Roberts R900 on/off problem - UK Vintage Radio Repair and Restoration Discussion Forum

howard · 12th Sep 2005, 9:58 pm

Hello again,

Ive just acquired an R900 which works and sounds very good indeed.

However, it has a faulty on/off switch in that to get it to work one has to nudge the button a couple of times. I took the chassis out and took a look at the switches. All of them have a sort of small staple shaped piece of metal on the side which moves when the switch is operated and I think holds each switch in position. The one on the on/off switch has come loose and is flicking about and I suspect thats the problem.

Does anyone know if this is repairable, or will I have to obtain and fit a new or second hand rack of switches ?

Howard

Steve_P · 12th Sep 2005, 10:40 pm

Howard,

This is a common problem. The R900 is a Battery-Mains set and this is what killed the switch.

You have a number of options.

1: Empty a load of switch cleaner into the switch. This was done in some quarters and it had varying results.
2: Replace the Switch.
3: There is a mod for this which I cant find right now. Anyone...?

Regards,

Steve P.

howard · 12th Sep 2005, 10:55 pm

Thanks Steve,

Ive tried the first solution, I cleaned all the switches .... an improvement in as much as that the radio now works but the on/off problem persists.

Howard

Steve_P · 13th Sep 2005, 6:13 pm

It sometimes works. Ah well....

Well you'll have to change the switch. Sorry old boy but it's the only way. The mod, which I still can't find, is to stop this happening again - because of the Battery/Mains option on this`set.

I haven't done mine for reasons involving my arm, which is still dead.

Cheers,

Steve.

Heatercathodeshort · 13th Sep 2005, 6:43 pm

Hello Howard,
How strange you should come up with this problem the day after I posted a cure for this. See the thread on the R606MB!
The switch will have to be replaced as a complete unit unfortunately. The reason for the failure is due to a large 470uf capacitor that is mounted on the switch side of the set resulting on a massive surge and flash when the contact is made. I have attached a ROBERTS mod sheet. If you can't read it send me a PM and I will send at higher resolution. Regards,J OHN.

howard · 14th Sep 2005, 7:21 am

Hello John,

Thanks for the service sheet which Ive downloaded OK and the section relating to this radio with a late serial number 25550 is legible.

I did phone Roberts spares yesterday to see if they still had a replacement switch unit but sadly they sold out many many years ago

Still, it switches on OK usually, but when it doesnt I just need to nudge the button. Im wondering if its the same unit as fitted to many other Roberts radios cos then I can pinch one off a scrap radio.

I'd like to get this one working properly cos it sounds better than most Roberts radios.

Howard

peter_sol · 14th Sep 2005, 8:06 am

Hi.If you can obtain a similar swith from anywhere you can dismantle the faulty section in situ and replece the sliding contacts as these are what will have burnt away then parallell up the two sectins to increase the current handling.

I have don this many times as changing the switch is an almost impossible task

I hope this is of some help

Regards

Peter.

howard · 15th Sep 2005, 8:25 am

Hello Peter,

Thats very useful information, thank you. I fear that'll be a really fiddly job

I like this Roberts R900 very much, so I'll do it

Howard

howard · 29th Oct 2005, 9:07 pm

Hello,

Well Ive fixed the on/off switch on my Roberts R900 and also one on a Roberts RFM3 which turned up the other day with the same problem.
What I did was to take out the on/off switch slider, which was easy on these two, by removing the little clip (the one that moves around on top and goes click) simply by pulling back the return spring which covers the end of it and then lifting it off .... oh and I did hold onto the switch so that it didnt go flying off ! Perched on the slider are two small brass contacts which just lift off. I cleaned the insides of these by sliding a piece of wet and dry sandpaper between the contacts, pinched the sides of the contacts back together, put them back in the slider and then reassembled the switch after stretching the return switch slightly

And bingo, both radios now switch on and off perfectly

About 10 minutes work apiece ....

Howard

PS: Sometimes, Im told, these on/off switches have an unused pair of pins, if so and the above fix didnt work you could connect the unused pin to the dodgy pin on each side to overcome this problem.

howard · 29th Oct 2005, 10:59 pm

Quote:

Originally Posted by howard

after stretching the return switch slightly

Oops, I meant after stretching the return spring slightly .....

Howard

jim_beacon · 29th Oct 2005, 11:05 pm

Howard,

thanks for that, I have a R900 with the same symptoms, and it's fast approaching the top of the pile!

Jim.

12th Sep 2005, 9:58 pm	#1
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	Roberts R900 on/off problem Hello again, Ive just acquired an R900 which works and sounds very good indeed. However, it has a faulty on/off switch in that to get it to work one has to nudge the button a couple of times. I took the chassis out and took a look at the switches. All of them have a sort of small staple shaped piece of metal on the side which moves when the switch is operated and I think holds each switch in position. The one on the on/off switch has come loose and is flicking about and I suspect thats the problem. Does anyone know if this is repairable, or will I have to obtain and fit a new or second hand rack of switches ? Howard

12th Sep 2005, 10:40 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Roberts R900 on/off problem Howard, This is a common problem. The R900 is a Battery-Mains set and this is what killed the switch. You have a number of options. 1: Empty a load of switch cleaner into the switch. This was done in some quarters and it had varying results. 2: Replace the Switch. 3: There is a mod for this which I cant find right now. Anyone...? Regards, Steve P.

12th Sep 2005, 10:55 pm	#3
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	Re: Roberts R900 on/off problem Thanks Steve, Ive tried the first solution, I cleaned all the switches .... an improvement in as much as that the radio now works but the on/off problem persists. Howard

13th Sep 2005, 6:13 pm	#4
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Roberts R900 on/off problem It sometimes works. Ah well.... Well you'll have to change the switch. Sorry old boy but it's the only way. The mod, which I still can't find, is to stop this happening again - because of the Battery/Mains option on this`set. I haven't done mine for reasons involving my arm, which is still dead. Cheers, Steve.

13th Sep 2005, 6:43 pm	#5
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Roberts R900 on/off problem Hello Howard, How strange you should come up with this problem the day after I posted a cure for this. See the thread on the R606MB! The switch will have to be replaced as a complete unit unfortunately. The reason for the failure is due to a large 470uf capacitor that is mounted on the switch side of the set resulting on a massive surge and flash when the contact is made. I have attached a ROBERTS mod sheet. If you can't read it send me a PM and I will send at higher resolution. Regards,J OHN. Attached Thumbnails

14th Sep 2005, 7:21 am	#6
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	Re: Roberts R900 on/off problem Hello John, Thanks for the service sheet which Ive downloaded OK and the section relating to this radio with a late serial number 25550 is legible. I did phone Roberts spares yesterday to see if they still had a replacement switch unit but sadly they sold out many many years ago Still, it switches on OK usually, but when it doesnt I just need to nudge the button. Im wondering if its the same unit as fitted to many other Roberts radios cos then I can pinch one off a scrap radio. I'd like to get this one working properly cos it sounds better than most Roberts radios. Howard Last edited by howard; 14th Sep 2005 at 7:30 am.

14th Sep 2005, 8:06 am	#7
peter_sol Octode Join Date: Aug 2003 Location: Welwyn Garden City, Herts. UK. Posts: 1,906	Re: Roberts R900 on/off problem Hi.If you can obtain a similar swith from anywhere you can dismantle the faulty section in situ and replece the sliding contacts as these are what will have burnt away then parallell up the two sectins to increase the current handling. I have don this many times as changing the switch is an almost impossible task I hope this is of some help Regards Peter.

15th Sep 2005, 8:25 am	#8
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	Re: Roberts R900 on/off problem Hello Peter, Thats very useful information, thank you. I fear that'll be a really fiddly job I like this Roberts R900 very much, so I'll do it Howard

29th Oct 2005, 9:07 pm	#9
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	Re: Roberts R900 on/off problem Hello, Well Ive fixed the on/off switch on my Roberts R900 and also one on a Roberts RFM3 which turned up the other day with the same problem. What I did was to take out the on/off switch slider, which was easy on these two, by removing the little clip (the one that moves around on top and goes click) simply by pulling back the return spring which covers the end of it and then lifting it off .... oh and I did hold onto the switch so that it didnt go flying off ! Perched on the slider are two small brass contacts which just lift off. I cleaned the insides of these by sliding a piece of wet and dry sandpaper between the contacts, pinched the sides of the contacts back together, put them back in the slider and then reassembled the switch after stretching the return switch slightly And bingo, both radios now switch on and off perfectly About 10 minutes work apiece .... Howard PS: Sometimes, Im told, these on/off switches have an unused pair of pins, if so and the above fix didnt work you could connect the unused pin to the dodgy pin on each side to overcome this problem.

29th Oct 2005, 11:05 pm	#11
jim_beacon Retired Dormant Member Join Date: Mar 2003 Location: Bishop's Waltham, Hants, UK. Posts: 939	Re: Roberts R900 on/off problem Howard, thanks for that, I have a R900 with the same symptoms, and it's fast approaching the top of the pile! Jim.