ON / OFF Switches and Safety.

[Ferguson 2000]

Hi,

The following is in response to a couple of threads that I have read recently and comes from fifty years experience of repairing television receivers.

If an on / off switch is thought to be faulty then it should be replaced. If a replacement is not available then it should still be removed, the wires can then be linked together, the joints insulated and an external double pole switch fitted.

The reason for the above is that over the years there have been a number of switches which have failed, arced internally, with the set appearing to work, and have continued to burn even after dis-connection of the mains supply.

Three makes of set come to mind, all famous manufacturers, but I am not sure if I should name them on this forum.

One was mounted on a srbp (paxolin) PCB and the replacement switch came with a fibre glass replacement. Another had wires added to connect the switch contacts to the PCB without the stress caused by the physical operation of the switch. The third was mounted to the plastic cabinet of the set. Anyone else remember them ?

The possible reasons for these failures are many. With the introduction of push button switches the strength of customers may have been underestimated. The use of standby via remote controls may have led to the assumption that the front panel switches would be rarely used.

Switches were rated for both surge (switch on) and continuous use and an incorrect rating could have been used as a replacement during the repair of the set. The surge current in later CTV's is substantial.

Happy restoring,

Geoffrey.

[FERNSEH]

In more recent times, (if you can call the eighties and nineties recent times) there was a good number of recalls of certain TV sets from manufactures because of arcing and insulation breakdowns in on-off switches.
Memories fade but one particular set that comes to mind was the ITT CVC40 series and also the Ferguson 59K7 ICC5 had an issue with the switch.

I'm sure there was many more.

DFWB.

[Philips210]

Hi

I remember the modification of adding the jumper wires to the mains switch on the ITT CVC30 and CVC32 receivers. These sets also suffered solder joint embrittlement on the scan correction board, particularly around the Pressac connector carrying the line scan current. Good sets generally apart from a fragile LOPTx.

Regards
Symon.

[slidertogrid]

I thinks some Sony sets were recalled for switch burning problems I think the replacement switch from Sony came complete with mains lead and instructions to fit jumper wires. I have never liked the all plastic press on press off switches. I always make sure my sets that are fitted with them are unplugged when not in use. Some sets have the filter capacitor wired before the mains fuse, the only fuse protection relying on the plug fuse being correctly rated.
Rich.

[FERNSEH]

One of the switches that often failed because of failure of the SRBP tag panel.
Two versions of this Lorlin switch were made, one with solder tags and the other with pins for mounting directly on to the PCB. Some had the reset contacts for the remote control system.
The same firm made a much better switch, a much bigger component in blue and white plastics.

DFWB.

[turretslug]

Some years ago (and maybe still ongoing to a degree), umpteen computer PSUs (ATX and similar) with DP push on/push off switch on flying lead were being skipped. These generally have metal-cased thermoset bodies with similar fixing arrangements and centres and were designed for the heavy hit of a supply-side rectifier and reservoir electrolytic and had lots of approval badges. I realise that there are often safety and originality questions over substituting this sort of component, but if the original component was rubbish and even unsafe then the argument is at least partially countered.

[Welsh Anorak]

Hi
All of us in the trade in the Nineties remember the Sony switch in the 2090 series - I've seen one or two that had very little cabinet left so it clearly was a serious issue. They used Preh switches which, oddly enough, gave little trouble in other receivers. However we know the Trinitron CRT's degaussing system takes a huge gulp of current so that probably led to their demise.They had to be replaced by a totally different switch and only by Sony service centres.
Philips sets of the late Nineties also come to mind, the switch often taking the PCB with it - hopefully that was all.
It was always a relief when a Ferguson 59P7 came in and all it needed was the on/off switch as pictured above replacing for the more reliable white version.
Other sets did give switch problems, but fairly few and far between, with PCB mounted ones giving rise to the most trouble.
Of course LCDs don't have that trouble - or do they? Many cheaper sets are fitted with rocker switches which fizz and crackle, but have to be replaced like for like.
Very few of the more quality makes have mains switches - those that do, such as Panasonic, are 'soft' switches with the PSU very much alive. The only recent one I can think of with a real mains switch is the Toshiba with the side mounted button - the expensive button cap fails but we change the 2-pole switch as well because it's usually fizzing.
Luckily times have changed from the five-amp fusewire across the live side of the mains switch just waiting for the unsuspecting engineer to grab the aerial lead and chassis at the same time...
Glyn

[McMurdo]

I do remember back in the early 90's having to order a special grundig power switch because the standby contacts didnt work, meaning the TV wouldnt automatically come out of standby if switched on by the mains switch.
The first time I had a tv in where it automatically entered standby when switching on I thought was faulty, and had to ring the manufacturer to be reassured it was that way by design. How times have changed.
One portable that came in had a live speaker grille. The mains switch had gone faulty so the button wouldn't latch in. To use the telly, the customer had nailed the button shut through the grille with a carpet tack! They only brought it in when the degauss coil melted due to an arcing positor. Needless to say I replaced the switch.

[1955APREN]

Hi everyone,
One of the Matsui 16 portables made by Decca had a Lorlin sw fitted, and there was a recall on this set to have it replaced. But when the back of the set was removed lots of the sets in this range had a different type of sw fitted.
This same sw was used by other makers (Ferguson TX90 & TX100) but I do not recall a mod being suggested by this maker. The two types of the Lorlin sw were stock, carried in the car kit.
Regards Derrick

[Welsh Anorak]

Yes - one PCB and one tagged - both with auxiliary 'ears' so we didn't have to carry four in case we encountered a remote set.
Dare I admit to doing a slight modification when one or the other was missing from the spares box?
Glyn

[greg_simons]

Originally Posted by Welsh Anorak

Hi
All of us in the trade in the Nineties remember the Sony switch in the 2090 series - I've seen one or two that had very little cabinet left so it clearly was a serious issue. They used Preh switches which, oddly enough, gave little trouble in other receivers.

Fair play to Sony, they made strenuous efforts to get back every single faulty TV. I did see a charred example of one of these sets, it wasn't a pretty sight, but fortunately no further damage to life or property had been caused.