Author Topic: Fixing 1962 Philips L4X25T SW receiver  (Read 3759 times)

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Offline Cliff Matthews

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Fixing 1962 Philips L4X25T SW receiver
« on: February 03, 2016, 12:22:18 pm »
I picked-up a Philips L4X25T last week, cleaned it up, loaded it with 6 new C cells and crossed my fingers.. (didn't work this time). What I get is a tremendously loud tone around 500hz and no switch, control or any thing I wiggle inside affects it. Quite likely this thing is going to need some recapping, but it looks worth the effort. Since the tone seems somewhere around the speakers resonance, I thought I'd ask what are the chances that one of the TO-1 output transistors is bad? The schematic shows an output stage that looks very odd..
 

Offline Radio Tech

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Re: Fixing 1962 Philips L4X25T SW receiver
« Reply #1 on: February 03, 2016, 01:10:08 pm »
A 1962? That is over 50 years old. First thing I would do is start replacing those old electrolytic capacitors.
I am not saying this as just being a "parts changer" but from experience.

Offline Cliff Matthews

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Re: Fixing 1962 Philips L4X25T SW receiver
« Reply #2 on: February 03, 2016, 02:18:48 pm »
A 1962? That is over 50 years old. First thing I would do is start replacing those old electrolytic capacitors.
I am not saying this as just being a "parts changer" but from experience.
Agreed (and subscribed, thanks!), but since the audio stage is totally DC isolated and the tone is so mind-blowing, wouldn't checking those transistors be a deal-breaker? (It'd be a shame to re-cap if those transistors were pooched and not reasonably obtainable).
 

Offline Cliff Matthews

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Offline Radio Tech

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Re: Fixing 1962 Philips L4X25T SW receiver
« Reply #4 on: February 03, 2016, 09:10:04 pm »
A 1962? That is over 50 years old. First thing I would do is start replacing those old electrolytic capacitors.
I am not saying this as just being a "parts changer" but from experience.
Agreed (and subscribed, thanks!), but since the audio stage is totally DC isolated and the tone is so mind-blowing, wouldn't checking those transistors be a deal-breaker? (It'd be a shame to re-cap if those transistors were pooched and not reasonably obtainable).

Yes I agree, checking the transistors can not hurt at all.  Also any high value resistors  should be checked, just to be sure they are in tolerance.  Also I would check that transformer to make sure there is no shorts, looks like a pc mount? May be able to lift component leads to get a good check.

And thanks :)


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