Well, it may sound weird, but I actually want to undo the 3TF7 resistor mod, and put a tube socket back where it goes.
As far as I can tell, for everything to look original (aside from the upgraded tube shields), The 3TF7 needs to be there, and some original cans need to be put back in the 2 electrolytic sockets. That's about it.
On that note. Anyone have some original bad electrolytic cans they've tossed aside? I have the new 'pencil' style 33@400 and 47@450 caps waiting to go in. Having the proper cans and clamps to re-stuff with would be ideal.

My luck won't be as good as finding an all matching module 390 of ANY manufacture for 50 bucks. I just don't get a chance to leave town for any kind of "fest". With what these fetch today, I feel the 1000 that I dropped on this miltronix matching module example was more than fair. It's about the best luck I'll have until I'm older and can get out to these radio meets.

I failed to mention that during the paper cap replacement that I will be testing them, and if they test good they will stay. I thought that they had already been gone through since it had came from miltronix, and according to what I had read in archived 390 posts etc, I was expecting to find BBODs. I guess by 61-62 they were phased out. So I guess the papers that are in there ARE original.
The yellow aerovox type are starting to unroll. Showing signs of physically coming unrolled is a good place to start I think. I went by the capacitor list in the Y2K manual, and bought two sets of complete replacements. 225P and 715P type, with an as close to original voltage rating for each cap as possible for each set except I went with 600V rating for the filter blocking caps. So far, using the 715P type seems a better choice based on temp stability alone. It might be a non-issue for either set, but since I have them both, why not? I'd read that the 715P are more round, and the 225P are more flat, so the 715P might hit the frame of the radio when the modules are put back in. I'll check and see.
I'll start checking resistors after the paper caps are gone through.

Why waste money on OD's when they were never original and add absolutely no value plus crowd the chassis? Dont fall under the 390/390A spell of a few...its simply their version of audiophools.

Only a true cap tester will tell the condition and an eye tube indicator is questionable at best. Best to change them now and not wait until they cause damage; keep them for the next owner.

Carl

If you use any replacement capacitors the mallory 150s are a good choice and close to the physical size of the originals.

@ Carl. I have 3 ways of testing caps. I have a modern multimeter with a cap test function that's only good up to 45uF. No leakage test on that one. Don't use it very much. Then I have a TO-6A that I think is good for leakage tests going down to .001mA (1uA) on the needle. And then I have a ZM-3A/U that I think is really good on accuracy of the capacitance scale. It's leakage test isn't very sensitive, so I use the TO-6A for that, and the multimeter for smaller caps that have leads that will fit in the little holes in the sockets.

As far as insulation resistance tests, I'll have to look up the specs on the ZM3 and TO6 to see which one is more thorough.

And as far as the 390 version of audiophools, I understand, and how! Those list archives are EXHAUSTING to read and are SO VERY opinion based, and full of off topic bull crap and hammy mods that I found myself just looking at original cap spec PDFs (when I can find them) and comparing them with new cap spec PDFs. I am by no means done with this research as there is definitely more than just Vishay to choose from. They just seemed to be a well loved, and time tested choice.

Im not familar with the ZM-3 but I have several TO's including the 6A as well as a ZM-11 and a Solar CB. Gotta thin the herd someday.

Carl

The zm-3 must've had James Brown and George Clinton on the design team, as it's easily the most funky looking piece of gear on the bench.

That is one funky looking instrument!

I have ZM-11 and AN/URM-90 (AKA ZM-30) bridges and I really like the way the ZM-11 is set up. I believe with the ZM-3 instead of checking leakage on non-electrolytic capacitors you instead set it up to measure insulation resistance. The TO-6 is more convenient I imagine.

One thing I really like about the ZM-11 is the way it generates HV for testing. It rectifies the output of a RF oscillator to supply the voltage and if a capacitor shorts or develops excessive leakage the oscillator stops without fireworks or drama.

Below is how a proper and staid military bridge is supposed to look. Actually, I sort of like the way your ZM-3 looks. They organized function by color and it is certainly UNIQUE!

Yeah, but unless I'm missing something in the instructions, the leakage test only goes down to 1mA. That's 1,000 uA on the lowest division of the needle! Otherwise it's great for checking uF.

It appears the ZM-3A only has a single range for leakage and with a full scale reading of 50 mils it would be very difficult to read low levels of leakage. It was built in a day when a filter cap with only a few mils of leakage current was considered normal. A typical modern 47uf 450V cap would have not more than 400 microamps of leakage operating at its rated working voltage. With the ZM-3, good electrolytic caps should normally just cause a barely perceptible movement of the needle.

To put things in perspective, Cornell Dublier provides this as the leakage spec for one of their more common lines of electrolytic capacitors:
Actual leakage current (in microamps) will be less than the calculated figure of: 3 times the square root of (capacitance times voltage).

The ZM-11 provides three leakage ranges with full scale readings of 1, 5, and 25 mils so it is easy to read leakage in the microamp range. But it doesn't have a snazzy paint job.

Rodger WQ9E

Thats how my 1941 Solar works. The rectifier is a 6L6 fed by a 6J5 RF oscillator.

The ZM-11 is a busy little thing and not for the fat fingered The manual takes a bit of reading also, not my strong suite as I discovered during my first pass at the meter

Carl

Carl,

Was your ZM-11 also built by Clough Brengle?

I first ran across RF HV power supplies in early Tektronix 500 series scopes. It didn't take much to cause those to shut down, a little conductive dust residue is all it takes.

Yes. Contract 52462, serial 544.

Carl

I had to give up eventually on reading this saga..LOl!! Having owned a URR391 for over 40 years..since before Vietnam...I found this quite a frustrating forum...Some wisdom but mostly not. I'll add my bit and hope it redirects your thinking.

You got an absolute bargain and if this was a US Government rebuild for NASA or the TV-show invasion of Iraq in 1991 even more so. If it was over $2000 it would still be a good buy....Going over and over the forum I get the distinct impression some donkey-breath has been messing about with this set ...Paint doesn't chip off in Collins radios because of ill aligned controls and nor do most of them get the problems you seem to have..... I say that because years of reading about them..and mine went to Japan to an expert collector as a genuine Collins after 40 years of heavenly performance...the sorts of problems you have, even in part, as a lump sum come up only when idiots try to fix them.

Oil etc and tuning slugs interfering with anything......sounds to me as though one of these incompetents has been playing with it....you don't drop oil around anywhere including the tuning mechanisms. If the tuning train has a problem I suggest (and will continue to suggest ) that you seek an acknowledged and very experienced Collins expert in those sets before you go too far. ...and there is at least one in the USA. Here's one suggestion Terry - W5OAS

In the meantime why not keep away from it...even if you DO own it and can do as you please...these sets are altar material....religious icons!! Try advertising on eHam. There are Collins clubs too. ..but avoid anyone not right at the top of the tree in experience... Someone will be around and if your set is properly sorted by someone who knows what they are doing rather than someone working off a forum and who doesn't appear to have the technical manual and if it costs $100 to $1000 you will still be ahead...and have a set which may well outlive you. Nothing better will ever be built...other than the 391 of course.

The 3TF7 is available from time to time on ebay. I suggest you get one or again advertise on eHam.

Yes they are got rid of and substituted by a resistor and there's lots of ancient suggestions but it's not recommended. Collins didn't build sets using superfluous circuitry just to belt up the price......

This set may but is very unlikely to need capacitors replaced, if it has been professionally rebuilt it will not be using junk caps. You talked about heat...look where the power transformer is placed. If wire wound resistors are burnt or if there are odd smell I wouldn't be running the set for days on end but getting it fixed.

My set was built in 1954....It had all original components and I replaced only the power electrolytics and two caps and one resistor in the audio module in all that time and the set was still dead on repeatable frequency and outperformed any other set I came across of any type. I did change half a dozen tubes in that time including the ballast tube...and the half dozen was because I replaced all the IF tubes as well as the RF's at the same time.

Resist the urge to screw around with one of the best sets ever built anywhere at any time unless you are a really on the ball techo as opposed to a self-confident meddler.. Hams often enough blunder their way through repairs to service equipment but some comparative few of the dying breed are really on the ball or were servicing them in the military....There's also a couple of experts in Japan.

I'd be asking on the forum or on Ham for a few of them to get in touch and after checking credentials...pay one them to get yours spot-on. Your comments on light socket adapters, volts watts and amps leaves me wondering just where you are technically and then you are speaking about sensitivity checks and adjustments. I could be wrong of course but even in just one of my engineering


roles...as a Tech teacher in electrical, I felt quite uncomfortable about your working on a URR 390...That is meant kindly.I don't care whether it's not my business or not..I only care about the set.

See where your electrolytics are made...see if you can get US made stuff rather than asian. There will be hams around, of the older fellows, with stacks of quite ok electrolytics of high quality...or again, and this is my repetition...seek out a Collins expert....he'd probably rather have the set before you start playing around with it...as that's too late, in terms of cleaning it up, at least leave it at that.

When people start talking about what's right and wrong with the dial mechanism and how they fixed it remember they almost certainly don't know how it should be and have made their own judgement. There was an element of toothiness but NOTHING should bind or jam....only bad wear or filthy environment or an incompetent will cause that...especially one who tears the set down.

Spinning the dial as though it is an Eddystone is not a great goal, just use the wrist flick gently..each channel is only a MHz after all....I can tell you that if you set it on frequency and record it and go up and down the channels for half an hour it should be precisely on the digital read out on where it was on your record. I tried it numerous times over the years and it never altered.

I don't want to go on forever but there is only one way to truly test performance of tubes in the set and that is by substitution. The numerous IF amplifier tubes are matched, thus their nomenclamature. There are no 5811 in the set so either. Tony C is right or someone mistakenly or ignorantly replaced a 5814 or something else with a bodgie tube. Forget what's in it and use what the manufacturer selected. If this is a revamp by some allegedly expert group then again...advertise on eHam to get in contact with people who know the sets well or have the sets....You can't replace half a 12AU7/12AT7 so if it's crook..junk it...no point in talking about it...

Your blackened antenna relay is likely a problem...If your set as otherwise fine you don't need it anyway so simply bypass it with temp wiring until you get another....again it sounds like this is either a fraudulent revamp or it has been screwed around with since. Same advice.

There is nothing you or anyone else can do to make this a better radio than Collins made so resist any suggestion you ought to do any mods. You do not need the associated sideband equipment as the BFO is perfectly fine for that. Don't worry about the functioning of the meters until you have it repaired learn how the set actually functions and get a manual and read it...but don't think that is an instant expertise,...please get expert help. Otherwise like this forum you will go around in circles and either ruin it or get so sick of it you'll flog it off for a pittance because only an expert would risk an amateur-repaired 390..and even they would have palpitations wondering what's been done LOL!!! I hope you'll find my definitive advice worthwhile...if not...................

Here's maybe some help from Surplus Sales of Nebraska apparent Email:grinnell@surplussales.com if still alive

See some of their gear for Collins below.....if the photos don't survive go to http://www.surplussales.com/collins/CollR390-A.html

I have had a 391 for 4o years as I said..perfect performance, silent background no “blowthrough” on any bandwidth I say again...forget messing about find yourself an expert and pay him..or pay the price.
R-390 Ballast Tube

(TUR) 3TF7
Hard to find 3TF7 ballst tube is essential to the proper operation of the R-390.

 
R-390 Power Cable

(COL) R390-PC
Has four contact connector, center thumbnut. We have discovered this IS NOT the actual R390 cable. The alignment keyway slot is in a different place. This aspect can be modified, if you have the ability. Be advised these cables will not plug into your R390 as-is. To compensate you for this trouble, we have discounted cables by $10 from Catalog 8 to $25.

$65 each


 
$25 each






R-390 / R390A Manuals
 
Part Number
Description
Price Each
 
(PUB) COL-R390
R390 Manual copy.
35.00
Add
(PUB) COL-R390A
R390A Manual copy.
35.00
Add
(PUB) COL-R390/UR
URR Organ. Maintenance Manual, copy.
25.00
Add
(PUB) COL-R390A/S
R390A Schematics, copy.
35.00
Add
(PUB) COL-R390A/U
R390A/URR Operations Manual 1/61, copy.
25.00
Add
(PUB) COL-R390URR
R390/URR Complete book 10/53, copy.
75.00
Add



Cheers

I disagree with you. I am by no means an R-390 expert but just by following the manual and my experience working on electronics I wad able to get mine working pretty darn good.

There are some very experienced techs here on the forum and those here who have worked on an R-390 would not have done so if they thought that they couldn't handle it which is how I felt until I got good advice here and read the manual on the R-390.

Many people here have had many years experience in electronics some as a ham some as their daily job and some both.

You dont need to be a glassy eyed fanatic to own and/or work on any Collins gear, there is nothing magical about them as wittnessed by how many contractors built the R-390A. Id suspect the military wasnt in awe of Collins over the R-390 and all its problems and wanted to have options. Note that Collins made few 390A's in comparison to the total. Mine is a 1956 run with all Collins modules.

The full set of manuals is invaluable, I prefer paper to CD and have originals plus copies.

I also spent time in the US Navy working on them at depot level aboard a tender and later refurbing for a company in the late 60's who bought hundreds as surplus. After awhile it got boring as its really an easy radio once you get used to its needs and quirks. Only those trying to remove your wallet foster the mystique and cruise the Collins forums as a flim flam artist.....I left that crowd well over a decade ago when the Orange Drop idiots were attacking anyone who didnt agree with them.

To each their own but I wouldnt own a R-391. To me the R-725 is the ultimate, being a marriage of the R-390 and R-390A. My autotune use is limited to the ATC/ART-13 and its a real gas watching it in action.

Carl

Finally. A mention of the R-725. I really like mine, although I regret having sold my R-390A EAC with all matching serial numbers. I think that there were only 250 R-725's made.

Agree 100% regarding Collins, orange drops etc. I don't confuse the radios themselves with the men (pardon my sexism) who built them, used them and maintained them. As an engineer, I can say that every design is a result of compromises. Cost, schedule, use of approved technology etc all limit what you can do. These rigs, as impressive as they are to behold, are not without warts. They suffer from component failures, abuse, and age just like everything else. The OP may regret some of his choices one day but he will have learned from them. I've made some mistakes with mine but the radios are working just fine. And I am better off for the experience of working on them.

Tony

I have heard rumors that such radios exist but I thought they were myths. My 67 EAC looks new inside, definitely didn't see service the inside of a depot. The panel slots show no signs of screws and all of the "green screws" are bright and unchipped (except for the small chips I may have put there). But the panel SN is 112 while the modules range from about 108 to 160. I would be surprised if the modules actually went through the entire assembly process together. The only way I would expect all the SNs to match is if they didn't stamp the modules until final assembly. I imagine a pile of IFs, a pile of power supplies etc and somebody taking units from each pile and putting them together into complete sets.

Tony

The R-725 doesn't have matching serial numbers unfortunately. Arvin Industries took new 67 EAC's and modified them with an auxiliary power supply addition, and a new 'super' IF deck. I'm sure they were disassembled en mass, with a mix and match at reassembly.

@ Socrates. I appreciate your honest approach with your view. My technical abilities are in the realm of 'there's a first for everything' and intermediate I think. So far the only thing I've done to the set is clean the chassis etc, and put a few proper tubes back where they needed to be, and as of last night, removed C553.

Here's where the curiosity begins. C553 was wired where it should have been...electrically, but was far buried underneath the coil it's attached to. Not where C553 is on the chassis markings, or in any pictures I've seen it located. In fact the actual cap was covering up the C511 marking. Ok. No biggie. Funny thing is there is a misprint on the IF chassis too....... It clearly says O553 instead of C553. It had me wondering if they -O-mitted C553, but there it was hiding under the coil.

The cap itself was marked "gen instr" company. Sheathed in clear tubing, and showing slight signs of corrosion at the ends, and like something had leaked out a bit in the clear wire covering (which I've saved for the new cap). One of the leads looked corroded all the way to the connection point.

Looks bad but tests perfect, but I think I'll leave it out in favor of a 715P .01@600V just to save myself some grief should it ever go.
Any caps that get removed in favor of replacements will be saved, good or not, simply because I believe they are original.

And in the end I did go with the orange drops just for the sake of uniformity as all the paper values were available in ODs, and it was mix n match with other manufacturers (from mouser at least). I figure too that this MAY add $$ value should it be placed on ebay by a family member if something happens to me. Couldn't hurt in this case. I always TRY to buy knowing that if something DOES happen to me, it won't be junk for someone to set out on the curb, but junk to be put on ebay and line the pockets of whoever is tending my final expenses. The list archives have made it clear that the fools that easily part with their $$ like the ODs, and uniformity might be a plus in the pictures.

At any rate. I'm not so overconfident that I'll undo, or begin working on a part of this set without knowing exactly how it will go. I understand this set is complicated. As of now, I think that the papers deserve at least a check. I'm going back and forth with replacing them all. It makes sense to. But then again this set is close enough to original that I second guess it. Not totally original. The front panel has been painted. It is NOT engraved. Can anyone verify if by 1961-62 the capeharts had engraved panels or not? The electrolytics? Sure. I'll do them right away just because they're not original anyways, AND the wrong values. The cap (50uF@50V) under the line filter will get re-stuffed too.

I plan on using this radio. Not all the time. I do lean more towards a 180A I have for the simple fact I'm not so worried to use it! But I do like the general coverage AM stuff too,and it sounds mighty fine on the 390.