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Silver ST858 aka Montgomery Ward Airline

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#1 Radiocollector

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Posted 06 October 2019 - 06:23 AM

Hi all,

I'm new to this forum as I've just acquired my first boombox. It's a Silver ST858 in lovely condition and it came with it's original Owners Manual, albeit a bit "dog eared".

I've cleaned the case, cleaned the switches (most of them) and potentiometers with a good quality switch cleaner akin to Deoxit and cleaned all the dust out of the cabinet. As it hadn't been turned on for many years, it took a while for the electrolytic capacitors to reform. This was evident on the lower end of the FM band say below 94 Mhz, where a strong local station on 92.3 Mhz would slowly fade to distortion then completely disappear after about 30 seconds. The radio now plays perfectly on all bands. Normally I would replace the electrolytics but decided to try to see if they reformed as I couldn't see any physical issues with the caps (bulging, leaking electrolyte or holes).

The cassette functions all work and cassettes play however this leads me to my question. I notice that only one channel seems to be working correctly as indicated by the VU meters. The right channel is fine however there's no indication of any output on the left VU meter and the audio is down on that channel as well. I have read that there's a switch in the audio line that might need cleaning, I can't find it or there may be a completely different issue. I'd love to see what others who know heaps about such issues might advise me on how to fix it so the grand old lady is back to fully operating condition.

The audio amp is fine, while on radio, FM Stereo is perfect, great output from both channels so the issue is in the cassette area or the input from the cassette to the amp section. Thanks to this great site, I've been able to download the Service Manual which will help.

Any suggestions would be greatly appreciated and I look forward to your replies. Thanks in advance.

Cheers from Australia...... Phil (Radiocollector)

#2 Superduper

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Posted 06 October 2019 - 12:02 PM

Most likely what you are experiencing is not capacitor reforming but because you didn’t wait long enough after deoxidizing solvent treatment. The symptoms you describe is very common afterwards. The meter & low audio imbalance is most likely the record/playback switch needs deep cleaning. That switch, also called record-bar is a long multi-pole switch usually on the main circuit board and thrown via the cassette deck mechanism by a lever.