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 Electronic restorations. 
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Post Electronic restorations.
Hi All,

I'm not really into home brewing as such, but I have carried out electronic restorations on some of my ancient radio gear. For instance, I have replaced all of the decoupling caps and well out of tolerance resistors in my Eddystone EA12.
I also regularly use an Eddystone S940 which used to develop a new fault every week. It seems to have settled down now but I often found carbon resistors, usually anode biasing ones, going very high or O/C. The radio had been badly stored and I think that damp played a great part in causing these resistors to fail.

Anyone else into restoration?

73,

Ian G1DRP

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73,

Ian G1DRP


Sun Dec 30, 2012 1:20 pm
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 Electronic restorations. 
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Hi Ian,

Up in sunny Werrington.

I have done a couple in the last year, purely as a means to 'buy cheap and sell dear' ... Firstly a beautiful old Grundig 650 International that I just peaked up and realigned (bought at £85 and sold at £150), and then I bought from another Amateur out at Baldwins Gate, a superb looking, but sadly 'quiet' GEC BRT 400 Receiver... Replaced a couple of caps and switched some valves around that had been put in the wrong holders, bit of spit and polish and sold that on for £200 making £65 profit.

I have loads of photographs of them (and others that I have tinkered with in the past couple of years)... Best one was an Eddystone 888A Amateur Band only Receiver.

I tell you the foregoing, as there is still money to be made working on stuff that is poorly advertised on eBay - with either a too short description, or no photographs, do them up, and re-sell on eBay and you can make a bit of pocket money, learn about different radios, and have the fun of working on them.

Sadly, my knowledge of Transistors, ICs and printed circuits is zero, as I have not done any technical learning since 'Valve and wire' days when I took my RAE in 1956 - so stuck in a time-warp!!

Seasonal Greetings and 73

.


Sun Dec 30, 2012 1:41 pm
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 Electronic restorations. 
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Hello Ian.
Yes, I've done a few, including several old domestic radios. The old waxed paper caps are nearly always leaky and should get replaced on sight! Any trace of lekage on audio grid-coupling caps can be disastrous for the output valve and often the output transformer as well.
Mains filter caps are almost guaranteed to go bang when power is applied after donkey's years sitting idle, and of course those high-value r's are notorious for going high.
I've found AGC lines are extremely prone to upset by tiny leakage in caps and resistors going high, and sometimes the symptoms can be strange.

As for transistor sets, the old Mullard AF11x are well-known for the 'tin whisker' problem which can be sorted (usually!) by snipping the screen lead. Other than that, it's usually down to broken tracks, smashed ferrite rods and dirty switches.
One thing I have noticed - when properly repaired, some of the old 6 transistor MW portables from the early 60's are far more sensitive than your typical modern multi-IC PLL wonderbox!

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Sun Dec 30, 2012 2:38 pm
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 Electronic restorations. 
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G3OBU wrote:
.


Hi Ian,

Up in sunny Werrington.

I have done a couple in the last year, purely as a means to 'buy cheap and sell dear' ... Firstly a beautiful old Grundig 650 International that I just peaked up and realigned (bought at £85 and sold at £150), and then I bought from another Amateur out at Baldwins Gate, a superb looking, but sadly 'quiet' GEC BRT 400 Receiver... Replaced a couple of caps and switched some valves around that had been put in the wrong holders, bit of spit and polish and sold that on for £200 making £65 profit.

I have loads of photographs of them (and others that I have tinkered with in the past couple of years)... Best one was an Eddystone 888A Amateur Band only Receiver.

I tell you the foregoing, as there is still money to be made working on stuff that is poorly advertised on eBay - with either a too short description, or no photographs, do them up, and re-sell on eBay and you can make a bit of pocket money, learn about different radios, and have the fun of working on them.

Sadly, my knowledge of Transistors, ICs and printed circuits is zero, as I have not done any technical learning since 'Valve and wire' days when I took my RAE in 1956 - so stuck in a time-warp!!

Seasonal Greetings and 73

.



Hi John,

I'm a huge fan of valve equipment as it is so much easier to understand what's going on and you can usually find a fault in very little time. I actually saw your BRT400 and considered buying it. I believe the BBC used them for monitoring purposes as the audio quality was so good.

VY 73,

Ian

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Ian G1DRP


Sun Dec 30, 2012 3:21 pm
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 Electronic restorations. 
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G1HBE wrote:
Hello Ian.
Yes, I've done a few, including several old domestic radios. The old waxed paper caps are nearly always leaky and should get replaced on sight! Any trace of lekage on audio grid-coupling caps can be disastrous for the output valve and often the output transformer as well.
Mains filter caps are almost guaranteed to go bang when power is applied after donkey's years sitting idle, and of course those high-value r's are notorious for going high.
I've found AGC lines are extremely prone to upset by tiny leakage in caps and resistors going high, and sometimes the symptoms can be strange.

As for transistor sets, the old Mullard AF11x are well-known for the 'tin whisker' problem which can be sorted (usually!) by snipping the screen lead. Other than that, it's usually down to broken tracks, smashed ferrite rods and dirty switches.
One thing I have noticed - when properly repaired, some of the old 6 transistor MW portables from the early 60's are far more sensitive than your typical modern multi-IC PLL wonderbox!


Hi Andy,

I repaired a 1967 Bush TR-130 a few months ago. All three AF117s had the tin whisker problem. My technique involves shorting the emitter, base and collector together and then discharging an electrolytic capacitor across the three leads and the screen lead. You can usually see the internal flash through the glass base. I usually charge the cap up to around 150 Volts.

I had a brief play with an SDR receiver and sold it on. I found it quite "alien" to me tuning a radio using a mouse.

VY 73,

Ian

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73,

Ian G1DRP


Sun Dec 30, 2012 3:26 pm
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