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Old 6th Apr 2021, 6:05 pm   #1
Radio Scotland
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Default Philips P3G38T Stone Dead

Received this today complete with broken dial glass :' (Put a battery in it and got a loud crackle when I adjusted the volume control, but nothing else. So whipped the covers off it and tapped the dreaded AF117's transistors with a screwdriver and it burst into life. MW was working well but nothing on LW. It played for a short while but now it's stone dead, not a crackle. Nothing,

Voltage is reaching the on/off switch. Shorted transistor or capacitor?

Cheers, Jay.
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Old 6th Apr 2021, 6:55 pm   #2
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Default Re: Philips 3G38T Stone Dead

Is that the right model number??
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Old 6th Apr 2021, 6:59 pm   #3
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Default Re: Philips 3G38T Stone Dead

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is that the right model number??
P3G38T/ 00 / 05

My mistake
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Old 6th Apr 2021, 7:00 pm   #4
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Default Re: Philips 3G38T Stone Dead

Your description of the symptoms suggests the AF117s are knackered. All the usual advice applies. There may also be a problem with the MW/LW wavechange contacts, which usually need a good clean.

Has the volume control crackling stopped as well as everything else?
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Old 6th Apr 2021, 7:09 pm   #5
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Default Re: Philips 3G38T Stone Dead

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Your description of the symptoms suggests the AF117s are knackered. All the usual advice applies. There may also be a problem with the MW/LW wavechange contacts, which usually need a good clean.

Has the volume control crackling stopped as well as everything else?
Well iv'e since discovered the mixer/osc is running as i'm hearing it on a nearby radio. Whilst i was probing the board the driver transistor (OC82D) Decided to fall apart on me. Could i replace it with a ACY18 ?


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Old 6th Apr 2021, 7:13 pm   #6
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Default Re: Philips 3G38T Stone Dead

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Has the volume control crackling stopped as well as everything else?
Originally it was totally silent then it started cracking again as i tapped the PCB / Components. But nothing now since the driver transistor fell apart. One of the AF117 transistors was particularly noisy when i tapped it


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Old 6th Apr 2021, 7:36 pm   #7
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Default Re: Philips 3G38T Stone Dead

The OC82D is a pretty run of the mill transistor, and lots of types will replace it, though it does depend on the circuit. In a typical 2 transformer amp design just about any PNP device can be used, including silicon types. Ideal subs would be OC71, OC72, OC81D, OC81, AC126, AC128 but try whatever you have to hand.
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Old 6th Apr 2021, 7:38 pm   #8
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Default Re: Philips 3G38T Stone Dead

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The OC82D is a pretty run of the mill transistor, and lots of types will replace it, though it does depend on the circuit. In a typical 2 transformer amp design just about any PNP device can be used, including silicon types. Ideal subs would be OC71, OC72, OC81D, OC81, AC126, AC128 but try whatever you have to hand.
Ideal. Could you change the title of this thread to the correct model number ?


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Old 7th Apr 2021, 12:05 pm   #9
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Default Re: Philips P3G38T Stone Dead

Well i changed the audio driver for an ACY18 and could hear stations on MW albeit quiet. Tapped the mixer/osc and it burst into life, So gonna swap it out. Infact i might get shot of all the AF117s. Still nothing on LW. Probably a band switch issue.
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Old 7th Apr 2021, 12:21 pm   #10
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Default Re: Philips P3G38T Stone Dead

The ACY18 should be fine, despite being intended as an industrial transistor.
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Old 7th Apr 2021, 12:33 pm   #11
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Default Re: Philips P3G38T Stone Dead

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The ACY18 should be fine, despite being intended as an industrial transistor.
Volume seems much the same as it was before. The leads on the mixer/osc had came loose from the tracks probably due to me tapping it. Soldered them up and all the AF117s seem to be behaving now,

Should i leave them or replace them to prevent future problems ?
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Old 7th Apr 2021, 12:46 pm   #12
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Default Re: Philips P3G38T Stone Dead

I would change them all while you have the radio dismantled. Do them one at a time. Any Ge transistor with an ft of 2MHz or better should be OK in a MW/LW radio, and Si types of the BC214/BC558/2N3906 class should be OK too if you have them.
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Old 7th Apr 2021, 12:52 pm   #13
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Default Re: Philips P3G38T Stone Dead

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I would change them all while you have the radio dismantled. Do them one at a time. Any Ge transistor with an ft of 2MHz or better should be OK in a MW/LW radio, and Si types of the BC214/BC558/2N3906 class should be OK too if you have them.
Yeah that's what i was thinking. I have suitable Ge transistors. May as well do the electro caps whilst i'm at it.



Thanks for your input


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Old 7th Apr 2021, 6:50 pm   #14
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Default Re: Philips P3G38T Stone Dead

I have a load of unbranded capacitors i was thinking of using to recap the radio. The ESR on them is around 8 ohms. Is this considered high ?


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Old 8th Apr 2021, 5:41 pm   #15
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Default Re: Philips P3G38T Stone Dead

Could anybody tell me if the contacts on this band switch should be on the outside or the inside, See pic below. And how do you dismantle it ? As in removing the metal part ?

https://i.postimg.cc/qBZL12r7/IMAG0309.jpg
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Old 8th Apr 2021, 5:51 pm   #16
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Default Re: Philips P3G38T Stone Dead

Hi Jay

I would suggest changing all of those horrible AF117 transistors to those Russian equivalents, and provided the IF's have not been twiddled then you should be OK, from what you say it burst into life when the AF117 transistors were tapped, this would then suggest the driver stage and output stage are OK, I would also check the printed circuit side for any dry joints and even minute breaks in those tracks.

Ken
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Old 8th Apr 2021, 6:37 pm   #17
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Default Re: Philips P3G38T Stone Dead

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Hi Jay

I would suggest changing all of those horrible AF117 transistors to those Russian equivalents, and provided the IF's have not been twiddled then you should be OK, from what you say it burst into life when the AF117 transistors were tapped, this would then suggest the driver stage and output stage are OK, I would also check the printed circuit side for any dry joints and even minute breaks in those tracks.

Ken
Yeah those are getting replaced soon as the replacements arrive. My main concern at the minute is a dodgy band switch which is giving me brain damage

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Old 8th Apr 2021, 7:23 pm   #18
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Default Re: Philips P3G38T Stone Dead

Everything that could go wrong with this radio has gone wrong First up the audio driver fell apart on me, Got that replaced and today i recapped the radio. It was sounding good till i decided to spray the band switch with cleaner as it wasn't receiving on LW.

Now i have misaligned contacts on the band switch and the volume is lower than it should be, And to make things worse the dial cord came off And theres a few dodgy connections that i need to sort out too.

But my first job is going to be fixing the band switch. Anybody know how these come apart and where the contacts are meant to be ? On the left of the switch the contacts are on the outside, (Sure thats were they're meant to be) On the right side they're on the inside..

See pic below
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Last edited by Radio Scotland; 8th Apr 2021 at 7:46 pm.
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Old 8th Apr 2021, 7:47 pm   #19
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Default Re: Philips P3G38T Stone Dead

There should be contacts on the outside, in all the switches of a similar type that I've worked on the moving contacts wipe both sides of the fixed contacts.

Lawrence.
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Old 8th Apr 2021, 7:53 pm   #20
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Default Re: Philips P3G38T Stone Dead

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There should be contacts on the outside, in all the switches of a similar type that I've worked on the moving contacts wipe both sides of the fixed contacts.

Lawrence.
Cheers, Any idea how to remove the metal bracket from the switch assembly ?



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