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 Post subject: My R-390A refurbishment
PostPosted: Jan Sun 03, 2016 10:10 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1358
Location: Champaign IL 61822
I got my EAC R-390A radio yesterday. Its in great mechanical and cosmetic shape.
It only needed a little cleanup with alcohol in a few places. The gear train works ok, though
it squeaks a bit. It will not need a full-scale cleanup, just a spot cleaning of congealed grease
with alcohol or toluene.

First question: it will need a little light lubrication. What particular brands and types
of grease and oil do you folks recommend? Most of my radios have needed penetrating
oil somewhere, so I just left some there; this set only has one of the front-panel "clamps"
that will need penetrating oil.

Now on to the electrics. Since it looked so nice I decided to turn it on with
only precautions against disasters. This set does have the two B+ line fuses,
which were wrong values so I replaced them with fast-blow correct ones.

Several places recommend replacing at least two caps. One is the 8 uF tantalum in the
first audio cathode. This was not leaking acid but measured 176 uF and remarkably,
even at 4.5 volts no leakage. I used a 5.6 uF 100V Panasonic as the only other
cap I had that would fit was a 12 uF and I don't think this set needs to be 3 dB down
a 11 Hz. The second must-replace cap is said to be the one between B+ and the mechanical
filters, and I agree ones peace of mind does require a good one there. This was not
a Vitamin Q but rather an "Astron" which tested perfect (at 9 volt however) which I replaced
with an absolute top of the line film 630 V Panasonic.

I reformed the 5 plug-in electrolytic sections. All were in good shape: 2 minutes
got all up to 280 volts at less than 1 mA leakage and 10 minutes to less than
500 uA at 315 volts. I let them soak (all in one can at once) at 315 volts for
an hour after which the worst section ( a 30 uF one) was 80 uA at 315 volts and
much less at 300 volts. I tried that one up to 350 volts at which point it still
was only 1 mA.

The set was supposed to come with all tubes. However, the rectifiers were not plugged in
but wrapped in bubble wrap. Well, one was a correct rectifier but the other was a 1L6!
So I installed 1N4007s. I will eventually check the series resistance to get the 6.3 VAC and the
B+ balanced.

So I turn it on, slowly, on a variac and dim-bulb, listening on headphones. Nothing! Well,
I did notice a vibrating sound at 40 volts power line that seemed to be not on the phones.
It was the antenna relay ... I forgot to set it so that relay would not operate. Fixing that,
all I heard a bit of scratchiness on the volume pot. No awful events either, happily. No smell,
except "old electronics".

I decided to first check the audio. Holding a lead with a whopping big 400- 1500 Hz signal on it near
the narrow-sharp audio filter switch resulted in plenty of sound, and the narrow filter worked.

Next I decided to check the oscillators. First, as it was easiest to reach (but NOT EASY to
pull the tube!!!), was the 2nd Xtal oscillator V401. I installed a tube extender on the tube (did I
mention that the set was missing the tube shields, despite the seller saying "all there",
and see later in this post). I put a scope on the grid and got oscillation on the lower
frequency crystals only. I tried swapping tubes with the other one of that kind
(even harder to pull!) which resulted in one additional crystal working. After much checking,
wiggling the xtals in their sockets and swapping a couple of crystals, I checked with the
scope on the cathode and plate .... oscillation on all crystals. The 7 pF of the scope probe
was loading the grid too much on the higher frequency crystals.

Next to check was the main PTO. This was checked by pulling the 3rd mixer and scoping the cathode.
It worked fine but is a few kHz off.

Next I tested the whole IF chain by applying a 455 kHz CW signal to the 3rd mixer plate
by wrapping a wire around the tube, coupling in through the stray capacitance. (The BFO had
been turned on, untested, the whole time.) A stong beat was heard, and all the various filter
positions worked more or less as expected. Though the signal level varied
between them the bandwidths were correct. The BFO of course works.

Next I tested the RF amp by applying a CW signal to the antenna terminals and a
scope probe to the 1st mixer grid. All the frequency bands up to 7Mz worked nicely
though some were mistuned a bit (the scope capacitance is not enough to cause this).
The upper bands don't go to that mixer so I moved the scope probe to the 2nd mixer.
These bands worked OK too.

Leaving the scope on the 2nd mixer grid and signal at the antenna, I tried each band.
The bands 8 MHz and above worked OK. Below that absolutely nothing.

Hmmmm ... this indicates a dead 1st oscillator. Murphy's Law of course states that
I had not checked that first. It is hard to reach. I removed the first mixer tube
and scoped the cathode. Yes, the first xtal oscillator is not working. I have not yet
tried to figure out why. I can't use a tube extender on it because, while the extender
plus tube would fit, I could never get both plugged in at once. I stopped
at this point and tried something else.

That was trying to figure out why I received no signals and no noise on the upper bands.
Well, that's not QUITE true ... when I had a test wire around some tubes I was weakly picking up both
FM stations and some 6MHz band religious shortwaves from Nashville that are very strong,
at the wrong frequencies, apparently due to spurious nonlinearities.

I had noticed that the RF meter was never below 1/3 scale when mode switches were
in normal positions. I tried checking the AGC line with various strength signals, and it does
work, sort of. But the behavior on the AGC line is odd, and does not work at all in the "slow"
position. There is something wrong with this very odd circuit and I will have to study
it carefully before proceeding. This explains no noise ... no high gains in the RF-IF chain.

Next steps are to borrow a tube tester and test all tubes, and study the odd AGC circuit.
The most bothersome thing is the dead 1st xtal oscillator.

More in this saga later.

Oh yes ... is Surplus Sales of Nebraska the right place to get the correct black IERC
tube shields? They have them, not cheap. But they have several kinds ... which is correct?
Not having tube shields means that alignment of the plate tank circuits will be wrong,
so I can't align until I get the tube shields.

Edit: I mentioned its hard to pull the tubes. I'm afraid of breaking one and cutting my
fingers. What about tube pullers? Do these work better than fingers? Are there
ones that will get onto those tight places? Suggestions of what to get?


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Mon 04, 2016 5:45 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 20591
Location: Warner Robins, GA
When you pull each tube spray sole contact cleaner in the tube pin holes. That should make the tubes a little easier to remove.


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Mon 04, 2016 7:00 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1358
Location: Champaign IL 61822
I have the radio working, mostly. There is something intermittent about the first
(17 Hz) xtal oscillator, could be a weak tube, a bad cable, or perhaps a bad part.
The mechanical filters are awesome.

The VFO is way, way off ... it can't even get to zero beat with the
.1 Hz filter. (All filters are spot on 455 kHz tested feeding a calibrated
synthesizer in at the IF frequency.) It centers about 459 kHz. This can be fixed
by adding a capacitor of course. But there seems to be a coil adjustment
in the PTO unit, as there is for the main frequency PTO. But I simply
cannot find instructions for adjusting it. Does anybody know how?


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Mon 04, 2016 8:31 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 20591
Location: Warner Robins, GA
Do you have the manual for the R-390A?

If not get it before trying to adjust anything.


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Tue 05, 2016 2:49 am 
Member

Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1358
Location: Champaign IL 61822
Oh, I have and have read all the manuals and as dar as I know all the web
pages on it.

The 1st xtal oscillator problem has been "refined".
That is, it oscillates fine, reliably ... but it wont start
by itself. if I touch a scope probe to pins 5 or 6
*plate or screen) it starts.

Somebody cut a wire to the audio meter and line
output circuit. HARD TO FIND!


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Tue 05, 2016 8:49 pm 
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Joined: May Sun 22, 2011 11:27 pm
Posts: 267
Location: Dallas,TX
I bought my IERC tube shields from Fair Radio. I sent an email to them and asked if they could put together a full set for my 390a. They did and emailed me a price. I believe I paid $119.00. That was a few years back. They're good folks and they have a lot of 390a parts.

Mike

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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Tue 05, 2016 9:51 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1358
Location: Champaign IL 61822
I just ordered tube shields from Fair Radio. The quote for all of them was almost $200 and
the 9 pin 12AU7 size ones are not IERC but I think it is WFM.

But I got thinking ... it works without tube shields except that I suspect that
not having them on the RF/IF amp/oscillator tubes causes mistuning. I really don't
see why it needs shields on the ballast, 0A2, and audio tubes (I used 1N4007s for
rectifiers) as well as some (but not all) AGC tubes and the calibrator tubes.

Leaving them off will cool the tubes. So I only ordered the ones I think are
really needed. Still over $100.


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Wed 06, 2016 3:21 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 20591
Location: Warner Robins, GA
At the time it may have been to be sure no signal leaked out of the receiver plus it would have ensured the tubes stayed in place if the receiver was used in a mobile environment or when it was shipped.


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Wed 06, 2016 7:59 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3692
Location: Monterey California USA
Further, the spec sheets from IERC at the time showed that bare bulb temperature is actually higher than when using the black heat sink shields, which transfer some heat to the chassis by conduction and radiate the rest. That being said, the black shields were primarily designed for radar installations that ran 24/7 with hundreds of tubes and reliability was crucial and was a study undertaken by the military for that application. They later got used in the 390A but in my opinion the advantage was not provable. These tubes don't get that hot anyway. I really think worrying about the black shields as if you have to have them is gilding the lily, so speak, especially at the silly prices these are going for from retailers and on eBay. If you sell the set later you can recover their cost, of course.

As said above, the shields on the ballast and several others were just to physically secure them. Using IERC's there is a waste of money if you have to buy them.

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California Highway Patrol Radio
Bell System Mobile Telephone History
http://www.wb6nvh.com


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Wed 06, 2016 4:54 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1358
Location: Champaign IL 61822
A comment and a QUESTION!

The comment is ... a modern important use of tube shields, especially
in radios that go up to 32 MHz, is to keep stray close FM stations out
of converter tubes. A tube is a nonnegligible part of a wavelength at
FM frequencies, and converter tubes are class C for the oscillator
frequency, so the converter oscillator harmonics work nicely. With no
antenna I can hear the FMs in my R-390A with no shields. Using
aluminum foil as a test shield on the converters with high frequency
oscillators they go away.

The question: a couple of the cams in my set are off, the 0.5
to 1 MHz one being off by 180 degrees. I have read all the
various manuals and online files that instruct rebuilding the
mechanicals, and I still don't see how to reset a single cam.
Do I loosen the clamp on the gear and the cam and shaft rotate as
one, the gear remaining fixed? My gearset just needs, except
for that one cam, alignment tweeks. Where is the best manual for this
final alignment? "The great thing about standards is that there are so many"
applies to manuals for the R-390A as well. This set will need a full
realignment, as everything is off a few kHz.

No one has yet answered my question about resetting the BFO PTO. I need help
if I am not to just add a parallel cap.


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Thu 07, 2016 8:14 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3692
Location: Monterey California USA
You did remove the end stops on the knob travel to set the BFO PTO, right? There is quite a range of travel then. Sometimes the ferrite slug falls off the BFO PTO shaft and you will have to take the can apart and glue it back on.

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California Highway Patrol Radio
Bell System Mobile Telephone History
http://www.wb6nvh.com


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Thu 07, 2016 4:36 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1358
Location: Champaign IL 61822
I keep finding instructions for these things. I found ones for the PTO.
I'll look harder for the BFO. I can't do anything until the Bristol
keys come from McMaster-Carr --- our machine shop stocks all
sizes up to but not including the two needed :(


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Thu 07, 2016 9:17 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3692
Location: Monterey California USA
If you remove the BFO knob, there is a set of travel stops under it (or should be) that limit shaft rotation to maybe 240 Degrees. You zero the BFO shaft on 455 kHz with the knob off and then re-install the knob. There are a number of turns that the BFO shaft will do without being prevented by the stops. If even then it won't tune to 455, a chunk of the ferrite may have fallen off inside the can and it's time for disassembly of the can. Note that forcing the BFO PTO shaft too far can force the ferrite slug off the drive shaft and/or crack and break it. That was one reason for the travel stops.
Duco cement or whatever the modern name for it is, works fine on broken ferrite items like this. About 25 years ago I unpacked a couple of brand new EAC R-390A's from their crates and the ferrite BFO slugs had fallen off the shafts while they were in storage! The glue had dried out.

Custom modified 390A's used in RTTY circuits had a turns counter dial (like on a pot) placed where the BFO pitch knob is on a stock set and roughly calibrated in HZ off center.

_________________
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California Highway Patrol Radio
Bell System Mobile Telephone History
http://www.wb6nvh.com


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Fri 08, 2016 5:14 am 
Member

Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1358
Location: Champaign IL 61822
Today I got my capacitors from Mouser and the Bristol splines
(you need the 3 inch long .096 and .111 inch ones) from McMaster-Carr.

So I decided to start with setting the end point on the PTO.
It took 10.12 turns of the dial, 1012 kHZ on the counter, to
actually change the frequency 1000 kHz. The adjustment screw on my
Cosmos PTO was 1.5 turn from the CW end ... not enough.

So I undertook to do the "remove a turn" thing.

When I got the outer case off it was obvious that this PTO had been run
a VERY long time with the heater on. It had also been opened before.
There was corrosion, rather serious, between the outer and middle
cans. This I cleaned off. I also cut the wires to the thermostat and
heater, and did not reconnect them at the end. Getting the middle
can off was not easy. The inner can's seal also
showed a bit of corrosion. Once inside, everything looked quite OK.
I removed 1 1/6 turn, leaving all the wire in a loop. I glued
the wire back with Super Glue ... its not going to get hot!

Putting it all back together and testing, I discover that the settings from
0 to 800 kHz are within 200 Hz. 900 and 1000 are off by 300 and 500 Hz!
In other words, a miracle ... I didn't need to touch the adjustment at all.

The various bandset crystals are not great: off by up to 2 kHz.

But altogether, a good day. I treated myself to a nice salmon risotto, a
Death by Chocolate cake, and a fancy Pawel Kwak beer.


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Sun 10, 2016 3:11 am 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1358
Location: Champaign IL 61822
I replaced all the paper caps except the two in the RF unit (a 0.047
cathode bypass and a .033 regulated B+ (150v) bypass). At 315 volts
all metal case ones had less than 100 nA leakage while all
brown bumblebees leaked about 5-15 uA per 0.01 uF.

The 2 uF AGC cap was truly bad. I installed a terminal strip
nearby and used a 0.22uF 400v (630v would be a tight fit)
Panasonic Mylar; now the AGC circuit works correctly

Except for the carrier meter which reads only 40% what it should
everything meets spec very easily. The meter itself tests perfect
in terms of mA but the resistance is too high. Neither meter is radioactive.


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Wed 13, 2016 7:33 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1358
Location: Champaign IL 61822
First: there used to be a mailing list for the R-390A. I've got the archives. Does it still exist?

I've been checking my receiver. It indeed works exactly as per the specs.

While doing so, I noticed what the people on the mailing list also noticed:
the thing's AGC simply does not work properly on SSB. It distorts terribly.

There is a highly touted mod, trivially reversible, by one Mr. Lankford,
adding two silicon diodes to the AGC system, that is supposed to be the
cat's meow. I tried it and it's doubly that! It does indeed make AGC work
well for SSB. BUT ... it has a side effect, of course: it reduces the audio output
of the detector by roughly a factor of two.

It turns out that even AM, from the usual source broadcast stations, was overloading the
audio cathode follower V601B (but not the first audio amp V501A.) Sine wave modulaion,
even at exactly 100%, was OK, as were the "finest efforts of Mr. Orban" or some say,
"the most evil efforts of Mr. Orban". But low S/N AM stations suffered bad clipping because
of the peak/average nature of noise. The mod fixes this by setting the AGC on the peak
modulation level rather than the average.

The downside, which is almost inaudible even to me, and completely immaterial on ordinary program material, is 6 dB of volume compression.

This leaves a similar effect in the limiter. This is clearly designed for the sine waves
of CW or RTTY. For those, at good S/N, when set at its lowest level, it does not clip at all. But
for other modes and low S/N it clips BADLY even at its lowest setting. This can probably be fixed by increasing R527 to 56K or adding another 27K resistor in parallel with R526. I will try this tonight. I could really use a good limiter form some impulse noise. Note that this reduces the audio even more, to 2/3 of its previous value. [Edit: I found a web posting saying the same thing ... however, is suggested trying it with a series 33k resistor on the back at the diode load. This is not the same thing and does not work.]


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 Post subject: Re: My R-390A refurbishment
PostPosted: Jan Fri 15, 2016 12:10 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3813
Location: Westminster, CO, USA
I run the Lankford diode mod and it works great. One caution is that the original article in HSN suggested 1N4148s I think. The reverse voltage rating on those is too low and one of the diodes will fail before long. I no longer recall which diode I ended up using but it has a much higher PIV rating.

I was on the list for years but things got pretty dull there, lots of OT stuff, squabbling, so I dropped off a few years ago. I have no idea if it is still running.

Tony

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 Post subject: Re: My R-390A refurbishment
PostPosted: Mar Wed 29, 2017 4:25 pm 
Member

Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1358
Location: Champaign IL 61822
This thread is over a year old, but I've been procrastinating working on my
Racal RA-17 which had all the paper caps cut out before
I got it.

And in the meantime I am vastly more impressed with the SSB AGC action on
my SX-88 and NC-400 than the otherwise better R390A.

So I went to work. I had installed the Lankford mod and it sort of worked.

I tried a couple of other published ones and finally settled on a very very simple and
easily reversible one. This mod assumes one also has paralleled C535 with
another 47 or 56 pF mica cap and retuned L513 and C525. It assumes that your
particular set has resistors to ground on the AGC line. These are on page 1 of
the schematic, R201 and R234. If you don't measure about 1.8Meg to ground
from terminal 4 of the AGC terminals on the back to ground (jumper to it removed) ,
you would need to add that somewhere.

Its very simple, see the areas in pink below.

Attachment:
AGCMod_sm2.png
AGCMod_sm2.png [ 99.93 KiB | Viewed 3171 times ]


Note that 44 Meg is just two common 22 Meg resistors in series. There is nothing magic about
1N3070, its any signal (50 ns or less) diode with a 200volt rating. A 1N914 or 1N4154 WILL blow!
Nor anything magic about the Zener, its just 18 to 25 volts. It reduces the dead time when
switching from long to medium time constant. The time constants with the stock capacitor values
are quite OK to me.
With this mod the long time constant for some reason works better than the original,
though its a bit slow. Its easy to rewire the switch for either two different caps to
ground in med and slow, or two different caps, one to ground in med and a different one
to the plate in slow, the needed wires are all there on the front panel. The added caps
go there. This is independent of this AGC circuit mod.

The mod has a severe side effect: the RF-IF gain goes way down. The sensitivity stays the
same if the gain control is set right. This is what prevents the overload on transients that
makes the set sound bad in the first place. Edit: Several previously described mods suggest
increasing R527 or decreasing R526. Tests indicate that decreasing R526 anything down to
13K is OK, but optional.

This leaves the loathsome limiter circuit. This apparently was used as a severe clipper
for RTTY and is useless for anything else. I tried published mods and none worked at all. I decided
on my own. This mod is separate from the AGC one. Its easy as it can be done entirely
on the front panel. It does, however, completely remove the "automatic" (mis)feature.
Its purely manual. But it works perfectly over the whole range of no clipping to very severe,
and works on CW, AM, SSB, RTTY, and quite nicely even on signals way down in the noise.
See the circuit below. My set has an audio taper pot for R120 which is quite annoying,
linear taper would be better.

Attachment:
LimiterMod.png
LimiterMod.png [ 64.58 KiB | Viewed 3177 times ]


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 Post subject: Re: My R-390A refurbishment
PostPosted: Mar Thu 30, 2017 4:07 am 
Member

Joined: Sep Thu 01, 2016 3:56 am
Posts: 296
Location: San Jose, Ca.
Hi, Did you ever get your high resistance c/l meter to work correctly? If not, changing R548 to 48 to 85 ohms works quite well, depending on meter resistance (85 for a 2k and 48 for a 1k meter).

On the agc, the original design provided for a 'delay' by R546 in applying agc voltage to the tubes. The purpose for this was to maintain high gain in the RF and mixers to allow the signal strength to become strong enough to overcome the 'noise' at low signal levels before reducing the gain of the RF and IF. This mod applies agc voltage to the RF, mixers, and 1st 3 IF's immediately. This causes reduced gain, as you have seen, and much lower audio output. This lower output also prevents the limiter from working correctly.

I have been using the '2 diode' mod for many years now and it works great on SSB, but I did add one mod to it to preserve the 'delay', and thus the original gain. I added a 68 mfd cap in series with the diode across R546. Edit: I also added a 120K res across that same diode.

Regards, Larry

PS: Sorry I did not participate in your 1st series of posting, but my original ID and access on this site was not working for a very long time, although I asked for help many times. I finally figured out that I'd have to create a new logon and how to do that - it was tricky.


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 Post subject: Re: My R-390A refurbishment
PostPosted: Mar Thu 30, 2017 3:43 pm 
Member

Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1358
Location: Champaign IL 61822
I had to go to 91 ohms for R548.

I have never found the "AGC delay" useful. Leaving
R546 no matter how done always increases the "rise" time
of the AGC (i.e. going more negative.) The proper way to do that
is to use a bunch of 1N3070's in series. But even without the delay
I still get absolutely adequate sensitivity on all bands, even the
30 MHz one with a somewhat inadequate mixer drive from the
third harmonic of 11 MHz. The receiver meets sensitivity specs.

The MUCH lower audio output is very intentional and indeed essential!

This is because of the way the first two audio stages work (the one
that has the 800Hz filter and the cathode follower after it.) There is
only 11 volts on the follower cathode and the circuit has a gain of three
from the limiter out to the follower cathode. This means that its easy
to overload. A good strength AM signal is fine, and is obviously what
it is designed for. Good strength CW is also OK if run on manual gain control.

BUT ... SSB and CW even with the Lankford AGC mod hopelessly
overload it, during the "blat" at the start of a big rise in AGC while
the AGC is charging up. Atmospheric noise also seriously overloads
it even on AM at very low S/N. My mod fixes that at the expense of
low audio, but short of totally redoing the audio, there is no fix for that.
The original 27/27K split of R526/R527 is a good compromise with my AGC.
For no overloads at all you need to make R526 maybe 18K, while
39K for it gets you back more gain at the
expense of overload on rising edges of strong SSB and CW signals.

I don't understand what you mean about the limiter. The original circuit
was incapable of light limiting on AM. It would do light limiting
on CW or SSB after my mod, but not AM. I am vastly happier with it
after the mod I did to it to make it manual. With R526 at 15K it won't
do really super tight limiting but would with it at 39K.

I suspect it was designed ONLY for use with RTTY (i.e. FM). It was useless for
low S/N anything.

I spent a LOT of time with a scope learning all this and with 5-Spice
simulating the circuits to see what was going on.


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