Concerning the 390A long as you follow the manual exactly you should be ok. At first I didn't want to touch my R-390 but when I got quoted a minimum of $1,000 for the basic restoration I took a good look at the manual and the receiver then decided that I could do what was needed. J know that I need to remove the RF deck sometime to clean the gears, but am delaying doing that for now.

None of the enlisted military guys that worked on these back in the day were Collins experts either and they seemed to do pretty well in keeping them in operation.

The R-390A is just a radio. More complex than most but there's no magic going on there that would preclude anyone with some talent from going after it. Mike has demonstrated in all of his past forum posts that he's more than up to the job at hand. There's no need for parochialism here, and I think many of us are quite unimpressed with the self-styled "Collins experts".

Again, I appreciate Socrates frankness. I still consider myself more or less green. If I'm about to pull a stupid newbie trick, especially with this set, I'll welcome any advice.

What we're talking about here though is paper and electrolytic replacement. From what I've learned so far, this is a common sense preventative maintenance job that could help the sets performance, and hinder much more expensive damage should one fail.
I've removed two papers so far (PIO and mylar), and each one is fine. I'm desoldering, labeling, and putting the caps away should any other owner decide that they should go back in.

I have a question about the cap dielectric though. Last night while looking around the IF deck I noticed two caps of the same value, and same voltage rating (I think) right next to each other, connected to ground, and going to the same tube (although not the same tube pins). One was a yellow Aerovox, and one was a PIO. Why? This set has NO BBODs. It just has me wondering why they used both instead of one or the other. One is better than the other at RF?
And if I wasn't clear enough before, is replacing them ALL with new 715P type ok, or even ideal? I also read hat all ODs have whats considered to be their "outer foil" end to the right side of their markings. I'll be sure to match those up also, although I doubt it makes a difference with todays caps or if they even have it.

I don't see anything wrong with the ODs and they may even do the job better than the PIO.

For me, the issue with OD's is that they are radial caps. The originals are axial. Then there is the fact that they tend to be larger than the originals. Combined with the color, they just look awfully out of place in there. However, they will work fine as long as you can fit them in. So, the "harm" is aesthetic rather than electrical. It's a matter of opinion, and we don't all have the same view on aesthetics.

The other thing is replacing the caps wholesale. This is a debatable practice in a '61 military set. especially if the caps you are replacing are the kind with glass seals. Those tend to fail much less often than unsealed caps. As for leakage, the designers took expected leakage into account for caps as they were in the 50's when the set was designed. Putting a modern cap with modern lowered leakage in is not going to make the radio work any better. So why not replace them for good measure? Well, you run the risk of damaging the set with each component that you dig out of there. So it's another tradeoff. I guess we each have to make a judgement that suits us.

At the risk of arguing out of both sides of my mouth (is that the correct expression?), Socrates has a point too. We would like to think that the radios we pass on are in better shape (or at least no worse) than when we got them. In the future, will the next owner look at what we've done and say "there's another Hammy Hambone job" as we hear from time to time around this place? This is where the "it's just a radio" argument falls a little bit short. This does cross my mind whenever I open mine up. It's definitely not an AA5.

Tony

My .02 worth-
I finally recapped my R-390A a couple of years ago. It might have been a collector's piece since it was an all-original Amelco which I bought in the early 1970s. However, I had a bad experience with my restored Hammarlund BC-779: I left some of the oil-filled bathtub capacitors in for appearance sake. They checked out OK with a few hundred microamps of leakage at well above the rated voltage. But after a couple of years two of them shorted out, and I had to track down the source of smoke coming from under the radio. I decided that it was worth it to fully recap the R-390A since I intend to use it (as I have for 40 years), and not put it on display.
Also, I've got 30 years on the resistor installed in place of the 3TF7. I have a spare tube in case I ever need it, but I doubt the kids will worry about that when they dispose of my estate. The 3TH7 will probably go into the same dumpster as the radio.
Ed W2EMN

I intend to USE this set on a regular basis. While I like the idea of all the original components in there doing their thing, the other side of that coin is, I also DON'T like the idea of all the original components in there doing their thing.

It's a nice set as it is, but I'd also like to keep it that way, and make sure it's at spec to operate as expected 50 years ago, 24-7, and be confident that when I start snoring in the la-z-boy at the desk, the smell of smoke and components popping and fizzing won't be what wakes me up.

With that in mind I crossed the bridge a little and did the papers in the IF deck today. I started there because it looked to be the most difficult, and if I could work my way around in there, then the rest should be ok too. I have to say, it wasn't trivial.

I think I'll get to that 2uF PIO some other time, as I've never tried to restuff one before, and will have to read up on how to open it.

Pics to be scorned or approved tomorrow.

I agree with you. I do the same when restoring vacuum tube electronics.

Could be a little more in focus, but I think it's good for cramming orange drops in there.

Flame on:

Looks good to me! Nice work Mike.

Flame off.



Tony

I see they used ceramic disc caps in some places (unless they are previous replacements) so why couldn't they use them throughout the whole receiver?

Not sure. Any ceramics I saw (not that I looked at every one) was a .005uF.

What I do know is that I'm done with the paper/mylars. 2uf oil cap, and RF deck too. The only paper I left in there was a stud mounted cap next to the 6dc6.

Weird multi section cap re-do got treated to octal sockets with 33 and 47uF pencil style caps. Amazing how they can shrink these things down as time goes on!
I went by the Y2K manual, chapter 11, page 17 for the cap order. The job is finished, but I have some .033uF and even more .01uF caps left over. Maybe some receivers used more or less caps as contracts went on?

I'll put it together tomorrow when I' less tired, and see how it goes...

The pictures show a nice installation of the orange drops. My question is, what would one of the expert R390-A rebuilders have done differently? We have some pictures here to compare with. So if someone can post pictures of what you get from the big builders, that would be very helpful in this discussion.

I have a nice R-390-A that I rebuilt myself. I never thought that the project was too much to handle. I did my research on the net, printed out the information in the new 2000 'manual'. I had the original manual for it when I bought it. Did an overall review of what I'd need to do, then did one module at a time. Including the RF chassis.

Everything works fine. Love the radio. The last thing I need to do is perform an alignment someday. No rush, because it works really well as it is now. Also can do the tests and tweeks they discuss in the new documentation.

But, this is a good time to show those of us who have rebuilt our sets, just where we fall short on the rebuilding techniques vs what the pros do.

I'll agree with the pictures differences. In 'just about' everything I've read on R-390A literature, Orange drops are the recommended choice. They are more expensive by comparison, but then again, so is this radio.

I put the radio back together this morning. Not without trouble though. Somehow the pto or the dial had gotten half a turn off. No biggie. Removed the spring and coupler, and got it back where it supposed to be. Was listening to it for a while. Sounds great!

One problem though. And here's where all the nay sayers get to have the joy of the I told ya so's they've been waiting for. The BFO now produces no beat note. I doubt the shaft got out of rotation while out because it is rather stiff. I can hear the circuit switching on as it did before. I figured maybe the extension shaft that couples the bfo shaft to the knob was slipping, as it's done this before, and needs to be really tight for it to work. ...Clamp broke on checking the tightness. So now I have plenty of time to go over the BFO section of the IF deck for proper component values. I looked over my work and checked it many times before re-installation, but stranger things have happened. Like when I was doing the audio deck.... I was pulling from the WRONG bag of caps the whole time, and when I was finished I was putting the old caps in the bag. Noticing they were all .01, looking at the audio deck, I soldered in all .033. Facepalm moment, but they got switched to the proper value quickly as this was the easiest part of the re-cap project.
So, It DOES happen.

Anyways, any thoughts you can offer up on this no beat note BFO while I search online for a clamp would be greatly appreciated!

It looks like neat work to me and I think your installation work is fine. There is nothing magic about orange drops but they are certainly good caps.

I imagine Fair Radio can supply you with a replacement coupler, Surplus Sales probably also has them.

Since the BFO worked before, re-check your work in that specific area. Also look for an errant drop of solder where it should not be. The BFO is just a simple variable oscillator so the parts and circuit will be pretty easy for you to check and you will increase your knowledge base as you go through the process. A scope will tell you if the BFO is oscillating, a frequency counter will quickly tell you where or you can figure it out with an external receiver. I use an older Tektronix scope (7854) but it is an early digitizing type that will sample the waveform and display the frequency. I am sure this is a feature of many of the newer scopes.

Finally, once you find the problem don't beat yourself up if it was due to a mistake on your part. Anyone who has restored any large number of vintage radio will have run across mistakes and a number of these will be factory original. One that comes to mind is my Hallicrafters SX-88 which was in nice shape but full of black beauty capacitors. I replaced all of the troublesome caps, a few out-of-spec resistors, cleaned and lubricated the dial mechanisms, and did a complete alignment. After this the receiver worked beautifully except for an intermittent crackling noise on the highest frequency range and it came from a coil connection that had never been soldered. For this expensive receiver Hallicrafters put a little dot of red inspection paint on each completed connection and this connection had paint but no solder ever. A second case is my Collins 32S-3 transmitter, a problem with intermittent loss of final drive was traced to a cold original solder joint. Even the gods of radio aren't perfect

Sooner or later anyone who restores a lot of vintage gear will make a mistake, the odds pretty much guarantee it. With any luck it will be a small mistake that doesn't create significant collateral damage.

Anyone who uses this as a "I told you so" opportunity is a small minded individual not worthy of your consideration. You will learn from this experience and it will be valuable in your future work.

Rodger WQ9E

I've labeled the pin connectors for the BFO for this picture, since they aren't.

I think I got them right. Right now I have them hooked up as -

BFO labeled pin 1 goes through a cap to pin 1 of V505
BFO labeled pin 2 goes to pin 7 of V505
BFO labeled pin 3 goes to ground.

If nobody beats me to it, I'll pop mine out and check the wiring to the BFO tonight. I've got it partly opened up anyway because all of this R-390a talk got me back on an alignment issue that I've been putting off for a long time.

Tony

My BFO PTO unit is made by :Artisan Electronics" instead of Progresstron, but we can reasonably assume that the pinout is the same. You have pins 2 and 3 (using your numbers) swapped. The center terminal should go to ground and the terminal furthest from the side of the chassis should go to pin 7 of the tube. By the way, my unit has the terminal numbers stamped on the face of the PTO just above the terminals. 1,3,2 instead of 1,2,3 as you show them.

Hope that gets it going.

Tony

Yikes!!
132.... because that makes so much more sense than 123!
Well, I'm at work at the moment, but I will put the center terminal (that I've labeled #2 to ground), and put the far right terminal (that I've labeled #3) to pin7 when I get home, and hope it's as simple as that.

Thank you Tony!!

Back in business. Thanks again!