Need help with a Phillips 90AR466/45 boombox

[tyson]

Hi,
Firstly, my apologies for those who have already seen this post in another section of the forum as i can't find how to delete it as it is more suited that my question is to be asked here , but I recently got a Phillips 466 portable AM\FM cassette radio from a local second hand goods store. It was claimed that it didn't work as it would not turn on. I tested it out and all I got was a pop from the speaker. No volume regardless of position of the volume control, no radio regardless if it was in FM or AM and when I engaged the tape deck, the motor only span for a second before cutting out (regardless if it was in play, fast forward or rewind). The tuning\battery meter also appears to be dead as it does not move at all when tuning or running off of battery power. It dates from 1976-1978 , Where would a good place to start looking for faults be?

Thanks for your help.

 

[hopey]

Try operating the record bar by Pushing REC and PLAY then STOP 50 times.

 

[tyson]

Tried it, no difference

 

[hopey]

Maybe faulty power caps. Try power from batteries or dc

 

[tyson]

I have replaced the main filter cap, the cap that appears to be coupling in the signal from the tuner/volume assembly (judging from what it looks like on the schematic) to the amp and the cap that goes from amp to speaker and it did not make a difference. I have tried it from a battery and same thing as if it was on mains. I tried to inject a 440hz tone through a 10uf cap into parts near the connecter that goes from tuner assy to the main PCB and i was able to get a faint tone to come out of the speaker from the amp with my signal generator set to full output.

 

[hopey]

There could be issues with the power/ sleep toggle switches and or the ear phone plug try pushing a headphone in and out a few times.

 

[tyson]

I took it completely apart and in doing so, hard wired the speaker to the connector that goes to the amp board so the headphone jack is out of circuit, I am planning on cleaning the switches with isopropyal alcohol when i can get to Jaycar next. Would working the switches and controls be enough in the meantime until i can clean them?

 

[hopey]

Not necessarily the only way to ensure they are working properly is to remove them from the PCB and disassemble then clean the contacts by hand.

 

[tyson]

Would using the stuff in a spray can work just as well? Disassembling and reassembling switches and I don't have the best track record.

 

[hopey]

Would using the stuff in a spray can work just as well? Disassembling and reassembling switches and I don't have the best track record.

It's only a temporary symptom can return if not eliminate at all. You can by pass if you very carefully trace logic.

 

[tyson]

Cleaned the switches, still noting. I think that it is a component issues as directly injecting a signal into the amplifier (bypassing all controls including volume and the switch) yields a very quiet sound from the amplifier dispute the amplitude on the signal generator being at max. Would replacing all the remaining caps in the amplifier be a good start (apart from the cap that couples the speaker to the amp and the signal into the amp as they have been replaced already)?

 

[hopey]

Post some photos are you sure this worth the trouble sometimes your better off buying a better radio.

 

[tyson]

I agree with you there, Sometimes it is just better to walk away while you are ahead. Its nothing really special, its just a mono AM\FM cassette and the parts that i can salvage will be worth more then the radio.