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Old 8th Apr 2021, 7:57 pm   #21
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Default Re: Philips P3G38T Stone Dead

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Cheers, Any idea how to remove the metal bracket from the switch assembly ?
No idea, I don't remember ever working on one of those receivers.

Lawrence.
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Old 9th Apr 2021, 7:20 pm   #22
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Default Re: Philips P3G38T Stone Dead

Well after spending a ton of time on this radio it's working again, Repaired the band switch. But still nothing on LW. And repaired quite a lot of broken wires. Problem is when the radio is out of the chassis the front panel which houses the controls and the ferrite rod hangs off the main PCB. Hence the broken connections, I replaced the mixer/osc with a ASY27. But the radio is still a bit deaf, Probably due to the ASY27 Having a gain of around 30 and the original AF117 stated as being no lower than 50 hfe.

Wasn't easy to change as it was buried under a lot of wiring, I'll pop something else in with more gain when I get a chance.
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Old 9th Apr 2021, 7:49 pm   #23
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Default Re: Philips P3G38T Stone Dead

I doubt if the transistor gain is significant. Given that LW doesn't work and you are confident the wavechange switch is OK, I suspect there is a fault with the wiring to the ferrite rod coils.
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Old 9th Apr 2021, 7:56 pm   #24
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Default Re: Philips P3G38T Stone Dead

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I doubt if the transistor gain is significant. Given that LW doesn't work and you are confident the wavechange switch is OK, I suspect there is a fault with the wiring to the ferrite rod coils.
I'm confident the MW Part is working, The band switch is a nightmare to work on. It still has the original AF117's in the IF Strip, That could be another cause of deafness. Gonna take a break from it for a few days as it's consuming too much of my time.


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Old 9th Apr 2021, 8:02 pm   #25
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Default Re: Philips P3G38T Stone Dead

You should certainly do the other AF117s. If one of them is knackered then the others probably are too, as they will be from the same production batch and will have experienced the same environmental conditions.
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Old 9th Apr 2021, 8:12 pm   #26
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Default Re: Philips P3G38T Stone Dead

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You should certainly do the other AF117s. If one of them is knackered then the others probably are too, as they will be from the same production batch and will have experienced the same environmental conditions.
The original AF117 mixer/osc was working but seemed a bit flakey. And i thought it could have been the cause of low gain hence why I changed it. They're better changed anyhow to eliminate future problems,

The set has an external aerial socket I'll try hooking that up and see if LW kicks in.


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Old 13th Apr 2021, 4:52 pm   #27
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Default Re: Philips P3G38T Stone Dead

Dug this out today for another quick look at it. It receives fine up till about 1,200 khz then nothing. Not a crackle, The mixer/osc substitute transistor I put in is meant to be good till 6 MHz. I'll try putting the AF117 back in and see how that goes. If it works then I'll know its my choice of transistor that is that problem,
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Old 17th Apr 2021, 2:05 pm   #28
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Default Re: Philips P3G38T Stone Dead

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Dug this out today for another quick look at it. It receives fine up till about 1,200 khz then nothing. Not a crackle, The mixer/osc substitute transistor I put in is meant to be good till 6 MHz. I'll try putting the AF117 back in and see how that goes. If it works then I'll know its my choice of transistor that is that problem,
Yup it didn't like the substitute mixer/osc. Even though its apparently good up till 6 mhz it no likey it
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Old 17th Apr 2021, 3:23 pm   #29
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Default Re: Philips P3G38T Stone Dead

This does happen sometimes. The mixer is the most fussy of the RF transistors. It's also possible that your replacement is out of spec.

You're learning lots about fixing old transistor radios anyway
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Old 17th Apr 2021, 3:40 pm   #30
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Default Re: Philips P3G38T Stone Dead

And that's what its all about Paul. I've swapped the IF transistors out, but don't have a replacement for the mixer, So I've stuck the AF117 back in for the time being with the screen lead cut

But I'm reluctant to put the radio back together with it left in place as it could play up further down the line.

Cheers, Jay.
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Last edited by Radio Scotland; 17th Apr 2021 at 3:53 pm. Reason: More info
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Old 17th Apr 2021, 8:12 pm   #31
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Default Re: Philips P3G38T Stone Dead

I've partly reassembled the radio, Had enough of it. I.F Transistors have been swapped and i'ts been recapped. Didn't have a replacement transistor for the mixer. So let's hope that bad boy AF117 behaves itself.

It works fine. But only on MW, The band switch is a pure nightmare, Don't think it can be disassembled. Even if it could it would be brutal to work on. Nothing on LW anyway.

Just need to fix the on/off switch and restring the dial cord. Can't wait for that


Wish I'd never laid eyes on the radio. But it's learned me a few things.......I think.

Cheers

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Old 23rd Apr 2021, 11:40 am   #32
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Default Re: Philips P3G38T Stone Dead

And the fun continues with this radio. Since reassembling it I've noticed the dial scale is off. More so at the bottom of the scale. Pretty sure it was OK before I started working on it, but can't be certain.

Can't see it being an alignment issue as all the cores have wax in them, So doesn't look as if anyone has been in there before.
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Old 23rd Apr 2021, 1:07 pm   #33
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Default Re: Philips P3G38T Stone Dead

You may need to do an RF realignment. This is pretty straightforward and can be done without instruments using off-air signals. You don't need to do an IF alignment if the factory alignment hasn't been changed.

Check the ferrite rod coils and associated wiring carefully though, especially given that LW still isn't working.
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Old 23rd Apr 2021, 1:12 pm   #34
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Default Re: Philips P3G38T Stone Dead

I've got all the gear needed to do an alignment paul. But I've a feeling that's not the problem, Think it might be something in the band switching that's causing it.

Can't think of any other reason why it would be off.
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Old 23rd Apr 2021, 1:33 pm   #35
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Default Re: Philips P3G38T Stone Dead

The dial scale being "off" can be down to two things:-

1. Pointer incorrectly positioned on the spindle, drive cord or W.H.Y.

2. Incorrect alignment, generally RF alignment.

If you've got the test gear why not just check the alignment at the calibration points at the HF and LF ends of each waveband?
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Old 23rd Apr 2021, 1:39 pm   #36
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Default Re: Philips P3G38T Stone Dead

It's not the pointer as that's aligned correctly per the manual. I'll try aligning the radio and see if that corrects the problem.
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Old 23rd Apr 2021, 3:04 pm   #37
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Default Re: Philips P3G38T Stone Dead

Fixed, Turns out it was an intermittent wax caked trimmer. Swapped it out and all seems good now.
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