Hi, I am new to tube radio repairs and have been reading as much as I can from various sources on tube radio restoration. I recently purchased an HMV model 62 52 little nipper radio. The electrolytic capacitor appears to be a 'two in one' and is marked 16 + 16 MFD 300 VW, 350 VP Type EDT6F made by Ducon. It is a large 4 cm tube tube under the chassis.

The positive end has two leads with one lead each going to what appears to be a terminal strip with a piece of bakelite (?)
What would I replace it with and how would the connections work at the positve ends? Also, if anyone can assist with the circuit diagram I would be very appreciative. Regards, Angelo.

The shell is the return path on these condensers. I replaced one of these on an Airzone receiver with two standard axial electrolytics of the same rating - 16μF 350vw.

Back when, they were fond of using "multi-section" electrolytics to save space. It's not unusual to find them mounted vertically on the chassis beside the valves, sometimes with 3 or 4 capacitance values within.

You can still buy the multis for a limited range of values, but they are expensive. Given that yours is under the chassis, then if you have sufficient space you'd be best advised to use two matching axial electros as Brad suggested.

However, you must use elctros which are designed for power filtering as they are built with high tolerance for ripple current.

With the above-the-chassis multi-section types, some people "gut them" and install modern electos inside the existing case to preserve the look of the original setup. Doing that requires care, especially with insulation of the pig tails.

And, as always with electrolytics, be careful to get the polarity right!

Thankyou for the quick response. I have sourced two identical 16μF sprague capacitors but they are 475 volts capacity which I understand are ok (because they are higher rated). Brad, is the reference to the 'shell' a reference to the terminal strip?

How would I go about getting the circuit diagram for this HMV model? There are a couple of paper capacitors that I can't read because there is a large deposit of what appears to be wax/brown substance deposit on them that has lifted the writing? Could I test them? Most of the others which are similar in size have a .01mfd reference on them. A couple of the resistors also have very faint stripes on them so it is difficult to determine their value.

Thanks again. New to all of this but enjoying it! Regards, Angelo

62-52 is common. Most of the series is much the same.

I will have a circuit.

I have had issues with some of the supermarket cheap 450V types, failing & not being good at filtering.

The sprague will do a better job you can use 22μF. as that has a heater rectifier 350V or above will be ok.

You can leave the other cap there, but do not leave it wired in. The post is positive, note where its wires go.
Photograph the pan before you remove anything.

If you are repairing sets with filament rectifiers, 500V is a better general value.

Marc

Thanks Marc. It is one composite cap and it reads 16 + 16 MFD so I assume I will either need a 34MFD or thereabouts or 2 x 16μF which are available.

If you are able to find the circuit diagram, it would be great. I have tried searching the net but HMV circuits were not as plentiful as AWA's.

Regards

These twin caps are usually arranged in a pi (π) filter circuit with a choke or resistor in between - hence the π filter. So 2 x 16μF is appropriate. This assumes they are part of the rectifier arrrangement - the circuit will sort this out.

Brad, is the reference to the 'shell' a reference to the terminal strip?

No, the case of the condenser, although I should point out that some of these condensers had paper wrappings and others had a metallic one. Either way, it is usually bolted to the chassis and this therefore becomes the return path. There is a chance yours will have a terminal at the side and this will be the negative. The other two terminals on the bottom of the case are the two positives.

Another radio that has these is the AWA Radiolette, model 500M. I've also replaced these with two axial electrolytics under the conditions I mentioned before. As has been said in an earlier post, it is okay to leave the original condenser in place for aesthetic reasons, provided that the two positive terminals are disconnected.

The Airzone Radiostar also had condensers like this but they were huge. Overall I cannot really see the point of this type of condenser. In the case of the Radiolette, there's more room under the chassis than on top of it.

G'day Angelo, if you supply an email addy the cct dia is available.

Regards

Paul

Thanks Paul. Much appreciated! You can send it at fenderreverbhotmail.com

Cheers.

Note the other posts.

The can contains two seperate caps and you need two seperate caps not one big one. I did not make that clear.

These are C17 & C21 in the 61-51 circuit.

I will send a copy of the four sheets for 61-51. It is virtually the same electrically. R5 & R6 in parallel was replaced later by a single 10K resistor (screens).

If the one in the set is 10K & a bit cooked, use two watt or replace as for 61-51. 10K is over the wattage red line for one watt.

Replace all paper type caps. I have repaired a few dozen of these. Good performer when set correctly.

Marc