Radio Rentals Model 60 - UK Vintage Radio Repair and Restoration Discussion Forum

davew · 9th May 2018, 9:55 pm

Re my RR Model 60 which forum members kindly identified for me, time to try and get it working..
There was a loud hum which was cured by replacing the first 8mF smoothing cap. I've also cleaned the pot and wavechange contacts.
Turning this gives a healthy crackle so I'm asuming IF stages probably OK?
I'm getting no signal but noise increase towards one end of the scale
Is this possibly a local oscillator problem?
I'll get down to some testing tomorrow
Thanks
Dave

Boater Sam · 9th May 2018, 10:41 pm

If you have noise on medium wave, changing at the ends of the scale, its a good bet that the local oscillator is not running, check the voltage at the grid with a high impedance meter, DMM will do.
There should be a few volts negative.

Boater Sam · 24th May 2018, 8:23 pm

Dave hasn't come back yet, but the thread jogged by failing memory, I have an RR 60 buried on the top shelf behind the shop speaker.

Risking life and limb I dug it out and managed to get it down to the bench without dropping it, its a heavy beast and most of it is in the thick bakelite case.
It had been restored over 2 years ago so time it had a run to keep the electrolytics on line. The waxed paper caps had been changed previously with poly film cherries.

It worked straight off but with some crackles.
This has to be the dream set for a service engineer. Remove 2 large headed screws from the back and the whole set slides out complete, no wires to disconnect or knobs to remove. Speaker screwed to the chassis, not the case.

Its got an isolating transformer though not an earthed chassis, the two pin mains socket is used to select the supply voltage by having 2 positions to insert it in.

This set had a 3 core mains lead fitted, the earth being taken in from the socket to the chassis, not the finest arrangement but I prefer the earth however connected.

The chassis once out will stand on either end or even upside down without any additional support measures. Its a brilliant design, so simple, so easy to work on.

The tuning scale was slightly out of sync with the stations on medium wave so a quick RF adjustment was made during which is became apparent that the crackles were due to a loose metalised valve bulb on the ECH35 valve base, a spot of superglue on one side only without removing the valve sorted that one.

Back in its case, there is loads of volume from the 8" speaker, lots of stations on medium wave even during the day, its a very sensitive set despite the ruementary aerial coupling arrangement. No warm up drift and it copes well with the interference off the shop strip lights. AVC works extremely well too.
It had got a bit dusty so a quick polish was called for, came up beautifully.

So there it is, a clever radio that was designed and tooled as a rental set, easy to repair in house, strongly made and its survived well.
Here is a vote for Radio Rentals Model 60 as the easiest set to work on, unless anyone has other ideas?

Sam.

davew · 24th May 2018, 10:36 pm

Sorry Sam, been away for a bit
Thanks for your replies
Yes, you're right it really is a nice design - I wondered about the lack of earth - Why go to all that expense of a mains transformers but only have a 2 core lead?
I suppose alot of sockets then were only 2 pin - I can remember plugs going into light fittings!
I haven't yet had time to investigate the set yet.
I had a spare ECH35 but this made no difference - I'll check next the voltages around the valve (including the grid as you suggested) and the connections to the Coils/trimmers etc
Any other suggestions/common faults known gratefully received!
Thanks
Dave

Boater Sam · 24th May 2018, 10:54 pm

Put a transistor radio next to the 60 and tune through the wave band, you should find an interaction if the local oscillator is running.

9th May 2018, 9:55 pm	#1
davew Tetrode Join Date: Feb 2004 Location: Deal, Kent, UK. Posts: 74	Radio Rentals Model 60 Re my RR Model 60 which forum members kindly identified for me, time to try and get it working.. There was a loud hum which was cured by replacing the first 8mF smoothing cap. I've also cleaned the pot and wavechange contacts. Turning this gives a healthy crackle so I'm asuming IF stages probably OK? I'm getting no signal but noise increase towards one end of the scale Is this possibly a local oscillator problem? I'll get down to some testing tomorrow Thanks Dave

9th May 2018, 10:41 pm	#2
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Radio Rentals Model 60 If you have noise on medium wave, changing at the ends of the scale, its a good bet that the local oscillator is not running, check the voltage at the grid with a high impedance meter, DMM will do. There should be a few volts negative.

24th May 2018, 8:23 pm	#3
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Radio Rentals Model 60 Dave hasn't come back yet, but the thread jogged by failing memory, I have an RR 60 buried on the top shelf behind the shop speaker. Risking life and limb I dug it out and managed to get it down to the bench without dropping it, its a heavy beast and most of it is in the thick bakelite case. It had been restored over 2 years ago so time it had a run to keep the electrolytics on line. The waxed paper caps had been changed previously with poly film cherries. It worked straight off but with some crackles. This has to be the dream set for a service engineer. Remove 2 large headed screws from the back and the whole set slides out complete, no wires to disconnect or knobs to remove. Speaker screwed to the chassis, not the case. Its got an isolating transformer though not an earthed chassis, the two pin mains socket is used to select the supply voltage by having 2 positions to insert it in. This set had a 3 core mains lead fitted, the earth being taken in from the socket to the chassis, not the finest arrangement but I prefer the earth however connected. The chassis once out will stand on either end or even upside down without any additional support measures. Its a brilliant design, so simple, so easy to work on. The tuning scale was slightly out of sync with the stations on medium wave so a quick RF adjustment was made during which is became apparent that the crackles were due to a loose metalised valve bulb on the ECH35 valve base, a spot of superglue on one side only without removing the valve sorted that one. Back in its case, there is loads of volume from the 8" speaker, lots of stations on medium wave even during the day, its a very sensitive set despite the ruementary aerial coupling arrangement. No warm up drift and it copes well with the interference off the shop strip lights. AVC works extremely well too. It had got a bit dusty so a quick polish was called for, came up beautifully. So there it is, a clever radio that was designed and tooled as a rental set, easy to repair in house, strongly made and its survived well. Here is a vote for Radio Rentals Model 60 as the easiest set to work on, unless anyone has other ideas? Sam.

24th May 2018, 10:36 pm	#4
davew Tetrode Join Date: Feb 2004 Location: Deal, Kent, UK. Posts: 74	Re: Radio Rentals Model 60 Sorry Sam, been away for a bit Thanks for your replies Yes, you're right it really is a nice design - I wondered about the lack of earth - Why go to all that expense of a mains transformers but only have a 2 core lead? I suppose alot of sockets then were only 2 pin - I can remember plugs going into light fittings! I haven't yet had time to investigate the set yet. I had a spare ECH35 but this made no difference - I'll check next the voltages around the valve (including the grid as you suggested) and the connections to the Coils/trimmers etc Any other suggestions/common faults known gratefully received! Thanks Dave

24th May 2018, 10:54 pm	#5
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Radio Rentals Model 60 Put a transistor radio next to the 60 and tune through the wave band, you should find an interaction if the local oscillator is running.