I've just bought an AWA 516M. I paid a bit more than I would have liked to but something about this one caught my eye and the 516M is a glaring hole in my AWA collection.
As it turns out it's one of the most original radios I've ever seen, absolutely untouched with the exception of a sliding bakelite switch (similar to an electric blanket switch) installed in the 2 core flex.
The 6A8G is dead, it looks like the radio was only used until it stopped working and then stored away.
My usual procedure with radios of this age is to replace all the paper caps and electros, check and replace resistors as needed and go from there. Out of curiosity I check the old paper caps as I go and very rarely find one that's not leaky.
This radio's only got three paper caps and I was amazed when I tested them to find they're as good as new! I want to keep this radio as original as possible but still as a working item. Is it a good idea to leave these caps in place,assuming all voltages are within spec?
My other dilemma is the electros, again I usually replace these without a thought. I recently discovered with later radios that the electros are quite often okay. After all other work is done, I power up the chassis with only the rectifier installed and monitor the electros for any rise in temperature and how quickly the B+ drops after power off. After a few on/off cycles, if the voltage starts to drop very slowly I assume the electros are okay, which they usually are. Very rarely I find one that causes a hum when the radios up and running and I've never had a subsequent failure. With the price of electros I'm quite happy with this procedure.
I've never tried this on electros this old and I'm not so sure I want to. It's quite often mentioned that you should 'reform' the electros but I've never discovered how to do this with basic equipment. I'm sure my above mentioned procedure is a version of reforming but probably not so safe on something this old. Does anyone have some ideas on this or should I just replace them regardless?
Cheers,
Warren

As it turns out it's one of the most original radios I've ever seen, absolutely untouched with the exception of a sliding bakelite switch (similar to an electric blanket switch) installed in the 2 core flex.

These were often installed to provide some convenience. Radios were rarely fitted with on-off switches, particularly those that were sold with bayonet adaptors instead of three pin plugtops. The Radiolettes were commonly fitted with bayonet adaptors and I've bought at least ten over the years with these still fitted. Because they can be inserted into a lamp socket in one of two ways a switch would not always provide any isolation of the active side of the primary circuit.

Some manufacturers fitted DPST switches which solved that problem but these were more expensive and thus reserved for upmarket models.

I've never tried this on electros this old and I'm not so sure I want to. It's quite often mentioned that you should 'reform' the electros but I've never discovered how to do this with basic equipment. I'm sure my above mentioned procedure is a version of reforming but probably not so safe on something this old. Does anyone have some ideas on this or should I just replace them regardless?

In my opinion, reforming condensers is a waste of time. It can work for a while with some but condensers are so cheap these days and while some whinge about shelling out $10.00 or even $20.00 to replace all large-capacity condensers it is money worth spending to make sure the radio performs at its best and is as safe to use as possible.

The author of last month's vintage radio article in Silicon Chip reformed some condensers in a HMV radio he recently restored and the letters column this month contains correspondence relating to reforming condensers and how ultimately futile it is in the long run.

With this in mind I will always recommend replacement of electrolytic and paper condensers. Replacements are readily available and are inexpensive.

Replacing old electos is cheap insurance. When an electo goes short circuit due to the effects of old age the collateral damage can be very costly.

The trouble is, modern replacements often don't look right in an old radio. I'd leave the old papercaps in place, and check them occasionally.

A capacitor tester is simple to build, and be used to reform electrolytics.

GTC frightened me so I've replaced them all for now. I'm keeping the old ones while I think about it some more. I've got an old 500M chassis I might put them into as a test bed for a while and see what happens. I've found the paper covers on the old Ducon electros, which are in good condition, slide off quite easily. I think I'll have a go at restuffing them for appearance sake.

There have been at least two articles in Silicon Chip on building reformers for electrolytics. In order to understand the procedures, they would be worth following up on.

One of the things with electrolitics is their ability to loose polarity over time. This results in some presenting as a short circuit which can burn the rectifier, or transformer.

It is most important that the voltage be brought up slowly & be currrent limited. I have the Rod Champness reformer built into the bench PSU and the 1938 Paton VTC "Valve & circuit tester also has a crude, reformer / tester for electrolytics built in.

It is my policy to replace all electrolytics as well as the paper caps.The only way to tst leaking papers is to apply DC volts via somthing like an insulation tester. VCT has one using a "Neon" tube

Of concern was related to an old Heathkit "Grid Dip Meter" I bought at a Hamfest. As I have found resistors in Heathkit stuff to be unreliable as they age badly. I never turned it on & overhauled first (retrospectively valid)

For interest I checked the filter electrolytics, which were leaking badly as expected and did not show any signs of redemption.

What horrified me was on comparing them to new ones, one of them failed? I have run that by the supplier, who at this point seems disinterested. It would be interesting to know how long they had ben in storage?

General formula for leakage is current in Microamps = 0.01 times Capacitance in μF, by Voltage applied. Some where in a book I have the current values that are not acceptable

Marc

It is my policy to replace all electrolytics as well as the paper caps.

This is also my policy because back in 1992 I let a Kriesler 11-20 keep playing as I fell asleep one night and I woke up to the stench of a baking power transformer and two baking filter caps. Whether the transformer cooked the caps or vice versa isn't the point and I don't worry about aesthetics below the chassis anymore. I want a perfectly safe radio (or as safe as a 60-70 year old radio can be) and this will always involve complete replacement of the condensers no matter what.

If I hadn't woken up for a 'Jimmy' that night I may have ended up suffocated from the smoke coming from the radio. I've still got too many years ahead of me to mess around reforming caps that should be binned.

Since then I don't leave radios on when I am likely to nod off but as an added precaution I will simply not operate any radio at all unless I or another person has replaced any component that is likely to fail or cause another component to fail.

When I purchase radios that are claimed to be restored I will still make sure the necessary restoration work has been done by removing the chassis for a quick look and not because I do not trust those people I know but simply as a self-preservation measure.

Im with Brad here. A couple of 'modern looking' caps is better than a smoking mess.
It is quite easy to purchase yellow axial caps that dont look to far out of place. Late 30's early 40's chassis that have the tall electros on top of the chassis, can be electrically disconnected and left in place for looks.

If the set is so rare/valuable then maybe leaving it as is is an option. And its not that much of an effort to re-stuff caps if you are so inclined.

edit: a 516M I would be more worried about the rubber insulated hook up wire under chassis.

a 516M I would be more worried about the rubber insulated hook up wire under chassis.

You make a good point. The rubber wiring in my Airzone 5A1A2 was in terrible condition and what was a big worry is that it criss-crossed in lots of places. I replaced all of it with modern but period-looking cloth covered wire. Took me ages.

The wire in my other 516M was crumbling, I learned how to lace wire for that restoration. The wire in this one is perfect, amazing for its age. Even the cardboard backing on the dial glass is still the original colour, they usually fade to a murky grey green. The only blemish is the dial pointer which seems to have been heat affected and is bubbled. I think I've got a spare off a 500M somewhere, although it's not quite right I think the only difference is the grub screw on the 516M so it should fit.

I have a Televerta here where the owner, or someone has run it without addressing issues. New transformer, or rewind required.

For all intent & purpose wax paper caps leak & always did and have now passed their use by date. They & anything with "Micamold" (USA) should be replaced on sight. Time spent testing them is better spent replacing them. Just check the resistors as you replace them & replace the dud ones of them when found.

Never power an unknown set before visual inspection, if they have rubber wire, its likely shot (had one this week).
There are ways of testing the critical items without powering and I rarely find cause to power a set "cold" just to see if it goes. Note the Televerta... that's only one scenario.

Marc

I too, once upon a time, let a piece of old equipment run to be greeted by the smell of a bubbling transformer and electro's.

Now I replace everything, stage by stage. The modern resistors and capacitors are reasonably priced and far better specs than those from days gone past.

Must admit I'm often surprised by the quality of sound reproduction from a fully rebuilt radio.

Those old sets certainly performed to a high degree.

One of the surprises I had was the noise from a 1929 Lyric 70 series.

This has a not outstanding, (but damn expensive) 50 as its output valve. AC filaments 375V on the plate and one 24 (I think) just providing the - 50V or more on the grid (-84 with the plate at 450V.

The old Rice Kellogg speaker had been refitted with a modern foam suspension cone. What nice noise it makes.

Marc

Those widely-hated Ducon papercaps can be restuffed with polyesters too. The wax for coating can be coloured the right shade with shoe polish, and made sufficiently sticky with a small amount of vaseline.

I think the look of the "guts" is just as important as the outside. Maybe less so under the chassis. So if any of you find some NOS Ducon papercaps, I'd be happy to take them off your hands!

Don't know if "find" is the right word here. I repair valve radios (as well as other things). Where I normally find a lot of paper caps is in my bin.

Never had a lot of call for them.

Marc