R390 dead.

[k3zrf]

I finally did the 12ba6's and a jumper on my R390A's....no rewiring and took all of a half hour or so.

I'll bet I spent at least $100.00 on those ballast tubes over the years.

Original some want but hell it's behind the front panel and under the top lid....out of sight out of mind.

[Steve - WB3HUZ]

Something to keep in mind is the original purpose of the ballast tube: to compensate for some wild swings in line voltage and the resulting current fluctuations.

And the R-390As were often used in RTTY circuits where frequency stability was critical.

[Todd, KA1KAQ]

THis is an R390. Not an R390A. 

Good to see you know the difference. That puts you ahead of many. 

Todd, I would rather the rig run like it was supposed to.  Its just preference. I will do it if my tube is bad. I have to work tomorrow but I will devote some more time to this thing and report back

And that's just it - you'll be running it the same either way. The ballast concept was only added to deal with the 'what ifs' of overseas duty. But as I said, it's nice to stuff a resistor in there and be able to swap it back to the 3TF7 in a few minutes without hassle if the mood hits you. Otherwise it perks away just fine, a hair more stable, and you won't be having to haul it out of the cabinet in a year or so for another $35 band aid as Johnny sez. Think of the 3TF7s you'll be helping to conserve!! 

And the R-390As were often used in RTTY circuits where frequency stability was critical.

Ohyestheywere. As with their predecessors. In fact, ASA had a field mod which added those nifty neat-o verniers to the BFO knob for more accurate retuning. Really slows down the BFO tuning rate a lot. They carried it forward when the A models hit the scene, but most of the ones I've come across were on R-390s.

The nomenclature escapes me at the moment, but they had a specific RATT/RTTY set up that utilized a pair of autotune R-391s with a matching antenna/preselector tuning unit, power supply, and diversity unit. FRR-33 or something like that, Johnny probably knows. A rack full of dials spinning away whenever you changed frequency.

 

[flintstone mop]

I think the reason why some folks posting are reporting that they have replaced the 3TF7 a few times is because they are running the radio at today's 120-130 volts supply. The HUZMAN advised me a LONG time ago to use an isloation transformer and adjust for 110V.
That's the way it's been for the last 15 yrs. I have replaced a number of tubes that get tired from 24/7 operation during the winter months. About every two years I go through my radio for a tune-up.

Got strange AGC problems? Isolate the troublesome, hard to replace filters used for bandwidth selection with a .01 good quality capacitor at the input AND output of the filter assembly. That was my strange coming and going AGC problem. Sometimes it would be a perfect radio and at a critical time of use strong sigs would overload the IF and massive distortion.
Rick Mish Myths: Excellent tech and loves the 390, 390A and another variant that uses 28 volt tubes (?)
He told me that most filter assy he services on the IF strip are bad and a little leakage takes place and will kill the AGC. And the .01 cap story killing the filters is plain BS.
And that running the radio at today's supply voltage is not a problem.

Fred

[WA3VJB]

Yeah, it's good to put a bucking transformer in there to drop things back to 110-115VAC. I've got a lot of filament transformers out of scrapped Collins 300-Gs and I've used one to drop the voltage on the entire receive rack. (SP600, R390, R390A)

And the 28V variant is the R392.

I think the reason why some folks posting are reporting that they have replaced the 3TF7 a few times is because they are running the radio at today's 120-130 volts supply.

Rick Mish Myths: Excellent tech and loves the 390, 390A and another variant that uses 28 volt tubes (?)
Fred

[ke7trp]

Fixed.. What a bear. Spent 40 minutes unhooking cables and lugging that damn thing out to the table.  The 6ba6 by the pto was dark.  Stuck in two big resistors in the balast tube socket. Pins 2 and 7.  Still dead. Replaced the 6ba6 and she came back to life.  When the balast tube went it took the 6ba6 with it or vise versa.  Thanks for all the help.  Tomorrow I am finally going to replace that damn on and off switch with the new one I got. Also the panel lights are out. I used LEDs with resistors and they still burned out. I think I am going to stash a small variac under the table and turn the voltage down to 110 for both recievers.

Thanks again for the help. I hope this lasts!  Those resistors get hot as hell. Two 22 ohm 10 watts wired up for 44 ohms.

C

[WQ9E]

Clark,
 
Glad to hear your R-390 is healthy again and now you don't have to deal with the ballast tube in the future.  By the way, your ballast tube is probably still OK.  The 6BA6 filament is in series with the ballast so when it opens there is no current flow through the ballast either, kind of like the old series string Christmas tree lights of the 40's and 50's.

The resistors will generate some heat since they are dissipating close to 4 watts (13.2 v at .3 A) and even though the resistors you used will easily handle that power 4 watts of power is going to generate some heat.  Think of it as being the same as the heat generated by a couple of dial lights.  The ballast tube also generates the same level of heat.

[Todd, KA1KAQ]

Clark, the on/off switches are notorious for welding themselves shut. Some guys leave their set switched on and use a power strip or variac to operate it, others add some kind of soft-start. If you choose to continue to use it as-designed, you'll probably want to sock away another spare switch.

[ke7trp]

I found that this switch is a cheap switch used in AC units.  I posted the info on AMfone.  I think $5 or something.  Its exactly the same switch. I might as well put a new one in since its out of the rack on the table.  Using the power strip meathod is what got me into this trouble. I forgot and left the power strip on for over a week while I was out of town on biz. Came back and the reciever was dead. 

Also. I found a small compact tube audio amp. It says "Voice of the theater" on it.  I am going to wire up the diode pick up point to the small amp and set it on the case of the reciever so I have better audio.  Thats my biggest complaint with R390s. Lack of audio punch. 

C

[ke7trp]

What are my options for the lamps over the FREQ dial?  They burn out all the time.  I put LEDs in but they also burned out. I checked the voltage today and its 27.5 volts AC on that lamp assembly. When I put it on a variac it will be down to the 26.5 its supposed to.  Should I use a Dropping resistor?  My LEDS are labeled 12 to 14 volts.

c

[flintstone mop]

Clark
The lamps I use are the exact replacement lamp used in the radio and at my shack I replace the lamps about every two-three years. And that's only because the glass gets dark from continous use. The 110 VAC might be the answer and less off-on action.
All these bad luck stories............hopefully you'll get up and running with more reliability.
Fred

[ke7trp]

WIred the LEDs in series with a diode and resistor.  Now its 12.5 volts per LED. That should fix it.  Also wired up the diode load to a "voice of music" mono amplifier.  It uses a single 6bq5.  Sounds great!  Now to put it all back together.

C

[ke7trp]

All done, Back in the rack fully functional.  It has a alot more RX now. The 6ba6 must have been weak.. I dont know.  Its strong. The audio is fantastic with the diode pickup. One thing I realized is that now the audio is not muted during break in mute. No big deal.  I have a remote RF gain knob at the operating position near the T3's remote key switch.  I can turn it down a bit and use it as a monitor.

One thing I realized this reciever has is "squelch" on the front panel.  This seems to do nothing on my radio.  What is this used for?  Does it work like a normal squelch and mine is not working?

THanks again for all the help guys!

C