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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 4th Mar 2017, 11:47 am   #1
DigitalNoMore
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Default Perdio C303 Challenge

I picked up this Perdio C303 Challenge in a batch of three mixed radios for not much money. It's got quite a quirky and not altogether un-pleasing look with its bright pink dial and two-tone case! Date wise it seems to be from the early 60s.

At first I struggled to find any service information but eventually discovered that the electronics is identical that used in the PR44 and PR76 models as described in Trader Service Sheet 1769.

On opening up the case I noticed that two of the coil connections to the ferrite rod aerial were hanging in space and that the original PP9 battery connector had been removed and a PP3 connector crudely twisted on. Referring to the service sheet I was soon able to trace where the ferrite rod coil connections should be soldered to and while I was at it I checked the continuity of all the coils. I then soldered and sleeved the connections to the battery connector.
Since this set uses three AF117 transistors I removed them all to check for tin whisker shorts. All three were suffering so I shorted E, B and C together and applied 35V repeatedly to zap the whiskers. I also applied a soldering iron for 10 seconds to be doubly sure. My transistor tester confirmed that all three were now clear of shorts. It'll be interesting to see how long they last before new whiskers form.
I removed and tested the speaker coupling electrolytic and main supply decoupling electrolytic as these can often be leaky but both turned out to be okay. Finally a spray of switch cleaner was applied to the very dirty wave-change switch.

Having replaced everything I connected my bench supply, selected medium wave and turned it on. A number of stations could be tuned in on both long and medium wave but were only fairly weak. Suspecting that the IFs may have been fiddled with I soon found that by adjusting these, as per the service sheet, I was soon able to improve reception dramatically and was then able to adjust the relevant trimmer capacitors such that the tuning dial was correctly aligned to the stations received.

Having finished the electronics I then gave the case a very light clean and left it at that. Performance seems pretty good for an early 60s radio with all original components. The sound is a bit distorted at low volumes but I suspect that's down to the Class B output stage.

So, it hasn't really lived up to its dubious name as it wasn't too much of a 'Challenge' to fix! It's another one rescued though and having looked on the web I'm not sure that there are too many of these around.
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Old 4th Mar 2017, 12:15 pm   #2
Boater Sam
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Default Re: Perdio C303 Challenge

I've seen one before but not common. Nice restore and as you say, original parts. I have had good success zapping and cooking AF117s, some done 3 years ago are still functioning.
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Old 4th Mar 2017, 12:34 pm   #3
DigitalNoMore
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Default Re: Perdio C303 Challenge

I've recently used up my stock of AF125s fixing IF modules in a Roberts R600 and a Roberts R707 so I thought that, since these AF117s are easily accessible, I'd try the zapping/cooking method.

Three years isn't bad. It would be interesting to bring together data from all the zapped/cooked AF11xs and do a statistical analysis to try and predict the likely timespan before the whiskers can be expected to recur.
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Old 5th Mar 2017, 9:45 am   #4
Steve_P
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Default Re: Perdio C303 Challenge

I am looking at Russian Germanium Transistors here as they were made well into the 90's and were used by the Russian Military.

http://www.ebay.co.uk/itm/5x-GT308V-...EAAOSwGtRXxdY8

No connection with the seller, etc...

Cheers,

Steve P.
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Old 5th Mar 2017, 11:25 am   #5
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Default Re: Perdio C303 Challenge

They look promising Steve and the price is not bad at all.

Have you bought and tried any yet?

Jerry
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