Where live chassies banned on Australia

[kx250rider]

Originally Posted by andy

That TV must have also had a defective antenna isolation block. No dangerous voltage should ever appear on the F connector regardless of which way the power line is connected. Even when the power is connected correctly, the chassis of a hot chassis TV still has a dangerous voltage on it, and needs to be fully isolated from anything the user can touch.

True in theory, but by the late 80s and 90s, the F-connector was common ground with the whole ground of the board, which was often connected to the neutral side of the line. Same deal on cable boxes and VCRs. The Sony TVs from the 70s also had the F-connector live. In fact, when I was working for a Sony shop in the 80s, there was a rule that you may NOT use the F-connector to feed the sets on the bench. We had to use a 75-300 ohm transformer and use the twinlead input. The boss got tired of buying SG-613s after a tech would blast the power supply by cross-polarize the TV with the antenna amplifier, which was in common with all of the other TVs on the bench. We did use isolation transformers on all sets being worked on, but not for bench-testing after repairs were finished. One of the worst cases I saw myself, was that I was in a customer's house, and the husband was trying to show me some sort of a hook-up problem he was having, and he laid the cable box ontop of the VCR... A big flash, and the house breaker tripped. The cable box and the VCR were welded together from one of the cable box's case screws and the metal case of the VCR. It was a Panasonic VHS machine from the 80s, and the cable box, if I recall, was a Zenith from the 80s. It also took out the power supplies in both units. Turned out that the customer had an old nonpolarized extension cord running into the wall cabinet where all this stuff was hooked up, and the VCR & cable box were reversed.

Charles

[yagosaga]

Hello,

I am repairing tv sets since 1973. The first non-life chassis I personnally saw was in 2005. It was an U.S. tv set... It was an incredibly exciting feeling to touch the chassis without being fried...

- Eckhard

[andy]

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[Telecolor 3007]

Many people died in Romania trying to repaier live chassie sets!
I can use a protection transformer or a transformer if you want to have a set like this, in order to don't have the phase of the electricity network on the chassie.

[wa2ise]

Originally Posted by Telecolor 3007

I can use a protection transformer or a transformer if you want to have a set like this, in order to don't have the phase of the electricity network on the chassie.

Ideally, the cabinet of this sort of set should completely insulate the user from the hot chassis. And also, the RF input F connector should not have a direct DC (or 50Hz AC path to the line as well. If this is done well, hot chassis sets are perfectly safe.

Of course you should use an isolation transformer when you service such a set on the bench.

[Telecolor 3007]

Well, usually Soviet sets had a transformer, but my vintage one is an exception: it haves autotransformer, not transformer, so there is the risk of live chassie; and the thing only works at 127 or 220 V - is not the model that also works at 110 V (I have an 220 V - 110 V transformer at my home). The Romanian "Electronica" Naţional V.S. 43-614 that I intend in the future to get me, haves no transformer, but works at 110 V or 220 V, so I can use the transformer that I have.