Roberts R505 - UK Vintage Radio Repair and Restoration Discussion Forum

jayzedkay · 19th May 2009, 11:28 am

Hi, I have just picked up a Roberts R505 that is in need of some attention internally, but quite nice externally.

The 'speaker isn't working, so where can I get a replacement for this? Secondly, the wafer switch is badly oxidised, I've cleaned it best as I could and tests OK (continuity/resistance), but I'm thinking of just replacing it with a modern equivalent as it's still unpredictable.

Also the vol/tone pots aren't reliable either, again attempted to clean with switch cleaner, but they are still dodgy. Again, any pointers to suitable replacements, or is it simply a browse through RS/Farnel or someone like that?

I read a back thread on cleaning the pots, but mine have four tiny rivets holding the carbon tracked back onto metal fronts? don't think they'd go back together reliably? Seems more trouble to clean/refurbish than replace?

Can anyone point me to where I can get a circuit diagram for it too?

Thanks in advance for any info/help on the matter.

Steve_P · 19th May 2009, 11:43 am

The manual is available up top there.

The speaker - well it's 4 ohm and maybe an advert on here? Or look around places like Farnell. How do you know it's the speaker though...?

The wavechange switch - just clean and retension it and it'll be fine. With the pots, spray down the front and operate fast.

Cheers,

Steve P.

jayzedkay · 19th May 2009, 1:04 pm

hi steve,

thanks for the prompt reply. i put the speaker on a signal generator and got nothing from it at all. so i clipped the speaker wires from the unit to a pc speaker set up and got some audio.

just had a nose at maplins upto now at speakers

you mention 'retension' the wafer switch? do you mean the pincer contacts? if so how do i do that without trashing them.

i think i have some other issues. the unit is drawing very little current. i read a back thread about quiescent current and surge current on turn on. my units drawing about 10mA when switched on, think it should be more than that? but i'll look into that when i have some reliable at switch on.

cheers.

Steve_P · 19th May 2009, 4:32 pm

Get the thing working first. Then do any adjustments like Quiescent Current.

Be very careful with the Wavechange Switch. Get a pair of fine pliers and gently squeee.

Cheers,

Steve P.

G0PKH - Pete · 19th May 2009, 4:47 pm

Would a signal generator provide enough output to operate a low impedance speaker ?

Most PC Speakers accept line level audio too.

Before binning the speaker I would be inclined to check the voice coil for some continuity. If you have no meter. Try connecting a 1.5V cell across the voice coil and listening for the click .

Just thoughts of course

Pete

AlanBeckett · 19th May 2009, 5:06 pm

Pete,
Depends. My old Advance will give you > half a Watt into 5 Ohms.
Alan

jayzedkay · 20th May 2009, 11:10 am

Thanks for the replies guys; 'speaker definately shot.

I got a compatible replacement. The unit worked, but was very very quite. I downloaded the service data sheet and went through the voltages. Circuit voltages seemed ok, maybe slightly out. I did what I could w.r.t injecting signals and checking etc. Discovered the vol pot was not good. I replaced the vol and tone pots and it is now working fine, nice and loud, good tone; as I expected in the first place.

I need to source some small shaft pots, the ones fitted are 6mm diameter. They'll do as interim, but it'd be good to get the original knobs back on. Been through Farnell and RS; everything is 6mm.

19th May 2009, 11:28 am	#1
jayzedkay Retired Dormant Member Join Date: May 2009 Location: West Yorkshire Posts: 3	Roberts R505 Hi, I have just picked up a Roberts R505 that is in need of some attention internally, but quite nice externally. The 'speaker isn't working, so where can I get a replacement for this? Secondly, the wafer switch is badly oxidised, I've cleaned it best as I could and tests OK (continuity/resistance), but I'm thinking of just replacing it with a modern equivalent as it's still unpredictable. Also the vol/tone pots aren't reliable either, again attempted to clean with switch cleaner, but they are still dodgy. Again, any pointers to suitable replacements, or is it simply a browse through RS/Farnel or someone like that? I read a back thread on cleaning the pots, but mine have four tiny rivets holding the carbon tracked back onto metal fronts? don't think they'd go back together reliably? Seems more trouble to clean/refurbish than replace? Can anyone point me to where I can get a circuit diagram for it too? Thanks in advance for any info/help on the matter. Last edited by Darren-UK; 19th May 2009 at 11:33 am. Reason: FSK problem fixed and paragraphed.

19th May 2009, 11:43 am	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Roberts R505 The manual is available up top there. The speaker - well it's 4 ohm and maybe an advert on here? Or look around places like Farnell. How do you know it's the speaker though...? The wavechange switch - just clean and retension it and it'll be fine. With the pots, spray down the front and operate fast. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

19th May 2009, 1:04 pm	#3
jayzedkay Retired Dormant Member Join Date: May 2009 Location: West Yorkshire Posts: 3	Re: Roberts R505 hi steve, thanks for the prompt reply. i put the speaker on a signal generator and got nothing from it at all. so i clipped the speaker wires from the unit to a pc speaker set up and got some audio. just had a nose at maplins upto now at speakers you mention 'retension' the wafer switch? do you mean the pincer contacts? if so how do i do that without trashing them. i think i have some other issues. the unit is drawing very little current. i read a back thread about quiescent current and surge current on turn on. my units drawing about 10mA when switched on, think it should be more than that? but i'll look into that when i have some reliable at switch on. cheers.

19th May 2009, 4:32 pm	#4
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Roberts R505 Get the thing working first. Then do any adjustments like Quiescent Current. Be very careful with the Wavechange Switch. Get a pair of fine pliers and gently squeee. Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

19th May 2009, 4:47 pm	#5
G0PKH - Pete Retired Dormant Member Join Date: Aug 2003 Location: Stansted Essex Posts: 263	Re: Roberts R505 Would a signal generator provide enough output to operate a low impedance speaker ? Most PC Speakers accept line level audio too. Before binning the speaker I would be inclined to check the voice coil for some continuity. If you have no meter. Try connecting a 1.5V cell across the voice coil and listening for the click . Just thoughts of course Pete

19th May 2009, 5:06 pm	#6
AlanBeckett Rest in Peace Join Date: Dec 2008 Location: Burton upon Trent, East Staffordshire, UK. Posts: 1,686	Re: Roberts R505 Pete, Depends. My old Advance will give you > half a Watt into 5 Ohms. Alan

20th May 2009, 11:10 am	#7
jayzedkay Retired Dormant Member Join Date: May 2009 Location: West Yorkshire Posts: 3	Re: Roberts R505 Thanks for the replies guys; 'speaker definately shot. I got a compatible replacement. The unit worked, but was very very quite. I downloaded the service data sheet and went through the voltages. Circuit voltages seemed ok, maybe slightly out. I did what I could w.r.t injecting signals and checking etc. Discovered the vol pot was not good. I replaced the vol and tone pots and it is now working fine, nice and loud, good tone; as I expected in the first place. I need to source some small shaft pots, the ones fitted are 6mm diameter. They'll do as interim, but it'd be good to get the original knobs back on. Been through Farnell and RS; everything is 6mm.