[R-390] Fw: Alignment help.more
Roger L Ruszkowski
[email protected]
Wed, 27 Mar 2002 09:01:33 -0800
Jim,
What are you doing to an R-390/A.
Since I was drafted and school trained as a repairman in 68 with 8 years
in service doing it daily
with a year as Instructor and now an owner, I have jus never needed tube
extenders to fix
an R390 or R390 /A.
The voltage get measured with the tube out of the socket.
If you need to do injection, pull the next tube up and with a cap to
isolate B+ from
your signal generator, inject into the plate pin of the tube socket.
You can stand the receiver up on either end and lay any deck out on the
bench and
get under it to work on it live. You can drop the front panel and work it
live.
The PTO comes out and can be worked held in hand.
Pull the diode load jumper.
Inject some audio into (60 cycle hum) into the audio deck and get
both audio paths sounding the same. (power will not be equal because of the
attenuator in the line side)
Put 455 into the IF deck and get it all working.
Do the RF deck mechanical alignment.
Get the band switch sync correct.
Get the crystal deck switch sync right.
Find the bands that work,
Work the bands that do not.
If you do not have the parts to adapt the mini BNC to the signal Gen,
put a cap on the wire lead and inject the signal Gen into the last
test point of the RF deck. (use a whole lot less than 150 UV because it
will get amplified in the last mixer) The last test point is a grid of the
the last mixer (6C4).
You will make more progress measuring resistors gone high in value.
doing visual inspection for bad solder, and replacing suspect caps by the
number.
Once you get to a tube stage, It works, It does not work. If your trying to
decide if one tube stage is OK not OK by measuring signal level in and out.
you are really going at it will out regard to what Elmer's have learned
about these
receiver working on them several a day years at a time for now nearly 50
years.
In the mid 70's after 20 years of prime time big time use, I was still
found that,
there is no good table that says what the stage gain of any stage should
be.
It has big gain. If big gain is not found fix it.
You can read all about calibrated AN/URM - 25 signal generators all week.
That is no where near a standard. It just says a tube device is adjusted
close.
You can read all about calibrated volt meters.
That is no where near a standard. It just says a tube device is adjusted
close.
We will talk about signal to noise like it was dead on, Its just what ever
we
got on the bench that day.
Once you get to a bad stage. Working from the head phones to the antenna,
you go in and do some voltage checks, this will find the smoked resistors.
You then do a very good eyeball. You know where you are looking and why you
are looking
there. You have isolated the problem to a bad stage. It is bad because it
does not have
a big gain as expected.
Get the ohm meter out and point to point verify every thing in the circuit.
Crud in deck short.
Cold solder joint.
Broken wire.
Over value resistor.
The caps are killing us after 50 years.
You can not measure then, most have a lower resistor parallel path.
So by the number you just swap them all out.
1 It is a 50 year old R390
2 Experience has shown these item to be problems in these receivers
3 A practical affordable test is not available to most owners.
4 Testing exceeds return on investment.
5 It is just been shown time and time again to do the replacement.
I am not saying change every cap on the bench.
You front paneled your receiver down to one two or three tubes.
(Yes Alice, you can do that to an R390 or R390/A)
You jammed a signal generator into a plate pin or two.
You have decided a stage is suspect.
So now your under the deck and hunting in a circuit between
two plate pin. This one is good. This one is bad.
That is a fixed number of parts in a fixed space.
List your problems here and get some specific help.
Quit trying to solve and reinvent it all by your self.
It is more fun that way. I do agree.
What is your real objective?
Do you want some tube extenders, or do you want to fix a receiver?
Roger KC6TRU San Diego.
"Jim Temple"
<jetemp@insightbb To: <[email protected]>
.com> cc:
Sent by: Subject: [R-390] Fw: Alignment help. (update).
r-390-admin@mailm
an.qth.net
03/26/02 04:12 PM
Hello to the group,
I have finally found some more time to work on my R-390A. I have received
several good suggestions, but find that I am stalled because I have no tube
socket test adapters (for testing voltages and resistances). I have
discovered that testing most voltages is impossible without some of these
adapters.
Before I can proceed much farther, I need at least one of the 9pin and 7pin
tube test adapters.
Perhaps someone on the list will assist me in obtaining the adapters needed
to proceed, efficiently, with test measurements. Someone must have a few
spares that they will sell. Thanks.
Regards,
Jim
73, KF4ICZ
----- Original Message -----
From: "Jim Temple" <[email protected]>
To: <[email protected]>
Sent: Thursday, March 07, 2002 3:09 PM
Subject: Alignment help.
> Hello to the group,
>
> I have owned a "massacre" R-390A since the end of Dec '01. Since that
time
> I have spent many, many hours in cleaning, recapping, and generally
solving
> one problem that reveals another problem. The solved problems generally
> relate to cleaning out the intrusive dirt and grime from the storage.
Many
> problems have been solved by reworking grounds and intermittent contacts,
as
> well as a few noisy caps and resistors.
>
> I am at the point where only the alignment remains, I think.
>
> What I am experiencing is this:
>
> 1. The equimpent I have is a good freq counter, VTVM, and Heathkit
signal
> generator. All work fine, except that as the alignment progresses, the
> radio becomes so sensitive at the higher bands, that the signal generator
> will not attenuate enough to keep the diode load at approx 7-8 volts. At
> this point I have been reducing the radio RF gain to reduce the voltage
> present at the diode load point. This works fine, except that the higher
> bands are ALIGNED WITH THE RADIO RF GAIN REDUCED to about 1:00 position.
>
> Now, after alignment, with the RF GAIN CONTROL UP FULL, the lower bands
work
> fine and the antenna peak control is fine. However, the higher bands
seem
> to overload and oscillate with a screeching or motorboat putting sound.
> When detuning the antenna peak control the overload seems to reduce
> somewhat, but with rotation of the antenna peak control, there is much
> popping and static.
>
> 2. I am getting the impression that the alignment must be performed with
> the RF gain control up full, and the signal generator attenuated enough
to
> present a diode load voltage of about 7 volts or so. If peaked with the
> radio RF gain reduced, my impression is that, after peaking, a normal RF
> gain position will introduce overload at the bands that were aligned with
> the RF gain reduced.
>
> SO NOW MY QUESTION..........
>
> Does the overload, screeching, and motorboat putt sounds seem to be a
true
> alignment problem (obtaining an attenuator), or is there a remaining
> component problem that is preventing a good alignment???
>
> Thanks for your past advice, and am looking forward to completing the
> restoration of this great radio.
>
> Sincerely,
>
> Jim
> 73, KF4ICZ
>
>
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