injection comes from the 1&10 and can be
right even if the 1&10's contribution to second injection is wrong.
The 100KC and the 1&10 are straight crystal oscillators (10 switched
crystals per decade) which employ Wadley error cancellation. The 500cps
or 100cps are PLLs with an LC VCO. The PLLs lock onto reference combs
from the Spectrum Generator, which in turn is fed by the Frequency Standard.
The R-1051(*) Synthesizer/Translator module is also used in the T-827 exciter.
HTH,
Dave Wise
SWL in Hillsboro Oregon
>-----Original Message-----
>From: r-1051-bounces at mailman.qth.net
>[mailto:r-1051-bounces at mailman.qth.net] On Behalf Of paul swed
>Sent: Wednesday, October 31, 2012 9:48 AM
>To: Terrence Harvey; R-1051 Discussion Group
>Subject: Re: [R-1051] R-1051 Digest, Vol 50, Issue 6
>
>Well thats a tough one. It can be in many places. If every
>frequency is off
>by a linear amount look at the freq standard. By the way you can go
>external and grab the 5 mc from another unit.
>If its just some frequency its most likely the frequency translator and
>those pesky crystals.
>I have seen lots of components drift in that unit. Adding caps
>to vcos to
>bring them back inline stuff.
>Don't know if anyone fixes them. These days the shipping is a killer.
>They are great boxes I have a 1051 and another transmit rcv unit don't
>recall the number. RT 914.
>Regards
>Paul.
>
>On Wed, Oct 31, 2012 at 11:35 AM, Terrence Harvey
><terrencelharvey at yahoo.com
>> wrote:
>
>> Hello Dave and group;
>>
>> I am an swl with and addiction to the 1051s. I own 4
>in various
>> states of operation except for the "fully operational" mode!
>Mostly I seem
>> to have frequency error probs on the three that fire up. (unit # 4 is
>> non-op with all modules being suspect) Indicated freq is
>actuallu 2-4 kc
>> off actual freq as measured on my R8B. One of my nicest
>cosmetic units goes
>> silent after 5-10 minutes of on time. It has a label
>indicating was from
>> Naval post Grad school in Monterey CA. Another, the nicest,
>has a pale
>> green front panel that might indicate was from an officers suite,
>> shipboard. Anyway, sorry for the ramble. Any tips or suggestions on
>> frequency error fix would be appreciated. One last thought,
>does anyone
>> on/off the list service these?
>>
>> Thanks and Regards,
>>
>> Terry Harvey,
>>
>> Crystal lake, IL
>>
>> 815 455 7872
>>
>> off list, terrencelharvey at yahoo.com
>>
>>
>> ________________________________
>> From: "r-1051-request at mailman.qth.net"
><r-1051-request at mailman.qth.net>
>> To: r-1051 at mailman.qth.net
>> Sent: Tuesday, October 30, 2012 12:00 PM
>> Subject: R-1051 Digest, Vol 50, Issue 6
>>
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>> Today's Topics:
>>
>> 1. Frequency Standard NTC Thermistor Retrofit FINAL (David Wise)
>>
>>
>>
>----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Mon, 29 Oct 2012 16:49:39 -0700
>> From: David Wise <David_Wise at Phoenix.com>
>> Subject: [R-1051] Frequency Standard NTC Thermistor Retrofit FINAL
>> To: "'r-1051 at mailman.qth.net'" <r-1051 at mailman.qth.net>
>> Message-ID:
>>
><FFF45F8A4E2B6F4CA4920B3B028CE73D01EA82B9EF at SCL-ExchMB.phoenix.com>
>> Content-Type: text/plain; charset="us-ascii"
>>
>> INTRODUCTION
>>
>>
>>
>> The R-1051 series Frequency Standard is a high-failure item.
> There are a
>>
>> lot of dead ones around. Usually they have a bad
>thermistor. Leaded PTC
>>
>> thermistors like the original are hard to find, but an NTC
>thermistor can
>> be
>>
>> used instead. It's easy and cheap, and it works fine.
>>
>>
>>
>> If anyone expresses interest, I'll post photos and sketches
>on SkyDrive.
>>
>>
>>
>> Warning: This mod is not applicable to the early R-1051
>plain frequency
>>
>> standard, P/N 666231-006, which uses an oscillator and
>rectifier in the
>>
>> oven control instead of a DC amplifier. If you have one of
>these, you're
>>
>> on your own, and good luck!
>>
>>
>>
>> DISCUSSION
>>
>>
>>
>> This mod replaces fixed resistor R13 with an NTC thermistor,
>and replaces
>>
>> PTC thermistor R2 with a fixed resistor.
>>
>>
>>
>> I used a 100K thermistor. At the time I wrote this, October
>2012, eBay
>> members
>>
>> "tayda2009" and "taishopetc" were selling a pack of 5 for
>$0.99 including
>> shipping.
>>
>> It's made by a Taiwanese company called Thinking; it's part number
>> TTC05104.
>>
>> The TTC05 datasheet is available at
>> http://www.thinking.com.tw/documents/en-TTC05.pdf .
>>
>> There is nothing special about this part; it has about the
>same R-T curve
>> as most
>>
>> TC thermistors. They don't put the curve on their website,
>but they'll
>> send you a
>>
>> pdf if you ask. I have it too.
>>
>>
>>
>> You have to modify circuit board A2A5A1, but it's easy and
>reversible.
>>
>> While working, refer to the A1 schematic, Figure 5-6 in NAVELEX
>> 0967-LP-970-9010.
>>
>>
>>
>> NTC thermistors are much more sensitive than PTC. An NTC
>thermistor placed
>>
>> directly into the old bridge circuit will provide too much
>gain, causing
>> the control
>>
>> circuit to oscillate. We work around this by adding a
>resistor in series,
>> to reduce
>>
>> the percent change of the total. This also makes the rate
>of change vary
>> with
>>
>> thermistor resistance Rt, but a second fixed resistor in
>parallel with Rt
>> makes
>>
>> the total approximately linear near operating temperature.
>>
>>
>>
>> Temperature trimpot R15's adjustment range is (5.3K/10K -
>4.3K/9K)*10V or
>> about 500mV.
>>
>> The original thermistor together with upper leg R13 puts out about
>> 6mV/degree.
>>
>> That's about 80 degrees of adjustment range, or 5 degrees
>per turn. (It's
>> a 15-turn pot.)
>>
>> This is really twitchy, and the slightest drift will throw
>it way off.
>>
>>
>>
>> It's possible to eliminate this problem. If you increase
>your thermistor
>> output,
>>
>> the degrees per turn go down correspondingly, but you have to change
>>
>> R23 to keep the loop stable. 4.7K/15K/11K makes about
>30mV/degree instead
>> of
>>
>> 6mV/degree, which makes R15 about 1 degree per turn.
>>
>>
>>
>> This resistor set is for R16 = 4.3K . If you have an R-1051H module
>> (3.9K),
>>
>> use 4.7K/18K/10K instead.
>>
>>
>>
>> My calculations said I had to change R23 to about 240K if it was 1.2M
>> before,
>>
>> but testing showed that 330K is optimal for my 4013399-0701
>with mains
>> regulation
>>
>> upgrade (see below). This should be good for all versions
>where R16 is
>> 4.3K* .
>>
>> For the R-1051H, I'd try 220K or 270K.
>>
>>
>>
>> * The NAVELEX schematic labels R2 as 3.9K but that's at 25
>degrees. It's
>> around
>>
>> 4.7K at 85. The R-1051H schematic also labels it 3.9K but
>that can't be
>> right
>>
>> because R16 is also 3.9K; it must be a different thermistor,
>one that's
>> about
>>
>> 4.3K at 85.
>>
>>
>>
>> PROCEDURE
>>
>>
>>
>> 0. Determine your crystal's turnover temperature. The manual says 85
>> degrees but
>>
>> mine was 82.
>>
>>
>>
>> 1. Connect a 3" to 5" cable to your new thermistor, which I
>call R913c.
>>
>> Try to arrange for the cable to be away from the crystal and
>> oscillator area when
>>
>> A1 is reinstalled in the oven. This will make sense
>after you have
>> read the entire
>>
>> procedure.
>>
>>
>>
>> 2. At the other end of the cable, put a connector, which I
>call J92. I
>> used a 2-contact
>>
>> socket that mates with the popular 0.1"-spaced square pins.
>>
>>
>>
>> 3. Arrange thermistor R913c in the bottom of the oven near
>the abandoned
>> R2.
>>
>> Make it lie flat and out of the way. The connector must
>reach the
>> upper left
>>
>> corner of board A1 when viewing the component side.
>Seal it in place.
>>
>> I used JB Weld.
>>
>>
>>
>> 4. Cut a piece of double-sided plated-through padboard, 1.0"
>long and 0.3"
>> wide;
>>
>> 10 pads by 3 pads. (You can use single-sided if you're careful
>> soldering.
>>
>> Arrange it with the pads up.)
>>
>> Solder square pins P92 at one end, extending off the board and
>> parallel to it.
>>
>> P92 will point toward the bottom of the oven after
>installation, and
>> thermistor
>>
>> connector J92 will mate to it.
>>
>>
>>
>> 5. On the padboard, tack three resistors, R913a (4.7K),
>R913b (15K), and
>> R902 (11K).
>>
>> Arrange R913a near A1 centerline, R902 near A1 edge, and
>R913b in the
>> middle.
>>
>> R913b goes across P92.
>>
>> One end of R902 goes to P92 pin 2 with the other end
>uncommitted for
>> now.
>>
>> One end of R913a goes to P92 pin 1 with the other end
>uncommitted for
>> now.
>>
>>
>>
>> R902 replaces thermistor R2 in the lower-left leg of the
>bridge, and
>> the R913 trio
>>
>> replaces fixed resistor R13 in the upper-left leg, with R913a the
>> series element,
>>
>> R913b the shunt element, and R913c the thermistor
>itself. R913b and
>> R913c
>>
>> are in parallel, and R913a is in series with them.
>>
>>
>>
>> 6. Prepare the top surface of R15, and glue the padboard to
>it. I used
>> super glue.
>>
>>
>>
>> 7. Remove R13 (4.7K) and P2 pin 3 (which goes to old thermistor R2).
>>
>>
>>
>> 8. Run a wire from R902/P92 to the left pad where R13 used to be.
>>
>> This pad also goes to where P2 pin 3 used to be. This is the
>> temperature
>>
>> sensing node.
>>
>>
>>
>> 9. Run a wire from the uncommitted end of R902 to ground, which is
>> available
>>
>> at an unused pad next to the top pin of R15.
>>
>>
>>
>> 10. Run a wire from the uncommitted end of R913a to the
>right pad where R13
>> used to be. This is +10V.
>>
>> 11. Remove R23 and replace with 330K. (220K-270K if R-1051H.)
>>
>>
>>
>> 12. Slide A1 partway into the oven, connect J92, then slide
>A1 in the rest
>> of the way.
>>
>>
>>
>> 13. Adjust R15 for the proper temperature.
>>
>>
>>
>> TESTING; USING A DIFFERENT NTC THERMISTOR
>>
>>
>>
>> Transient response is important. General Dynamics selected
>R23 to control
>> this.
>>
>> R23 determines the gain of the amplifier, excluding the output
>> transistor. In older
>>
>> A1's where Q7's (2N697) collector load resistor R24 is 2.2K,
>the nominal
>> value was
>>
>> 1.2M, which gives a transconductance of about 230mA/V . The
>latest A1 for
>> the
>>
>> R-1051H is 1.2K and 820K, giving about 280mA/V,making up for
>the lower
>> output
>>
>> of their 3900-ohm thermistor. Larger values tighten control
>but increase
>> ringing,
>>
>> while smaller values reduce ringing but degrade regulation.
>>
>>
>>
>> The resistor values I provided above are okay for the
>Thinking TTC05104.
>>
>> Other parts may need different values. There are three goals:
>>
>>
>>
>> 1. Control loop is stable,
>>
>> 2. Setpoint is achievable within R15's trim range, and
>>
>> 3. Bridge voltage vs T is linear around the setpoint.
>>
>>
>>
>> Ask the manufacturer for your thermistor's R-T table; they
>don't usually
>> put
>>
>> them on their websites. With that and a programmable
>calculator, you can
>>
>> come up with usable values. Although you can assess
>stability with just a
>>
>> VOM, a storage or digitizing scope or a chart recorder makes it MUCH
>> easier.
>>
>> You need an extremely slow sweep rate. I used a
>triangle-wave function
>>
>> generator set to .00002Hz as X input. That's 250s/div .
>>
>>
>>
>> Monitor Q7 collector during the transient you get when switching from
>>
>> operate to standby. (It's less stable in standby, because the higher
>>
>> supply voltage increases system gain.) Your amplifier may have more
>>
>> gain than mine, or less. Watch the scope trace and you'll
>be able to tell
>>
>> what's right for you. Keep the insulating lid of the oven in place;
>> otherwise
>>
>> you'll choose too much gain.
>>
>>
>>
>> MAINS REGULATION UPGRADE - 4013399-0701 ONLY
>>
>>
>>
>> What a fascinating journey. My particular Frequency Standard (P/N
>> 4013399-0701)
>>
>> does not have a preregulator, and R24 is referred directly
>to unregulated
>> +28V.
>>
>> This gets away from the R-1051B's embarrassing "dead oven in standby"
>> problem,
>>
>> but it makes the oven sensitive to variations in the power
>source. If the
>> mains voltage
>>
>> rises, so will the temperature. However, I discovered that,
>on a shorter
>> time scale,
>>
>> this ciruit actually creates negative feedback, above and
>beyond what's
>> obvious in the
>>
>> schematic. Let's say the oven temperature is rising. The
>amplifier will
>> pass less current
>>
>> to the heater. With less load, the +28V line rises, increasing the
>> current through R23,
>>
>> which increases heater current. I discovered this when I
>tried to improve
>> the temperature
>>
>> regulation by reducing mains sensitivity. A simple way to
>accomplish that
>> is to add a
>>
>> resistor from +28 to the thermistor side of the bridge, so the supply
>> appears equally in
>>
>> both bridge arms and thus cancels out. When I did this, the
>oven went
>> unstable, because
>>
>> I had eliminated a hidden source of negative feedback. I could have
>> reduced thermistor
>>
>> gain, but why bother since I'm already changing R23?
>>
>>
>>
>> With 330K in R23, 820K is appropriate for compensation.
>>
>>
>>
>> PRESERVING ORIGINAL R23
>>
>>
>>
>> If you want to leave R23 alone, you can scale your new
>thermistor's output
>> back
>>
>> down to the original level with a different choice of
>scaling/linearizing
>> resistors.
>>
>> The disadvantage is a twitchy R15, same as it was
>originally. I don't
>> know why
>>
>> you'd do this just to preserve one 1/4W carbon comp resistor, but...
>>
>>
>>
>> I calculated some combinations to save you the work.
>They're for TTC05104,
>>
>> with R16 = 4.3K . If you are doing an R-1051H with 3.9K,
>bump R902 down
>> 10%.
>>
>>
>>
>> Resistors mV/degree
>>
>> a/b/902
>>
>>
>>
>> 22/10/27 8.5
>>
>> 24/9.1/30 7.2
>>
>> 27/9.1/33 6.5
>>
>> 30/9.1/36 6 <--- worked for me
>>
>> 33/9.1/39 5.5
>>
>>
>>
>> SUMMARY
>>
>>
>>
>> Thinking TTC05104, scaled and linearized by 4.7K/15K/11K, with 330K
>> feedback,
>>
>> and (4013399-0701 only) 820K compensation. This should work for all
>> modules
>>
>> originally using a 4700-ohm thermistor. You can even reuse
>your old R13
>>
>> for R913a.
>>
>>
>>
>> For the R-1051H, which uses a 3900-ohm thermistor, I'd try
>220K or 270K,
>> but I
>>
>> don't have hardware to try it.
>>
>>
>>
>> Dave Wise
>>
>> SWL in Hillsboro, Oregon
>>
>>
>>
>> ------------------------------
>>
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>>
>>
>> End of R-1051 Digest, Vol 50, Issue 6
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