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 Post subject: Re: R388 delimma
PostPosted: Feb Tue 06, 2018 5:59 am 
Member

Joined: Sep Thu 01, 2016 3:56 am
Posts: 221
Location: San Jose, Ca.
As Tom said, it's a good idea to have the heater switch in the back turned off. It powers the VFO and 2nd xtal osc heaters. The 3rd heater is the 17mc/200kc plug in osc xtal unit on the RF deck and is hard wired on. Although the heater switch does stick on some times, I think it's a good idea to leave it on and check it periodically. It's a 75 degree C oven, so will be very warm, but not burning hot. If it's stuck on, it will do some damage after a while.

Regards, Larry


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 Post subject: Re: R388 delimma
PostPosted: Feb Tue 06, 2018 2:57 pm 
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Joined: Jul Tue 21, 2009 1:38 pm
Posts: 886
Location: SW WA state
Get yourself IERC type tube shields: They do a MUCH better job at dissipating heat than the standard shiny metal ones do!

db gain wrote:
Now to find out what tube shields it needs and post a wtb. I appreciate every comment, thanks for the help folks.


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 Post subject: Re: R388 delimma
PostPosted: Feb Wed 07, 2018 1:02 pm 
Member

Joined: Nov Wed 15, 2006 7:56 am
Posts: 1174
Location: germany
I would love to have an R389 receiver, but the ones I have seen are usually too expensive. The R389 and R390 were the top for their time.

Joe[/quote]

I have restorated the VLF Radio, that is a night mare ! :shock:
And what it will find from the Antenna?
SAQ (if they are not in repair..) at christmas, 17.2kc
some russian Alphas (Radio Navigation)
the time of germany DCF77
the wheater in RTTY DCF49
... no music

R390 I dont have one.
51j4 is running here, nice radio.

greetings
Martin


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 Post subject: Re: R388 delimma
PostPosted: Feb Wed 07, 2018 3:00 pm 
Member

Joined: Jul Tue 21, 2009 1:38 pm
Posts: 886
Location: SW WA state
Hallo, Martin!

We have a lot of NDB's (aircraft beacons) here... That's my main focus.
Are you still using LW broadcast in Europe?

-Tom


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 Post subject: Re: R388 delimma
PostPosted: Feb Wed 07, 2018 3:05 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 5757
It would be fun to try out a R-389 but the price of admission is too high for that level of fun for me. I suspect that my RAK, RBA, and Drake MSR-2 receivers could also hear anything the R-389 can at VLF since ambient noise level is the limiting factor that low in the spectrum. When I first got the RAK I put out a Beverage into a vacant farm field one winter and when the conditions were good it was impressive what this early regen brought in but for most of us (me included) VLF isn't something you will use often so a VLF specialist is a "shelf queen" most of the time. Of course the R-389 is also a good BCB receiver but the R-390 and 390A do fine there as do many other of the classic better vintage receivers.

I have a Telefunken ELK-639 which uses a separate VLF front end, like the Drake MSR-2, to tune down into the VLF range and I suspect it also does very well there but I have never given it a proper test in that range. It had an AGC issue that was a pain to find (bad active device) and after that process I moved on to another restoration shortly after completing the 639.

Rodger WQ9E


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 Post subject: Re: R388 delimma
PostPosted: Feb Wed 07, 2018 6:49 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1148
Location: Champaign IL 61822
Tom Herman wrote:
Hallo, Martin!

We have a lot of NDB's (aircraft beacons) here... That's my main focus.
Are you still using LW broadcast in Europe?

-Tom


Yes, they still have LW (or LF) broadcast in Europe. I received the BBC, Ireland,
and Algeria (last two on same frequency, sometimes one much stronger than the other) ...
here in Illinois last week! This after 4 decades of futile trying! Last night, no.

There's lots here in the US to receive on a good antenna. There are CW beacons galore,
and numerous DGPS (Differential GPS) stations that are easily decodable, plus
a navigation/weather station at 518kHz (not true LF) also (yesterday it was
giving a warning area for the "Tesla to Mars!!! ... after it was safely in orbit, and
a statement that the barge that the booster missed was "drifting").
Plus lots of decodable hams on 630 meters, and once I got a ham on 2200 meters,
but that one was too weak to decode.

I get WWVB at sometimes 40 dB S/N, as well as good S/N on military
submarine communications at about 24 and 73 kHz.

This was not with a boatanchor ... next step is to try my BC-453 on beacons,
and feeding my computer for digital. This will be harder than the Airspy.


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 Post subject: Re: R388 delimma
PostPosted: Feb Wed 07, 2018 8:29 pm 
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Joined: Nov Wed 15, 2006 7:56 am
Posts: 1174
Location: germany
yes we have some LW broadcast here, mostly from france. But they are also on the way to shut down them ..

A special fun is to connect a VLF radio (my favorite is the Telefunken Monster Radio E108Lw4) with a decoder system for RTTY , I have a box from Wavecom, the W4010.
This apparatus feeds a small Camping TV by video cable to display the text of the german weather service for shipping. DWD = 147kc RTTY

The RTTY is done by shifting the TX frequency, so you must pick up that by using a BFO !

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greetings
Martin


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 Post subject: Re: R388 delimma
PostPosted: Feb Mon 12, 2018 5:40 am 
Member

Joined: Aug Fri 29, 2014 6:17 pm
Posts: 2564
Location: Vincennes Indiana
So far with the 390a I've swapped the mini bnc's attached to the c connector with that of the twinax input (normally all 390s are aligned to the twinax input, and the twinax input it fed to a tuning mechanism not in the circuit path of the c connector - swapping the mini bnc conns rectifies this but one should still realign the rig) so I can use a simple c adapter, adjusted the IF gain to a sane level per Chuck Rippel IF tuning tips, and enjoyed tuning around, albeit with an antenna no longer than 12 feet. The set is sensitive enough to tune to its own noise via the antenna trimmer with the antenna disconnected. The audio is really nice in the 8 and 16Kc positions on clean sigs.

Some notes;
The tube shields are not ierc, they're clevite branded as I recall and use a coil spring at the top of each shield that rests on the top of the tube when in position. They're also not black but more like cadmium plated or whatever it is Anyone know if these are stock? It's a 1961 Capehart if that helps.

A sound that goes something like "puck" comes from the inners of the 390 at a regular interval after warmup, I assume this is the pto oven clicking on and off.

Next is a fine tuning of the mecha filters per the manual, the 8Kc filter has about 20dB less signal as shown by the carrier meter than the 4Kc or 16Kc.

This thing has been a lot of fun to fool around with, have yet to even plug in the r388. By the way, on the r388, do the matchstick caps go bad internally like silver mica disease, or do they perhaps leak through their mountings?


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 Post subject: Re: R388 delimma
PostPosted: Feb Mon 12, 2018 10:22 am 
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Joined: Sep Thu 01, 2016 3:56 am
Posts: 221
Location: San Jose, Ca.
Good news on the R-390A. If you haven't already, there is one thing you should really do before powering it on again. Verify it's good or replace the mech filter killer cap C553. You don't want to accidently damage one. If one is down already, that could be a sign of a problem.

Regards, Larry


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 Post subject: Re: R388 delimma
PostPosted: Feb Mon 12, 2018 3:04 pm 
Member

Joined: Jul Tue 21, 2009 1:38 pm
Posts: 886
Location: SW WA state
db gain wrote:
The tube shields are not ierc, they're clevite branded as I recall and use a coil spring at the top of each shield that rests on the top of the tube when in position. They're also not black but more like cadmium plated or whatever it is Anyone know if these are stock?

A sound that goes something like "puck" comes from the inners of the 390 at a regular interval after warmup, I assume this is the pto oven clicking on and off.

Next is a fine tuning of the mecha filters per the manual, the 8Kc filter has about 20dB less signal as shown by the carrier meter than the 4Kc or 16Kc.

This thing has been a lot of fun to fool around with, have yet to even plug in the r388. By the way, on the r388, do the matchstick caps go bad internally like silver mica disease, or do they perhaps leak through their mountings?


Not sure if those tube shields are stock or not. Standard, shiny metal plated tube shields should be replaced with IERC or similar: They are black, and have physical contacts that conduct heat away from the sides of the tubes and effectively convection cool them.

I'd go to the "oven" switch on the back of the unit and turn it OFF.

The R-388 Matchstick caps go bad with age and develop leakage resistance. They are ALL bad, just to varying degrees, but will get continually WORSE until they dramatically fail.
It has nothing to do with mounting or resistance to ground at mounting points.

Later R-390A's have the ability to tune both the input and output padding capacitors. Hopefully, you can tune the one filter to bring it up to the level of the others.
If not, you may need to replace it.

Best of Luck! -Tom


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 Post subject: Re: R388 delimma
PostPosted: Feb Tue 13, 2018 5:05 am 
Member

Joined: Aug Fri 29, 2014 6:17 pm
Posts: 2564
Location: Vincennes Indiana
Lar H wrote:
Good news on the R-390A. If you haven't already, there is one thing you should really do before powering it on again. Verify it's good or replace the mech filter killer cap C553. You don't want to accidently damage one. If one is down already, that could be a sign of a problem.

Regards, Larry


Hi Lar, will do. The guy who sold it to me said the problem caps had been replaced but I was thinking the same thing as you it may be hurt by continued use if the cap is bad, I normally run the 390 in 8kc filter and don't recall if it was less lossy compared to the other filters when I first got it or if the difference in insertion loss is a new thing.


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 Post subject: Re: R388 delimma
PostPosted: Feb Tue 13, 2018 5:14 am 
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Joined: Aug Fri 29, 2014 6:17 pm
Posts: 2564
Location: Vincennes Indiana
"Not sure if those tube shields are stock or not. Standard, shiny metal plated tube shields should be replaced with IERC or similar: They are black, and have physical contacts that conduct heat away from the sides of the tubes and effectively convection cool them."
Thanks, will see if I can grab some.

"I'd go to the "oven" switch on the back of the unit and turn it OFF."
Far as I can tell, the switch is off but the pto oven isn't switched, it is full time and has to be cut to keep it from operating.

"The R-388 Matchstick caps go bad with age and develop leakage resistance. They are ALL bad, just to varying degrees, but will get continually WORSE until they dramatically fail.
It has nothing to do with mounting or resistance to ground at mounting points."
Thanks for the info.

"Later R-390A's have the ability to tune both the input and output padding capacitors. Hopefully, you can tune the one filter to bring it up to the level of the others.
If not, you may need to replace it."
Will be checking it tomorrow.

Something I noted today. while playing the 390, I had the r388 sitting a foot away from the 389 on the floor, no ac cord or anything connected to the 388. laying atop the 390 was a set of headphones, with the cord and plug draped over the 390, the floor, and the nearby 388. When I went to move the headset, the scraping of the metal plug tip on the dust cover of the 388 made the 390 pop and scratch in the headphones I was then using. I tried it a few more times to see if it was repeatable, and it surely is. The antenna in use with the 390 is just say 12 feet of wire, traipsing up to the window, stuck into the unbalanced input. I can't imagine what little power is being radiated by that scraping headphone "antenna" the 390 is picking up.


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 Post subject: Re: R388 delimma
PostPosted: Feb Tue 13, 2018 6:41 am 
Member

Joined: Sep Thu 01, 2016 3:56 am
Posts: 221
Location: San Jose, Ca.
The mech filters have a silver mica across the input and output. These are at the age where they go bad. I've seen a few bad ones on the filters that have reduced output. They are 110 pf without trimmers and 82 pf with trimmers. I hope it's just a cap problem.

If the pto heater is getting power with the switch off, perhaps it's a bad switch. I've not heard of a mod to keep them on.

Regards, Larry


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 Post subject: Re: R388 delimma
PostPosted: Feb Wed 14, 2018 6:41 am 
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Joined: Aug Fri 29, 2014 6:17 pm
Posts: 2564
Location: Vincennes Indiana
Thanks for the info Lar, will be putting it to use.


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 Post subject: Re: R388 delimma
PostPosted: Feb Wed 14, 2018 6:58 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 19244
Location: Warner Robins, GA
rsingl wrote:
Don,

The better audio is derived via the "diode load" output and this is true of numerous Collins receivers.

Rodger WQ9E


Without doing any mods to the internal amp.

One could go the route I chose with a R-390 which was to connect the local audio level control wiper terminal to the local audio out terminal. That way I still reatined the use of the audio filters along with the use of the local audio level control.


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 Post subject: Re: R388 delimma
PostPosted: Feb Sat 17, 2018 5:55 am 
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Joined: Aug Fri 29, 2014 6:17 pm
Posts: 2564
Location: Vincennes Indiana
A question for 390a owners;
Does your 390a have a switch position past the cal position?
Mine does, unmarked, has detente action like the rest of the switch positions, and I am wondering *** is going on here. In that position the radio receives normally as far as I can tell.


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 Post subject: Re: R388 delimma
PostPosted: Feb Sat 17, 2018 6:27 am 
Member

Joined: Sep Thu 01, 2016 3:56 am
Posts: 221
Location: San Jose, Ca.
Yes, I believe that all 390A's have that 6th position on the function switch. It was for the squelch function that did not make it into production. The knob is supposed to be stopped at the cal position with the washer tab that sticks out and stops it there.

Regards, Larry


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 Post subject: Re: R388 delimma
PostPosted: Feb Sun 18, 2018 4:27 am 
Member

Joined: Aug Fri 29, 2014 6:17 pm
Posts: 2564
Location: Vincennes Indiana
Thanks Lar, was wondering if it had been replaced with a switch with more stops.


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