Speaker problem with Ferguson 656RG Stereophonic Radiogram

[Total_amateur]

Hi.

I have a Ferguson Stereophonic Radiogram, early 1960's, that until recently has worked fine. However, I have noticed today that the left hand speaker no longer works either with the radio or the record player. I am a complete amateur when it comes to electronics, has anyone any ideas on what is causing the problem? I haven't performed any checks as yet, to be honest I wouldn't know what I'm looking for, so don't know whether it is a speaker problem or a valve problem.

Any ideas would be greatly appreciated.

Thank you.

[Stylo N M]

Hi, and welcome to the forums, it would help if you could give us the model number of the radiogram in question, this is usually found somewhere on the back of the unit.

Now firstly, do you have any basic equipment, for example a test meter or multimeter, in order to make some basic checks? Please remember to ensure that the unit is unplugged from the mains, before you make any internal examinations and always stay safe.

As regards to what the problem may be, this could be anything from a loose wire, an open circuit winding on a faulty output sound transformer
(if your unit has one not all do) or a dry solder joint/crack in a contact, or even a failed output valve or circuit voltage. It may be best to start by checking the speaker contacts, and other wiring going to and from the speaker.

I'm going to be a bit tied up all day on Monday, so perhaps other members will be able to guide you through some basic steps, and will have a bit more exspirence on how to explain what to look for.

Paul

[Boater Sam]

Swop the speakers leads over, does the non working channel now work? if so it was the speaker duff.

Beyond that you sound as though you need help, post on here for someone local to mentor you or fix it for you.

[Herald1360]

https://www.vintage-radio.net/forum/...0&postcount=14

Wonder how this one will pan out?

Too far away from me to offer any direct support.

[Edward Huggins]

Many are swift to blame the speaker. If only it were that easy - as speakers very rarely fail. Another way to check out the speaker is to test it in series with a 1.5V battery.
If you get a rustling noise, or see cone movement, it will mean that the speaker is not open circuit and that the fault will lay in the valve amplifier of that channel.

[Total_amateur]

Thank you to everyone who has posted offering advice. I have had trouble logging in so apologies for lateness of response. My Ferguson Stereophonic is Model number 656RG. From information I have been able to obtain from other sites it was manufactured in 1961 (?) and is classed as a Broadcast Receiver - or past WW2 Tuner.

I do not possess any meters to check the equipment and as mentioned originally. I wouldn't know what to do with them anyway!

I will spend some time moving the Radiogram tomorrow so I can get the back off and inspect the speakers and check for any loose wires. I have checked the sound output from the speakers with both Radio and Record player and the left hand speaker doesn't work in either mode. I will put an update on here tomorrow.

Once again many thanks for advice already given, it is much appreciated.

[ekjdm14]

Just a note, be aware that even if the set is switched off there can still be dangerous voltages contained in the capacitors if it's been powered up recently so be careful where you put your hands. I doubt it's likely a loose wire unless the unit has been moved/knocked but depending on how it's been maintained it could potentially be an output transformer gone open due to leaking capacitors.

Obviously this is just speculation but a fairly common scenario with valve equipment that's unrestored. A post in the help/services wanted section might be in order to find someone closer to you who could help with the set or guide you in diagnosis/repair since your first priority is staying safe.

One last thing, please don't be tempted to continue using the set with it's remaining channel lest the fault which took out the left side is also present and stressing components in the right channel. Sorry I can't be more positive, but the last thing I'd want is either you or the radiogram to get hurt in any way.

[Total_amateur]

I have now had a look at the equipment inside the Radiogram, all the wiring seems secure to/from the speakers and all the valves appear to be working, lights are on! I can't see anything obvious.

Previously when both speakers worked and I turned the Balance control knob on the front of the panel to the right, all the sound came from the right hand speaker. When I turned the knob to the left the left hand speaker crackled until the knob was fully turned to the left when full sound came out. This happened when I used either the Record Player or the Radio function.

Now when I do the same, the right hand speaker remains on when the knob is turned to the right, in both Radio and Record Player mode, but when I turn the knob to the left, I can still hear sound from the right hand speaker in Radio mode, but in Record Player mode no sound at all is heard from either speaker.

As Dan suggests (and thanks for the advice) I guess I'll need to see whether there is anyone local to me who can help because clearly whatever the fault, I don't have the skills to fix it, and I don't want to scrap the Radiogram despite its age and apparent unpopularity.

[ekjdm14]

That sounds a little more hopeful at least, from the latest information I feel it's highly likely to be a failed/dirty balance control potentiometer. It may be possible to bring it back to life with a good dose of Servisol Super 10 hosed directly into the case (there's usually a gap somewhere to point the straw in) & then vigorously working the control back & forth a good few times.

If this fails to cure it then further checking would be needed to confirm it's death & a suitable replacement fitted. Certainly not as bad as an output transformer going open.

[Edward Huggins]

Getting a large Radiogram serviced in your own home presents a number of difficulties as the Repairer has to come out to you and do it in real time, which may not always be possible. Well worth you locating the balance control potentiometer from the inside and spraying as already advised. This is safe to do (the unit must be unplugged) and if it works, as it may well do, this will save you much time and money - plus the satisfaction of doing it yourself..

[Total_amateur]

Thank you all for your expert advice....I'm learning so much! As I replaced the stylus on the record player recently I thought I'd better check I hadn't caused any damage which may be the cause of the sound problem. The player is fitted with a turnover stylus (?) and I replaced both needles. On looking again at the cartridge I have noticed that there seems to be an unconnected cable running up the arm to the cartridge but I cant find anywhere that it fits. The cartridge seems to have 3 pins which all have individual cables attached to them.
Anyway I found a local radio repair man and went to see him yesterday..he couldn't understand the sound issue I had until I mentioned the loose cable in the arm and he suggested that was what the problem was. I have had another look today and still cannot find where to plug the loose cable into. Should it be plugged in to anything or is it there should I need to update to a cartridge which has 4 pins?
In the meantime I'll take up the suggestion of getting some Servisol Super 10 and see if I can locate the Balance Control Potentiometer...tho from what I have seen from the inside of the casing, it could be tricky. I have tried to pull the Balance control knob from the front of the unit to see if I can get to the Potentiometer that way, but it is not budging...not sure whether I'd damage the unit if I keep on pulling...!
Once again, many thanks for all your assistance

[19Seventy7]

I'm by no means an expert but I have some knowledge of record players, other forum members correct me if I'm wrong.

By "turn over stylus" do you mean the cartridge (which the styli/needles go into) if so, have you hand sound from the left hand channel after replacing the cartridge? It's possible that the wires for LH and RH aren't connected to the respective pins on the cartridge.

Perhaps try change some of the wires round with the spare one, take note of which wire went where, though. The spare wire might be the LH connection

Good luck

[julie_m]

If the cartridge is a BSR TC8S, then it will have only three pins: left signal, right signal and a common return. Most other stereo cartridges have separate left and right returns, and a mono cartridge will only have 2 pins; so BSR fitted 4 wires in their tonearms so as to cover all eventualities.

If you did not disconnect any of the cartridge wires, don't go swapping them: this will not do any damage but if the record player has ever worked at all, they must already be in the right places. Though, you might want to check that they are making proper contact.

[Edward Huggins]

Don't try to force/pull that balance control knob off. There is little point as you will need to do this from the inside as it were so you can actually get to the round casing of the potentiometer. You also offered to try to photograph the internal electronics, but in fairness this is unlikely to tell us much unless, say, a capacitor may have exploded. If your cartridge is the original it will be fitted with a BSR TC8S stereo cartridge and these use 3 pins, not 4. Just google "BSR TC8S cartridge" to visually confirm.

[vidjoman]

I see no point wasting time on the cartridge right now. The original post says no sound on RADIO or RECORDS so it's a fault common to both.
It could be the balance control that need cleaning but has to be done from the inside. Photos would help us to help you.

[Michael Maurice]

I've serviced several of these of the past years. To say the circuit is unusual is putting it mildly!

In radio mode the valves are connected in such a way that the output stage is a mono push pull amplifier.

In Gram mode, the output stages are separated into left and right amplifiers operating in single ended mode.

If you've got a fault with one speaker on both radio and gram, then I would suggest you have a fault with the speaker wiring.

[Total_amateur]

Thanks again for all your kind replies. I have checked the cartridge and it certainly looks like a BSR TC8S, have seen one exactly like it on Google search so I'm happy I haven't got a loose wire....I never uncoupled any wiring to the cartridge when I change the stylus.
As for the speaker wiring, again I have not messed with any and from my visual checks all the wiring to both speakers seems robust and intact.
Thanks for your advice about the control knob Edward. I had considered trying to pull the knob off to see if I could gain access to the Balance control potentiometer (?) but clearly I need to see if I can locate it from inside. I will endeavour to take some photos...tho I am unsure how to load them on here for anyone to have a look at.
Michael, if as you say, In Gram mode the output stages are separated into left and right amplifiers could this be where the problem lies...is there a piece of equipment responsible for this separation and could this be faulty, leaving me with no sound distributed to the left hand speaker?
Once again many thanks everyone. I do feel like I'm making progress...!

[AC/HL]

To post pictures: https://www.vintage-radio.net/forum/...ad.php?t=77650

[Michael Maurice]

Originally Posted by Total_amateur

As for the speaker wiring, again I have not messed with any and from my visual checks all the wiring to both speakers seems robust and intact.

At the back of the gram, you'll find the ext speaker connections and what is actually a very crude switch. may I suggest that could be where the fault lies.

Originally Posted by Total_amateur

Michael, if as you say, In Gram mode the output stages are separated into left and right amplifiers could this be where the problem lies...is there a piece of equipment responsible for this separation and could this be faulty, leaving me with no sound distributed to the left hand speaker?
Once again many thanks everyone. I do feel like I'm making progress...!

The point I'm making is that you have no sound in one speaker on BOTH gram and radio. In Radio mode both speakers are effectively paralleled so that you get mono sound from the amplifier which is in push pull mode.

The balance control only works in gram mode.

[Nuvistor]

Hi Michael,
I don’t have a circuit for this set but Thorn produced this type of circuit in at least two different ways. One with separate single ended output transformers and the switching performed in the secondaries of the output transformers. The other circuit is a pushpull transformer for mono and a second output transformer for for one the pentodes with any required switching. I think the second type was called “ Phantom push pull”.

Do you know which type this RG uses?

Ref. Page 500 https://www.americanradiohistory.com...RC-1966-03.pdf

And the Ferguson 658RG circuit available from the service data link above.