Do you have a Roberts Revival R250 or R550 radio with no sound or crackles when the volume is turned? It’s a common problem with these radios after a few years use. The on/off switch attached to the volume control can break causing no sound so the control needs replacement. Or if the speaker makes a crackling sound all you need some switch cleaner or if that fails a soldering iron and some spare parts and it’s a fairly easy fix.
Warning – this gets technical but it’s really not difficult and you can have your radio working again in an hour or so. Please take take when using soldering irons.
Crackly or noisy controls may be fixed using some switch cleaner which is available from outlets like Maplin for under £5 look for aerosol Switch Cleaner. Make sure it has a small flexible tube with the can so you can direct the cleaner inside the volume control. It works best if you place the end of the tube in the small slot by each of the three wired connections (see below) and turn the control back and forth fully after squirting in the cleaner. No need to use too much – just a quick press is all it should need. You don’t need to remove the volume control as in the picture below.
Roberts R250 / R550 volume control
If there’s no sound at all (see Roberts R250 / R550 – No Sound Faults) and the on/off switch has broken or the crackle remains after cleaning you will need to replace the volume control.
Finding replacement volume controls is not too difficult however getting one the right size is. You need a 10KΩ (kilo ohm) logarithmic potentiometer with a switch. You may notice the original one fitted is in fact a 20K pot or rather two 20K (stereo) pots wired in parallel to make 10K. The shaft length needs to be at least 15mm with a flat area to fit the volume knob. Most parts I’ve found have a 6mm splined shaft (see below the 2 on the right) so need filing or grinding flat. If the shaft is too short you may need to shorten the daughter board fixing studs (see later).
Roberts radio R250 / R550 volume controls
Replacing the volume control requires removal of the main radio PCB (see other post for how to do this) to gain access to the daughter board that contains the volume control. Remove the two daughter board mountain screws (they may be held with red lock paint that will crack and free). Next unsolder the grey ribbon cable that attaches the daughter board to the main board.
The volume control can then be removed from the daughter board by unsoldering the small board that connects the potentiometer or removing the wires if there’s no additional board. Solder braid or solder suckers helps the unsoldering process along with small pliers to avoid burning fingers! Please take care when using soldering irons they do get hot enough to melt tin.
If you have found replacement pots like those shown you need some small lengths of wire to connect the pot and switch to the daughter board. There are five connections the two outer ones are for the on/off switch and the inner three and the volume potentiometer. An example of fitting a shorter replacement is shown below.
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- Shortened volume control mounts
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- Replacement volume control wiring
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- Replacement control shortened to fit
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- Replacement control daughter board wiring
Finally, fit the daughter board back using the two small screws making sure not to over tighten and break the plastic mounts then reconnect and solder the ribbon cable. You should now have a working crackle free radio. Worth checking it works before installing the main board back into the cabinet by reconnecting the power and speaker cables temporarily resting the main board on the back of the cabinet.
10/03/2020 at 11:54 am
Hello
Do you have any advice for this problem effecting the tuning switch which crackles when you try to tune the radio? It crackles so loud you can’t hear the station so you can’t tune it in by sound only by luck.
Grateful any help.
Best wishes
Hugh
10/03/2020 at 10:08 pm
Hi Hugh, thanks for the question and hope you find the site useful.
Cleaning the three (LW/MW/FM) radio button tuning switches with aerosol switch cleaner will probably help. For the switches use a lubricating cleaner and direct the spray inside the central slots in each switch on the printed circuit board.
Or do you mean when turning the tuning knob rather than switch? The crackle can be caused by tarnishing of the tuning capacitor’s contacts. The tuning capacitor is the large square semi-transparent device on the main printed circuit board near the tuning knob. It is possible to pull the plastic cover off the capacitor after straightening the two small tags that hold it in place. You can then see if the contacts look black and try some alcohol or non lubricant based switch cleaner that’s safe on plastics. I think the main contact is in the centre. Rotate the tuning back and forth immediately after applying the switch cleaner to improve the contact.
Let it dry out or use a hair dryer so the solvent evaporates or the capacitance will change and the stations will be in the wrong place on the dial.
If it still crackles you can replace the capacitor but you will need to retune the four adjustable trimmers on top. This is not easy without test equipment for both AM and FM bands. You need to set the local oscillator trimmer to set the frequency to the tuning dial and then trim the waveband for max signal strength.
Good luck and let us know how you get on.
12/11/2021 at 3:52 pm
Hello there, I have a Roberts 250 that crackled really badly. I have applie the switch cleaner and MW and LW are brilliant. My only problem is I can not tune any FM stations at all. Do you have any suggestions? Thanks
12/11/2021 at 6:25 pm
Hi Amanda – it could be a number of things. Have you tried the switch cleaner on the FM push button and changing between FM and MW several times? The tuning capacitor stator can also become tarnished and stop FM from working. It’s possible to remove the plastic cover and apply a very small amount of switch cleaner (not the oily kind) that may bring it back to life. Does it crackle at all on FM? If it’s completely dead and the FM switch cleaner does not work it’s more involved.
12/11/2021 at 11:07 pm
Hello there Rick, yes I have tried cleaner on the switches but I can try that again. I will also try the tuning capacitor as you suggested as I have not tried that. The noise on FM is a low buzz like when you are trying to tune a station but the tone is constant and does not seem to alter at all. I appreciate your comments and reply. Thank you very much.
13/11/2021 at 11:33 am
Hmm, could be the local oscillator stopped due to tuning cap stator high resistance but unlikely if it’s all through the tuning range. The buff coloured ceramic caps 103n can also go short circuit and cause IF problem on FM. A simple ohms check can identify. See https://storycase.co.uk/radio/radio/roberts-r250-no-mw-lw-hiss-fault
13/11/2021 at 11:45 am
I’ve had to replace the RF chip – if you can still buy them. Roberts radio spares used to supply.
Chip failure most likely due to wrong power adapter which often takes the audio chip out as well. Since your works on am it’s unlikely. There’s a 5v regulator – looks like a small transistor that I’ve also had fail but don’t remember what symptoms were.
Hope one of these helps
16/11/2021 at 11:43 pm
Hi Rick I tried the switch cleaner and no joy. If I do have to replace the two capacitors C23 and C24 what is the voltage and resistance please? Sorry to be a nuisance this is the First radio I have looked at. I appreciate any help you can give me. I need to try and borrow an Ohmeter to test them. Thank you
17/11/2021 at 8:01 pm
From my scribbles of voltages on the circuit – https://storycase.co.uk/radio/wp-content/uploads/2012/11/Roberts-R250.pdf it looks like pins 8 (C23) of the IC (BA-4236L) read 5.3v when faulty. But the note also shows down to > 3.5v. The table has the IC voltage readings for working MW and faulty FM I assume. I remember when I removed the suspect cap it read very low resistance near 0 ohms on the lowest range (0-200 ohm scale on the digital meter). I was surprised as ceramic caps should of course have no resistance – The insulation layer had broken down and failed. Yours may have a completely different fault but you could try measuring the voltages around the IC to see if any clues.
08/09/2022 at 9:12 am
Hello,Is there a Roberts Radio repairer in Hove who could replace my on/off switch. I’ve rung the company and they are out of stock on this part.
David Geere
08/09/2022 at 8:57 pm
Hi David – you could try a local Repair Cafe – there’s one in Brighton – https://www.repaircafe.org/en/cafe/brighton-repair-cafe/location/
May help to bring along a replacement volume control like one featured in the post . Hope this helps.
04/10/2022 at 4:19 pm
Hello,
Where do I obtain an on/off switch for my Roberts (model 250) radio if that shop in Hove, Sussex say they are out of stock. We have a Repair shop in our village once a month so taking it along there with the part is a good suggestion.
Thanks,
David Geere
06/11/2022 at 8:19 pm
Hi David, apologies for delay in replying – gremlins in WordPress. As the on/off switch is part of the volume control it’s tricky to find an exact replacement. Googling “10k log pot switched” had quick look and found Amazon have this https://www.amazon.co.uk/Logarithmic-16mm-Potentiometer-Switch-Pack/dp/B08GCTC616 it may fit or give you an idea of what to look for.
07/11/2022 at 4:17 pm
HI I HAVE ROBERTS RADIIO BUT DOSENT WORK WHEN SWITCHED ON BUT IT DOE S MAKE A TICKING NOISE LIKE CLOCK ANY IDEAS WHAT PROBLAM COULD BE REGARD S
07/11/2022 at 10:23 pm
Hi Roy, if your radio is a R250 or R550 as in this post there are a few things to try. Firstly, are you running it on a genuine 9v power adapter or battery? Lightweight replacement power adapters of the switching type can cause this type of interference. Secondly, is the same ticking noise on AM and FM wavebands? If so it could be an audio fault with the volume control or amplifier chip – see R250 no sound faults post. The wave change switches can get badly tarnished contacts that can prevent the radio working causing odd noises so try to changing between FM and MW repeatedly to see if it starts working ideally apply switch cleaner to the wave change push button contacts.
If still no joy it will need more investigation.
25/02/2023 at 11:23 am
Hello ,
I have a mulberry 250 and the on off switch doesn’t appear to click on and off .
It wasn’t working at all so I used switch cleaner and if I move the volume/ on off switch slowly I can get to a level where it works , but if I go higher on the volume scale it goes silent.
I feel like there’s a slight click higher up the volume scale almost as if the on off switch has moved , is this possible?
I can use the radio at this middle / working volume area and switch on and off at the plug, but it bothers me that its not working correctly.
I also took the back off to apply switch cleaner more directly to the on off switch but no further improvement was made.
I did have to reattach the speaker and the long cylinder with copper wire around both ends had also cone loose (what is this?)
I suspect its a new switch required, I clicked on the amazone link above but sold out!
Thank you in advance for any help
Love these little radios
08/05/2023 at 7:56 am
Hi James, apologies for late reply – somehow your comment was misdirected as spam.
Yes the volume control switch contact has broken and needs replacing. Try searching for “10k log potentiometer switch”. Any value between 5k to 50k would work. They are difficult to find with the right length shaft length and thread size – assuming your R250 has the metal cased control fitted. This pot on Amazon has a 10mm thread so is too big unfortunately. The thread and shaft need to be similar diameter.
If you mainly power your R250 from mains adapter you could solder a wire across the switch to permanently short circuit it so you can adjust the volume without it going silent. Not ideal but may work until you find a replacement. I don’t have any switched pots left either!