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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 21st Jul 2021, 8:11 pm   #1
BBCmicro
Triode
 
Join Date: Aug 2006
Location: Dundee, Scotland, UK.
Posts: 27
Default Roberts R600 no LW/MW

Hi all,

Got a nice looking R600 recently.

When it arrived it would sound for 1 second on power on before tailing to nothing, so replaced caps on main board.

Sounded fine but then dodgy AF11X transistors in the LP1171 module made performance intermittent to say least.

Took another module of unknown state from a junk set that has AF12X transistors in it, and replaced the caps as really didn't want to have to pull the module in and out as they are a ****** to do so might as well sort out while I had it out.

Probably a bad idea, as now don't know if LW/MW worked or not before recap!

Wiggling the module about (but not tapping) yielded brief results, but now nothing.

I have cleaned the selector switches and resoldered their joints. I have tuned a radio near by to MW and swept the r600 up and down the band and no squeals from the second radio which a search on this forum tells me that the AM oscillator may not be working?

I have access to a soldering iron and a multimeter only, so any advice on what to check next would be appreciated!

Cheers
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Old 21st Jul 2021, 9:33 pm   #2
BBCmicro
Triode
 
Join Date: Aug 2006
Location: Dundee, Scotland, UK.
Posts: 27
Default Re: Roberts R600 no LW/MW

Problem solved, thanks to the fantastic schematic here https://www.vintage-radio.net/forum/...ad.php?t=30889 found the oscillator transistor AF125 and replaced with an AF124 I had lying around.

Only once I'd put it all together did I realise that maybe the wiggling temporarily fixing the problem rather than tapping meant that perhaps the legs on the AF125 were just shorting where they were crossed ...

Oh well, I've now taken the module out and put it back about 9 times so can do it in about three minutes!!!!
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Old 22nd Jul 2021, 7:28 am   #3
vinrads
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Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 2,869
Default Re: Roberts R600 no LW/MW

Also watch out for breaks in the printed cct near near the connecting wires , Mick.
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