Live chassis sets made past the late 80s?

[japlytic]

When I was doing research on the Philips Discoverer (14GR1220), I found the chassis was a GR1AX and was introduced in 1989, with the last two models introduced in 1993 (20GR1250 and 14PT121A).

I originally thought the Discoverer was a Japanese rebadge, but actually has a genuine Philips chassis.

The whole GR1AX chassis is at mains potential, and I thought the production of live chassis TV sets were discontinued around the late 80s.

I still wonder why a live chassis set was still in production up to the mid 90s?

[Wizard]

Re: Live chassis sets made past the late 80s?

Many hot chassis existed on cheap TVs that used linear regulator and the flyback transformer was the isolation for supplying different cold side DC or pulses to the chassis. Even JVC did this up to around 1999 or so.

True hot chassis died out long ago when makers went from tube, or transistors and small scale ICs to ones that has microcontroller and one jungle IC design.

Still, use caution when working on electronics that is directly plugged to the wall. Small area is hot. We always use isolation transformer for safety when working on stuff daily.

Cheers, Wizard

[larrymoencurly]

Re: Live chassis sets made past the late 80s?

I had a Sanyo 19" from about 1995 like that, so it used optical isolators for the direct video and audio inputs. I finally had throw it away last year because the front half of the cabinet had become so brittle that I was afraid the CRT would fall out while the TV was just sitting on the shelf.

[Krankshaft]

Re: Live chassis sets made past the late 80s?

I have a cheap Sharp 20" TV VCR built in 01 that wasn't isolated.

It has a 130V B+ regulator for the flyback transformer the heatsink it is on is hot.

An onboard switcher powers everything else.

[japlytic]

Re: Live chassis sets made past the late 80s?

I have a cheap Sharp 20" TV VCR built in 01 that wasn't isolated.

It has a 130V B+ regulator for the flyback transformer the heatsink it is on is hot.

An onboard switcher powers everything else.

The VCR section would have to be isolated, because there is a risk a child could put their hand inside and touch the metal. For this TV/VCR unit, is the TV section the only section which is entirely at mains potential?

[Krankshaft]

Re: Live chassis sets made past the late 80s?

The VCR is run off a small switcher so it's isolated only the 130V B+ on the primary of the FBT is unisolated which is supplied through a line connected linear regulator.

Touch that regulator heatsink without an ISO and your hair will stand on end .

Modern CRTs derive the flyback B+ from the switcher too don't know why they did it this way. They already had a switcher right there just add an extra winding. Guess they didn't want to invest in more copper and the linear reg was cheaper.