1985 Roberts R900 Harpenden 1/10/06 £8 - UK Vintage Radio Repair and Restoration Discussion Forum

howard · 2nd Oct 2006, 4:21 pm

Hello,

I bought a load of radios at Harpenden yesterday and this Roberts R900 I won in the auction for £8. This is an early R900 with the raised grille and with the Roberts badge at the bottom. It didn't take a lot of effort to restore so I will be brief.

This R900 was working, with an extremely noisy volume control, but worst of all it buzzed horribly

I pressed down on the grille and then the perspex dial and it was the dial that was making all the noise.

These come apart quite easily, remove the handle (press down and pull handle sides away from pivot screws underneath), take off the bottom, remove the bottom aerial screw, the two screws on the sides above the handle pivot screws, pull off the two loudspeaker clips and a little white clip that fits into the power supply, give the underside of the top panel a shove with a long screwdriver and the chassis will emerge from the top. There is one more power clip to pull off on the PCB before the chassis is freed from the case. To remove the perspex dial, pull off the knobs (doesnt require much effort !), undo the circular earphone securing nut, pull off the two trims and off it comes. I then cleaned the case, the handle, dial, knobs and trims in upholstery cleaner and toothbrush.

I squirted some switch cleaner into the volume and both tone pots and into the off/on and waveband switches, and to stop the buzzing, stuck thin strips of electrical tape along the top of the chassis on which the perspex dial rests. I then reassembled the set, tested it and it was working well and the buzzing was gone

This is nowhere near as well built (or interesting) a radio as Roberts earlier flagship model the R707, with its MDF case and hard vinyl cover, a small PCB with a couple of ICs on it, and its little flimsy potentiometers. When powered via its inboard mains transformer, it hums a bit but not seriously so. It performs well though, picking up everthing on all wavebands and now that the buzzing has stopped, it will comfortably play very loud and its sound quality is very good

This R900 is almost unmarked and methinks was a bargain for £8

Howard

Paul_RK · 2nd Oct 2006, 5:24 pm

Hello Howard,

A very nice example you have there now

The R900 came as a welcome surprise to me, as when I bought my own (a later version) I wasn't expecting it to be nearly so heavy or to sound nearly so good. The loudspeakers used by Roberts in particular models seem to have varied somewhat about this time. The R900's immediate predecessor was the R800, and my R800 has a small and lightweight plastic-framed 'speaker that's a bit of a horror. Just about good enough for the little Rambler, but sorely out of place in a larger portable. My R900's unit is at the other end of the scale with a 2.5" diameter magnet - that, and a substantial mains transformer, must contribute quite a proportion of the set's weight.

Regards,
Paul

howard · 2nd Oct 2006, 8:37 pm

Hello Paul,

I am pleased with this R900

The R800 is not a good sounding radio, its loudspeaker is much too small ! The R707 is the only Roberts radio which sounds as good as, indeed better than, this one. The transformer hum has gone away now too

Howard

Stewart · 2nd Oct 2006, 10:51 pm

I agree that the R900 is one of the best sounding Roberts sets - on mains it can push out 4Wrms which is quite respectable.

I dont know why, but the offset volume & tuning controls have always offended my eye slightly but the sound more than makes up for it! As has been said the internal construction isn't up to the earlier standard but at least they didn't cut corners with that speaker. They obviously learnt a lesson with the R800!

Is your set an early 900 though Howard? I always took the version with the flat front profile to be the original version with the profiled front face coming later? I'd be interested to know...

howard · 3rd Oct 2006, 12:11 pm

Hello Stewart,

I now have four R900s, all acquired very cheaply (two just needing the on/off switch sorted, a simple repair) and their serial numbers are as follows -

Red raised grille 10432
Blue raised grille 11938
Grey cloth flat grille 21008
Blue flock flat grille 25550

I don't think Roberts restarted the serial number from zero when the case design was revised so the sets with the raised grilles are the earlier ones.

And here are three of them, all nice, all sound excellent, the fourth one needs a new volume pot which Roberts no longer stock and as I have no idea where to get a replacement I fear it will be broken for spares

Howard

Stewart · 3rd Oct 2006, 12:58 pm

That's interesting Howard....must confess I'd not bothered to check up on the searial numbers of my sets.

The later cabinet styling is much more in line with all the predecessors' look, so I just assumed that it came first!

howard · 3rd Oct 2006, 1:11 pm

Hello Stewart,

I thought exactly the same ! One other clue that the sets with the raised grilles are earlier is that the earliest one here, the red one, has the old small jack plug socket for an earphone, the later blue one and the sets with the flat grilles take a larger jack plug.

Howard

Stewart · 3rd Oct 2006, 10:01 pm

Howard, your mention of jack sockets reminds me of a supplement to the Roberts service manual for this set!

I qoute:

1. First production sets [sic] were fitted with a 3.5mm jack socket.

2. S/no. 7001 up [sic] C66 added 10nF ceramic added to IC3, pins 2-4.

3. S/no. 12001 up changed to 6.35mm with series resistors to limit output.

(4 & 5 a raft of circuit changes)

6. S/no. 14379-14902 inclusive do NOT incorporate 3

7. S/no. 17001 up [sic] more circuit changes.

8. S/no. 26726 up loudspeaker change (part no.s given and implication that roll surround type no longer fitted.

The cover of the original issue manual shows a picture of the raised front - rather confirming that this came first. Interesting to note that the supplement doesn't mention a change in cabinet!

2nd Oct 2006, 4:21 pm	#1
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	1985 Roberts R900 Harpenden 1/10/06 £8 Hello, I bought a load of radios at Harpenden yesterday and this Roberts R900 I won in the auction for £8. This is an early R900 with the raised grille and with the Roberts badge at the bottom. It didn't take a lot of effort to restore so I will be brief. This R900 was working, with an extremely noisy volume control, but worst of all it buzzed horribly I pressed down on the grille and then the perspex dial and it was the dial that was making all the noise. These come apart quite easily, remove the handle (press down and pull handle sides away from pivot screws underneath), take off the bottom, remove the bottom aerial screw, the two screws on the sides above the handle pivot screws, pull off the two loudspeaker clips and a little white clip that fits into the power supply, give the underside of the top panel a shove with a long screwdriver and the chassis will emerge from the top. There is one more power clip to pull off on the PCB before the chassis is freed from the case. To remove the perspex dial, pull off the knobs (doesnt require much effort !), undo the circular earphone securing nut, pull off the two trims and off it comes. I then cleaned the case, the handle, dial, knobs and trims in upholstery cleaner and toothbrush. I squirted some switch cleaner into the volume and both tone pots and into the off/on and waveband switches, and to stop the buzzing, stuck thin strips of electrical tape along the top of the chassis on which the perspex dial rests. I then reassembled the set, tested it and it was working well and the buzzing was gone This is nowhere near as well built (or interesting) a radio as Roberts earlier flagship model the R707, with its MDF case and hard vinyl cover, a small PCB with a couple of ICs on it, and its little flimsy potentiometers. When powered via its inboard mains transformer, it hums a bit but not seriously so. It performs well though, picking up everthing on all wavebands and now that the buzzing has stopped, it will comfortably play very loud and its sound quality is very good This R900 is almost unmarked and methinks was a bargain for £8 Howard Attached Thumbnails Last edited by howard; 2nd Oct 2006 at 4:32 pm.

2nd Oct 2006, 5:24 pm	#2
Paul_RK Dekatron Join Date: Nov 2003 Location: Fakenham, Norfolk, UK. Posts: 4,255	Re: 1985 Roberts R900 Harpenden 1/10/06 £8 Hello Howard, A very nice example you have there now The R900 came as a welcome surprise to me, as when I bought my own (a later version) I wasn't expecting it to be nearly so heavy or to sound nearly so good. The loudspeakers used by Roberts in particular models seem to have varied somewhat about this time. The R900's immediate predecessor was the R800, and my R800 has a small and lightweight plastic-framed 'speaker that's a bit of a horror. Just about good enough for the little Rambler, but sorely out of place in a larger portable. My R900's unit is at the other end of the scale with a 2.5" diameter magnet - that, and a substantial mains transformer, must contribute quite a proportion of the set's weight. Regards, Paul

2nd Oct 2006, 8:37 pm	#3
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	Re: 1985 Roberts R900 Harpenden 1/10/06 £8 Hello Paul, I am pleased with this R900 The R800 is not a good sounding radio, its loudspeaker is much too small ! The R707 is the only Roberts radio which sounds as good as, indeed better than, this one. The transformer hum has gone away now too Howard

2nd Oct 2006, 10:51 pm	#4
Stewart Retired Dormant Member Join Date: Jul 2003 Location: N.E. Surrey, UK. Posts: 361	Re: 1985 Roberts R900 Harpenden 1/10/06 £8 I agree that the R900 is one of the best sounding Roberts sets - on mains it can push out 4Wrms which is quite respectable. I dont know why, but the offset volume & tuning controls have always offended my eye slightly but the sound more than makes up for it! As has been said the internal construction isn't up to the earlier standard but at least they didn't cut corners with that speaker. They obviously learnt a lesson with the R800! Is your set an early 900 though Howard? I always took the version with the flat front profile to be the original version with the profiled front face coming later? I'd be interested to know...

3rd Oct 2006, 12:11 pm	#5
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	Re: 1985 Roberts R900 Harpenden 1/10/06 £8 Hello Stewart, I now have four R900s, all acquired very cheaply (two just needing the on/off switch sorted, a simple repair) and their serial numbers are as follows - Red raised grille 10432 Blue raised grille 11938 Grey cloth flat grille 21008 Blue flock flat grille 25550 I don't think Roberts restarted the serial number from zero when the case design was revised so the sets with the raised grilles are the earlier ones. And here are three of them, all nice, all sound excellent, the fourth one needs a new volume pot which Roberts no longer stock and as I have no idea where to get a replacement I fear it will be broken for spares Howard Attached Thumbnails

3rd Oct 2006, 12:58 pm	#6
Stewart Retired Dormant Member Join Date: Jul 2003 Location: N.E. Surrey, UK. Posts: 361	Re: 1985 Roberts R900 Harpenden 1/10/06 £8 That's interesting Howard....must confess I'd not bothered to check up on the searial numbers of my sets. The later cabinet styling is much more in line with all the predecessors' look, so I just assumed that it came first!

3rd Oct 2006, 1:11 pm	#7
howard Nonode Join Date: May 2005 Location: Godalming, Surrey, UK. Posts: 2,593	Re: 1985 Roberts R900 Harpenden 1/10/06 £8 Hello Stewart, I thought exactly the same ! One other clue that the sets with the raised grilles are earlier is that the earliest one here, the red one, has the old small jack plug socket for an earphone, the later blue one and the sets with the flat grilles take a larger jack plug. Howard

3rd Oct 2006, 10:01 pm	#8
Stewart Retired Dormant Member Join Date: Jul 2003 Location: N.E. Surrey, UK. Posts: 361	Re: 1985 Roberts R900 Harpenden 1/10/06 £8 Howard, your mention of jack sockets reminds me of a supplement to the Roberts service manual for this set! I qoute: 1. First production sets [sic] were fitted with a 3.5mm jack socket. 2. S/no. 7001 up [sic] C66 added 10nF ceramic added to IC3, pins 2-4. 3. S/no. 12001 up changed to 6.35mm with series resistors to limit output. (4 & 5 a raft of circuit changes) 6. S/no. 14379-14902 inclusive do NOT incorporate 3 7. S/no. 17001 up [sic] more circuit changes. 8. S/no. 26726 up loudspeaker change (part no.s given and implication that roll surround type no longer fitted. The cover of the original issue manual shows a picture of the raised front - rather confirming that this came first. Interesting to note that the supplement doesn't mention a change in cabinet!