IF DECK TIPS R390A IF Deck Alignment

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IF DECK TIPS
R390A IF Deck Alignment (Chuck Rippel)
R390's made after 1954 and those with mod 2 stamped on the IF chassis have a field
change installed to the mechanical filters. Filter input and output trimmer capacitors
have been added. The 4 input trimmer capacitors are found by removing the 2
square can on top of the IF chassis using the single nut in the top. The 4 output
trimmer capacitors are located behind 4 holes in the left hand side of the IF deck.
The IF chassis will need to be loose but still electrically connected to complete these
procedures.
An accurate counter, analog VTVM and a signal generator capable of outputting
455.00 KC, is required for these alignments.
Connect the VTVM to the Diode Load bus on the rear and configure it to read a
negative voltage of approximately -7vdc. Set the receiver FUNCTION control to
MGC, BFO to OFF and the LOCAL GAIN control to a comfortable level. Lift and tilt the
IF deck resting the front captive (green) screw over the front panel. You should be
able to gain access to the mechanical filter trimmer capacitors through the large
ventilation holes in the main chassis.
Locate the cable running from the rear of the IF deck to the *IF OUT* BNC connector
in the rear panel, upper left side. Unplug the cable from the IF deck only. Also
unplug J-513 and the one next to it. Plug the cable running from the rear IF Out jack
into J-513 on the IF deck. Connect the output of your 455.000 kc generator.
Mechanical Filter Alignment-
• Set the 455kc generator output level so that the VTVM reads about -2.5V.
• With the IF deck oriented so that the bandwidth control is towards you,
set the bandwidth to 2Kc and align 1 of the four top trimmers.
• Adjust C-569 which is at 9 o'clock for a peak on the VTVM.
• Next, align the output trimmer in the left side of the IF deck, C-567
• Set the BW to 4KC
• Align the top trimmer, C-568 located at 12 o'clock
• Align the side trimmer, C-566 located at rear, bottom.
• Set the BW to 8kc
• Align the top trimmer, C-570 located at 6 o'clock.
• Align the side trimmer, C-565 located at front, top.
• Set the BW to 16kc
• Align the top trimmer, C-571 located at 3 o'clock
Align the side trimmer, C-564 located at front, bottom.
IF Transformer Alignment-
• Select the 16KC filter
• Set the generator frequency to 467kc.
Note: The generator output should be increased until the VTVM
indicates approximately -2vdc.
Do not be alarmed if that level is over 0.1 volts.
• Adjust the top slug (secondary) of T-501 for a peak reading on the VTVM
• Adjust the bottom slug (primary) of T-502 for a peak reading on the VTVM
• Set the generator frequency to 443kc. Note: The generator output should
be increased until the VTVM indicates approximately -2vdc.
Again, do not be surprised if that level is over 0.1 volts.
• Adjust the bottom slug (primary) of T-501 for a peak reading on the VTVM
• Adjust the top slug (secondary) of T-502 for a peak reading on the VTVM
• Decrease the generator output and adjust the frequency
to 455kc Note: The generator output should be decreased until the
VTVM indicates approximately -3vdc.
• Select the 4kc filter then peak top and bottom of T-503 only
AGC Alignment-
• Verify the generator is still outputting 455.00kc.
Set the FUNCTIONswitch to AGC and connect the VTVM between the
AGC bus on TB-102 3 & 4 located on the rear panel & ground.
• Adjust the generator output for a reading of approximately -5vdc on the
VTVM. Peak Z-503.
BFO Alignment-
• Verify that generator is still at 455.00kc
• Turn on the BFO and exactly zero beat it against the 455.00
generator frequency.
• Loosen the bristo spline socket on the BFO shaft coupler,
• Verify that you still have exact zero beat.
• Set the BFO Pitch control to indicate exactly 0.
• Then, tighten the bristol socket on the non-mar clamp on the BFO
shaft coupler
• The filters have been aligned to 455 kc.
(When a station broadcasting in AM is zero beat, the carrier will be in the
center of the filter selected).
• Re-install the IF chassis in the receiver.
Setting the IF Gain Control for best performance
The most common single item responsible for holding an R390A back is not lack of
sensitivity. Rather it is internally generated IF deck noise. In an otherwise properly
operating R390A, the cause of this excessive noise is IF gain control being set to
high. Even the mfg spec of setting the IF deck gain such that -7vdc at the diode load
when fed by 150uv @455kc into J-513 is far too hot.
Here is a recently refined procedure to set the IF deck gain control. Anyone can
perform the procedure whether they have access to a signal generator or not.
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Procedure to set R390A IF Gain-
Once the receiver has been fully mechanically and electrically aligned, the final
procedure to perform before buttoning it up is to set the IF gain control. Many
otherwise very sensitive R390A's are thought not to be due to weak signals being
covered by noise generated by excess IF deck gain.
Allow the receiver to warm up for at least 1 hour then:
• Disconnect the antenna
• Set receiver for 15.2 mHz
• Set the FUNCTION control to MGC
• Select the 4kc filter with the BANDWIDTH
• Set RF GAIN control to 10 or maximum
• Peak the ANTENNA TRIM for maximum noise as indicated on
the LINE LEVEL meter
• Set Line Meter switch to -10db scale
• Set Line Gain control to full CW or 10.
• Adjust IF gain control, R-519 to cause Line Level meter
to indicate between -4 to -7 db.
• Re-zero the carrier meter control, R-523
• Set controls above for normal operation and reconnect the antenna
Discussion:
This will yield the best compromise on all bands. I usually poll those bands which I
normally spec out. Then, using an HP signal generator set for internal modulation of
800 hz @ 30%, massage the gain setting and even specific signal path tube
selections for the best overall performance.
Contribution by Chuck Rippel, WA4HHG
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RF Deck Test-
I also encourage you to do a quick test that will verify the condition of your RF deck
and state of alignment. The procedure is as follows:
1-Disconnect the antenna
2-Set the Line Gain and Line Meter controls for a relative -5
db indication on the Line Level meter.
3-Adjust the antenna trimer for a relative peak on the Line
Level meter and note the position of the control.
Discussion: An R390A with a properly operating RF deck is capable of
peaking on its own internal noise as indicated by the Line Level meter.
Further, that peak with no antenna connected should be coincident with
the Ant Trim control indicating 0. Having the peak not occur at all indicates
an RF deck failure or poor/improper alignment. Additionally, improper
alignment can also be the case when the noise peak as indicated by the
Line Level meter not coincident with the 0 (+- .5) position on the Antenna
Trim control. Chuck Rippel
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From: "Chuck Rippel" <crippel@...>
Date: Thu, 23 Oct 1997 09:01:39 +0500
Subject: [R-390] R390A AGC Problem
Now, I too am wrestling with an R390A AGC problem.
The basic symptom is: the receiver overloads for lack of AGC voltage. I develop only
about 2.2v v/s about 7.5v on a known working radio at the rear AGC jumper for a
60db signal on the Carrier Meter. The time constants seem to be ok, just does not
produce enough voltage. I replaced the 82K, 1W R549 which has drifted up to about
103K (seen it before) and had 82K 2W spares around.
Changing the IF deck out with a known working unit has no effect. The problem stays
with the radio.
I removed the RF deck and proved out the AGC bus checking both continuity and to-
ground resistances as compared with another deck. To ground resistance was about
1.9M so its hard to believe that the RF deck is loading the bus down yet, the AGC bus
goes no where else.
Tonight, I plan to swap RF decks just to further isolate the problem. Assuming its in
the RF deck, my plan is to read the current at the AGC bus and compare it with a
known, good radio. Maybe someting is breaking down?? If it's in the RF deck, the
problem should be mentally easy to locate by just breaking the AGC bus within the
deck and watching for the voltage drop.
This is a I have not seen before and would appreciate some input if anyone has a
thought on it.
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Date: Thu, 23 Oct 1997 23:10:02 +0500
From: "Chuck Rippel" <crippel@...>
Subject: [R-390] R390A AGC Problem Solved
Reference my earlier post about the AGC problem I was having with an R390A.
Essentially, there was not AGC as the control voltage measured at the AGC jumber
to ground was only -2v. It would rise when the RF deck was unplugged.
Tonight, after doing my usual routine on restoring an RF deck, I installed another in
the radio for test purposes. The test deck worked just fine. I made some note on the
operating parameters of the working deck with respect to AGC. I left my millivolt
meter which had been set up to read current across the rear panel AGC bus. I had
removed the jumper between terminals 3&4 on TB-102 in configured the meter to
read current between those two points. Since I already knew the IF deck was good,
any anomoly would be caused by the AGC bus in the RF deck. The current across
the AGC bus was typically 4ua with an off air signal that nominally measured 70 on
the carrier meter. Did not use a signal generator because I felt that actual program
material would reveal the resulting distortion from a no AGC caused overload
quicker.
I reinstalled the defective deck and tested it. Same problem and the current
measured was >150ua. I then physically removed the deck from the main chassis,
connected it electrically and powered up the radio. Same input signal except the
AGC voltage was normal. What gives?
Looking across the bottom of the deck, I found that a .005 capacitor (no number in my
print) that was connected to pin 4 of V202 was pushing on C-273 causing the hot
end to ground (under a wiring harness so the potential problem was hidden from
sight/visual inspection), thus killing the AGC to V202 and V201. Thus, the overload. I
re-positioned the component and the AGC problem is fixed.
This failure looks like it has been that way since mfg. There were 3 RF deck
installation screws missing so I expect that someone had done some digging looking
for this problem. This radio is a Capeheart but in nearly new in appearance and both
electrical and mechanical operation. It now has a very hot RF deck which easily
peaks on its own noise (and that's not very much) when the Antenna Trim control is
rotated with no antennas attached.
The person that is getting this radio is getting an exceptional R390A. This radio is no
mongrel. thus far, all the Capheart modules match the main chassis.
R390A AGC Specs:
70 db as measured on the Carrier Meter results in:
(All measured at Terminals 3 and 4 of TB-102)
(-6) to (-7) Volts
4ua current between terminals 3&4, bus connector removed
Use an analogue VTVM as the dynamic nature of the changing voltage
would make measurement with a DVM very difficult.
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Date: Tue, 28 Oct 1997 08:59:34 -0800
From: "James M. Toney, Jr." <tcltd@...>
Subject: Re: [R-390] (R-390) Why filters go bad - viz. bad caps
> ……what kills the mechanical filters in relation to (what) capacitors go bad.
> This probably relates to the compilation that I think was going on on the
> BA List a few weeks back, just before the establishment of the 390 mailing
> list I think - a record was being compiled of bad components……………
Brien, there is a capacitor in the input side of the mechical filter circuit, it is a 200V
cap (I think); the other side of the filters are grounded; if cap shorts filter killing
voltage goes thru filters to ground. Fix is to replace 200V cap with a 1KV and isolate
ground with a 1KV cap in series between filters and ground. Jim
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Date: Sun, 09 Nov 1997 21:28:49 -0600
From: Tom Norris <badger@...>
Subject: [R-390] Re: More on Electronic Assistance Corp./Hammarlund
At 10:14 PM 11/9/97 EST, you wrote:
>We have recently had a correspondent on the R-390 list server who *has*
>such a radio -- still with the ceramic filters! This may be one of the
>rarest R-390As around !!! He is correct in pointing out that the audio
>quality would be better than had the mechanical filters been installed.
>For the military, however, there was a practical degradation in intermod
>suppression in the harsh RF environment of a ship with multiple HF transmitters.
Indeed, the audio is much better on AM with the ceramic filter deck! The AM audio is
"fuller" and hasn't the ringing of the "real" filters. I swept the deck at one point, and the
skirts are just a tad less steep. This deck is part of SN 127 EAC contract 23137-
PC-60. It is not a good a performer on crowded bands though, so at the moment I
have a 1954 Motorola deck installed......
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From: John Kolb <jlkolb@...>
Date: Wed Dec 17, 1997 9:38 pm
Subject: Re: [R-390] More 4KC filter wierdness
<snip>... Let me describe Older Collins filters from a few I've opened. There are a
number ( 7 - 11 ) of metal alloy disks, typ 1/2" diameter, 1/8" thick in a row with equal
sized gaps, held together with a bonding wire welded to each disk. attached to the
two end disks is a fine wire, 1/2" long, about 36 gauge diameter. A set of solonoid
coils at each end surround these wires. The electrical signal is applied to the coil at
one end, which creates a magnetic field, causing the wire to vibrate the first disk. The
disks are like tuning forks, resonant at freqs near the IF freq of the filter. If the applied
signal is close in freq to the resonant freq of one of the disks, it will be passed on to
the end wire, which vibrates, inducing an electrical signal in the other coil. If the freqs
are too far from the resonant freq of any of the disks they won't pass. There's also a
small magnet at each end, parallel to the transducer wire, creating a fixed magnetic
bias on the transducer wire.
Most of the filters I've seen had custom rubber cushions supporting the transducer
assemblies at each end. Not much chance for change here. I've heard that some of
the older filters used a standard rubber grommet to hold the works and that would fall
apart with great age, causing the works to rattle around and break the wires between
the coil and terminals, if you were lucky; if you are unlucky, the works would be bent
beyond repair by the rattling around.
If the transducer wire were to break off, you get a very high insersion loss, but that
wouldn't recover. It may be that a speck of dust or flake of rosin flux got into the filter
and jammed between the coil bobbin and transducer wire. If so, operation may
cause vibration which would eventually change it's position.
Collins filter data sheets may have limits on the applied signal voltage or DC voltage
or current through the filter (You generally should not let plate current flow through
the filter ) but they do not spec a maximum number of operating hours or vibrations.
Haven't heard of any filters dieing of old age other than the ones noted above. I have
opened and repaired a few filters where the coil wire was broken between the coil
and the terminal (wire fatigue??) or one case of no solder on the terminal.
------------------------------------------------------------------------------------------
From: crippel@...
Date: Thu Dec 18, 1997 2:01 am
Subject: Re: [R-390] More 4KC filter wierdness
I have seen this happen before. Take the square filter cover off and wiggle the wires
going to the 4KC filter (its the one in the far rear). They are hard to solder and I have
seen them be soldered cold or even break loose.
---------------------------------------------------------------------------------------
From: "Chuck Rippel" <crippel@...>
Date: Sun Jan 25, 1998 1:51 pm
Subject: Re: [R-390] R-390a Repair
> Hello all, It is time to ask for help in repairing my first R-390A. I > have a Stewart
Warner >S/N 1831. On all bands 7Mhz and below, the sensitivity seems to be down
maybe 20DB or so. >The calibrator shows the same weakness >in signal level. V202
tests fine, replaced anyway. >The 17Mhz osc signal is present at V202 cathode. All
voltages and resistance's at V202 check >fine. Z213-1 thru 3 tune and are peaking. I
have removed the RF unit and inspected for >problems. Wafer switches and contacts
have ohmed out. Any ideas?
Check for a leaking/shorted capacitor inside the IF cans, Z-216-1, 2 or 3. Also, one of
those IF transformers could be bad.
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From: Colin Thompson <burkec@...>
Date: Sat Jan 31, 1998 8:57 pm
Subject: [R-390] AGC settings
In the past there has been some talk about the appropriate AGC settings. I would
encourage all of you to try the Med or Slow settings, espcially for stronger broadcast
quality signals. The increase in fidelity is startling. For those of use used to SSB and
faster time constants, this may seem contrary. At one point when considering
modifying the AGC for better SSB, Chuck Rippel reminded me that the R-390A is an
AM reciever. The faster AGC mods would be a compromise in the AM mode. The
more I use these great recievers, the more I come to know them and understand this.
I have had some email dialog with John Thorpe; Lowe HF225, HF150 and AOR7030
designer. All superior sounding recievers. JT was famous for his slower AGC
constants. He also restored a R-390A to use as bench mark for designing the
AOR7030. Slower AGC settings? Food for thought.
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From: trinit69@... (Tom Marcotte N5OFF)
Date: Sun Feb 1, 1998 7:22 am
Subject: [R-390] 390A cap fail/fix
Another data point for the common failure list.
I had to replace C-523 and R-551.
C-523 is a .005 uF bypass cap in the IF deck. It would short out at line voltages over
90V. At that point, B+ was shorted through R-551 causing it to let the smoke out of
itself. I had the IF deck running external to this new rig, and thus could witness the
failure.
Replaced the cap and resistor.
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Date: Sat, 27 Feb 1999 08:20:55 -0600
From: Dallas Lankford <[email protected]>
Subject: Q-spoiling resistors in the IF cans: purpose
I have also seen cut (but not cut off) Q-spoiling resistors in an R-390A IF deck and all
those IF transformers peaked to 455 kHz. Since this is clearly not how the IF deck
came off the production line, I did not mention it previously. The worst case of this I
have ever seen was with Q-spoiling resistors cut so that you could not see the cuts
without very close inspection (= magnification). I finally found these "invisibly cut" Q-
spoiling resistors because of intermittent jumps and drops of signal levels of about
10 dB per the carrier meter. Heating and vibration apparently caused enough
movement of one of the cut resistor leads to open and close the cut intermittently.
And yes, I will echo what Chuck said. An R-390A works much better with the Q-
spoiling resistors not cut , and the IF transformers stagger tuned (not all aligned to
455 kHz as some people are going to do regardless of the correct way to do it). I
never cease to be amazed at some people thinking they know better than the Collins
engineers who designed, tested, redesigned, and retested the R-390A.
For those who think they know better, I would suggest a reeducation program,
beginning with reading "Final Engineering Report On Radio Receivers R-389()/URR
And R-390()/URR," September 15, 1953, A Publication Of The Research And
Development Laboratories, Collins Radio Company, Cedar Rapids, Iowa (as
required background reading for learning about the
R-390A), and Cost Reduction Program For Radio Receivers, R-390/391x/URR, Final
Progress Report," A Publication Of The Research And Development Laboratories,
Collins Radio Company, Cedar Rapids, Iowa (which is the story of the development
of the R-390A). Though stagger tuning is not specifically mentioned in this report (to
the best of my knowledge), we do find on page 15," New interstage coupling
transformers were designed to give the required flat top over a wide frequency
range." What do you think this means? And your first two guesses don't count.
Chuck Rippel wrote:
> Just as an FYI... the stagger tuning of the T501/T502 accomodates
> the bandwidths of the 8 (really 11) and 16kc filters. When I perform
> that procedure, I select the 16kc filter then perform the stagger tune
> alignment on T501/T502.
>
> The tuning of T501 and T502 will appear somewhat more broad than
> you might otherwise expect due in part to the Q-spoiling resistors
> installed in the transformers. I have seen receivers where those have
> been incorrectly cut out and the transformers all tuned to 455 kc.
> Needless to say, the R-390A works much better if that is not done.
>
> > From TM 11-5820-358-35 (8 Dec 1961), pages 3 & 4, para 2(c) "Equipment
> > Modification Chart": "IF transformers T502 through T503 stagger-tuned at the
factory". Per the chart and its notes, this stagger-tuning applied as Mod
> > 1 on all Order No. 363-Phila-54 receivers, and also to Order No. 08719-Phila-55
(serial numbers 600 and higher only, no Mod # indicated).
> >
> > 73, Jerry W5KP
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Date: Sat, 5 Jun 1999 12:35:57 EDT
From: [email protected]
Subject: Re: [R-390] Dirty but not so quick total setup
According to T.O. 31R1-2URR-452 (USAF Field and Depot Maintenance Manual),
page 4, Modification Table it states: "IF transformers T502 through T503 stagger
tuned at factory on Order No. 363-Phila-54, IF chassis MOD number 1....................."
with a sub note stating: "This was also done to receivers on Order No. 08719-
Phila-55 with serial numbers 600 and higher." The T.O. that I have is dated
8-12-1961 with change 12 dated 7-15-1975 I realize that this does not cover
everything but it is one piece of the information being discussed.
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Z-503 AGC TRANSFORMER REPLACEMENT
Date: Sat, 27 Feb 1999 21:29:48 -0500
From: "Chuck Rippel" <[email protected]>
Subject: [R-390] Re: Z-503 Replacement
As a suggestion to you and for the further edification of the list.
Z-503 is the AGC transformer. It can open but more often than not, the core binds in
the form. If it is forced during alignment, the core can break of the form will come
loose, rotate and break the feed wires. Before aligning it, put a >very, very< small
shot of WD-40 into the coil form and wait overnight. For some reason, Z-503 cores
can badly bind to the forms. I have found the WD-40 breaks loose whatever the
binding agent is allowing for easy alignment without breakage. I have also yet to see
any ill effects resulting from frugal introduction of WD-40 into the coil.
If yours is open or the form is broken and not repairable, I think I have may have a
very Z-503 few >coils only< from American Trans-Coil and you can have one for the
asking. This assembly consists of the plastic (?) coil form with the coil installed and
two tinned wires only. I had a Z-503 open up and was able to replace it without
removing the entire coil assembly from the IF chassis (which is difficult, just look
underneath). I simply dissassembled
Z503 and replaced the open coil as follows:
Remove the 2 nuts holding the sheet metal cover from Z-503
Remove the 2 nuts holding the top insulator (with the tuning tool opening in it).
Carefully work the insulator off the coil while unsoldering the coil feed wires that pass
through it.
Closely cut or better, unsolder the 2 small wires which feed Z-503 and are attached
to the vertical feed wires in the coil form.
Carefully twist and pull on the Z-503 coil assembly lifiting it clear of the coil mount.
At this point, its not a bad idea to check the internal, fixed value capacitor by taking
one lead loose and putting a megger on it. These have been known to leak.
Replace if required or simply re-attach the lead if it checks ok.
To install the new coil:
Put a small amount of epoxy glue on the bottom of the new coil form and install it in
the bottom insulator of the coil assembly.
Resolder the two Z-503 feed wires to the vertical wires in the coil form reattaching
them as closely to where the old ones were as possible.
Put a small amount of epoxy on the top of the coil form and reinstall the top insulator
being careful to make sure the vertical feed wires go through the top grommets.
Solder the vertical feed wires in the top grommets.
Reinstall the 2 nuts which secure the insulator to the coil base assy.
Reinstall the coil cover and hold down nuts.
Put a very small shot of WD-40 into the coil form to loosen the core and provide for
easy tuning.
Allow the glue to cure overnight.
After the glue is cured, realign the coil by injecting a 455.0 kc signal into J-513 on the
IF deck at about 300uv.... (of course, the rx is already warmed up and operating, the
Function switch set to AGC and your VTVM attached to the rear agc bus and
ground) . Simply tune the transformer for a peak on the VTVM.
You are done. Chuck Rippel, WA4HHG R390A List Co-Administrator
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Date: Tue, 5 Oct 1999 09:58:02 -0700 (PDT)
From: John Kolb <[email protected]>
Subject: Re: [R-390] Mech filter query
> I'm refurbing a spare R-390A IF unit - had a bad 8kc filter that was hacked
> out before I got it. Just so happens that the one and only spare part in my
> tons of junque box goodies is.... an 8kc filter !
>
> Anywho - does the in/out phasing of the filters matter?
>
> If the answer is yes, then I guess I get to stare at it some more. Also, if
> yes then I wud assume that the lead connections on the top and bottom of the
> filter are layed out physically to match the winding phasing.?.