UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)
Register FAQ Forum Rules Calendar Mark Forums Read

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Closed Thread
 
Thread Tools
Old 14th Oct 2009, 5:14 pm   #1
petermain1
Diode
 
Join Date: Oct 2009
Location: london
Posts: 2
Default Roberts R200

Hi I would like to repair my R200.
The symptoms are that it is very quiet and only just receives stations probably only two.
I do not have any knowledge of this radio but am able to disassemble and have good skills with a soldering iron.
Would you be able to take me through the repair steps?
Thanks for your kind help
peter
petermain1 is offline  
Old 14th Oct 2009, 5:45 pm   #2
Steve_P
Dekatron
 
Steve_P's Avatar
 
Join Date: Sep 2003
Location: Bolton
Posts: 6,537
Default Re: Roberts R200

Start by cleaning all the switches - Servisol will do. Then see if the antenna coil has been disturbed.

Which version have you got? You can get all three versions in the one sheet up top there.

Check capacitors and also possibly the AM diode.

Cheers,

Steve P.
__________________
If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?
Steve_P is offline  
Old 14th Oct 2009, 6:03 pm   #3
mark pirate
Dekatron
 
mark pirate's Avatar
 
Join Date: Mar 2008
Location: Worthing, West Sussex, UK
Posts: 3,056
Default Re: Roberts R200

This could be the dreaded AF117 transistors
With the radio on,try giving them a tap, this will either restore volume or go off totally!

Mark
mark pirate is offline  
Old 14th Oct 2009, 9:39 pm   #4
petermain1
Diode
 
Join Date: Oct 2009
Location: london
Posts: 2
Default Re: Roberts R200

Thanks Steve, I will get some servisol and give it a go.
Mark, I tried giving them a tap but no improvement. To be honest the reception has got worse.
I am not sure which exact model it is. There are three black and four silver transisters. It is hard to read them but it looks like OCR1
thanks both
Peter
petermain1 is offline  
Old 14th Oct 2009, 11:13 pm   #5
Darren-UK
Dekatron
 
Join Date: Apr 2003
Location: Blackpool, Lancashire.
Posts: 4,091
Default Re: Roberts R200

If there's three black transistors it'll be the first version which, as it happens, is the more reliable one despite being the oldest. The black transistors will be OC44, OC45, OC45 and what you've interpreted as OCR1 will be OC81.

On LW and given your location you should be able to receive BBC R4 at 1500m (That point is marked "Light" on these radios) plus a couple of other weaker stations at each end of the scale. On MW you should be able to receive an abundance of stations across the scale and with varying clarity.

Do first as others have suggested; Servisol and check aerial coils haven't shifted. The latter should be fixed to the ferrite rod with wax or maybe a splash of paint. Re the Servisol, get a can of 'Super 10'. Apply it to the wavechanger and operate the switch several times immediately afterwards. Note that if you overdo the Servisol the radio may do weird things for a little while; it'll settle after a short time if it does.

To access the wavechanger you will need to remove the chassis to the extent permitted by the 'speaker wires. If you don't know how to do this, first remove the knobs, then the two wooden wedges, lower the chassis so the tuning scale leaves the aperture and then lift out the chassis. DO NOT pull the chassis out by tugging on the ferrite aerial, this is often a cause of damage. On this point, check to make sure the ferrite rod hasn't fractured but if it has it should be obvious.

Having Servisolled the wavechanger and, while you're at it, the volume control, tune to a decent station ('decent' meaning good signal) on both wavebands and see if it comes in at the correct point on the tuning scale (This is assuming the Servisol and aerial check hasn't cured the problem). If it does but the radio is still weak, there could be an IF alignment issue. If it doesn't, there could be an oscillator and general alignment issue.

Other possibilities include a faulty OC44 (rare but not unknown), an output stage fault or a fault with a small capacitor which lurks inside one of the IF cans.

There'll also be a few of those red+yellow Plessey electrolytics grinning at you from the chassis and these are known to give trouble with age. There'll be some Hunts capacitors too but, unlike in valved sets, they don't give too much trouble in transistorised efforts.

I note you thought tapping the transistors made things worse. Check for a dry joint at that particular transistor while the chassis is out.

Couple of other points before I buzz off; remember that ferrite rod aerials are directional and thus need to point towards the transmitter. Just rotate the radio on its turntable (if it's still present) until best reception is obtained.

The second pre-buzz off point is the battery; make sure it's up to the job and spitting out something approaching 9v on load. That is obvious, I know, but it's happened before in these forums.........every possible fault investigated, only to find out the battery was duff to begin with.

Hope that helps.
__________________
Darren.
Darren-UK is offline  
Old 15th Oct 2009, 10:10 am   #6
PWH
Hexode
 
Join Date: Mar 2003
Location: Waiheke Island, New Zealand
Posts: 322
Default Re: Roberts R200

Also check the capacitors near the aerial input. get a 0.1 or similar and place across the contacts of the ones in situ. It may just burst into song and then you know which to change (personally I would do them all anyway)
PWH is offline  
Old 15th Oct 2009, 1:08 pm   #7
Steve_P
Dekatron
 
Steve_P's Avatar
 
Join Date: Sep 2003
Location: Bolton
Posts: 6,537
Default Re: Roberts R200

Quick guess - C4.

Cheers,

Steve P.
__________________
If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?
Steve_P is offline  
Old 15th Oct 2009, 9:32 pm   #8
Phil G4SPZ
Nonode
 
Phil G4SPZ's Avatar
 
Join Date: Apr 2005
Location: Bewdley, Worcestershire
Posts: 2,049
Default Re: Roberts R200

This may be a silly question, but is the battery in good condition? I have one of these sets and it is not very tolerant of low battery volts.
__________________
Phil (BVWS/Radiophile/G-QRP-C 2101)

"Never let anything digital know you are in a hurry"
Phil G4SPZ is offline  
Old 16th Oct 2009, 11:36 am   #9
Herald1360
Dekatron
 
Herald1360's Avatar
 
Join Date: Feb 2007
Location: Witney
Posts: 6,674
Default Re: Roberts R200

Quote:
Originally Posted by Darren-UK View Post
Couple of other points before I buzz off; remember that ferrite rod aerials are directional and thus need to point towards the transmitter. Just rotate the radio on its turntable (if it's still present) until best reception is obtained.
ISTR that ferrite rod aerials need to be broadside to the transmitter, you get a null if the axis of the rod is pointing at the transmitter.

Of course, rotating the radio for best reception is still just as valid

Chris
Herald1360 is offline  
Closed Thread

Thread Tools



All times are GMT. The time now is 2:35 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at http://www.vintage-radio.net.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Copyright ©2002 - 2014, S&P Technology.