Delco 981968

[Reece]

The Delco radio under examination uses tubes that work on 12VDC of B voltage, with a transistor output. This was a hybrid design that existed during the transition from all tubes to all transistors in the late fifties early sixties. Since it needs no high voltage, there is no vibrator in the set. Any vibration that was noted on that rear choke was due to ripple from the battery charger. The best test for that radio would be to hook it to a car battery so it gets a proper smooth supply.

I always respect a car battery for the power that it contains. A short can cause a big flash and burns or in the worst case the battery and its acid blows up. I make my connections carefully and make certain that there are none that might short, recalling that the chassis of the car is negative, too. Good idea to put a fuse in the test line, also.

I haven't worked on one of these hybrids so not sure, but the speaker may have to have a certain impedance. Do you know if the speaker under test is the right one for this set? The schematic shows that there is a shorting switch which apparently operates automatically when you unplug the speaker in order to save the transistor from running with no load. If you pull the speaker plug and then test before and after the choke I would imagine that any output that it still had would be louder before the choke since there would be a dead short after it, although with a dead short I wouldn't expect to hear very much of anything. Maybe one of the car radio gurus will chime in. If no one here, there are some over on ARF.