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Old 26th Mar 2015, 12:54 am   #1
Phil G4SPZ
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Default Sony ICF-7601L VHF/L/MW/SW multi-band portable receiver, 1988

This set has been on my to-do pile ever since I obtained it, several years ago, and I've just found the fault, which was so simple I feel embarrassed sharing it with you.

When I got it, the set would work on an external 6 volt supply but not on its internal batteries. So I thought, simple, clean the switch contacts in the external power socket - these disconnect the positive side of the battery when an external power source is plugged in. A spray of Servisol seemed to put things right, and the set worked perfectly so it went on the shelf.

A week or so later I switched it on, but it was dead - same fault. I cleaned the socket again, exercised the contacts by repeatedly plugging and unplugging a suitable coaxial power plug, and life was restored.

By now you'll have spotted the pattern - a few days later the set was dead again, and this time remained so. I looked quickly at the coaxial power socket, but having nothing remotely similar in stock I resolved to bridge-out the switch contacts at some future date. And tonight I got a Round Tuit at last. But which contacts to bridge out on the PCB? I managed to find a circuit diagram and PCB layout on the internet, so armed with the knowledge of how the board was wired, I checked the continuity of the switch contacts inside the power socket. Perfect!

To cut a long story short, there was a bad connection in the negative side where the battery joins the B- land on the PCB. The solid wire forming the negative battery spring contact runs in a continuous length right up to the PCB. This wire seemed springy but very hard, almost like stainless steel, and I found it impossible to solder. So I fashioned a length of thin single-strand tinned copper wire such that it was mechanically clamped by the negative battery contact spring at one end, and soldered it to the battery minus connection on the PCB at the other. Instant result

I can only assume that my applications of Servisol had initially cleaned up a poor contact somewhere along the negative connection. The set worked on an external supply because the centre pin of the coaxial power socket, which is negative on this radio, goes straight to chassis on the PCB.

Current consumption is less than 20mA so a set of four AA alkaline cells should last for ages. This is a rather nice little radio that performs very well and has excellent sensitivity on all bands including Long Wave.

Phil
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Last edited by Phil G4SPZ; 26th Mar 2015 at 12:57 am. Reason: Clarity
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Old 26th Mar 2015, 12:15 pm   #2
SeanStevens
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Default Re: Sony ICF-7601L VHF/L/MW/SW multi-band portable receiver, 1988

They are fiddly to work on but fine radios the Sony ICFs

I've had several - they all performed well, although one never turned off its amp when switched off - so flat batteries ensued!




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Old 31st Mar 2015, 10:05 pm   #3
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Default Re: Sony ICF-7601L VHF/L/MW/SW multi-band portable receiver, 1988

Nice little sets these, very high gained, sounds ok for a small set a good go anywhere compact little radio. Well done on finding the fault.
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Old 31st Mar 2015, 10:17 pm   #4
Phil G4SPZ
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Default Re: Sony ICF-7601L VHF/L/MW/SW multi-band portable receiver, 1988

Thanks, both, it had been niggling away at me for a while but I kept finding more interesting things to do! Glad that it's fixed now though. I've been using it daily just to make sure, but it's behaved itself so far...
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