I mentioned in a previous thread that I may be able to obtain this radio. Well, I now own it and the photo will appear when Brad places it up.
An AWA Pressmatic, 6 valve, Model 690MA Mantle Radio, as I was told by my father, one of the last AWA made. Can anyone confirm this?.
The radio is in excellent condition but on a quick inspection seems like the mains transformer is cooked!!
I have cleaned it and it now is in the queue with the other 17 that need attention.
Next weekend I hope to have the whole of my late father's radio workshop finally moved from Newcastle, north to Maclean. So far 63 boxes with one more wagon and trailer load to go. Does anyone else have one of these?
Peter

I find mains transformer failures rare. I thought I had the first one in forty years recently.

Often you can tell by its smell. The one that gave me issues was an AWA in a Bandmaster.

What causes you to think that it is cooked, was it fired up when it should not have been?

Marc

I've had two transformers go on me in about 23 years. The first almost lead to disaster - I fell asleep one night back in 1992 whilst listening to a Kriesler 11-20 and woke up to a room full of smoke and the associated acrid stench of molten transformer wax. I can thank the man upstairs that I am a light sleeper.

The second was about four years ago when I acquired a dead AWA Radiolette 500M. The transformer was already kaput in that one. I've several spare chassis in this model so a replacement wasn't an issue.

I think overall, power transformers do have a good reliability record and are most likely to cark it only when overloaded by a fault within the rest of the receiver.

Brad: A lot of that was due to the reluctance to use any form of fuse.

I have a Radiola I sent you Pics of, that has 100 Ohm resistors on the plates of the 6X5. While it is not their intended purpose, or the only AWA with them, they do make good fuses: especially with 6X5's reputation.

I have actually added a fuse to a Stromberg Carlson, where there was a high probability of a moving wire on a light causing a short.

The heater circuits of the Bench power supply, I built, have thermal reset fuses in its heater circuits.

Many do not appreciate the danger to transformers, of firing up sets without inspection.

I have a Breville 730 that has just become part of my collection yesterday

Mains wiring dodgy, dead short on dial lights (rubber wire). That's why you look before you leap.

This one would be a guaranteed smoker: If turned on.


Marc

When I powered it up I heard a crackling sound, I thought aahhh, typical reception static from crook capacitors then I smelt something so shut it down. I pulled the radio from it case and the tranny was HOT from only a few minutes running. It should not get hot in such a short time. Looking closer I can see fused insulation varnish coming from the tranny vents. I am an electrician with electronics quals, so I know all about burnt trannys. Maybe a short on the secondary side, who knows.
It has not been a runner for many years according to the old lady that owned it.
I usually runs radios up on my test bench with a lamp in series but I can't get to my bench at the moment.
I would like to dive in a see but as I said, other radios in the queue and still setting up my workshop. I will let everyone know what I find.

Nice to see someone with electrical background working on radio's. My main backgroung is in chemistry.

The Bandmaster I just sent home made those sort of noises intermittently. It finally did go short properly so I caught it.

I was only giving it short bursts with a meter on it, so I did not cook it. (I thought it had cooked) It turned out to be a combination of metal oxide flaking off of the inside of the transformer cover and the heater wires of the 5Y3 being squashed by a large 2 x 8mfd block cap. Stupid place to run wires.

As with the 730 mentioned above; After fixing several hundred of these things you know instinctively, that you never power them up without checking and I never use a dim bulb. You never power an unknown transformer set up with the rectifier valve in.

If the set has old paper capacitors in it, they will leak 730's are doing that. The set will not be powered until all of them and the electrolytics are replaced.

At the point that I abandoned it the screen resistor for conv & IF, the AGC resistors, Plate resistor & grid resistors on 6V6 had also been replaced.

Set was going to run well. Valves not tested yet.

The main danger to the transformer is short circuits like the dial light in the 730. The second killer is the HT electrolytics. These are chemical and rely on oxide to "form" the insulator on the positive electrode.

When the set has been abandoned for a few years, the caps "dry out", or worse normally loose this layer of insulating oxide. This then causes them to present as a short circuit; This can then cook the transformer.

Never forget that many sets were abandoned when they broke down, or the Monkeys have been in there and killed it by putting things where they should not be & then having no idea how to sort it.

Marc

I know where you are coming from Marc, I think any damage that maybe have been done was done by the previous owner. As a rule, I never just switch a radio on, it just got my curiosity. When I am ready I will take the correct steps in powering up and testing.
Pete

If you have not done it I would be tempted to remove the covers of the transformer if it's one that has covers over the wires.

By the looks of that radio it should not have rubber wire. I have had a couple that had smoked when the rubber turned to jelly. Fortunately the windings had not let go.

The bandmaster's transformer wire failed to impress it has tags, so was easy to rewire & make safer.

From your description you may not be that lucky?

I found out why the 730's screen resistor cooked it's ECH33 was seriously shorted, which is not unusual for a pentagrid.

It now needs two filter electrolytics replaced before attempting to fire it up.

Marc