On the workbench – Vintage RCA portable TV

RCA 8-PT-7030 Portable Television

Years ago I picked up this old RCA portable television, model 8-PT-7030 manufactured in 1956. Someone on the rec.antiques.radio+phono Usenet group was giving it away for the cost of shipping, which was around $30. At the time it had a broken high voltage rectifier tube. Other than that, I was unsure of it operating condition. It sat around for close to 10 years.

The first thing I needed was a schematic, and at the time I was unable to locate one online. It occurred to me that my friend Mel W0MDM might have one at his TV repair shop in Estherville. The next time I was passing though I stopped to sell hello and see if he had schematics, and sure enough, he did.

The first problem I ran into in the repair process was a lot of melted wax on the back of the rectifier tube socket, which had migrated into the socket itself. I’m not sure if this wax melts out of the high voltage transformer, or if it’s there to prevent arcing. Either way, it had made a bit of a mess. I tried picking the wax out with some dental picks, but wasn’t entirely successful. I got busy with work so the set got put on the shelf in the backroom for the next 10 years or so.

Last month I dug it out and decided to see if I could make it work. I used my hot air soldering station to blow the wax out of the tube socket and replaced the bad tube. The set still didn’t turn on.

I was able to find a full service manual for the set, a copy of which I have uploaded here. This was very helpful, as it allowed me to discover that the chassis comes apart into two halves for easier service.

I don’t have a tube tester, so I’m not able to check any of the tubes. I also didn’t have a cord that would allow me to power it up on the bench with the cabinet removed. I could have rigged up a “suicide cord” to power it, but I decided against it. At a minimum the set needs the selenium rectifiers and the electrolytic filter caps replaced. And then there’s an almost 100% chance that some or all of the 31 wax/paper capacitors are bad. Five of those are not available in the correct values and voltages. The available parts would cost around $55, but still no guarantee that all 16 tubes are good. Or that the CRT is good.

While this would be a fun project, I decided to just clean it up as a display piece for now. Even if it worked, there’s no analog signals left to display so I would have to feed this with an RF modulator to get a picture. It would look pretty neat in my basement bar, but even not working it will make a nice display piece.

The chassis removed from the cabinet

 

Hamfest Find – Vintage Bearcat III Scanner

When I was kid my grandma always had a police scanner going. My brother and I thought it was pretty neat to hear the police, firemen, and ambulance talking. I can’t remember exactly which radio she had, but I do remember that it was a Bearcat, and that it had the red LEDs and there were lockout switches for each channel.

Later on when I was in high school I bought my own police scanner, a Bearcat BC70xlt. Two of the channels I had programmed were local 2m ham radio repeaters. Not having a ham radio license, my brother and I both put CB radios in our cars, as did many of my friends. We had a lot of fun with those CBs, but they sure left a lot to be desired.

We noticed that one of the kids at our high school had a lot of antennas on his car, so one day I asked about them. It turns out that he was a ham, and he told me I needed to throw away that CB and get a ham radio license, which I eventually did. That kid turned out to be a lifelong friend, we still chat on Facebook several times a week.

Fast forward 25 or so years later and I ran across this old Electra Bearcat III police scanner at the Cedar Rapids hamfest. It immediately reminded me of my grandma, and how her police scanner changed my life by sparking an interest in radio communications. The guy was asking $10 for it, with the original box, manual, power cord, and mobile mounting bracket. How could I pass that up?

The radio was in mint condition inside and out. No dust bunnies and very clean. The only real cleaning it needed were the knobs, which I scrubbed with a toothbrush and some Simple Green. A quick wipe down of the rest of the radio and looked great.

Of course, this being a crystal set, I knew it wasn’t going to hear any of the channels our local public safety agencies were using. Even worse, once I got it home I realized that the BC3 used optional IF boards to listen to two different bands. This radio only had one installed, and it was UHF, and I needed VHF. But I found another BC3 on eBay for a bit over $15 shipped, so I went ahead and ordered it so I could rob the IF board from it. It even had a couple of crystals that would work for me locally.

Next I needed crystals. Certainly ICM or Jan would have them. Nope. Both are out of business. Looks like it was back to eBay. Several sellers had scanner crystals, and I finally found a seller that had what I needed. I ordered five crystals for $50 shipped, a lot more than I really wanted to pay, but what good was this thing without the crystals? Once they arrived I installed them and sure enough, I heard the fire department being paged out and the police dispatcher as well.

I put the scanner on the bench and tested with an IFR-1100 service monitor and the receiver is actually quite hot, at about 0.2uV of sensitivity. Not bad for a scanner that’s nearly 40 years old! I considered re-capping it, but since it was working just fine I decided not to bother.

This unit is now living in my basement bar, right next to some 70s vintage pinball machines. It looks right at home there, and every time I see it I can picture grandmas scanner on top of her refrigerator, and I’m reminded of childhood visits to grandma and grandpas house.