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Old 1st Jun 2006, 8:45 pm   #1
shaun harris
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Default Dead Roberts R600

Hi,

I've got a Roberts R600 that has always worked fine up till now. It's been stored in a cupboard for a few months until today.

I got it out and put in a battery and nothing; no hiss crackle or anything. Has anyone out there got any ideas where I should start to look?

Any help or advice would be greatly appreciated.

Thanks, Shaun.

Last edited by Darren-UK; 20th Jul 2007 at 4:18 pm. Reason: General tidying.
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Old 1st Jun 2006, 9:10 pm   #2
Darren-UK
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Default Re: dead roberts R600

Hi Shaun,

If there is absolutely no noise of any description on any waveband, or not a pop, crackle or splutter from the on/off switch when you switch it on, it's unlikely to be a transistor fault. However, be aware that unfortunately this is yet another model which suffers from the AF117 nuisance ( a forum search will reveal discussions on this ). By what you've said, however, I suspect a power supply fault or a break in the circuit somewhere.

Before we move on, I'll briefly explain the transistor situation with this model. The Trader service data ( which probably differs from the Roberts data in respect of circuit description ) states the presence of eleven transistors. However, details are only given for six of these. The remaining five are hidden inside the FM tuning and IF modules; Roberts ( at the time ) advising that these modules only be replaced by their appointed service agents - hence no data on the servicing of modules is given. Inside these modules will be found the infamous AF11x series transistors.

In the first paragraph of this post I stated that I suspect a supply fault or circuit break in the case of your R600. I would stress that sometimes one or more faulty AF11x's can cause a totally dead radio, but the usual situation is that a radio with a duff AF11x will do something at the loudspeaker. This will likely be only a pop, crackle or splutter at switch-on, or you may hear a weak hiss at the 'speaker which persists regardless of waveband selection. If this latter occurs, the problem is likely to be in the IF module.

By what you've said, I feel we should first look for faults other than within the module. If we have to go there later then so be it. The following are simple checks:-

1. Check the battery snaps are making proper contact, the positive snap can work loose due to stretching and fail to make proper contact. Also, a loose rivet is a common problem on this snap.

2. Switch on and press each wavechange button firmly then see if the speaker splutters into life.

3. Look for another of the famous Roberts faults - a shorted earphone socket. Either test it by plugging in an earphone and listening therethrough, or short the terminals, two at a time, then see what happens.

If those simple checks fail, it may well be time to tackle the modules and the little transistor chappies who lurk within.
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Old 2nd Jun 2006, 9:58 pm   #3
shaun harris
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Default Re: dead roberts R600

Thanks for the advice Darren. I tried all you suggested and nothing at all, still dead.

shaun.

Last edited by Darren-UK; 20th Jul 2007 at 3:38 pm. Reason: General tidying.
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Old 3rd Jun 2006, 11:31 am   #4
Darren-UK
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Default Re: dead roberts R600

Quote:
Originally Posted by shaun harris
thanks for the advice darren i tried all you suggested an nothing at all......
Sorry about that Shaun. Roberts of that period also suffered from poor soldering, often on the modules, so there is a few further not-too-technical checks you can do.

Remove the chassis; turn the carrying handle clear of the tuning scale, remove the base and battery (if fitted). You will see two screws on anodised brackets, one each side, which secure the chassis. Remove those and also that which secures the telescopic aerial. Push chassis out through the top of the cabinet to the extent the speaker wires and external aerial wires will allow. You can disconnect the latter if you wish, but do not disconnect the loudspeaker (this is not as stupidly obvious as it may seem; radios don't like been powered up with no output load such as a speaker or an ammeter).

With chassis out as far as it will, look for any squashed or otherwise damaged wires. Look also at the wires to the loudspeaker - make sure they are connected securely. Pull battery leads out and connect battery, switch on and make sure a wavechange button is depressed. Best use MW.

Next, get a small screwdriver and with the handle end tap sharply the two modules ( silver boxes ). As I've said, I still suspect your R600 is unlikely to have a transistor fault though. Tapping sharply the modules may just reveal a dry joint/poor soldered connection. If no luck there, take a non-metallic thingy such as a pencil and with its blunt end poke around the circuit boards with particular emphasis on the soldered joints. If no joy, try carefully flexing the boards. This may reveal a cracked track but I mean it when I say 'carefully' as this little trick can end up causing damage and making matters worse.

If still no joy, then it really is time for the meter. Are you not confident enough to just use a simple voltmeter ? That would tell you all sorts of useful things.

All the above is general talk; if radio is totally dead on all bands the problem is likely to be power supply or loudspeaker or output stage. Faults on specific bands can be somewhat easier to diagnose. Try what I've suggested herein anyway.
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Old 3rd Jun 2006, 1:51 pm   #5
shaun harris
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Default Re: dead roberts R600

Thanks again for the advice Darren.

I'll take the thing apart this afternoon and have a poke around. If I can't get it to work then maybe someone out there could repair the thing for me.

Watch this space, I gotta feeling I'll be back - might need more of your wisdom.

Cheers, Shaun.

Last edited by Darren-UK; 20th Jul 2007 at 4:15 pm. Reason: General tidying.
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Old 3rd Jun 2006, 9:37 pm   #6
shaun harris
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Default Re: dead roberts R600

Hey guys, the Roberts lives again

I took it apart this afternoon and did as Darren suggested; checked all leads and tapped the big silver thingies gently with my screw driver.

Then, almost as I was gonna attempt the Avometer, I noticed a wire on the that didnt look quite right. So out with the soldering iron an resoldered the wire back on. Hey presto life so once again it lives; only problem now is it wont pick up Radio 2.

Every other station seems ok but not Radio 2. Maybe I should leave well alone, but must admit I'm now thinking about having a go at the two old Bush VTR 103's that have stood silently on the shelf for ages now.

Any bright ideas darren ?

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Old 3rd Jun 2006, 11:27 pm   #7
Darren-UK
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Default Re: dead roberts R600

Well done Shaun, by persisting you now have a working Roberts and have learnt a bit about them in the process

Regarding R2, make sure you're using a good PP9 as FM is the first band to go iffy when the battery begins to run down. Are other FM stations ok and with good volume and no distortion at higher volume ? If not a weak battery, all I can suggest otherwise is an alignment problem.

Good luck with the VTR103s, but remember to start a new thread if you require any help with them. They're very easy to work on and nowhere near as problematic as certain Roberts sets can be.
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Old 3rd Jun 2006, 11:46 pm   #8
Paul Stenning
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Default Re: dead roberts R600

I am also wondering, as Darren suggested, whether it can't receive Radio 2 because the tuning is a bit out of alignment - so Radio 2 is off the bottom of the scale. Let us know whether the other stations are in the right places on the band or not.

Or are the other stations are in the right places and there is silence where Radio 2 should be? Or is it just that Radio 2 is there but weak? Are Radio 3 and Radio 4 received easily and clearly, or are they a bit problematic too? And how easy are those stations to receive on another portable set?

Sorry for all the questions, but the more clues we have the better able we are to point you in the right direction.
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Old 4th Jun 2006, 11:47 am   #9
shaun harris
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Default Re: dead roberts R600

Thanks to you all for all the help and advice you have all given.

All seems ok with the stations about where they should be on the scale but, try as I might, R2 is just not there. All my other radios pick it up ok though; I suppose its looking like its out of alignment.

For now, I'm happy that I've managed to get it working again and so won't worry to much about R2.

Regarding the Bush VTR103's, I'll have a go at them at some point, but as I picked up a near-mint one this morning at the local carboot sale for a fiver I'm not bothered at the moment.

Thanks again,
Shaun.

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