[R-390] Below 8mhz problem.
Roger L Ruszkowski
[email protected]
Tue, 22 Jan 2002 16:53:08 -0800
Jim,
More than one problem here.
So what did you expect?
The receiver will not hear the signal generator at all, so I have not been
able to align the variable IF's.
No signals but the Cal tones are killers.
It sounds like an oxidized contact point in the antenna relay. As its from
the massacre
you will likely find some crud in the box.
Do some ohm meter checks on the antenna relay Pin inside on
Mini BNC to pin in triax connector . Pin to pin should give
continuity and pin to ground should be open.
Do you hear the antenna relay click as you go into cal mode and
out of cal mode to mgc?
Strap the break-in pin on the back terminal board to ground.
Operate the break-in switch off and on.
Do you hear the relay in the audio deck click and kill the audio hiss?
Do you hear the antenna relay click?
If a the relay is clicking and a couple operations do not clear it.
It will open up and can be fixed. Some course paper ("newsprint")
can be used to clean the contacts. Rain condensation has likely
dirtied the contacts.
Get a very good small Philips screw driver and really lean into it as you
take the very small screws out of the cover plate on the relay and
look into the contact cavity. (dead spider or what ever in there).
Poor performance under 8.
is .5 - 1, 2-3 and 4-7 all equally bad?
Look into the first mixer tube socket for crud.
Look into the fist mixer Z cans for crud.
Again likely just weather oxidation in a contact.
Look at the RF band switch for crud.
Likely you will pull a can off its contacts, open it up
and put it back down and every thing will work no
trouble found The normal experience.
Pull it all apart and clean the contacts (De Oxit preferred)
Use what ever you have but
1.) do not ever tell this mail reflector you did it.
2.) If what you use causes other problems always infer
the trouble came with the receiver and was not self inflected.
Work over the antenna relay and get some signals coming through.
Read the manual. Read Chuck Ripples web pages.
Down load and read the handbook.
As this was one of those receivers you will want to one day
pull the every deck. pull all the tubes and all the RF deck cans
and give every contact a cleaning.
On the first IF .5 - 8 Mhz.
Again, just because its been outside, you may find a cap
in the RF cans to be shorted. These will come apart and
can be cleaned up. The little rubber disk between the
cap sections gets stiff. Read Chucks and Dave Medley's
R390/A and R390 web sight maintenance tips. The adjustment
caps are in the RF and crystal decks and share a common
problem. Do not take down any you do not have to. If and only
if it is shown to be the problem. Aggravation exceeds return on investment.
Then go read the books again,
Get all the stuff you need to treat the items correctly.
Then go read the books again.
Acquire a large rewarding stock of choice beverage.
Do not start celebrating prior to completion of the task.
Then just jump in and do it.
Do not be intimidated.
If it goes wrong stop and ask.
It may take an hour or two to get mail back at 0 dark thirty
But some one will gladly talk you through it.
When its all done, just let your self go and revel in it.
While your at it you will want to give the gear train a good bath.
a 32 to 40 hour ordeal is about typical.
Your only going to do it once and your only have to do it
because some fool let those fine receivers set out over
winter in the weather.
A good semi PM could get done on the depot bench in 4 hours.
8 hours was average for a tech his first year out of school.
(to do it all and do it right)
So 16 hours your first few times around is ok.
Roger KC6TRU
"Jim Temple"
<[email protected] To: <[email protected]>
ville.edu> cc:
Sent by: Subject: [R-390] Below 8mhz problem.
[email protected]
h.net
01/22/2002 02:58 PM
Hello to the group,
I recently bought a "massacre" R-390 and completely tore it down and
cleaned
and replaced all the "problem" caps.
I have already replaced the 100pF cap at T-207 with no luck.
The problem I have is that the calibrator is strong and loud on all bands
8mhz and above, and below 8mhz is barely audible and extremely faint.
The receiver will not hear the signal generator at all, so I have not been
able to align the variable IF's.
The fixed IF hears fine, but the signal is injected directly into the IF
module. With the variable IF's, the signal can not be heard while input
into
the balanced antenna input.
Perhaps a kind soul has experience with the problem described and will
offer
some hints as to a possible fix.
Thanks.
Jim Temple
Louisville, KY.
73, KF4ICZ
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