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#1 |
Badcaps Veteran
Join Date: Sep 2019
City & State: Southampton
My Country: United Kingdom
I'm a: Knowledge Seeker
Posts: 231
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![]() Hi all,
I am trying to diagnose this small radio/cassette player where the audio cuts out after a few seconds - then comes back, then repeats. I've checked the voltage and current coming from the PS board and it seems fine. I've also powered it from a bench PS and the fault remains. All of the electrolytics on the audio board are normal with no high ESR's or bulging tops. Any ideas? I've attached the service manual for the unit. Many thanks. |
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#2 |
Badcaps Veteran
Join Date: Jan 2016
City & State: Sochi
My Country: russia
I'm a: Knowledge Seeker
Posts: 852
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![]() Check the headphone jack, there is a contact lock for the speakers.
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#3 |
Badcaps Veteran
Join Date: Sep 2019
City & State: Southampton
My Country: United Kingdom
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Posts: 231
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![]() It doesn't seem to be the headphone jack. I've connected directly to the outputs of the TA8229K (P3+P5) and it still happens
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#4 |
Badcaps Veteran
Join Date: Sep 2019
City & State: Southampton
My Country: United Kingdom
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Posts: 231
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![]() I've connected to the input pins (P11 + P12) same problem it cuts out.
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#5 |
Badcaps Veteran
Join Date: Jan 2016
City & State: Sochi
My Country: russia
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Posts: 852
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![]() Does the sound disappear on all functions "FM", "AM", "TAPE"?
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#6 |
Badcaps Veteran
Join Date: Sep 2019
City & State: Southampton
My Country: United Kingdom
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Posts: 231
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![]() yes it does on FM/AM/SW (the tape deck is non functional due to lack of belts).
I've checked the supply voltage to the tuner IC (CXA1238S) (and when working the supply is 4.2V then it disapears to 0.2V when there is no audio o/p |
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#7 |
Great Sage 齊天大聖
Join Date: Dec 2009
City & State: Europe
My Country: some shithole run by Israeli agents
I'm a: Professional Tech
Posts: 26,788
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![]() check the input to the amp i.c. - it could be cutting out from an internal fault.
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#8 |
Badcaps Veteran
Join Date: Jan 2016
City & State: Sochi
My Country: russia
I'm a: Knowledge Seeker
Posts: 852
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![]() If there is a bolon with liquid for cleaning contacts, then you can puff to the contact groups of the switches and click them back and forth (contact may disappear in them).
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#9 |
Badcaps Veteran
Join Date: Sep 2019
City & State: Southampton
My Country: United Kingdom
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![]() I think it might be the amplifier that is intermittantly shorting which drags the supply down.
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#10 |
Badcaps Veteran
Join Date: Sep 2019
City & State: Southampton
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![]() The switches have been disasembled and cleaned with super 10
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#11 |
Badcaps Veteran
Join Date: Jun 2012
City & State: ☻
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Posts: 8,146
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![]() The supply to IC301 should be 7.6 volts on pin 1, Pin 18 is a 4.8v output that is switched by the ic, This output controls the base of Q303 which supplies 4.1 volts to the tuner board, that's why that voltage is changing.
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#12 |
Badcaps Veteran
Join Date: Jun 2012
City & State: ☻
My Country: Canada
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