Help Restoring Old Tube Radio

If you thinking of learning electronics by restoring a tube radio then in one simple big word. NO !

Valves have very high voltages and can cause severe and irreversible malfunctioning in your heart. There are simpler and safer ways to start electronic DIY.

Restoring a tube radio is not impossible or difficult but probably not right for learner. The process can be frustrating and it may actually put you off DIY. Remember people used to do “Radio Engineering” courses in the past to become a repair guy.

Your radio looks in fine condition and shows the care your folks must have bestowed on it. However, NALCO possibly made the worst radios in India. They had a tie up with ECKO of England and their earlier models were branded NELCO-ECKO. They could never complete with high quality products from Murphy, Bush and Philips, eventually exiting the consumer electronic business by mid 70’s. NELCO was a failure for Ratan Tata as he was the CEO

Your radio is probably one of the last model as I can see a proper power transformer. The earlier models did not have a PT and the mains voltage was stepped down by means of a high wattage resistor. To make matters worse, some models had “live” chassis! Today can you visualize a consumer electronic product made this way? The certifying managers at UL will probably get heart attack by only hearing about it.

Having said that, it is not too difficult to resurrect your radio. I am 99% sure the valves are ok. They would last a lifetime under normal use. I would check and replace most of the capacitors. The PSU cap which will be a 50+50ufd/250volt electrolyte will surely need to be changed. There will be several thick, squarish maroon colored capacitors. These are very delicate and if they physically look fine then I won’t touch them. There values will be in the pF region.

The resistors too probably will be ok except some which work under stress. Check for fine wires going in and coming out of the ferrite antenna. And finally check the tuning gang. It is that big, industrial type thingy that rotates as you tune the frequencies.

Depending upon the situation you will start from the back end or the front end. I will first check the PSU, then AF section and then move on to the RF section. This is scalling up on the complexity chain. Checking the IF, modulator and AF section as you go along. Those Aluminum can in your are IF tuning coils. To align these you will need a RF Modulators. Many oldtime radio repair shops had one.

Its such a coincidence that right now I am restoring an earlier version of the NELCO-ECKO radio. This is based on the “all American 5” design. My father had it from the 60’s and for last several months I have been giving it a complete servicing. It had died several years ago and the replacement too died My father is not too comfortable with the modern radios and I think his old radio coming alive should be a joyous.

Attach is a pic of my work in progress. Please note two very important tools needed to restore a valve radio. The RF signal generator (that black box on left top) and the Variac (the round thing on right top). Do let me know if you need any assistance.

PS: I think this topic is in the wrong section of the forum. Perhaps DIY thread would be better.

Screamgigi/aks07,
That RF sig gen of yours is CLASSIC!!
Oh, -m-y- gosh! where did you pick that piece of gear up?? from the trenches of Normandy during WWII??
Do you have to crank a handle to generate power or does it run on electricity??
But I like the pairing - vintage tube gear being fed a RF signal from an equally vintage RF sig gen!
(sorry I'm ripping into your test gear but it's supposed to be good-natured).

Bombaywalla-ji

Lol. Nice catch

Yes that is vintage. Manufacturing date is Jun 1944. It uses a pair of 6SN7 and 6SL7 as modulator. It’s got excellent components inside. Cornell Dublier, Sprague Silver mica capacities. Completely sealed tuning gang and mill spec switches and pots. Even the mains lead is original and in excellent condition. And as you can see that frequency dial is illuminated and even that tiny bulb is original! Needs about 20 minute to warm up and hold the dialled signal without drifting. Very high precision. I calibrated it with a digital world band receiver and its accurate down to 2khz even in the 10 meters ham band which is quite extraordinary.

And now the best part. It is made in India by British Physical Laboratories. For younger members that is BPL of today. I have had this piece for about 25 years. Used to have lots of fun by creating RF interference for neighbourhood when the janta wanted to hear the “Binaca Geetmala”

You are right about the pairing. Actually tube gears are best attended by tube test equipment and I am very happy to report possession of a VTVM, a Tube Tester and a monster tube bench power supply. In fact its really difficult to accurately measure a 1R resistor with a modern digital multimeter which is a usually a child’s play from my VTVM

aks07 schrieb:

Bombaywalla-ji Lol. Nice catch Yes that is vintage. Manufacturing date is Jun 1944.

ha,ha! I was not off at all!! That was the year they stormed the beach & paid a heavy price but won eventually.

aks07 schrieb:

And now the best part. It is made in India by British Physical Laboratories. For younger members that is BPL of today.

Thank you, I leant something new today - that BPL stands for British Physical Laboratories. I wondered what that acronym stood for.

aks07 schrieb:

I have had this piece for about 25 years. Used to have lots of fun by creating RF interference for neighbourhood when the janta wanted to hear the “Binaca Geetmala”

you naughty, naughty boy!!!

aks07 schrieb:

You are right about the pairing. Actually tube gears are best attended by tube test equipment and I am very happy to report possession of a VTVM, a Tube Tester and a monster tube bench power supply. In fact its really difficult to accurately measure a 1R resistor with a modern digital multimeter which is a usually a child’s play from my VTVM :)

holy macaroni! you have a VTVM???? Oh boy, I if I visit you in Jamshedpur I would love a tour of your testbench equipment - I think that the pieces you have hold more intrigue for me than the actual tube amps themselves. I do not know of anybody else here who has a VTVM!

In this merriment we seem to have scared away the OP. Not a bad thing actually This was not the road the take.

VTVM's are fairly normal stuff. I bought one NOS and before that I was using one that was bought from a radio repair shop.

aks07 schrieb:

In this merriment we seem to have scared away the OP. Not a bad thing actually This was not the road the take.

yeah! you might have saved his life!!