Roberts R505 tuning query - UK Vintage Radio Repair and Restoration Discussion Forum

Kranky Cat · 31st Dec 2016, 6:47 pm

Hello,

I have Roberts R505 that has a strange issue. (It has had this issue as far back as we can remember, so it might have been like this from new).

It's quite hard to describe but here goes: On VHF, when tuning, each station takes up a lot of space before the radio tunes past the station and back to free air, this is happening much more than I've had with any other radio, the major downside of this is it's very difficult to find when it's tuned in correctly - and if the station hasn't been tuned spot-on, it will soon drift off tune. It's a bit like AFC on other radios, as the radio clings on to a station, but it's actually a nuisance to use.

I've only used Japanese radios and modern Roberts radios to compare this to.

Should it do this, and could you suggest where to look if it sounds like a fault?

Edward Huggins · 1st Jan 2017, 11:38 am

Some people would regards this as a good thing - a kind of band-spreading. It does allow for very accurate tuning to reach the RF peak.

Nuvistor · 1st Jan 2017, 1:34 pm

The set does have AFC, sets from the 70's did tend to have quite a large 'pull in' range, there were a lot less stations with more space between them on the dial then.
I would be surprised if it was a fault, I cannot find a on/off switch for AFC, another feature of some sets in the 70's.
If you tune across the station, notice the travel of the pointer between hearing the station and losing it, put the pointer in the middle of that range, it should be near enough as long as it is not distorted.
Frank

Kranky Cat · 1st Jan 2017, 8:06 pm

Hello Edward,

Thank you for your advice.
Philip

Kranky Cat · 1st Jan 2017, 8:12 pm

Hello Frank,
I didn't know the R505 had AFC - it's just working in a different way than I'm used to. There's certainly a lot of stations available round this way to clutter the tuning band. (North Hertfordshire).
The radio still has all its dial pointers so I will try your tuning tip!
Thank you.
Philip

MotorBikeLes · 2nd Jan 2017, 12:59 am

I prefer a radio with switched AFC, but I recall at some stage (in the '70's I think) when "Automatic AFC" became flavour of the month. It sounds like that is what your R505 has (assuming no AFC On/Off switch).
Les.

ukcol · 2nd Jan 2017, 10:57 am

From the electronic point of view it would be very easy to add an AFC defeat switch between pin 8 of the VHF tuner and chassis. The problem arises with how to do it so that the user has easy access to the switch without hacking the cabinet about.

Goldieoldie · 2nd Jan 2017, 11:02 am

You could try reducing the sensitivity while tuning by reducing the length of the telescopic aerial .That might help by the afc having less to hang on to
Cheers Pete

Nuvistor · 2nd Jan 2017, 11:06 am

With the pull in range and no defeat switch, these 70's radios can be difficult to tune a weak station that is close to a strong one, not really a major problem then but probably more so now.

Fitting a switch that looks good is not something I could do, the electrical side is easy, the cabinet mods not so.

Frank

31st Dec 2016, 6:47 pm	#1
Kranky Cat Retired Dormant Member Join Date: Dec 2016 Location: London, UK. Posts: 3	Roberts R505 tuning query Hello, I have Roberts R505 that has a strange issue. (It has had this issue as far back as we can remember, so it might have been like this from new). It's quite hard to describe but here goes: On VHF, when tuning, each station takes up a lot of space before the radio tunes past the station and back to free air, this is happening much more than I've had with any other radio, the major downside of this is it's very difficult to find when it's tuned in correctly - and if the station hasn't been tuned spot-on, it will soon drift off tune. It's a bit like AFC on other radios, as the radio clings on to a station, but it's actually a nuisance to use. I've only used Japanese radios and modern Roberts radios to compare this to. Should it do this, and could you suggest where to look if it sounds like a fault?

1st Jan 2017, 11:38 am	#2
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,335	Re: Roberts R505 tuning query Some people would regards this as a good thing - a kind of band-spreading. It does allow for very accurate tuning to reach the RF peak. __________________ Edward.

1st Jan 2017, 1:34 pm	#3
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: Roberts R505 tuning query The set does have AFC, sets from the 70's did tend to have quite a large 'pull in' range, there were a lot less stations with more space between them on the dial then. I would be surprised if it was a fault, I cannot find a on/off switch for AFC, another feature of some sets in the 70's. If you tune across the station, notice the travel of the pointer between hearing the station and losing it, put the pointer in the middle of that range, it should be near enough as long as it is not distorted. Frank

1st Jan 2017, 8:06 pm	#4
Kranky Cat Retired Dormant Member Join Date: Dec 2016 Location: London, UK. Posts: 3	Re: Roberts R505 tuning query Hello Edward, Thank you for your advice. Philip

1st Jan 2017, 8:12 pm	#5
Kranky Cat Retired Dormant Member Join Date: Dec 2016 Location: London, UK. Posts: 3	Re: Roberts R505 tuning query Hello Frank, I didn't know the R505 had AFC - it's just working in a different way than I'm used to. There's certainly a lot of stations available round this way to clutter the tuning band. (North Hertfordshire). The radio still has all its dial pointers so I will try your tuning tip! Thank you. Philip

2nd Jan 2017, 12:59 am	#6
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	Re: Roberts R505 tuning query I prefer a radio with switched AFC, but I recall at some stage (in the '70's I think) when "Automatic AFC" became flavour of the month. It sounds like that is what your R505 has (assuming no AFC On/Off switch). Les.

2nd Jan 2017, 10:57 am	#7
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	Re: Roberts R505 tuning query From the electronic point of view it would be very easy to add an AFC defeat switch between pin 8 of the VHF tuner and chassis. The problem arises with how to do it so that the user has easy access to the switch without hacking the cabinet about.

2nd Jan 2017, 11:02 am	#8
Goldieoldie Octode Join Date: Jul 2014 Location: Petersfield, Hampshire, UK. Posts: 1,043	Re: Roberts R505 tuning query You could try reducing the sensitivity while tuning by reducing the length of the telescopic aerial .That might help by the afc having less to hang on to Cheers Pete

2nd Jan 2017, 11:06 am	#9
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: Roberts R505 tuning query With the pull in range and no defeat switch, these 70's radios can be difficult to tune a weak station that is close to a strong one, not really a major problem then but probably more so now. Fitting a switch that looks good is not something I could do, the electrical side is easy, the cabinet mods not so. Frank