Roberts R707

[mhennessy]

Hi all,

Many of you will know the Roberts R707. It was the flagship model for many years - this example is from 1973, so roughly mid-way in the run. Thanks are due to Skywave for finding me this set

This model has been well covered here before, but this example is slightly unusual because it has a "chunky", heavily grained Rexine covering, and slightly lighter teak side panels. Normally, the Rexine is much smoother, and the sides are a shade or two darker. Personally, I prefer this.

The cabinet:

A quick check showed that the set appeared to work, albeit with some intermittency, so I put the chassis to one side to work on the case. Just 3 screws release the chassis, then you have to remove the DC input connector, the loudspeaker and the battery carrier. Before I do anything, I give the set a good clean with foam cleanser and scrub the Rexine and grill with a nail brush to make sure there are no unpleasant surprises.

These sets are rather challenging to restore well. So much depends on what you have as a starting point, and there's a degree of luck involved as well. The main problem is the grille, which is pressed/expanded aluminium. It's soft, so picks up scratches and dents really easily.

You might think that the dents can only happen in the area of the loudspeaker cut-out, so it's a simple matter to push the dents out from inside. Not so! Roberts inexplicably routed out a recess either side of the loudspeaker aperture, and this is invariably where the dents gather. OK, so we need to remove the grille and hammer it flat. Yes, but the grille is glued on at the factory. Whether you can remove it in one piece without making it worse is a matter of luck - and in this case, luck was on my side.

Step one is to find a suitable piece of wood, and cut it to size - then you can place the grille onto it. The edges of the grille are folded down, which is why the timber needs to be the right size. To get the dents out, a combination of rolling and hitting is required - a wall-paper roller is a good tool for this. Of course, it will never be perfect because the material has stretched on impact, but it can be reasonable with patience.

The flattened grille needs to be glued back in place otherwise it won't be flat. For this, I used some incredibly strong double-sided tape - I was worried that any glue might seep through the holes in the grille. Of course, it will never be 100% flat in the area of the loudspeaker. I did contemplate installing a couple of thin strips of birch ply to give the grille something to sit against, but my woodwork tools are currently buried under old radios. Maybe next time...

Before glueing back on, the side cheeks need rubbing down. Remove the handle and DC input trim, and then unhook the grey piping and fold it down out of the way. I start with 240 grit unless it's really bad - luckily, these sets were oiled from new, so there's no varnish or lacquer to remove first. After steaming out any dents and dings, 240 is followed by 320, which is followed by Danish Oil.

After 3 coats, the cabinet is given another clean with foam cleaner to remove all the dust (and evidence of a previous battery leak). Then the cleaned up handle and badge can be reapplied. The rear panel needed attention; these are thin hardboard covered in Rexine and with a layer of thick black card glued to the inside - this invariably needs glueing back in place. Finally, the trim around the DC input connector can be cleaned with metal polish before being put back in place.


The chassis:

Remove the knobs, the strips at the top and bottom, then the scale. You have to unsolder connections to the sockets first, which is a pain. Then the scale can be cleaned, which means several rub-downs with metal polish to remove the scratches. I learned a while back to leave the sockets attached to the panel, otherwise the panel will crack when you lever off the securing star-washers. Compared to Hacker, these panels are really thin, and pick up scratches easily. Inevitably. the metal polish leaves residues around the sockets, so you'll need to take the time to remove these with a soft cloth or brush.

The tuning had some "dead" spots caused by worn teeth, so I carefully swapped the gears from a scrap set. That was easier said than done, but well worth it. Obviously, lubricate everything that moves while it's all apart. And check that the rubber grommets between tuner and chassis are in good condition, otherwise the tuning spindle leans to one side...

Paying closer attention to the chassis, it was working well on FM and SW, but dead on MW and LW. The oscillator wasn't. I cleaned the switch bank several times, but no joy, so decided to dive into the module. I discovered that someone had been here before me, and had cut the PCB tracks to the screen connections of the AF115s. However, after a while, the tin whiskers reach more than one electrode, and cause all sorts of strange behaviour. So I blasted them away and reinstalled them, carefully bridging the cut tracks with fine TCW. No, I didn't convert to silicon on this occasion...

When it came to reinstalling the connections between the main PCB and the switchboard, I decided to start again. This resulted in a much neater job than normal, and in many ways was easier than the usual trick of bending the board out of the way once enough of the wires had been unsoldered. And thankfully, the module worked perfectly - clearly the leakage caused by the whiskers in the first IF transistor were enough to stop it oscillating at lower frequencies...

After a line-up (audio and RF, IF was fine), the chassis was reassembled. But the loudspeaker, battery tray and side brackets were damaged by a previous battery leak - time to raid my spares supply. Luckily, I have a fair few of these sets - shame they're all scappers really... I also took the time to neatly twist all the wires between the chassis and loudspeaker, DC input socket and battery tray. It's worth making sure the connections at the input socket are neat, otherwise the battery will foul them...

Next, give the knobs a bath, and polish the metal bits. I went through my stocks of scrap R707s to find the best set - these are vulnerable designs that pick up scratches or dents easily, and the "brights" frequently fall off.

The final job was to replace the aerial - these are fragile and always kinked or broken. Some people can fix them; I can't! Luckily, I discovered 2 brand new aerials in a BBC local radio workshop, and it's been some years since we last used these sets in anger!

Performance:

These aren't bad sets. Quite sensitive on FM, and tune to 104MHz, unlike many sets of the period. The AFC action isn't very good, and the switch is back to front - press to switch AFC off! Not bad on AM either, although not as good as a Hacker. Strangely, when you switch to LW, a 100K resistor is added in series with the audio feed, so it's quieter than the other bands. No-doubt there was a good reason for this...

The sound is pretty good, I have to concede. Not as full-bodied as a Hacker, and it's brighter when you turn the treble up. From the diagram, it looks like they might not have fully implemented the FM de-emphasis (must measure it), but with the treble full up, the treble is ear-splitting. Some people like that, of course. The bass is reasonable, but boomy with the bass at full. It's a small loudspeaker, and there is a lot of bass boost available, so the amplifier can run out of steam if you're not careful. But, of all the Roberts sets I've got, it's probably the best of the bunch. and a welcome addition to my "restored" pile

I didn't take any in-progress pictures, but will add some to this thread with the next set I tackle (father-in-law wants one). For now, here are the "after" pictures. Enjoy

Thanks for reading,

Mark

[Jonster]

Lovely sets those! I have three of them; one fully working and two dead ones with cosmetic issues. Yours might spur me on to finish making one good one out of the two faulty ones I have here.

[Nickthedentist]

Fascinating write-up, Mark.

I hadn't realised that the grilles were so vulnerable. My set is mint, even in the speaker grille department, so I'll treat it with even more respect now.

Mine came from a relative who told me his had been issued to his department (DHS?) as part of a flood warning system by the GLC in the early 1970s (pre-Thames Barrier days, of course). A bit too sophisticated for that, you would have thought. I understand that it was never actually used, just stored in a locked cupboard.

I was interested to hear that they were used in the BBC too - to monitor transmissions?

From what I've read in the past, and what you say, I get the impression that they're not quite as good as the better Hackers in many respects, which is probably why I've never found them very appealing. But still a lovely radio in real terms.

Nick.

[mhennessy]

Thanks for the comments

Yes, take care of your grille. That's always been the biggest weak point on a Roberts - the later stripy ones are even worse - it's basically impossible to flatten one of those. They don't come away from the set easily, and the black stripes can come off with foam cleanser. I must admit that although my grill looks good in the photos above, in certain lights and certain angles, you can see issues. Not bad for a first attempt, but I will revisit it later once I have more experience with these...

I much prefer Hackers from the build quality and serviceability point of view, and they have the edge in performance as well. The R707 isn't bad though

These were very common in local radio - typically used in newsrooms and offices (although most of what people wanted to hear would have been available via the "ringmain selector"). Engineers had them too, and would use them for a variety of purposes - for example, as part of a pre-OB reccy, one of these would be taken out to ensure the off-air signal was good enough for cue purposes. As it happens, I have a pair of R747s sat on the desk here, ex Radio Manchester - they are really beat up, and the chances of producing one from the two are below zero - both have PO sockets mounted on the top panels (obscuring the Royal Warrants - the shame!), both have torn Rexine, badly scratched and dented grills, only one good aerial, no tuning knobs, badly dented sides. But they both work, and would be fine for a grubby shed or garage. Nothing leads an easy life in the BBC

All the best,

Mark

[ThePillenwerfer]

Those ex-Beeb ones sound good. Nice and usable but no fear of damaging them plus a bit of history. They were probably the last decent-looking ones they made.

Good work on the 707.

- Joe

[Mark the Mender]

Nice one Mark, nice to see a transistor set so well restored and written up.

cheers Mark

[mark pirate]

You have done a good job with the speaker grille.

Mark

[GJR 11L]

Nice sets these Mark, the only ones I've seen with that thicker, more interesting formed vinyl covering are my late ones with the stripey grilles and the cast aluminium dial plate fastening strips with a row of station markers. Every one of my earlier sets (non-stripey grille) has the flatter, Rexine covering so what you have there appears to be quite an oddity.

Were it not from 1973, so way too early for the striped grille, I'd have assumed that it would be a newer cabinet using the earlier grille, most probably that way from the factory.

Nice work too and to those who haven't heard one, do have a listen if you get a shot. They're lovely, especially when neatly restored like this example.

[howard]

Well done Mark

I hope those AF11* in the IF module last OK, we always replace them on sight with AF12* equivalents for peace of mind ....

The R707 was definitely the best transistor radio built by Roberts and IMHO complement the Hacker sets of the time really well. They do sound different to Hackers but I like their sound quality, they are more laid back sounding and classical music comes over really well.

Howard

[mhennessy]

Hi Both,

Thanks for your comments

Regarding the age, I'm going by a date-code sticker on the IF module - I assume that it's original to the case, but can't be 100% sure, of course. The serial number is 79264. I've got another scrap set with chunky Rexine, and that is 78966.

Just had a look in the Roberts database on Paul's Yahoo site to see if there are any clues. I note a reference to a post September 1972 scale (61235) and another mentioning frequencies (68594), but all my sets have the same scale (in metres) and cover a range of 10022 to 79262. The earliest one has a central badge and plain buttons. I note that there aren't too many 70,000 sets in the database, and the latest is 80378, so my one is indeed very late.

As for the extruded aluminium strips, I've just found a couple in my spares box, and I think these belong to 78966, but can't be sure. I know that they didn't come with 79264.

Perhaps I'll have to do a historical survey (like I'm currently doing with Hunters)

Regarding the AF11x issue, I must admit that I'd planned to use AF12x replacements, but I haven't got any, and they are quite expensive to buy. I have a number of Hacker sets that have acquired AF127s, and because the access is so much better in a Hacker, I'd planned to put AF117s in the Hackers and save up the AF127s for the Mullard modules - seemed like a good plan, but (a) I haven't got around to it yet, (b) the AF127 doesn't perform as well at HF - in theory at least...

So far, my success rate for treatment has been nearly 100%, and there have been no re-occurrences yet. I know it's inevitable that they grow again, but hope to find some AF12x stock before then.

I haven't tried silicon replacements yet. I would be tempted to experiment, if only the physical access wasn't so terrible. I plan to modify a scrap chassis so that the switchboard is no longer in the way, but need to be sure increased wire lengths don't upset the operation of the set...

About the sound quality, it's difficult to discuss because the tone controls have so much range, and you can alter the character quite significantly - it's entirely possible that you hear something I don't because you are using different settings. Certainly, I'm not sure that "laid back" springs to mind - you do have to be careful with the treble control! I must admit, there are times when I wish some of the Hacker sets had a bit more range with their tone controls. I'm working on a Sovereign II at the moment, and will put them side by side when it's finished.

Thanks once again for the feedback

Mark

[GJR 11L]

Mark, for your interest, the serial number of my late, black-striped grille R707 is 77756, it also has station markers that slide on the aluminium edging to the rear of the scale which look to me to be the type also found on R505s.
When I went to check just now, I was almost sure that the set's serial number was in the high 80000s, imagine my surprise on finding that it's actually lower than yours, yet the set I have is one of those whose full history is known to me and it was supplied new with the striped grille and those other detail differences.

None of the above however should affect the discussion around your beautifully restored set which is, after all, the purpose of this thread. My apologies to the mods and to other members for going a little o/t.

[mhennessy]

Hi John,

That's really interesting, given that I have two sets that are later than yours, yet both have the old grill. The evidence suggests that neither of my two sets have the original chassis and/or rear panels. I'll ask Paul King about this in due course...

Personally, I'm very happy to discuss these details of the model, and happy to leave it to the mods to decide if the thread should be split if it develops further

All the best,

Mark