Bush ac/dc AM/FM radio - UK Vintage Radio Repair and Restoration Discussion Forum

flyingtech55 · 4th Jan 2018, 5:36 pm

Hi folks

First off, apologies for a rather vague question here but I'm hoping it'll jog someone's memory as the question has been asked and answered before but I can't find it.

I have a Bush AC/DC radio which was bought by my parents and latterly used by my late father. The problem is that the VHF stopped working quite a long time ago, AM fine. It has a sort of diecast box looking FM tuner head and uses basically a Mazda version of the UCC85 as the active device. My father (ex Marconi, Chelmsford) was unable to find the fault and I've had a go at it and I haven't been able to find it either. It looks like the oscillator isn't running. I've tried all the obvious stuff and the voltages around the oscillator aren't correct. Somewhere in my forgetory I remember that a chap mentioned something about a trimmer in the tuner head that develops a fault that stops the oscillator. Often a tiny 'tweak' clears the short and the oscillator bursts into life. Obviously I want to avoid randomly tweaking the FM head unit. I seem to remember there was a picture showing which trimmer was the guilty one and I thought 'Ah ha I must remember that' and I have of course now forgotten.

Can someone please enlighten me.

Thanks

Tim

Nuvistor · 4th Jan 2018, 5:42 pm

This the type of item?
https://www.vintage-radio.net/forum/...ad.php?t=97989

flyingtech55 · 4th Jan 2018, 5:52 pm

Wow....that was quick. That looks suspiciously like the thread that I remember. Thanks a lot Frank...brilliant.

mark2collection · 5th Jan 2018, 5:21 pm

Our Bush VHF61 had a similar issue. After recapping the set, performance was improved no end, but it would still crackle/cut out on FM (one of the original issues before the work).

Removing the die cast cover revealed (from memory) two vari-caps, looking suspiciously silver plated under the tarnish. Having previously marked their positions, I sprayed a little Ambersil contact cleaner (not Servisol, it can be a bit oily in this application) on the vari-caps, rotated each control in turn, 360-odd degrees, half a dozen times or so. Putting the vari-caps back where they were, I then ran through the alignment procedure.

Touch wood, hasn't missed a beat in 10 years ...

Mark

Boater Sam · 6th Jan 2018, 3:23 am

Just give it a tweak, its the bottom one from memory, and it will go, with a bit of luck!

4th Jan 2018, 5:36 pm	#1
flyingtech55 Octode Join Date: Nov 2005 Location: Ayrshire, UK. Posts: 1,096	Bush ac/dc AM/FM radio Hi folks First off, apologies for a rather vague question here but I'm hoping it'll jog someone's memory as the question has been asked and answered before but I can't find it. I have a Bush AC/DC radio which was bought by my parents and latterly used by my late father. The problem is that the VHF stopped working quite a long time ago, AM fine. It has a sort of diecast box looking FM tuner head and uses basically a Mazda version of the UCC85 as the active device. My father (ex Marconi, Chelmsford) was unable to find the fault and I've had a go at it and I haven't been able to find it either. It looks like the oscillator isn't running. I've tried all the obvious stuff and the voltages around the oscillator aren't correct. Somewhere in my forgetory I remember that a chap mentioned something about a trimmer in the tuner head that develops a fault that stops the oscillator. Often a tiny 'tweak' clears the short and the oscillator bursts into life. Obviously I want to avoid randomly tweaking the FM head unit. I seem to remember there was a picture showing which trimmer was the guilty one and I thought 'Ah ha I must remember that' and I have of course now forgotten. Can someone please enlighten me. Thanks Tim __________________ All those moments will be lost in time, like tears in rain.

4th Jan 2018, 5:42 pm	#2
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,432	Re: Bush ac/dc AM/FM radio This the type of item? https://www.vintage-radio.net/forum/...ad.php?t=97989 __________________ Frank

4th Jan 2018, 5:52 pm	#3
flyingtech55 Octode Join Date: Nov 2005 Location: Ayrshire, UK. Posts: 1,096	Re: Bush ac/dc AM/FM radio Wow....that was quick. That looks suspiciously like the thread that I remember. Thanks a lot Frank...brilliant. __________________ All those moments will be lost in time, like tears in rain. Last edited by flyingtech55; 4th Jan 2018 at 6:09 pm. Reason: Inserted Frank's name

5th Jan 2018, 5:21 pm	#4
mark2collection Hexode Join Date: Jul 2010 Location: Royal Berkshire, UK. Posts: 471	Re: Bush ac/dc AM/FM radio Our Bush VHF61 had a similar issue. After recapping the set, performance was improved no end, but it would still crackle/cut out on FM (one of the original issues before the work). Removing the die cast cover revealed (from memory) two vari-caps, looking suspiciously silver plated under the tarnish. Having previously marked their positions, I sprayed a little Ambersil contact cleaner (not Servisol, it can be a bit oily in this application) on the vari-caps, rotated each control in turn, 360-odd degrees, half a dozen times or so. Putting the vari-caps back where they were, I then ran through the alignment procedure. Touch wood, hasn't missed a beat in 10 years ... Mark

6th Jan 2018, 3:23 am	#5
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Bush ac/dc AM/FM radio Just give it a tweak, its the bottom one from memory, and it will go, with a bit of luck!