I have a Crosley D-25 that did not play. I recapped it and changed some resistors that were open or outside of their margin of error. I replaced some brittle or broken wires, mainly ground or B-. All the orignal tubes were checked and tested good. The B+ all checked correctly with the schematic. I brought the radio us slowly and it played. It picked up local stations well....I played the radio for short periods of time and all went well. After putting it back into its cabinet problems started: the dial knob was sensitve and caused the volume to change. I took it back out and the same problem persisted. I changed the tubes---same result. When the radio plays it becomes more and more broken up in reception; as I touch any place on the chassis or antenna the volume increases then fades. I've exhausted my humble knowledge and am open to any and all suggestions. Here is the schematic:

http://www.nostalgiaair.org/PagesByMode ... 003729.pdf

Thanks,
Mike

Did you clean the tuning capacitor?

Unlike many radios, it does not appear that the frame of the tuning capacitor in this radio connects to the chassis. It is probably isolated by rubber grommets of some sort. Perhaps these have deteriorated any you are getting an intermittent short to the chassis?

You could test by connecting an ohmmeter between the capacitor frame and the chassis (radio unplugged). The resistance should be infinite, or at least very high. Then see if there is any change as you wiggle the capacitor frame.

Thank you both. I will test the tuner today and clean. I had taken some dirt off the blades, in fact I had to straighten some blades that were touching, but only cleaned the section I was working on.

Thanks again,
Mike

There is usually a brass spring in the center of the tuner that grounds the rotor axle. Spray some contact cleaner where it touches the axle and turn the tuner to clean it.
Don

Hey! I have a radio again! It passed OldBears test. While I was cleaning I noticed when I put the radio back together (to return it to the cabinet) I screwed the speaker support (rear) with a longer screw and this was touching the tuning capacitor. Backed it out and "presto". It is always amazing to me how simple things can be yet if I wasn't recleaning I would never have found the problem.

Thanks to all,
Mike

I was working on an RCA 66X1 and it had a come and go static noise. You could tap just about anywhere on the radio and the noise/growling would start. As it turned out, the tuning capacitor rubbers had carbonized and distorted. The tension applied by the dial string then pulled the tuning cap pulley about a quarter inch out of alignment. The pulley was intermittently rubbing against a metal bracket holding a smaller dial string pulley. I had to remove the tuning cap, scrape the remnants from the chassis, and used 9/16 OD grommets as a replacement. It can be very difficult getting the grommets into the chassis holes so heat them for a minute or two with a hair dryer so they become pliable. Then they can be easily inserted into the holes with long-nose pliers. On this particular model, the tuning cap is isolated from chassis ground so having good mounting grommets is important.

Thank you for the input. I will keep this in mind if the problem comes back. To date the radio is "rockin"---or "talkin" since there is no am music on the dial.

Welcome to forum,
Mike

Nice to be here; thanks.
I can't speak for all vintage radio, but the RCA from the 40's I've worked on all had the tuning capacitor mounting degradation. It's real easy to spot with an LED flashlight; the rubbers will appear flattened out with a lot of cracks. They fossilize over time, turning into a coal or charcoal like substance that turns to dust when disturbed. Sometimes, pieces of it will adhere to the chassis or tuning capacitor and has to be chiseled off.

Welcome and thanks for the information

That's really unfortunate and almost the same situation here except for one station, WMNI 920 kHz. Years ago, music was the mainstay but then shifted to sports, then talk radio, and now we're getting a flood of religious broadcasting. One PBS station, WOSU 820 kHz, actually left the air since it was already broadcasting the same junk on FM. Then to my delight, I was able to hear three different stations roll in at night depending on the propagation. A day later, to my horror, a new station suddenly appeared with Catholic broadcasting.

One solution would be to build an AM transmitter and broadcast your vintage music mp3 files throughout the house.

http://www.ramseyelectronics.com/cgi-bi ... n&key=AM25

http://www.electronixandmore.com/project/10.html

http://www.dogstar.dantimax.dk/tubestuf/amtx-3.htm

I think that's an interesting way to employ transformers T1 & T2. I think I will build this power supply to see if I can get some of the AC hum out of my RCA 66X1 AC-DC radio. Notice DC is used for the tube filaments.

Just go to the Homebrew Radios section of this site where several working AM transmitter projects are described, read up, and build one of those.
Don