A utility may have tweaked the LV distribution voltage level over the years at your local transformer. It won't change that setting unless compelled by competent reports (eg. from a sparky) of voltage levels that are outside its acceptable range, as it is a cost. The utility won't normally monitor down at that level, unless for some special reason (ie. as it is a cost). So it is down to luck as to how close you are to the local distribution transformer, and what other PV/loads are on your phase, and whether you have PV or loads (that vary your local wall voltage to a level allowed variation allowed within domestic wiring).

I think some newer smart meters allow display of incoming grid voltage (mine doesn't), so a plug in power meter, or some logging setup (eg. of an unloaded wall-wart output) may be enlightening over a few days or weeks (or even years), given that it is worth appreciating for all vintage equipment users.

"A shorted turn on the 6.3 volt winding would cause the transformer to melt."

I was referring to shorting of adjacent turns in the 6.3v secondary winding taking out only at most a few turns off the total, so dropping the voltage without much increasing the current. But of course a shorted turn is still a short. So wrong thinking, so can assume no such reason for low voltage. Thanks for correcting that wrong thinking.
Does this mean that If something is happening between turns it must have a high resistance. Or there is a crook connection say joining the lead out to the winding, if there is a leadout needed for this winding?


"Re solar, there is a proposal to start charging people to connect to the grid"

Another way around this is smart meters that can turn off solar at need of the transmission system.


"If the transformer gets hot, then you worry. "

Have in the past attached an electronic thermometer detector to the laminations with a bit of bluetac. It always settled at about 20C above ambient temperature after an hour or so ie 40-45C on a normal day. Certainly not too hot to touch.
Re oscillation will get back to that. The radio came with large composition resistors providing screen, and not set up like a four terminal voltage divider; rather 1meg for the 6J7 and two set up as a three terminal voltage divider for the RF valves. I changed this to a four terminal divider back in the '90s (even wrote letters to Ray Tonks and Neville Williams about it, they thought this was the way to go). Did have oscillation because of poor lead dress which Andrew Kay sorted out for me - just putting the screen bias leads close to the chassis was enough.
In the meantime I have realised that my radio might have been set up like the STC831 (the 1939 follow-up) which basically has the same screen bias set-up that my radio originally came with (maybe a factory modification away from the AORSM circuit); I can find no sign of a large four terminal voltage divider ever having been there - eg no signs of clean spots on the chassis where its brackets would have been. Ray Tonks made the comment that the large wire-wound voltage dividers were unreliable. Maybe that was STC's reason. Anyway I intend to go back to the original set-up replacing the large composition resistors with ceramic wire-wounds.

The first HT filter cap is 16μF (two 32s in series with balancing resistors) - can easily change that back to 8uF.

"There seems to be some ambiguity with regard to Australian Standards."
Old valve radios probably always have had issues at the extremes of the voltage range. Can't expect them to operate like modern appliances with a switchmode power supply. I just have to make sure it is safe now.

there is no obligation to comply with any standard.

That may be the case, however, at the international trade level, manufacturers are guided by national standards and if their gear encounters over-voltage-related problems then they will point to that country's standard.

In the WA case during the late 1970s / early 1980s, we were using American equipment rated 220-240 volts. I don't recall the specifics of the argument but my guess is that in WA where 250 was "normal" any sustained drift upwards from that was terminal for that American gear which was probably pushing its comfortable edge of tolerance at 240 volts.

I'm sure you meant 1980s rather than 1908s.

In the 1970s my father was able to get WA lights globes that were rated at 260V. This was because the normal globes were blowing far too often. If there was anything that the Chinese could do right, it was with light globes - they last forever, almost. Just in time for the loony left to outlaw them.

It is ideal to have a standard & the insurance industry from my experience loves ways of crawling out of paying out, or insuring for things like flooding. Like where my new house is and the old ones were they wrote, without me asking, telling me they would not insure it for flood.

To my knowledge the spot its sitting on has not been inundated in the last 150 years.

Pye TVs made at Marrickville had a special 265v mains transformer tap for WA.

The insurance industry is a racket. It can take, typically, several years for a commercial claim to be successful and this is even before accounting for any litigation, which there is usually some of. Where I work, the claim threshold is $100,000.00 which means that of a damage repair bill is $99,999.99 then the firm cops the hit, not the insurer. One exception is for motor accidents, where a written off vehicle is replaced for free. All insurers have their own legal teams and when it comes to large claims, their instructions are simple - require the customer to take the insurer to court.

To my knowledge the spot its sitting on has not been inundated in the last 150 years.

I guess if it rains long enough and hard enough just about any location is subject to flood damage.

Frankly, after the number of devastating bush fires we've had in recent years, it's a wonder to me that there are any insurance companies left in that sector.

I'm sure you meant 1980s rather than 1908s.

Yes, fixed.

In the 1970s my father was able to get WA lights globes that were rated at 260V.

I recall being told that, pre-LEDs, the authority responsible for traffic lights in NSW used higher than 240V incandescent bulbs and, when in the 'off' state, ran them at a voltage just low enough to prevent illumination, both measures apparently aimed at increasing the life of the filaments.

I can't vouch for any of that, although it seems logical.

If the reference is re house the new one is about a foot higher due to the construction method and we have held the property since the 1870's.

Traffic light globes were 240V, 150W with an ES base as far as I remember. Anything electrical has certain tolerances. Most of the time the supply in NSW hovers between 235V and 247V and a 240V-rated globe should be able to handle it, especially those with heavier filaments. They were also Australian-made back then too, which in my opinion helped. The globes we import are garbage.

"Most of the time the supply in NSW hovers between 235V and 247V and a 240V-rated globe should be able to handle it, especially those with heavier filaments."

I can't see how you can extrapolate from measurements at your location in NSW to a general NSW wide claim.

Nor do I see how 'heavier filaments' can 'handle it' is a reasonable generic statement - were you commenting on perhaps PV related midday increases over many hours that cause some level of shortened service life of an incandescent, or some kind of transient over-voltage excursion that breaks a filament immediately, or that heavier filaments have better filament diameter tolerance, or ...

Sorry Trobbins missed your first post. I have no log of mains voltage - just what I have seen during the day on the readout of my solar inverter and what I have noticed when working on the radio.

There has been a fair bit of work on poles and wires locally over the last several years - about 80 years old area. I guess that would be attended by a voltage survey. The 20 year old subdivision where I live has underground power fed from the older pole and wires. I would have thought the system is adequately maintained.

Have resistance tested the radio transformer out of the radio, frame to windings. All top out over 2000Mohm within the 10second test time limit for the tester. The tester is a cheapy I admit but gives me confidence to get the radio further checked when all work is finished.

Have been considering making a shorted turns tester using a neon eg

https://www.premierguitar.com/the-super-secret-transformer-tester

I would get the transformer rewound if I have any serious doubts.

A development on the transformer issue is that when removed to replace the lead-out spaghetti, it was cleaned up and the part number revealed under the grime and by pealing back a partly overlapping cotton tape. Instead of SP5118-C as given in AORSM it turns out to be SP5117-C. So either AORSM is wrong or it has received a replacement at some time. Looking at AORSM, in 1938 the year of manufacture of the radio, SP5118-C transformer was also used for 630, 620, and 600 models. Unfortunately I wasn't able to find SP5117-C being used anywhere before or after 1938, though the mains transformer part number is not always included in parts lists or on schematics.

As I have said before the radio suffered a disaster at one time, though I don't know the details, except that it occurred when shifted for installation of a TV, so I assumed maybe the mains lead was plugged in the wrong way round, (since the active and neutral bakelite plug and socket were missing, maybe removed by a serviceman to prevent a repetition), putting 240V on the 220V tap, or maybe active went to earth somehow if a separate earth was fitted. So the transformer might have gone west amongst all this requiring a change.

Another development is that photos of an 830 chassis were posted on Radiomuseum in September this year. The radio is an 830-X which has a wider cabinet than my 830-Q, but has the same chassis. Chassis number is 1240, 6 behind my 1234; very likely made on the same day so should be identical. I said somewhere that wires go everywhere in this chassis - you will see what I mean.

The address is https://www.radiomuseum.org/r/stcaus_830x_ch_830.html

Photos are given of the cabinet and chassis, including under the bonnet, so to speak. This reveals that my radio did indeed have a large wire-wound four terminal voltage divider at one time to supply 3 x 6U7 and 6A8 screen biases, and first audio screen bias. I had never been able to see where this had been mounted since there was no shadow in the grime of the L brackets usually used to mount these voltage dividers. The reason revealed in the photo is that the divider tube was mounted on a post at each end, with the screws going right through the diameter of the tube, and with the posts leaving no shadow in the grime of the chassis.

I had already reproduced this set-up with a 25,000 ohm w/w resistor that I picked up. But there were stability problems due to the long leads from the voltage divider, and in the end went back to the circuit as received, that is three terminal voltage divider for the 6U7 and 6A8 screen biases, and a 1Mohm from HT for the 6J7 bias. This set up is much more compact with only one short lead needed and seems to work nicely. It also left a lot of room to install a mains fuse and a 150mA dial light in the HT centre tap earth lead.

Will submit some photos of the chassis with these set-ups, tomorrow hopefully.

Edit to Post # 29:

there was no shadow in the grime of the L brackets usually used

from

there was shadow in the grime of the L brackets usually used


Needed because this was the main reason I thought that there had never been a large w/w voltage divider.