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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 ?

[img]************************qBZL12r7/IMAG0309.jpg[/img]

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

ms660 8th Apr 2021 7:57 pm

Re: Philips P3G38T Stone Dead
 
Quote:

Originally Posted by Radio Scotland (Post 1362089)
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.

Radio Scotland 9th Apr 2021 7:20 pm

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.

paulsherwin 9th Apr 2021 7:49 pm

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.

Radio Scotland 9th Apr 2021 7:56 pm

Re: Philips P3G38T Stone Dead
 
Quote:

Originally Posted by paulsherwin (Post 1362444)
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.


Cheers, Jay.

paulsherwin 9th Apr 2021 8:02 pm

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.

Radio Scotland 9th Apr 2021 8:12 pm

Re: Philips P3G38T Stone Dead
 
Quote:

Originally Posted by paulsherwin (Post 1362449)
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.


Cheers

Radio Scotland 13th Apr 2021 4:52 pm

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,

Radio Scotland 17th Apr 2021 2:05 pm

Re: Philips P3G38T Stone Dead
 
Quote:

Originally Posted by Radio Scotland (Post 1363965)
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

paulsherwin 17th Apr 2021 3:23 pm

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 :)

Radio Scotland 17th Apr 2021 3:40 pm

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.

Radio Scotland 17th Apr 2021 8:12 pm

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 :beer:

Radio Scotland 23rd Apr 2021 11:40 am

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.

paulsherwin 23rd Apr 2021 1:07 pm

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.

Radio Scotland 23rd Apr 2021 1:12 pm

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.

Station X 23rd Apr 2021 1:33 pm

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?

Radio Scotland 23rd Apr 2021 1:39 pm

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.

Radio Scotland 23rd Apr 2021 3:04 pm

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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