RGD Radiogram 'Three- Fifteen'

[Jordan T]

Hello all,

Last night I came across the above Radiogram at a bargain price of £10. Long story short; I now have it home, given it a good polish and clean, however I'm having difficulties getting it to play properly.

Now before I go into the issues, here's a bit about me; I'm a Mechanical Design Engineer by trade, so I'm good with anything mechanical, but my electronics knowledge is limited past what you would have learnt outside of secondary school.

Onto the fun bit; the problems. Both the radio and the deck have issues. None of the radio's frequencies work. SW, MW, LW and FM. Nothing. The Deck works OK mechanically. You can stack 3 singles, and it'll load all 3 records as it should. Starts, stops and ejects well. Albeit it could still do with a strip down and a oil (which I shouldn't struggle too much with).

However, onto the biggest problem. The volume control/tone control seems to not be working as it should. When I first played the unit, the control worked reasonably but with a lot of static. So as I do with all static based issues like this, I sprayed some electrical contact cleaner into the pot. This seems to have made the control worse. Can these units be bought new or is it a case of carefully stripping down and inspecting the internals?

Taking the backing off. I did discover a date stamped into the casing; 14th October 1955. Also that the aerial is glued onto the backing board (I think this is the FM antenna?). This is disconnected, so where would I connect this? I'll take some photos of this when I next open it up.

This is my first vintage radio project and I'm really enjoying tinkering with it.

I look forward to hearing your responses.

Best regards, Jordan.

[Station X]

Hello and welcome to the forums.

You'll find the service sheet for your radiogram here:-

https://www.service-data.com/product...70/7177/a15670

[Jordan T]

Thank you and purchased!

Regards,

Jordan

[Edward Huggins]

A very early FM radiogram which will sound super when fixed. The Collaro RC54 autochanger is one of the most complex and should test your mechanical skills if ever needed! From your Post can we assume it plays well on Gram, the volume control issue notwithstanding? Can you post a pic of the aerial plug/connector and the rear of the radio chassis where the sockets are. However, I don't this this will solve the problem because if the radio is only partially working, or without any aerial, you should hear something on LW or MW at least. It sounds like the tuner section will need signal tracing in order to fault find. Do you have multimeter and a soldering iron? One thing you can do is to carefully remove the 6 valves (not the tuning indicator) noting their location, and buff the pins with emery cloth and try again.

[Herald1360]

A couple of points for starters......

Don't operate the unit again until you have at least checked out the capacitor(s) from audio preamp anode(s) to output valve grid(s)- they go leaky (low insulation resistance) and this can cause expensive damage if you're unlucky. Check out "That" capacitor in the stickies at the top of this forum area to see what I mean. It's C57 in the circuit.

If you're not familiar with vinyl technology, this player will damage stereo discs unless someone has already fitted a stereo or stereo compatible mono cartridge to the arm in place of the original low vertical compliance mono one.

Otherwise- it's well worth getting the data sheet mentioned- it may not make much sense to start with, but it's a great reference and will help with ongoing discussions as you work through the electronic side of the unit. The circuit may look bewildering, but it's just a stylized way to show how all the components are interconnected and is easier to understand than a literal wiring diagram would be, though if there is one of those too it's very useful for finding where particular parts are located!

Keep coming back for help and directions- you've rescued a nice piece of kit there, which a few years ago would have been worth nothing and hard even to give away! There's another stickie https://www.vintage-radio.net/forum/...ad.php?t=26411 all about this!

Oh and welcome on board too!

[regentone001]

The aerial glued to the back panel is the FM dipole and should be plugged into the dipole sockets either on the chassis or the small panel on the back of the radiogram.
These are excellent chassis and give very good results when working. The no signal problem could be due to dirty contacts on the wavechange switch bank.

Steve

[paulsherwin]

You got a lot of kit for £10, and it will certainly sound and look good once sorted out, but you are in for a fair bit of work, so you will need to pick up a few skills and some basic test gear.

As a minimum you will need a basic electrical soldering iron (Antex make good cheapies), a cheap digital multimeter (acceptable ones are available for under £10 though you can spend a lot more), and a can of switch cleaner such as Servisol 10.

As mentioned by Chris, it's likely to be full of leaky wax and Hunts Mouldseal capacitors, many or all of which will need changing. Don't just dive in and change them all though, especially as a beginner, as you will inevitably make wiring errors as you are working.

Maybe you could let us know if you are seriously interested in pursuing this, given that it's certainly not a question of a quick squirt of WD40 in the back. You can learn the necessary skills, but if you're not going to enjoy that side of things then it would be better to pass this on to somebody else.

First steps:

Change the capacitor described by Chris
Clean all the switches and pots with Servisol
Remove the valves one at a time, dip the pins in Servisol, put them back and rock them from side to side in their sockets

If there is still no radio output, check all the circuit voltages against the service info using a meter. Remember that you need some sort of aerial for the FM to work.

To clean the volume pot you will need to get the Servisol inside through a hole or gap of some sort. If this isn't possible then you will need to dismantle it.

Be aware that valves use high voltages, and while you are very unlikely to kill yourself if in good health, you can certainly give yourself a very unpleasant shock.

[emeritus]

I've got one of those, bought new by my father, and presently stored in the back of the shed since I brought it back from my late mother's house a couple of years ago. There are a number of 2 pin sockets on the chassis that were for use with matching plugs, but ordinary 1/8" wander plugs fit. The radio has a built-in ferrite rod for AM, as well an exterior AM aerial socket that we never had to use when I was a child. For FM I later used to use a loft-mounted dipole connected via 75Ω TV coax without a balun rather than the built-in set-back aerial. In mine, the grease in the bearings of the tuning mechanism has got very stiff and it really will need a good strip-down and clean before I can use it again. Certainly excellent sound quality, a single output valve operating in Class A, delivering 3W into an efficient speaker that will produce more volume than modern systems of much higher wattage. When I was with Plessey, an engineer who had worked on their consumer goods division told me that Plessey made the chassis for these models. He didn't have the service manual for my version, but did give me the manual for a similar version for the US market (just think, we used to export stuff to the US in those days).

A rather splendid item well worth getting going. If you feel stuck a post in the "Repairs wanted" section here may well find someone near you to give advice and help with the electronics (my usual fee is a pub lunch and a lift home!).

[John10b]

Certainly a difficult first project, with switch bank, FM etc, but also very interesting, and good looking Cabinet.
In addition to what you have already been told may I suggest you get a good note book, and record each step,it’s surprising what you forget you have done
( at least I do ), I also take pics along the way. Good luck.
Cheers
John

[Edward Huggins]

Noting the comment in Post #5, I can see a stereo or stereo-compatible cartridge has already been fitted into the tone arm. It looks like an Acos GP91 series.

[Jordan T]

Wow all these responses, I really wasn't expecting so many.

Thank you all for your initial comments and words of advice so far.

Just to put a few of your minds at ease, I'm deadly serious about getting this Radiogram back to it's early health.

I have a multi-meter, and soldering equipment to hand in the garage.

I think the best way for me to get through this project will be meet up anyone local and post as many pictures on here for a bit of step by step help ahaha.

So plan of attack for my next post will be:

Remove the back. Take more photo's of the aerial and plug in ports etc...

Once this is done, I will consult you all again on testing components on the circuit board.

Thank you for your responses so far. How fun is this!

Jordan

[regentone001]

I have several of the Regentone version of these and if I remember correctly there are not many waxies in them. The main one to change would be the grid coupler but other than that they are in low voltage areas of the circuit.
Good luck and enjoy
Steve

[John10b]

Edward how did you manage to identify cartridge, from the pics I’ve seen I can’t even get a glimpse of cartridge?
Cheers
John

[Jordan T]

Morning Chaps.

As mentioned by Chris (Herald13/60), I'm not going to switch the radiogram on again until I replace the 'audio coupling capacitor'. Would anyone be able to point me into the direction of a modern equivalent?

Thanks,

Jordan

[TrevorG3VLF]

C57 trader
Get a 47nF capacitor with a 500V capability or more. Polypropylene is often recommended.
Can get from many places including RS, Cricklewood, Bowood, CPC, etc.

Check R36 trader, 560k.

[paulsherwin]

Any modern cap with the correct value and voltage rating will be fine. A 500V rating is probably unnecessarily high but will do no harm. 400V and 630V are more common ratings, and either of these will be OK. The value of the cap isn't critical and you can just fit the nearest value you can find.

[Edward Huggins]

Originally Posted by John10b

Edward how did you manage to identify cartridge, from the pics I’ve seen I can’t even get a glimpse of cartridge?

John, well I'm just a silly old obsessive who's been at this game for over 60 years now...

I can tell by the profile of the projecting LPS/78 stylus flip-under lever - how's that for nerdishness?!

Of course, I may be proven wrong.....

[crackle]

I think the data from up above is R&TVS not Trader so it may be useful to quote those circuit number references if that is where the OP got the service information.

C57 is in fact the audio coupling capacitor and it is wise to change it regardless, for a modern 0.047uF 630 volt capacitor.
R36 is not really relevant and can be ignored for now if we are talking about the R&TVS service sheets. I dont think it would make much noticeable difference if it was 680k or 470k.
What is often thought of as being important is the cathode resistor (R42) of the output valve V5, and the electrolytic capacitor C40 as together they control the grid bias voltage on the output valve.

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.

Mike

[regentone001]

Great advice Crackle. There are two red and black Plessey electrolytics in these chassis the bias bypass cap as you mentioned and the one in the FM discriminator circuit.
Be sure to mount the replacements the right way around polarity wise