sony: Sony ICF-2001D RF stage design versions

The original Service Manual (1985, 85C02129-1 9-951-647-11) lists the 2SK152-1 at several positions, namely Q302 LW/MW RF AMP and Q303 AM RF AMP. 

However I found several versions of the Small PCB assembly (RF Input and I/O sockets, at least these ones exist:

• 1-614-277-12 and 1-614-277-13 (label at the copper trace side) - Older boards, older style "SMD" components.
• 1-614-277-15 (label at the oposite side of copper trace) - Later board, redesigned PCB copper traces, uses common SMD components at trace side.

At least on 1-614-277-15 PCB assemblies, both Q302 and Q303 uses the 2SK152-2 installed from factory. 

The 2SK152-1 and 2SK152-2 have different specifications, namely IDSS operating current. Therefore the reference voltage points at Dreno and Source of these 2SK152-1 JFETs listed in the Service Manual may not apply entirely to the 2SK152-2.  I observed large variations, especially on the Q302, despite the radio being operating very well. That said, those reference voltages are still useful as a starting point for troubleshooting.

 

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Hi

 

I am trying to recover my ICF-2010.

Up to now I completed a series of tasks including the replacement of the Ribbon for 2 standard 9 ans 13 ways and replacemento of all capacitors.

Finally it turns on and FM is working nicely.

Now I am in a dedlock witk the AM recepction because there is only noise.

Do you, for chance any clue regarding this problem?

I've already changed the 2SK152-1 transistors and Q302 and Q303.

The voltages of the transistors on the Jack Board are a mess.

 

Thanks for any suggestion to proceed with the diagnostic.

 

Best regards,

 

Luis Boucinhas

 

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Hi, Luis, Didn't notice your message, sorry.

The fault can be caused by all sorts of things,  really, from broken/corroded PCB copper traces, to open resistors, to shorted/leaking capacitors, or defective transistors.

As a general troubleshooting procedure, I follow these steps: 

- Check the power supply voltages at the test points, according to the service manual;

- If you have a RF signal generator and an oscilloscope (highly recommended), inject RF signal at the IF stages and check the output signal at the last IF stage or just listening to the deccodeed audio signal. The approach is to start from the audio stage and go backwards, from the last IF stage to the first one;

- If the IF stages are OK, then inject RF signal at the corresponding RF band; Testing MW band first would be easier, before checking the SW bands.

- Once a fault is found in the signal path, it is time to check the components around it.

Good luck with your radio!

Cheers,

Jose

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