1953 Masteradio D120 Sandown MW/LW 5 valve midget radio

[howard]

Hello again,

This is the second of the ivory Masteradio Sandown midget radios that I bought at the last Royal Wootton Bassett event for £5. This is a later model than the one below, a Sandown D120A built from 1953 with a complement of Brimar 12AH8, 12BA6, 12AT6, 35L6 and 35W4 valves and a factory fitted resistive dropper rather than a line cord dropper. This one worked on arrival but not very well, and its dial cord was slack and the pointer stuck. Oddly, in place of the 12BA6 IF valve a 6BJ6 valve had been fitted. There is an R&TVS service sheet covering this model available here for £1.99 .........

http://www.service-data.com/product.php/3591/4734

This was a fairly straightforward a restoration, the chassis was cleaned with white spirit, the valve pins/sockets, volume pot and waveband switch cleaned with DeoxiT and all the wax tubular capacitors replaced with new Vishay and RS polyesters. All ressitors were checked and one had gone way out of spec so that was replaced. The mains lead was replaced with a new 2 core lead and the dial cord replaced. The set was switched on and it was now working better, but not as well as the D120 Sandown Star and its loudspeaker buzzed a bit so I pinched the loudspeaker out of the third Sandown, a D120SA SW/MW set with a cracked case. I checked with Ron Bryan how to go about reinstating a 12BA6 into the set as it has more gain than the 6BJ6 so definitely a worthwhile correction but its pin connections are slightly different. It was in fact a straightforward change, a ground connection was moved from pin 7 to pin 2, the 12BA6 fitted and it worked fine indeed with more gain. The set was then realigned, IF checked out fine and RF alignment tweaked up the set nicely.

The cabinet and knobs were gently cleaned in upholstery cleaner and the ivory cabinet polished with Brasso.

So a second nice example of the Masteradio Sandown midget radio, it works well picking up just about everything on MW and LW and it sounds fine for a set its modest size and it's in very good condition. Not bad at all for a total outlay of less than £10.

Howard

[Herald1360]

That's a nice neat little set. And it looks like a dream to work on with that uncluttered underchassis. Even the wavechange switch is a simple easily obtained 3p2w.

I wonder why the detector and agc diodes are commoned up, given that a DDT is used? Maybe it saved a resistor and capacitor....

[Tim]

Hi Howard. Another splendid job.
Is the mains switch in the neutral?

[howard]

Originally Posted by Tim

...........Is the mains switch in the neutral?

Hello Tim,

The chassis is live when switched off, but not when switched on.

Howard

[Herald1360]

That's a "Yes" then....

[danwdanw]

Hi Howard, yet again a very neat and tidy restoration. I do like the white sets, and although I dont have any yet I am always hoping to pick one up. Once again a first class job. Regards, Brendan.

[howard]

Originally Posted by howard

Hello Tim, The chassis is live when switched off, but not when switched on.
Howard

I recently revisited this set as it wasn't working quite as well as the other two Sandowns that I have recently restored. I noticed that this one had had a replacement switched volume potentiometer fitted and on close examination I found it to be a 250k ohm log pot and not a 500k ohm pot. So I fitted a NOS 500K ohm log pot with a dual pole switch and surprisingly it made a significant difference to its audio performance. I also rechecked its resistors and replaced a couple more which were out of spec. Finally, I think these sets originally had rubber feet secured by the four chassis screws underneath so I fitted 4 NOS small rubber feet.

It does work as well as the other two now, and it's safer to use too as it's disconnected from the mains when switched off and the four potentially live chassis screws underneath are properly covered.

Howard

[Sideband]

Originally Posted by howard

Hello Tim,

The chassis is live when switched off, but not when switched on.

Howard

If you get this situation again Howard, make sure the (single pole switch) is in the LIVE side of the mains and obviously that the chassis is connected to the neutral side of the mains. Alternatively fit a pot with a double-pole switch if possible.

If the single pole switch is in the neutral side, the chassis becomes live via the heater chain and dropper when switched off.


Rich.

[howard]

I've made a video of this Sandown too lasting just over a minute ....

http://www.youtube.com/watch?v=aN30dhQATEA

Howard