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 Return to top of page · Post #: 1 · Written at 8:45:33 PM on 16 November 2018.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4337

Once upon a time & frequently, I have made comment on the risks associated with powering old mains equipment which has been abandoned for some time. One continuously harps on inspecting first to see if its safe to power. One of the major unseen hazards it the Electrolytic capacitor.

With time, the oxide layer in Electrolytic caps deteriorates. It is the insulator & when it is gone the cap loses its polarity & presents as a short circuit: The term is loses "form". Replacement is more commonly the answer,rather than try to redeem them (re-form).

Many of these old devices were abandoned, as they broke down, another reason for checking.

I have been waiting but today is my lucky day: The photo I am sending Brad (when the email works) shows dramatically what can happen,when you ignore the various forms of the advice above, presented, by others as well..

Burnt out transformer
Snake


 
 Return to top of page · Post #: 2 · Written at 10:46:45 AM on 17 November 2018.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6347

Well said, Marc, and I often have the same feeling - 'is the message sinking in, etc'...

One of the pranks we used to play on others when I was an apprentice was to deliberately blow up under-rated capacitors to startle anyone in proximity to 'ground zero'. This didn't go for long because the downside was that it was costing money and wasting good components.

The end result was the same - foil everywhere and a lot of mess to clean up. The difference is that the pranks were what one may loosely describe as 'controlled conditions' and even though it was a dangerous practice we did take steps to make sure the victims heard the noise but couldn't be showered in shrapnel. An old valve radio with dried condensers and left to run without supervision, one thing I also know a bit about, is a different story and has the potential to bugger a radio or even kill its owner.

Because of an experience I once had with a Kriesler 11-20, I do not stuff around. Some people see a benefit in keeping old components in service when they really should be replaced but I don't. I will not operate any valve radio at all if it still has its original filters in place and am more likely to simply do a clean sweep and replace all electrolytic and paper capacitors without even bothering to check whether the originals are still fine or not.

If a radio requires realignment following that practice then I realign. I'd rather spend time on that than spend time on making a silk purse from a sow's ear and reforming condensers that should just be binned. The average Aussie radio can be re-capped for around $25.00 on a self-serve basis. A lost life costs a lot more and not just in monetary terms.

Radios that I set up just as display pieces get a slightly different treatment that some also don't like - I cut off the cord at its terminals and re-install the chassis so the radio cannot be played until it is seen to correctly.

As for e-mail, I hope to have it running late tomorrow afternoon.


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A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 3 · Written at 11:21:07 AM on 17 November 2018.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4337

I should also send another photo of a hidden danger working on radio in the bush. There are no mice in my workshop. This due principally to the efforts of the resident 4ft long, organic disposal unit. Seeing that she was nesting a bit too close to my feet, the hole has now been pumped full of expanding foam.


 
 Return to top of page · Post #: 4 · Written at 7:36:43 PM on 20 November 2018.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6347

Photos uploaded.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 5 · Written at 7:38:37 PM on 20 November 2018.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6010

I can almost smell that transformer from here. Once smelt, never forgotten.


 
 Return to top of page · Post #: 6 · Written at 7:58:47 AM on 21 November 2018.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4337

Its now a case of cause rather than effect: For those who like adding fuses... it's intact. The unit is a Thorn (in my side) Chassis stamped 6752

OP transformers (Rola) stamped 13 June 68. (6GW8's) Even the dial string has been toasted. I will feed the electrolytics (probable cause) to the reformer & step them up in voltage: It will lock up if there is an overload.

Havn't had time to work out what the rectifier is (not valve) but its not beyond suspicion either. Fuel pump in the Ute has a higher priority. Modular service: The vacuum pump is not meant to be pumping oil out. Only refitted it in the 80's??


 
 Return to top of page · Post #: 7 · Written at 8:12:15 AM on 21 November 2018.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1903

Talking about disasters, worn diaphragms in those pumps can allow petrol to leak into the sump. Dramatic explosion can follow! I once saw the aftermath....

Quick fix and improvement for the ute Marc:

Fit an EK fuel pump and wiper motor. The EK (electric) wiper motor is a drop-in replacement for the vacuum motor. Nice if you can find an original switch though.

Re small transformers and fuses - as you know, no conventional fuse can protect a small power transformer. Thermal fuses in contact with the windings are the only way.


 
 Return to top of page · Post #: 8 · Written at 2:29:20 PM on 23 November 2018.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4337

Ute is 1958 MKII Zephyr (unrestored) Apparently a Mini one is a drop in fit, although one from a later Zodiac should also. Think I have a switch. The idea is to keep it original, however.

Did have a thermal fuse go in a powered speaker: Offsite no real obvious reason so I cut it out & put a new one in, insulation test etc & let it run several hours. Never got hot? Still going. It is a Pity this one did not have one. One should be able to add one without making it intrinsically unsafe, where there is a risk of overheating.

Fun things to solder (not a good idea). One needs a good heatsink between it & the heat, or its a goner if its not a reset type.


 
 Return to top of page · Post #: 9 · Written at 4:15:10 PM on 23 November 2018.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6347

Microtemps can blow due to surges which is why they appear to blow for no apparent reason. A hospital I used to work at copped a big surge over one weekend, which blew the microtemps in nine electric patient beds. I didn't find out about it until complaints rolled in about the flat batteries.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 10 · Written at 8:22:42 PM on 23 November 2018.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4337

The place where that was being used has no form of protection other than a basic surge type power board on the computer & printer. Here it is a different story.

This as I have noted before, is a lightning prone area. As a consequence there are very few of what I call critical circuits without protection. So far in many decades I have not has a surge kill at the houses. This in the face of the spur that I am on having an aerial almost cut through, a transformer destroyed, and a house needing rewiring & all of the electrical goods, including the HW service & fuse box, replaced. A pump did get a punch through and a contactor loose a terminal with one strike: It was on an LV aerial line 460m.

I did note in one surge board they have copied, or discovered my idea. Aside from caps to get rid of the RF that is riding on the mains, there are two MOV,s. The configuration (as noted previously) is one big one broadside across Neutral & Active and another Active to ground. All sockets are wired correctly. All faults & non compliance etc. was eliminated when the feeders were put underground. All of the 1962 installed fuse boxes were replaced.

The object of this combination is not only to try & bring down the surge but to actually kill the circuit. The best way to do that is to trip the RCD, which is what it does do. Most of the power consuming / wasting wall warts on the computer are on a contactor: One switch kills the lot. As these are all low power consumers master has a 3A fuse.

It is imperative that MOV's are in a housing that they cannot set alight as, apparently some have been known to explode.


 
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