A Tale of Two R390A's

[Josh]

So I shipped an R390 to kali, and of ofc they dropped it. I had sturdy foam sheets all around and extra padding too. They popped heads off front panel screws, bent the kilocycle shaft, and dinged the bottom corners. Ok so it weighed in at 77 pounds but I didn't pay them to drop it.

That was the rig I sold the technician, I also sent, to the exact same address, a R390A IF deck to have the filters swapped and aligned and then returned to me.
Ofc they also dropped that 6 pound package the size of a shoebox, and despite my multitudinous layers of bubble wrap they bent the IF can that contains the 100Hz xtal filter into a parallelogram. So the tech noted the if xformer ding and he hammered it into shape and proceeded with the alignment. Shipped it back to me and it got here this am.

The box looks dandy, fine even, so I wasn't expecting anything amiss. I peeled layer after layer of bubble wrap and ofc the same IF can is a parallelogram once again. The desired shape for these devices is a rectangle, so you know. The words of the immortal Barry L Williams come to mind here; stop fooling around with R390As and get a Perseus.

Anyway, I hope to have the R390A in operation today to begin a strict diet of radio piracy, Cuban numbers, Russian naval and Chinese air defense cw and etc signals meet for a spy radio. These rigs are very sensitive and have few if any spurs, are naturally emp proof, and have a long history of being an exemplary spy radio. I have a fetish for ex NSA, NSG, ASA, and other USG sigint gear.

In the meantime between shipping and receiving said packages, I weakened and went and got another R390A, a complete Imperial model, with only Teledyne innards.
Imperial, Teledyne, and Amelco are reputed to be all the same people under different banners, and made some of the best R390As to exist, according to cognoscenti. Odd for a R390 to have its original inners as the service depots generally put in whatever module was needed from stock on hand and sent the radio back, later repairing the recalcitrant module and placing it on the shelf for the next rig that needs it. I mused that anyone who has a R390A really needs a parts rig in case something other than tubes or commonly available parts freaks out. Buying a hulk is far cheaper than buying the same parts separately on ebay, so I bit. And now I'm torn because while it is very clean, works well enough to have weak reception, and is rare because it has all its original bits and pieces and is eminently worthy of a restoration, that would put me right back into the need for a parts donor. Radio is a terrible hobby.

https://www.radioblvd.com/R-390A%20Rebuild.htm

[Token]

Radio is a terrible addiction.

^^^^ Fixed that for ya.

T!

[Josh]

Radio is a terrible addiction.

^^^^ Fixed that for ya.

T!

Indeed.

As I placed the tubes back in the if deck I also made sure to employ tube shields that had the beryllium finger stock thingy inside to transfer more heat. This is a pain since not every tube shield i run across in my stock of parts has the insert, making the shield a tube cooker rather than a tube shield. Some tubes, such as rf amps, mixers, and most of the if deck need shields so they don't rfi themselves, others are fine without them and will run almost as cool without a shield as with the best tube shields (known as ierc tube shields). So I'm closer to having an almost completely restored R390A/URR, but know eventually those ierc tube shields will have to be sought out, purchased, and installed. One addiction leads to another.

A word to the wise; if your tube shields (supposing you have tube gear, perhaps not even radio related) aren't of the ierc variety where an insert or the shield itself doesn't make physical contact with the tube wall, you can expect very short tube life as the shields concentrate the heat and reflect it back into the tube. The only thing better than a naked tube is a tube with a ierc shield, far as tube life goes.

Here's some data on the oh so very important tube shields;
https://pearl-hifi.com/03_Prod_Serv/Coolers/PEARL_Tube_Coolers.pdf

Here's what they look like;
https://tubeworldexpress.com/collections/tube-shields/shields
http://www.surplussales.com/Tubes-Sock-Acc/TubeShields-1.html
(I'm not affiliated in any way with the above businesses)

I think I'll try some blueing or at least a freaking black sharpie on the non - ierc tube shields I do have and use the infra red thermometer on them for some before and fater testing.

Also, if you do run older tube gear, most of them were designed for 115v ac mains and you can upset them a bit by feeding them straight house current wich today is around 125v in some places. A bucking transformer or variac can be used to reduce the line voltage to what the gear was designed to see, increasing rube life and probably extending the life of the transformer.