Philips B3G63A

[DonaldStott]

Oops, looks like I've tapped into stories about the seedy underworld of some 1950's service engineers.

As I said "... I have very limited experience in this field" so will gracefully yield to those with the detailed knowledge of such matters.

I'll just stick with the current challenge of priming and painting my repaired Bakelite case ...

[DonaldStott]

Oops again - maybe it's Karma or simply one step forward , two steps back but we have a slight problem I hadn't noticed before.

Discovered it when I was looking to measure up for the new mains cable and inspecting the tags on the chassis. I noticed that a thin wire was loose at the top of what appears to be identified as C35 from Trader Service Sheet 1374. I've attached a couple of pictures that hopefully show what I'm talking about?

Simple question, where does that loose wire connect to - it's not obvious?

What should it look like?

C35 is a strange looking beastie and the Trader Service Sheet states that the value is 400pF but there is a note that says this is 270pF plus wire-wound 130pF. Apparently it's part of the tuned anode oscillator associated with L.W. and the triode-heptode valve V3. Put simply, it sounds important!

Hope someone can help!

[ronbryan]

The wire is the adjustment mechanism on the trimmer capacitor. To reduce capacitance the wire is unwound from the ceramic tube. The free end is not meant to connect to anything.

Philips said you should get another trimmer if you unwound too much as far as I recall. Not possible these days of course.

Ron

[DonaldStott]

Hi Ron - thanks ever so much for an ultra- quick response.

I was convinced that I'd pulled the wire off its connection - never realised that capacitance would be controlled in such a simple manner.

Panic over - this is something else I've learned today!

Thanks again Ron, I can now go back to enjoying my weekend...

[DonaldStott]

Great weekend - got the radio back up and working after reconnecting the loudspeaker and a new mains cable.

All the previous scratchiness from the controls has now gone and both tuning dial cords working as they should!

Not got any aerials sorted out yet but quite strong signals mid-gang on the MW although a bit bright in terms of Tone, nothing on LW apart from background noise and absolutely nothing on FM - early days.

[boxdoctor]

Hi Donald,
Sounds like its coming along nicely!
You should be getting something on long-wave where you live, France Inter (162Khz) or possibly R.T.E. 2 on 252 Khz at least. They will not be strong signals though. Have a good look at the ferrite rod connections, and see if there is a wire off.
No VHF may be that the EF80's have lost emission, and new ones (or EF183/184s) will cure this. My B3G63A did not work on VHF when I got it for this reason. Its most unlikely to be a fault in the VHF tuner unit, but a defect in the F.M. Intermediate frequency stages (unlikely) could be the cause. Cheers, Tony.

[paulsherwin]

You should be getting a good LW signal on 198kHz from Westerglen.

[DonaldStott]

Thanks Paul

Found this information about Westerglen services available: -

Frequency kW Service
198 kHz 50 BBC Radio 4
909 kHz 50 BBC Radio 5 Live
810 kHz 100 BBC Radio Scotland
1089 kHz 50 Talksport
1215 kHz 50 Absolute Radio

The Medium Wave stations are fine - I'll search for BBC Radio 4 on 198kHz tonight...

[DonaldStott]

Originally Posted by boxdoctor

You should be getting something on long-wave where you live, France Inter (162Khz) or possibly R.T.E. 2 on 252 Khz at least. They will not be strong signals though. Have a good look at the ferrite rod connections, and see if there is a wire off.

Thanks Tony - see my reply above to Paul. I'll try and find the stations you suggest tonight and also check out the ferrite rod connections.

I retained the old length of wire from the back cover that forms an FM internal aerial along with its original wander plug - just plugged that into the Aerial socket on the back of the set and FM came to life. BBC Radios 1-4 and Classic FM (compression - groan!) all quite clear.

For starters there are two issues, volume is quite low on FM and tone is very bright - some sibilance as well?

I don't have any of the test equipment required for AM or FM alignment but hopefully there are still some adjustments I can make?

Next area of R&D (for me) is to figure out the Dipole, Aerial and Ground sockets on the back of the set - currently the FM internal aerial is plugged into the Aerial socket with a wander plug. I looked at some of the Threads on here about making a simple Dipole internal aerial but not sure how to proceed

Anyway, really pleased that this 1956 Philips Valve Radio is back with us again - my Grandfather would have been thrilled!

[DonaldStott]

Originally Posted by Andrewausfa

I've got the same issue with the plate aerial as you on a couple of my own Philips sets. I'm going to recreate by using kitchen foil backed with lining paper (pound a roll from Poundland). I just have to work out the best glue for the job, PVA won't do.

Has anyone used or considered this: -

http://www.lakeland.co.uk/p70144/Parchment-Lined-Foil

5 metres for £1.99 - I suppose the conundrum is if it's non-stick what do you stick it down with?

[paulsherwin]

I wouldn't put much effort into sorting out the internal plate aerial.They are pretty hopeless unless you are next door to the transmitter.

FM radios of this era were really designed to use a big dipole on a mast on the chimney, similar to a VHF TV aerial. If you just have a manky bit of wire attatched then performance is unlikely to be great. Try moving the wire about and the signal may improve. Poundland sometimes sell set top telescopic dipoles which are better than nothing. An FM dipole is easy to make - just two 75cm lengths of wire - or you could try using one of those flat ribbon aerials sold for use with FM tuners.

Without checking, I suspect that the Aerial and Earth sockets are for AM, and the Dipole sockets are for FM.

You shouldn't need to realign anything unless somebody has been twiddling.

[DonaldStott]

Thanks again Paul - I suppose the plate aerial work is just for completeness - as I said, 5 metres for £1.99, won't break the bank.

I'm interested in your idea of using two 75cm lengths of wire as a Dipole - I'm assuming these are lengths for the horizontal arms and not the total length from the radio sockets. Is there any risk of RF interference from the leading wires to the horizontal arms?

What puzzles me is how plugging the internal FM aerial wire into the AM aerial socket can have improved FM Reception?

Any ideas on improving the low volume on FM and the tone brightness??

And one last point, for now, have a look at one of my original pictures: - https://www.vintage-radio.net/forum/...pictureid=3370

On the left hand side you will see a short length of wire connected by a wander plug that ran from the Earth/Ground socket and was attached at the opposite end to the metal chassis - any ideas??

[paulsherwin]

The normal way to make a dipole is to attach the two 75cm lengths of wire to a stick such as a garden cane, and connect the two ends at the centre to the centre and braid of a length of 75 ohm coax (the sort used for TV aerial wiring). You connect the other end to the radio. Strictly speaking you should use a balun at the radio end to match the impedences, but I wouldn't bother at this stage as it will work well enough without.

You were probably getting some reception using the Aerial connection because signal was leaking into the VHF front end. This suggests you have quite a good signal.

The chassis wander plug would be to connect the chassis to radio earth if a proper earth connection wasn't available.

[boxdoctor]

Originally Posted by paulsherwin

You should be getting a good LW signal on 198kHz from Westerglen.

Ahem! Yes, Paul. Sorry about that. For some reason I completely forgot about Radio4 Long Wave. Cheers, Tony....

[DonaldStott]

Thanks Paul for the dipole information - I've got loads of standard 2.5mm twin core and earth cable I could use. I'll just strip the cable out from the outer grey insulation and use that with a garden cane or dowel. How crucial is the 75cm length?

I've got some suitable 75Ω coax as well but it will be a bit messy at the radio end where I need two wander plugs?

[paulsherwin]

75cm is around a quarter of the wavelength at 100MHz. A bit shorter will resonate at a higher frequency and a bit longer will resonate at a lower frequency. It isn't all that critical. As it happens, I built my loft dipole from an offcut of 2+E, it's as good as anything.

As I said in your wanted thread, most Philips sets use standard 4mm banana plugs rather than wander plugs. If you actually need 3mm wander plugs you can make them from a phono plug by squashing the tip a bit, or use an automotive split pin with the wire soldered to the end. Or you can do what many of us do - stick the wire in the hole and fix it in place with a matchstick.

[julie_m]

The length of the aerial determines the frequency at which it is most efficient. If you only ever listened to one radio station, you could design an aerial to perform best at its frequency. In practice, there is usually enough give and take to cover the full broadcast band 88 - 108 MHz.

Mathematically, each side of the dipole should be one quarter of the wavelength of the wanted station frequency. That's 299 792 458 / ( 4 * f ) metres, where f is the frequency of the station that you will be listening to the most. 75 cm. makes a perfect dipole at 100 MHz., but since these sets usually only tune up to 101 MHz., you probably would be best off using 79.3 cm. for 94.5 MHz.

In really poor signal areas (such as the bottom of a valley; I am only half-joking when I say I have an uphill trek to get to the river) making each arm of the dipole 3/4 of a wavelength can help pull in stations -- but then you end up with the best part of 5 metres of aerial, which some people seem to find hard to like. It's also more critical with regard to the length. If you managed to receive anything listenable with a stump of an aerial, you probably won't need to go to.such lengths.

[DonaldStott]

Last question for tonight, honest - does it have to be 75Ω coax cable - I've got some loudspeaker cable with 4mm banana plugs that fit neatly in the Dipole sockets??

[paulsherwin]

Well, it may work, and it will do no harm to try.

[julie_m]

It can't do any harm; the worst that can happen is that it won't work.

When I lived in a stronger signal area, I would commonly see an FM aerial made from a length of speaker cable, split for 75 cm. and blu-tacked to the wall behind a piece of furnitiure.