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-   -   Philips P3G38T Stone Dead (https://www.vintage-radio.net/forum/showthread.php?t=178613)

Radio Scotland 6th Apr 2021 6:05 pm

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.

poppydog 6th Apr 2021 6:55 pm

Re: Philips 3G38T Stone Dead
 
Is that the right model number??

Radio Scotland 6th Apr 2021 6:59 pm

Re: Philips 3G38T Stone Dead
 
Quote:

Originally Posted by poppydog (Post 1361213)
is that the right model number??

P3G38T/ 00 / 05

My mistake

paulsherwin 6th Apr 2021 7:00 pm

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?

Radio Scotland 6th Apr 2021 7:09 pm

Re: Philips 3G38T Stone Dead
 
Quote:

Originally Posted by paulsherwin (Post 1361218)
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 ?


Cheers.

Radio Scotland 6th Apr 2021 7:13 pm

Re: Philips 3G38T Stone Dead
 
Quote:

Originally Posted by paulsherwin (Post 1361218)

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


Cheers

paulsherwin 6th Apr 2021 7:36 pm

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.

Radio Scotland 6th Apr 2021 7:38 pm

Re: Philips 3G38T Stone Dead
 
Quote:

Originally Posted by paulsherwin (Post 1361237)
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 ?


Cheers
jay

Radio Scotland 7th Apr 2021 12:05 pm

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.

paulsherwin 7th Apr 2021 12:21 pm

Re: Philips P3G38T Stone Dead
 
The ACY18 should be fine, despite being intended as an industrial transistor.

Radio Scotland 7th Apr 2021 12:33 pm

Re: Philips P3G38T Stone Dead
 
Quote:

Originally Posted by paulsherwin (Post 1361448)
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 ? ???

paulsherwin 7th Apr 2021 12:46 pm

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.

Radio Scotland 7th Apr 2021 12:52 pm

Re: Philips P3G38T Stone Dead
 
Quote:

Originally Posted by paulsherwin (Post 1361458)
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 :thumbsup:


Cheers
Jay.

Radio Scotland 7th Apr 2021 6:50 pm

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 ?


Cheers
Jay.

Radio Scotland 8th Apr 2021 5:41 pm

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

Radio Tech 8th Apr 2021 5:51 pm

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

Radio Scotland 8th Apr 2021 6:37 pm

Re: Philips P3G38T Stone Dead
 
Quote:

Originally Posted by Radio Tech (Post 1362036)
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 >:(

Cheers
Jay

Radio Scotland 8th Apr 2021 7:23 pm

Re: Philips P3G38T Stone Dead
 
1 Attachment(s)
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

ms660 8th Apr 2021 7:47 pm

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.

Radio Scotland 8th Apr 2021 7:53 pm

Re: Philips P3G38T Stone Dead
 
Quote:

Originally Posted by ms660 (Post 1362086)
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 ?



Jay


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