Bakelite Crosley Multiband Restore

[StarMover]

Well, I finished with the recap. When tested the 5Y3GT began sparkling then got hot. At least a bad tube, possibly a short somewhere. I ordered a trio of tubes for $10 on ebay, so we'll see. Next time I'll bring it up on a dim bulb as the wise folks here suggested. Should have done that in the first place, but too anxious to take the time. Lesson learned.

[jeyurkon]

Any progress?
John

[sanford12]

I collect and restore old radios for my main hobby and you will find that when you get this radio running right it's a very good performer. Most old radios you find only need a the caps and electrolytics and an alignment. A good place to go for schematics and other info on old radios is Nostalgia Air here's the link
http://www.nostalgiaair.org/. Good luck with your radio.

[StarMover]

I'm gonna have to get the schematic because something isn't right. The dim bulb test worked, but when I plugged in to 110, a resistor got hot and started smoking. I think the 6V6 is fried as well. This project is getting over my head. It needs more than I have skills.

[Jeffhs]

I can't imagine how your radio passed the dim-bulb test if a resistor started smoking when you plugged the set directly into the line. There is still a major problem with the power supply, especially if the 5Y3 rectifier tube is running hotter than normal (as you mentioned in a previous post; you also mentioned the tube was "sparkling", which means trouble as well). The resistor you mention is burning for exactly that reason--the component is being called on to handle more current than that for which it is rated. Did you replace the filter cap when you recapped the chassis? If so, that rules out a shorted filter and leaves either a shorted high-power tube (such as the 6V6 you mentioned) or, worst case, the power transformer. When a resistor burns and smokes in any piece of electronic gear, you can be sure there is a serious short somewhere that must be corrected before the equipment is used again.

The 5Y3 rectifier running hotter than normal is a danger sign as well, as I mentioned above. There is one other possibility--I don't know whether or if this would apply to a transformer-powered radio, but I'll put it in here anyway. Does the dial light work when the radio is switched on? If not, I'd replace it ASAP. I mention this because in some radios, the pilot light is part of the power supply; for example, I have a 1951 Zenith H-511 that uses a pilot lamp as a current limiter. The lamp glows very dimly when the radio is switched on from a cold start, then brightens as the set warms up. When the tubes are fully warmed up and the set starts to play, the pilot light is at its maximum brightness. If there is a short anywhere in the power supply (or if the 3-section electrolytic filter cap is deformed from years or decades of disuse), the pilot light will burn out with a bright flash. If the radio is used without the pilot lamp in the circuit (e.g. the bulb is burned out), the 35W4 rectifier tube will glow brighter and run hotter than normal, leading to premature failure of the tube.

Note that the foregoing applies to series-string radios with pilot lamps; as I said earlier, I don't know if the same applies to transformer-powered sets. Again, that the 5Y3 rectifier tube in yours is "sparkling" and also running hotter than normal, not to mention the burning resistor (which is probably a large power resistor in the supply circuit, near the transformer), are unmistakable indications of a very serious short in the power supply.

[StarMover]

I will gladly box this radio up and ship it to anyone who is willing to try and save it. I'd rather give it away than ruin it. It is too big of a project given my electronics skills. PM me...

[Reece]

The pilot light does not affect the B+ in a transformer set. Check your electrolytic capacitors. If you installed any of them backwards, this could be the problem. There is a strip on the side of the caps with minus signs on it pointing to one end. The wire from this end will come out of the outer aluminum can of the cap. The positive wire from the other end emerges from an insulating disk. If you find one backwards, replace it with a new one because it will be damaged. By the way, the voltage rating of these caps ought to be the same or slightly above the voltage rating of the original caps. This means that such caps used in the cathode circuits of tubes ought to have lower voltage ratings than the filter caps used in the B+ circuit.

Check all your B+ wiring. There could be a short somewhere causing B+ voltage to be shorted to ground.

Did the transformer pass its test before you even started on this radio? Try this: pull all the tubes. Plug the radio in to the dim bulb tester and turn on, using about a 60 watt bulb. Bulb should not light, or only very dimly. If it lights bright, your transformer primary is bad.

If you got a dim bulb on that test, a good sign, now put all the tubes back in EXCEPT for the rectifier. Plug the set into the wall and see if tubes light. If all is OK watch carefully for a few minutes, feel the transformer, listen, sniff.

If all looks OK, leave the rectifier tube out still. Turn the set over and check the AC voltage between the two plate terminals on the rectifier. Should be several hundred volts. Now check between each plate and transformer secondary center tap. Each should be approximately half of the previous figure.

If all these tests are OK, your transformer is OK and you have a short somewhere in the B+ wiring, or an electrolytic reversed. Don't try the radio again with the rectifier tube until all B+ wiring has been checked.

Download and print out the schematic and then using a highlighter, trace every circuit in the radio, highlighting it when you are sure of it. This takes time and concentration so don't do it when you're tired. Spread it out over several sessions if necessary. It's a good exercise and you'll see how the actual wiring is done versus the drawing. This should lead you to find the problem.

BTW, the cord and plug on that set would have been moulded rubber. Cloth cords went out depending on the manufacturer around 1936-37.

Reece

[Phil Nelson]

Did you test the radio at any stage while recapping? When a radio works (even if poorly), I briefly try it out after replacing every cap or two, to make sure I didn't space out and miswire something. I also check off each cap on the schematic and parts list as I go.

If the radio worked OK before you replaced the last two electrolytics, they are obvious culprits. It's easy to connect one backwards. Also, when you have more than one component disconnected at a time, it's easy to forget where the chinbone connected to the neckbone.

If you didn't test the radio or keep notes, I would carefully doublecheck the wiring of every capacitor that you replaced, using the schematic as your guide. Is it the right value? Are both ends connected to the places where the schematic says they should go? Note that schematics sometimes show parts located close together which are far away in the physical radio, and vice versa. Using an ohmmeter to check connections may help sort things out.

Finally, is it possible that you mixed up the tubes and accidentally swapped two of them when putting them back in the sockets? Sounds obscure, but many people have done that in a moment of inattention with tubes scattered around the workbench.

I would not give up and send it to someone else at this stage. A printout of the schematic and an ohmmeter can help you confirm that all of your capacitor replacements are correct.

This article has general advice about recapping: http://antiqueradio.org/recap.htm .

Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html