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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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8th Apr 2021, 8:57 pm | #21 |
Dekatron
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Re: Philips P3G38T Stone Dead
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9th Apr 2021, 8:20 pm | #22 |
Heptode
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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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9th Apr 2021, 8:49 pm | #23 |
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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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9th Apr 2021, 8:56 pm | #24 | |
Heptode
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Re: Philips P3G38T Stone Dead
Quote:
Cheers, Jay.
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9th Apr 2021, 9:02 pm | #25 |
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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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9th Apr 2021, 9:12 pm | #26 | |
Heptode
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Re: Philips P3G38T Stone Dead
Quote:
The set has an external aerial socket I'll try hooking that up and see if LW kicks in. Cheers
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13th Apr 2021, 5:52 pm | #27 |
Heptode
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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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17th Apr 2021, 3:05 pm | #28 | |
Heptode
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Re: Philips P3G38T Stone Dead
Quote:
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17th Apr 2021, 4:23 pm | #29 |
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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 |
17th Apr 2021, 4:40 pm | #30 |
Heptode
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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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Help!! I've been electrocuted by a glass thing that glows Last edited by Radio Scotland; 17th Apr 2021 at 4:53 pm. Reason: More info |
17th Apr 2021, 9:12 pm | #31 |
Heptode
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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 Jay
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23rd Apr 2021, 12:40 pm | #32 |
Heptode
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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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23rd Apr 2021, 2:07 pm | #33 |
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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. |
23rd Apr 2021, 2:12 pm | #34 |
Heptode
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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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23rd Apr 2021, 2:33 pm | #35 |
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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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23rd Apr 2021, 2:39 pm | #36 |
Heptode
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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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23rd Apr 2021, 4:04 pm | #37 |
Heptode
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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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