I'm in the process of restoring an old Motorola AC/DC transistor radio. Unfortunately the radio was plastered with Mad Magazine stickers, and one of them covered the paper label with the model number. The interior doesn't have any indication of the model number.
It's an eight-transistor AC/DC AM/FM radio with two PC boards, one for the RF, IF, and detector stages and one for the AF power amplifier and power supply.
I replaced the electrolytic capacitors and it works well except for an unacceptably-large residual AC hum. The power supply to the AF output transistor is around 90 volts with 4 volts of ripple. (The output transistor drives a step-down output transformer feeding the speaker.) The rest of the stages are fed from a dropping resistor down to 12 volts, so they have essential zero power supply ripple.
I doubled the size of the first filter capacitor (the one feeding the AF output transistor) and there was no perceptible reduction in the hum, so I suspect there is either some circuit fault in the AF amplifier negative feedback circuitry or else the circuit was badly-designed to begin with. Either way, a schematic would be a big help, so I'd be grateful if someone could identify the model number of this radio.
Update: The good folks at Antique Radio Forum found one for sale on eBay. It's a Motorola Model TT11EH. I was able to buy a Sams Photofact for it from SMC Electronics.
Update 2: Someone asked whether the TT11EH has Motorola's "PLAcir" plated circuit boards and/or a Motorola "Golden Voice" speaker, so I opened it back up and took some photos. I don't know if a "PLAcir" board is made using the same process as an ordinary etched PC board, but the boards in this radio appear to be etched copper-clad phenolic. I did manage to lift a few traces while re-capping it. The board doesn't have a "PLAcir" legend on it.
I can't see all of the speaker structure as the power supply is mounted on the back of the speaker, but it doesn't have any visible "Golden Voice" legend.
While attempting to unsolder and remove the old can-type multisection electrolytic, I broke off the corner of the PC board where it was mounted, so I had to kludge the wiring of the replacement capacitors.
