Repairing a Roberts R707-timeconsuming or what?

['LIVEWIRE?']

I've recently replaced the three AF11x transistors in the RF/IF Module of a 707. Hadn't done one for quite a while. It's still not reassembled fully and I must have spent 3 or 4 hours on thething! As most will know, to remove the module, the switch bank has to be removed first, which involves desoldering at least some of the links between it and the main board, many of 'em short bare wires. If there is a quicker way then I don't know of one, does anyone??

[G6Tanuki]

Alas, you just have to put up with it... the crazy hand-stitched wiring is just one of the 'uniquely British' features of these radios.

Had they been production-engineered by someone like Sony or Hitachi there would have been neat ribbon-cables with keyed plugs/sockets at either end to interconnect the different boards.

All I can suggest to anyone else doing this job is 'Take lots of photos as you unsolder things'.

[mark pirate]

Having done this job in the past, I certainly agree that it is a pig to do!
I really dislike those modules, earlier Roberts sets were a pleasure to work on, but these sets do sound very nice though, especially on FM.

Mark

[Tim]

It has been a few years since I did our charity shop find 707 for SWMBO, but ISTR it was not necessary to remove ALL the wiring from the switch bank, in order for it to swing far enough out of the way. I also seem to remember it took a whole morning to do! Worth it though, and set has been working ever since.

[Herald1360]

Originally Posted by G6Tanuki

Had they been production-engineered by someone like Sony or Hitachi there would have been neat ribbon-cables with keyed plugs/sockets at either end to interconnect the different boards.

Did such techniques exist in the '60s?

Even so, it would have been easy enough to use Mullard Modules in an accessible way.

[paulsherwin]

I don't think there was any awareness of the tin whisker problem when these radios were designed, and the modules were expected to last indefinitely. Service access was simply not a consideration.

[flyingtech55]

Certainly when failure did occur, you were not expected to repair the modules. You were meant to renew them as a spare part. I remember doing this in the workshop when we were a Roberts dealer. Even then though the modules were expensive and the job was fiddly. The modules became unobtainable after some time and Roberts sent out a sheet which explained how to replace the transistors with AF12x but you were supposed to change a couple of passive components as well. I think it was the emitter resistors otherwise the module could become unstable; a 680 ohm springs to mind. The main problem with this was that the print was/is really thin and spidery and it's very easy to damage it. As I say, they were never meant to be repaired in the first place. It's all a long time ago and many things have passed through my forgetery in the mean time.

HTH

TimR

['LIVEWIRE?']

To cap it all, either there is another fault in the module, or I have connected one of the AF12x transistors incorrectly! After carefully reconnecting the switch bank, refitting the scale & knobs, etc., I powered up the R707 and switched on, only to be greeted by silence on all wavebands. Earlier this evening I disconnected as many of the wires from the switch bank as were required to be able to move it. Next I'll probably have to remove and open the module again. Doh!!!!

[G6Tanuki]

Originally Posted by Herald1360

Did such techniques exist in the '60s?

I have a small 1967 Toshiba AM/FM radio, from when they were boasting [IC|FET] on the front - and its three PCBs [one for the FM strip, a common AM/FM intermediate panel, and an audio-board which contains the aforementioned Integrated Circuit] are all interconnected by a rather elegantly crafted set of flat printed-flexible harnesses with plugs/sockets each end.

I can separate out the different boards in a minute or so.

[Herald1360]

Oh all right then

[Tim]

To cap it all, either there is another fault in the module, or I have connected one of the AF12x transistors incorrectly! After carefully reconnecting the switch bank, refitting the scale & knobs, etc., I powered up the R707 and switched on, only to be greeted by silence on all wavebands. Earlier this evening I disconnected as many of the wires from the switch bank as were required to be able to move it. Next I'll probably have to remove and open the module again. Doh!!!!

Oh No! I dread that happening, but have been lucky up to now, all mine have so far worked first time(Lets hope Murphy's not reading reading this...) I always test it before properly reassembling the set. Is it possible to try the module temporarily on flying leads?

[Mike Noble]

After searching this site I found a thread which indicated it was possible to remove the module without taking out the switch assembly. As my R707 had recently stopped working on AM and was quiet on FM I thought I would try.
I found that it is possible to remove the module and leave the switch assembly in place. Just removing the connections to switch assembly that are in the way of the module connections gives enough access.
It took 2 1/2 hours to repair but as this is the first attempt it's not too long. The radio is now working great. One faulty transistor but all three replaced. It really was no worse than an R600 module.
Hope this helps anyone thinking about trying this repair.
Mike

[wireless_john]

I've just started this! I have an R707 that's OK on FM, but dead otherwise. Spent quite a bit of time switch cleaning and poking around for dry joints but it's looking like it's going to have to have the AF11xs replaced. I think I will remove the switch module even though it looks as if it's going to take a while. Removing the IF module with the switch bank in place brings to mind the expression ' wallpapering the hall through the letterbox!'

John

[mark pirate]

Good luck John, be prepared for it to take around three hours.
Having done one before I can honestly say that it is a not a nice job, but my set is still working well.
I have another very nice example that is also dead on AM, but as FM is fine I can't see me taking it on in the near future...

Mark

[wireless_john]

Thanks Mark! For the benefit of those who haven't seen or attempted this - here's a few photographs of what's involved.

The small red pcb is the switch bank which has to be removed from the larger brown pcb underneath. This then allows access to the connections to the IF module on the other side of the brown pcb. Rats nest!

[crackle]

What you need are some trained nanites with miniature solder suckers and soldering irons.
Mike

[mark pirate]

Those photos really bring back just what a pain it was to get the module out
The module itself was not too bad to work on, but I did dig out my little Antex soldering iron rather than the 45w Weller!

Mark

[wireless_john]

I have had the lid off a module before from an Ekco 455. That turned out to be dodgy soldering and a duff electrolytic so I never did change the AF117s. It's still working and should the need arise, much easier to get at.

[Radiocruncher]

I've done a couple of LP1171 modules recently. The first one I just swapped the transistors for AF127's, put it back in and it worked perfectly. The second was a spare so didn't take long but this time I decided to pop the electrolytics out and test them. One was shot. I believe it was a 2.5uf from memory. I'm now wondering whether to pull the module back out of the R600 and check the caps. I did videos on this. https://youtu.be/AIwCON4x3yU
https://youtu.be/djT-mMBy2cI
I am going to be doing a Roberts R707 module soon when I get the time.

Graham

[Nuvistor]

We were a Roberts agent and the modules occasionally had to be replaced, this was in tbe 70's when it was a module swap, much cheaper for the customer than repairing. What gets to me is I would think nothing of stripping the set down and sorting them out.
I don't think I could do it now.
Frank