I found this a few weeks ago, i was able to get the cassette player to barely spin when i tried it out, but could not get anything else to work
I took it apart and checked the fuse, 0 ohms resistance
I also plugged it in and checked tested the output form the transformer with a multimeter, i got 0.47V for an instant
I also tested the contact switch in the AC plug, it seems to work fine, continuity when the plug is in place, none when its removed.
At this point i suspect its the transformer not operating, but i don’t have any replacements.
Can i use this power brick to test if it will work?
The label on the back of the deck says 15W, but i would just test the radio, it will also run on ( 8 ) D batteries but i have none, so i would wire this brick onto the battery terminals (which appear to bypass the transformer).
If the device draws more then 500mA will it damage the transformer or could it cause a fire?
Thanks
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Can’t click on any of the images. The AC adapter will probably work for testing if you keep the volume down and only use it for a few seconds. If you don’t want to buy some D cells, use some alligator clips and connect to the car’s battery or a jumper pack for more in depth testing.
Very basic power supply in that radio. Nothing to protect the 120 volt side of that transformer in the event of a power surge from a local lightning strike or utility company equipment failure.
The wall wort power supply may be able to power the radio but there will be an initial high draw on it for a second or two when you flip on the radio. Voltage sag should level out after that so you should be able to check the radio tuner for starters.
Most of those little bricks have slow blow/fusable links (one time use) links internally.
Never had one burn and have hooked them up to stuff that draws more than rated current.
Your wall transformer should be OK under any load except a dead short for at least a few seconds. That should be long enough to hear something from the radio, even static. Radio and even the audio amp shouldn’t draw much power, the cassette motor does so do not test it with that transformer.
The usual point of failure with portable radios of this kind is the AC mains transformer or it’s rectifier circuit, so if the temporary power supply is successful that’s where to check next. Normally the transformer toasts. It’s usually “ran wide open” with no reserve capacity so they could use the smallest cheapest one possible in production. With a 2 lead output, another one of that physical size or larger will usually work so long as it has nominal 12VAC output (which will usually read ~15VAC unloaded on your DMM). With a 3 lead output you’ll need to research the numbers found on the transformer or schematic diagram to be certain, but most of these are 12VAC nominal on both sides; one for the cassette motor only and the other for the rest. A little trickier replacing these. If the transformer is OK check the rectifier diode bridge(s). If one diode is bad replace them all; one new one can toast the rest and they’re cheap. Check for DC output when you’re done; if a new diode died or if you still have no operation it’s probably because an old rectifier diode shorted introducing AC where it didn’t belong and in those cases I usually stop and scrap the unit as further diagnosis and repair will likely exceed replacement cost with consumer grade portable receivers.
If you need more info, PM me as the answers will get long and likely boring to those not into radio repair.
