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Old 8th Jun 2018, 5:28 pm   #1
FiveBobRepairs
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Join Date: Jun 2018
Location: Oxford, Oxfordshire, UK.
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Default Just Saying Hello

Just saying hello, and a short intro.

I’m a (long ago) qualified electronics engineer, but spent my career in software development

Among other things that keep me busy in retirement, I have rediscovered a long dormant interest in repair and restoration of vintage transistor radios. First it was a Roberts R505 that I found for £5 in a local antique shop, then another R505 from another antique shop, then a third R505 from Ebay. I am indepted to these forums for all the advice I found, assisting me with these sets, all three of which have been successfully restored.

I have just begun on an R700 that I picked up at a garage sale, looking a bit unloved, but complete. I might be on the scrounge for some specific advice later re. the R700 but it is progressing well so far - all faults understood, and all cosmetic scars already healed.

Choice of User Name harps back to teenage years, 1970s. As a schoolkid with an interest in electronics, it became clear to my parents and their friends that I could fix broken radios and TVs. So my pocket money was boosted by a fixed price of 5/-, plus parts. Seem to remember I saw the inside of one or two Roberts in these days too!
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Old 8th Jun 2018, 8:42 pm   #2
Cobaltblue
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Location: Exeter and Poole, UK.
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Default Re: Just Saying Hello

Nice Intro 5bob

Sounds like you will enjoy it here

Welcome to the forum

Cheers

Mike T
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Old 8th Jun 2018, 9:54 pm   #3
ukcol
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Default Re: Just Saying Hello

Hello and welcome.

The R700 uses the AF11* series of transistors and suffers the so-called "tin whisker" problem. There is a lot of information here on the problem and suitable replacement transistors, just enter "tin whiskers" in the Search this Website box at the top of this page.

If you like the Roberts models you are likely to like those produced by Hacker. They were very good quality sets and can be picked up quite cheaply now.
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Old 8th Jun 2018, 10:16 pm   #4
FiveBobRepairs
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Default Re: Just Saying Hello

Yes indeed, the AF117 AM mixer oscillator is top of my list. I only got AM working at all by disconnecting the screen. An AF114 in the FM IF is next on my list of ‘understood faults’, as it only works on FM (momentarily) if you whack that transistor with a pencil.

I am planning to replace all the AF11* with AF12*, I’d planned for that when I brought the R700 home. But without these forums I’d have known nothing about AF11* tin whiskers, or AF12* (or even silicon) alternatives. Hence the reason I am so impressed by the wealth of knowledge here.

Great work, everybody!
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Old 9th Jun 2018, 11:07 am   #5
ukcol
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Default Re: Just Saying Hello

The AF127 is in short supply now and tends to be expensive. The Russian GT322B is an excellent substitute in the same package as the 127 but with a different pin-out configuration. They can be sourced reasonably cheaply on ebay.
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