Moving on, finally!

[CitroJim]

Perhaps we could substitute metal rectifiers...?

No, too tame.. How about a few mercury vapour rectifiers?



Or if that's a bit too much then how about some little ones?



I used to work on equipment containing these and similar ones... We used to keep spare ones hot ready for instant service. Cold ones took a long while to heat and vaporise the mercury...

The glow from them is magical

[white exec]

I'd quite forgotten about those mercury arc rectifers. Remember seeing them as a kid at Electrical Engineers' Exhibition at Earls Court.
One of the most spooky and frightening things I'd ever seen. Have a vague recollection that the London Trolleybus system used them for the 600v dc. Frankensteinian stuff!

[bobins]

About 15 years ago I remember visiting a couple of the old deep level air raid shelters under London - the lifts down to the shelter levels were still being merrily powered by some Mercury arc rectifiers. On a return visit a few years later, I think they'd been replaced I have a feeling they give off (un)healthy amounts of UV

[Gibbo2286]

I'd quite forgotten about those mercury arc rectifers.

Mercury vapour, another of the terrible hazards we oldies manage to live through.

[Hell Razor5543]

OK, which would happen first? The Mercury Arc Rectifier hitting the ground after being dropped, or the techie making it through the door 100' away?

[CitroJim]

I'd quite forgotten about those mercury arc rectifers.

Mercury vapour, another of the terrible hazards we oldies manage to live through.

Indeed, and back in the day when I worked with MARs operationally I mentioned we used to keep a bank of them on true hot standby to replace failed ones quickly... Those hot ones we used to handle with genuine asbestos gloves!

To detect those that had failed in service they had a small magnetic compass strapped around their envelopes. If the needle deflected we knew that one had failed...

Many MARS were indeed used for providing DC traction current for public transport - including London Underground. Another popular place for them was old cinemas to produce the DC supply for projector arc lamps... If those ran on AC mains it could cause visible flicker on the picture...

The ones I worked with were three-phase rectifiers used to generate the EHT supply (several Kv at several amps) for the PA stages of large HF radio transmitters... On those transmitters sending morse you could 'read' the morse from the flashing glow of the rectifiers!

[Peter.N.]

When I was at school there was a 3rd rail train substation at Chelsfield, station where I got off to go to school, I remember staring through the windows and being fascinated by the glow inside, that would have been in the early '50s

When I started work in the local Radio/TV/cycle shop we had a battery charger with one in it - a bit smaller I must admit, it also had four baretters for the lines of 2 v accumulators, although we rarely had more than two on at a time.

Peter

[CitroJim]

Ahh, now that would have been a charger for the purpose of charging wireless accumulators I take it Peter...

It seemed quite common for wireless battery recharging to be entrusted to the local cycle shop and many went on to become full radio/TV dealers and servicers... An odd relationship...

The last one I remember was in Olney, the next town to me.. Minney Radio... Sadly I can't find a picture of it... It was a proper time-warp..

[white exec]

I vaguely remember a house my grandmother lived in in Northfields, south Ealing. The house had no electricity until the late '50s. Her battery radio had a 2v glass-jar wet accumulator, which the local hardware/cycle shop would recharge, plus an extraordinary EverReady dry battery, which I vaguely remember produced lots of volts, but lasted quite a long time. Presumably the 2v was for the valve heaters?

[CitroJim]

Presumably the 2v was for the valve heaters?

That's right Chris. The big EverReady dry battery would have produced the HT - 90v or 120v was a common voltage from them. They latest for ages as the HT current was only a few mA but the heater accumulator would not last nearly as long as the heaters did draw a fair current..

Some older battery wirelesses also had a tapped 9v grid bias battery...

Valve battery wirelesses lasted right up until the late 50s and by then a combined 1.5v/90v battery was available for them... Many were made by EverReady and Vidor - presumably as a ready market for their batteries! I had a few such wirelesses as a kid and the batteries cost a fortune relative to my pocket money. Generally the 1.5v filament side flattened well before the 90v side so a bit more life could be got from it by running the filaments from a separate U2 1.5v battery...

You just had to be careful as 90v applied to the valves before the 1.5v filament supply could damage them but those valves were cheaper than batteries in those days...

[Peter.N.]

Oh the nostalgia Yes it was for charging 2v accumulators which was one of my jobs when I first went there - until I dropped one through a carboy of sulphuric acid, then I think someone else got the job.

The words 'Accumulators Charged' were still over the window of the shop until it was taken over by a building society.

Peter

[CitroJim]

until I dropped one through a carboy of sulphuric acid, then I think someone else got the job.

Oh dear bet that caused a bit of 'fun' clearing up the resulting mess Peter...

[Peter.N.]

It didn't do the shed a lot of good, it was made of asbestos with a wooden frame.

Peter

[CitroJim]

It didn't do the shed a lot of good, it was made of asbestos with a wooden frame.

Bet you were popular!!

I remember as a kid our local garage, the one dad was always buying cars from, had a little dedicated battery charging hut and it was always full charging batteries..

The acid smell from it was so over-powering it almost knocked you for six as you walked past...

Years back I worked on a UPS system that was supplied by banks of 2V glass lead-acid accumulators to create two 440v batteries that would deliver something in the region of 500A for at least 30 minutes so we're talking big...

Those batteries lived in a large room of their own, specifically designed and ventilated, and were on permanent float-charge...

For years after the batteries were decommissioned and the room turned into an office I could still smell the batteries - despite the room being originally ceramic tiled like a massive bathroom the smell of sulphuric acid had so penetrated the very fabric of the place... The smell lingered for a good five years and maybe longer...

Every few months I had the job of checking the specific gravity of each cell and topping them up as required... That took a full day...

[Peter.N.]

Striking a match could well have got rid of it