Roberts R250 picked for scraps. Willing to get work again - UK Vintage Radio Repair and Restoration Discussion Forum

marslo911 · 11th Jul 2022, 11:04 pm

Hi Guys and warm welcome to community. I have managed to get an Old Roberts Radio model R250. This model came to me without any sign of life. The original battery was missing, managed to transfer some voltage using lab power supply. Now couple things.

There was no obvious sound of clicking buttons or any sound of power or on off. Measured the TDA 7231 and I couldn't get any amplification of the voltage. Replaced the chip. Now I am getting a bit of noise off the speaker however, it's not a volume you'd like to get. It's pretty silent to be honest. Now when I click the buttons I can hear spike of the noise from the speaker. But that's it. There is no sound of the station (rolling the tunning knob back and forth) but not receiving.

Does anyone had a little play with this radio in the past?

Panda23 · 20th Jul 2022, 8:11 pm

Hello there this link might be of some help to you. https://storycase.co.uk/radio/common...control-fault/

David G4EBT · 20th Jul 2022, 8:54 pm

An all too common problem with Revivals is that unusually, the centre pin of the power supply is negative - not positive. If a positive centre pin power supply is plugged in and the radio switched on, it causes the audio IC to fail, and the RF chip too and takes out one or two other items.

All of which Roberts could have prevented had the installed a one penny 'idiot diode' tp protect the radio in the event on wrong polarity.

I'm not saying that's what's happened, but it's what happened to one owned by my son, the repair of which I covered in a forum thread some time ago, which might turn up in a forum search.

Good luck with it.

Panda23 · 21st Jul 2022, 9:36 am

On this link is a video helping with problems with reverse polarity if that is the problem https://youtu.be/S_X6aM2catA
Hope one of these can help you...
Regards Amanda

Hybrid tellies · 21st Jul 2022, 10:34 am

I repaired a damaged Roberts R250 revival for a friend a few years back. He used a standard 9v wall wort PSU which used incorrect polarity. The results were dramatic. The electrolytic capacitor across the 9v line exploded with bits of aluminium blown right across the radios innards and the output IC had split in its casing after I cleaned out he mess and replacing the output IC all was well and its still working today.

My own Roberts R250 which I have owned from new started playing up with the the volume dropping to very faint levels. An investigation revealed that the main switch bank was playing up. I tried various switch cleaning sprays but to no avail. Despite being as delicate as possible some of the spray found its way into the tuning capacitor which has knocked out the RF alignment.
I have now put the radio to one side whilst I decide what to to with it.
Yes its a nice looking radio but the chassis it not the best of designs and leaves a lot to be desired.

11th Jul 2022, 11:04 pm	#1
marslo911 Diode Join Date: Jul 2022 Location: Tamworth, Staffordshire, UK. Posts: 1	Roberts R250 picked for scraps. Willing to get work again Hi Guys and warm welcome to community. I have managed to get an Old Roberts Radio model R250. This model came to me without any sign of life. The original battery was missing, managed to transfer some voltage using lab power supply. Now couple things. There was no obvious sound of clicking buttons or any sound of power or on off. Measured the TDA 7231 and I couldn't get any amplification of the voltage. Replaced the chip. Now I am getting a bit of noise off the speaker however, it's not a volume you'd like to get. It's pretty silent to be honest. Now when I click the buttons I can hear spike of the noise from the speaker. But that's it. There is no sound of the station (rolling the tunning knob back and forth) but not receiving. Does anyone had a little play with this radio in the past? Last edited by Cobaltblue; 13th Jul 2022 at 9:48 am. Reason: corrected model number

20th Jul 2022, 8:11 pm	#2
Panda23 Pentode Join Date: Nov 2021 Location: Ashfield, Nottinghamshire, UK. Posts: 162	Re: Roberts R250 picked for scraps. Willing to get work again Hello there this link might be of some help to you. https://storycase.co.uk/radio/common...control-fault/

20th Jul 2022, 8:54 pm	#3
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,763	Re: Roberts R250 picked for scraps. Willing to get work again An all too common problem with Revivals is that unusually, the centre pin of the power supply is negative - not positive. If a positive centre pin power supply is plugged in and the radio switched on, it causes the audio IC to fail, and the RF chip too and takes out one or two other items. All of which Roberts could have prevented had the installed a one penny 'idiot diode' tp protect the radio in the event on wrong polarity. I'm not saying that's what's happened, but it's what happened to one owned by my son, the repair of which I covered in a forum thread some time ago, which might turn up in a forum search. Good luck with it. __________________ David. BVWS Member. G-QRP Club member 1339.

21st Jul 2022, 9:36 am	#4
Panda23 Pentode Join Date: Nov 2021 Location: Ashfield, Nottinghamshire, UK. Posts: 162	Re: Roberts R250 picked for scraps. Willing to get work again On this link is a video helping with problems with reverse polarity if that is the problem https://youtu.be/S_X6aM2catA Hope one of these can help you... Regards Amanda

21st Jul 2022, 10:34 am	#5
Hybrid tellies Nonode Join Date: Jan 2004 Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area. Posts: 2,967	Re: Roberts R250 picked for scraps. Willing to get work again I repaired a damaged Roberts R250 revival for a friend a few years back. He used a standard 9v wall wort PSU which used incorrect polarity. The results were dramatic. The electrolytic capacitor across the 9v line exploded with bits of aluminium blown right across the radios innards and the output IC had split in its casing after I cleaned out he mess and replacing the output IC all was well and its still working today. My own Roberts R250 which I have owned from new started playing up with the the volume dropping to very faint levels. An investigation revealed that the main switch bank was playing up. I tried various switch cleaning sprays but to no avail. Despite being as delicate as possible some of the spray found its way into the tuning capacitor which has knocked out the RF alignment. I have now put the radio to one side whilst I decide what to to with it. Yes its a nice looking radio but the chassis it not the best of designs and leaves a lot to be desired. __________________ Simon BVWS member