Roberts R700

[Rolytoad]

Hello all.

My wife recently gave me a vintage Roberts to tinker with. It is a Roberts r700. I see from other posts that this will be a swine to fix but am nothing if not brave. I would therefore be grateful to anyone who can email me a wiring diagram so that I have some basis to start from. I know it would seem foolish to embark on such a difficult task with no experience but the opportunities for learning are great and the expense small. Also if there is anyone out there willing to put up with aconstant litany of 'what do I do next?' questions I would be most grateful. Can anyone recomend a good book on the basics as well.

[Station X]

You can obtain the Service Sheet for this model by clicking on the link at the top right of this page.

[Rolytoad]

cheers Station x. I should have spotted that, my excuse was it was 4 in the morning. I am now in business and able to make a proper inspection etc

[Rolytoad]

I have managed to get some pops and whistles from the poor old beast. I imediately found a dry solder joint which I have sorted. However the previous owner has obviously had a play as there is nothing remotely like an inteligible radio signal. It did however pick up a car passing that had copper ht leads so not completely dead. Crackles like hell whenever the tuning knob is touched. I think I'll start by stripping down cleaning and reassembling this unit.

[Station X]

There's info on repairing transistor radios here:-

http://www.vintage-radio.com/repair-...tors-work.html

Don't forget that these radios contain the dreaded AF11x series transistors.

http://www.vintage-radio.com/repair-...or-faults.html

https://www.vintage-radio.net/forum/...ad.php?t=22356

[Darren-UK]

As Graham has implied above, don't assume the radio is duff because someone else has been in there previously. Roberts radios of this period suffered several faults; some of them we jokingly say Roberts included as standard, whilst the AF11x transistor nuisance is common to these and radios by many other manufacturers.

I note you've said the radio crackles badly when the tuning control is operated. This sounds like two or more fouling veins on the gang or a problem with excessive dirt/dust therein. You may just be lucky and find the crackling tuning problem is the cause of the other faults, but nonetheless be prepared to tackle the module and AF11x's because if that isn't where the problem currently lies, it will be sooner or later.

A search of the forums will provide much info on the R600/700/707 and their usual problems. There is also this index in our archives which may prove of some value.

[geofy]

Pops and crackles suggest that the AF11* are still working apart maybe from the oscillator stage.

Try sorting out the tuner before componding the fault with transistor swaps. Have the RF/IF transformers been played with, a signal generator would be useful here to see if the radio is aligned.

Geof

[Steve_P]

1: Clean wavechange switches and tuning cap. Straighten any vanes that look bent.
2: Inject a signal at the Volume Control and see if it gets out. (In your case it probably will.)
3: Switch to MW. Anything? If not, inject a signal of 470kHz at the base of TR6. If this does not get out, look at TR6, TR7 and TR8 and the associated area.
4: If it does get out, but no stations, try LW and check TR6 and Antenna Input circuit.
5: With AM ok, go to FM. Inject 10.7 kHz at Base of TR3. If this does not get out, go forward. TR3, 4 and 5 and the diodes MR4 and MR5.
6: If it does get out, look at TR1 and TR2.

Common Areas of trouble : AFIIx transistors, tuning vanes, wavechange buttons, wiring.

This set has 2 separate IF's, one for AM, one for FM. Yes, both can be faulty with these transistors. Quick fixes - Flick them: sometimes brings them back. Chop the screen leads. If you have to change them, you can fit AC12x's or take a silicon route with BF450's.

Read this lot - start here and keep pressing next:

http://www.vintage-radio.com/repair-...tors-work.html

Circuit diagram available here:

http://www.service-data.com/email/list/roberts.htm

Scroll down and there it will be. Should be in your in-box in seconds.

Cheers,

Steve P

[Rolytoad]

Ye Gods!
[does a wee victory dance]
I have done it. I have it working. Yippee.
I now have a great pair of r700's. Thanks everyone who helped me on my way. In a fit of rapture I also bought a r606 for £1 and was amazed at how different it was inside to the 'r700' . The r606 had a knackered volume / on offf switch but after stripping it down I managed to reassemble it correctly and get that going as well. My Roberts collection is now scattered throughout the house giving me great radio reception everywhere. I replaced the af114's in the first r700 for af125's which were tiny compared to the af114's. My advice to anyone doing this is have a good look at where the different feeds from the af114's are going to, then cut the wires. Don't try removing them intact, that way lies madness.Annecdotal advice; the r606 on off switch has three fixed wires leading to the circuit board. Check where they go and what terminals they attach to. Cut them, remove them, replace with flexible wires so you can EASILY replace and remove the switch. Why these are rigid in the orriginal is a mystery as the live feeds to the bottom of the switch are flexible wire.[shrugs]

[Colin]

.... I think you're hooked! ;-)

[Mike Phelan]

Well done. Now, all you need is a Hacker or three .....

[howard]

Well done Roly

The Roberts R700 once sorted is a good FM radio and it was Roberts very first FM radio. I should treat yourself to a Roberts R707 next, the model which followed on from this one as it's larger and a better built set, with SW, and sounds better too.

Howard