Stewart Warner

R390A Rebuild

Continued

2nd LO

The 2nd LO was pretty much uneventful. It was really pretty clean to begin with. I didn't take to many pictures as it's pretty straight forward. I took it down to a bare chasses, replaced all the carbon comp resistors, replaced some caps. I left the original mica's in as they all checked okay.
Here it is complete. I did find that I had some frequency error with the receiver when it was all complete and I was doing alignment. The PTO was spot on and I discovered that the error was coming from the 2nd LO. Turns out some of the crystals were slightly off frequency. Unfortunately it also turns out tht adjusting the trimmers does not warp frequency, it only impacts amplitude of the frequency it is oscillating at. I did not fix this problem. Someday I do plan to get some crystals and change the offending ones and see if that corrects it. The error is small and for now I can live with it. Next up was the chassis.

Chassis

Chassis was pretty uneventful as well. It was pretty dirty though. I did the front panel along with the chassis. I didn't do anything to the front panel but strip it down and wash it. Other than that I did not try refinishing the front panel. It looks pretty good. I did replace the selenium rectifier with a semiconductor bridge. I also discovered I had a shot antenna switch as well. Contacts were shot. I ended up getting a new ant switch, think I got it off ebay if I remember right. But other than that all I did was strip the chassis down, wash it, and then used fine steel wool to shine it up.

Here's the finished ant switch. This is the one I got off ebay, cleaned up very well and works good.		Here's the completed chassis. You can see the bridge rectifier I put in to replace the selenium rectifier. I also used the original line filter, it checks and works fine. Next up, the RF deck.

RF Deck

Here's a few shots before digging into it. It was pretty dirty over all. The parts are really packed into the calibration osc section. And there's some of those ugly BBOD's.
Above shots are the deck coming apart. Took it down to a bare chasses. Replaced all the carbon comps with metal film. Replaced most caps, I did leave the micas in the coil sections, they seemed to be okay and checked good.

Here it is rebuilt. Really came out good, really shines. Performance is great. It aligned right up very nicely when finished. Next up the gear train.

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