RGD Radiogram 'Three- Fifteen'

[Sideband]

Originally Posted by crackle

Just a thought, what switch cleaner are you using, don't use the stuff that comes from car accessory or hardware shops for electronics.
I use Servisol Super 10, it has always done the job for me at half the price of some other stuff about.

That's good advice from Mike....some of the cleaners are just not suitable for electronics....I've seen some dissolve the carbon track of a pot...and sometimes the pot itself (plastic ones).

Also don't be tempted to squirt WD40 over the switches....it probably won't harm them but is unlikely to provide a satisfactory result.

All these cleaners have their place but it's better to use Servisol or similar for electronics.

[John10b]

Edward what can I say, well done, I certainly could not identify that cartridge from the pics I’ve seen.
Cheers
John

[Jordan T]

Evening chaps,
Would the capacitor below suffice? It’s the same rating, voltage and polypropylene.

https://rover.ebay.com/rover/0/0/0?m...2F190915805343

Cheers,

Jordan

[crackle]

Yes they would probably do, but I have never heard of that make before.
I usually by these sort. https://www.ebay.co.uk/itm/123451841967? and I have bought from that seller before with no problems.

Mike

[Jordan T]

Cheers for that Mike. Interesting as I looked at that listing, but was under the impression that Polypropylene caps were more reliable than Polyester caps?

Jordan

[paulsherwin]

Don't worry about capacitor technology. Any modern plastic film capacitor will be fine. Just buy on price, and perhaps appearance if this is important to you.

[Herald1360]

Not so much "more reliable" as better suited for certain more demanding applications (of which interstage coupling in old valve radios isn't one......).

Don't forget the original paper capacitor would have been fine for 20 years or so. That technology would in all likelihood still be available if the plastic film types weren't cheaper to make as well as more reliable and smaller.

[crackle]

I keep both the brown radial and bright yellow axial caps in stock. The brown ones are normally cheaper and if I am not going to the bother of re-stuffing the old shell, I think they look less obtrusive under the chassis than the bright yellow ones.


Mike

[Jordan T]

Thanks for that. I've ordered the brown ones and will update you all when they arrive, before I install.

Also, I've ordered some Servisol Super 10 at the same time.

cheers,

Jordan

[McMurdo]

I use those brown ones too, the Illinois Capacitor (IC) brand are pretty good and discreetly coloured. I'm sure you know that RGD were aimed at the higher end of the market, selling on their earlier reputation as a luxury manufacturer. No point in skimping on parts!

[Techman]

Originally Posted by Jordan T

Would the capacitor below suffice? It’s the same rating, voltage and polypropylene.

I use these all the time now and find them excellent. They test well within tolerance regarding their values and I've had no problems with them so far. I've no idea who makes them or where they originate from.

[Jordan T]

Good evening all,

got in from work and I was happy to see my Capacitors had been delivered.

So this evening I decided to start removing the radio unit from the chassis/body (what's the correct terminology for the wooden body?).

I've taken some photo's of the unit. at first glance I don't have a clue where to begin.

Higher definition photo's can be found on my flickr page. see link below;

https://www.***********/photos/502490...57702684357584

Any help? haha

Cheers,

Jordan

[crackle]

Hi Jordan
Please would it be OK to use your photos to put in the Radio Museum as there are none of this model of radiogram on there at the moment.

I call the overall wooden case of the radiogram the "cabinet" and the metal lump you pulled out of it with the radio and amplifier components on is the "chassis".
You can probably see for yourself which are the wax paper capacitors. They are sticky waxy cylinders with a wire at each end.
But first get the service manual and start identifying which each one is. You could print out the photo in B&W and write on it the capacitor reference numbers.. I then transfer the numbers to the B&W image on the PC for future ref.
If you are unsure post your marked up image on here for someone to check.

Only replace one capacitor at a time with one of the correct nearest value and same or higher voltage.
The small value capacitors from about 500pf or less may be mica or polystyrene types and should normally be left alone.
It is important to minimise disturbance of the components in and around the FM RF part of the circuit, as moving a component here can effect the tuning and alignment.

Mike

[Edward Huggins]

Don't forget to leave the speaker connected! Also removing each valve and cleaning the pins with emery cloth and spraying the sockets is well worth doing at this early stage.

[Jordan T]

evening all,

You'll be pleased to know that I managed to change the capacitor with no problems at all and cleaned all of the valves while i was there. I noticed at the same time that the FM band cord had broken, so repaired that while i was there.

Fitted everything back together and the radiogram worked better than before. I had all the radio waves including FM which I didn't have before. However I noticed that now everything was working as it should, the sound quality from the speaker was poor especially in the mid range and when the volume was low.

I took the speaker out and was told by a friend to gently press the cone of the speaker down and see if it scraped or had signs of resistance; in which I noticed it had quite a lot.

So for now I've fitted a 4ohm 4" speaker which I had laying about in the garage. The sound quality is now really really good. Play's so well and extremely powerful!

Now I would eventually like to return to a 10" speaker like the original. What would you folks recommend? I can't see any markings on the original so don't know what ohm or wattage it is.

thanks,

Jordan

[G6Tanuki]

The speaker is probably 3 Ohm impedance - that was the standard up until semiconductors started to make an appearance.

Your 'scratchy' old speaker could be scratchy because - through disuse - rust has built up between the central cylindrical part of the magnet and the voice-coil. In the past I've managed to get a significant improvement by driving the speaker really hard [some heavy metal music - played with the volume TURNED UP TO ELEVEN!] for a few hours will give it a good exercising - then you use a small vacuum-cleaner in the centre of the speaker to suck out the rust/dust. The little battery-powered vacuum-cleaners sold for cleaning keyboards are great for this - a small-enough nozzle to get into the space, but not so much 'suck' you risk damaging things.

[cathoderay57]

Are there any removable screws or bolts at the rear of the speaker? If so, don't undo them - yet! If there is evidence of rust on the speaker frame the advice given above might possibly work. However, usually the speaker cone will have warped slightly. It doesn't take much for the coil tube at the centre to bind on the pole piece (magnet). If you are lucky you might see at the rear base of the cone an adjustable diaphragm with 2 nuts that can be slackened to allow the cone to be re-centred. If the circular diaphragm is simply glued to the frame the solution will not be so simple. Photos of the front, side and rear of the speaker would be good. Cheers, Jerry

[Jordan T]

Hi all,

Apologies for the late reply.

Please find photo’s of the apeaker attached.

Regards,

Jordan

[vintage_8bit]

If all else fails....
By pushing the cone GENTLY from its present alignment, sideways you sometimes find a point where the rubbing stops. I have in the past then used a small hand held plant sprayer to slightly dampen the cone in that area. As the cone dries, say over the next 24hrs the cone shrinks slightly in that direction, and can pull the speech coil back to centre. You may have to repeat again. This is unlikely to work of course if the build-up of debris round the coil is causing the problem.

Colin

[SteveCG]

Some designs of loudspeaker suffer from cone sag - that is the suspension no longer holds it centred - just through age. Sometimes mounting the loudspeaker so that what was at the top is now the bottom (ie a 180 degree rotate) is sufficient to clear the problem. Even simpler - You could just try the loudspeaker out without mounting it by connecting up again, play some music through it and just rotate the loudspeaker to hear if there is any improvement.