What is a hot SS chassis?

[Rod Beauvex]

How does that work in Solid State?

[maxhifi]

All hot chassis means is the chassis ground is connected to one side of the AC line. It's bo different in a tube or solid state TV

[Jon A.]

Some are biased against hot chassis solid-state sets just because, well, they're solid-state. As for hot chassis tube sets, I've never heard a peep against them because of that. It's about preference, not superiority.

[zeno]

Originally Posted by Rod Beauvex

How does that work in Solid State?

This is a most the time answer, in general.........

A cold chassis uses a big, heavy, expensive power transformer
OR a more complex switching supply with a small transformer.
The AC ground is separated or isolated from the main chassis ground.

A hot chassis one side of the chassis ground goes to one side of
the AC line. So if plugged in backwards the metal ground of the
chassis has 120 VAC on it. Sets with bridge rectifires are hot either way.
Thats why you have polarized plugs, plastic insulated knobs & shafts cardboard insulators, antenna isolation etc.

Its cheaper to build a hot chassis. When video & audio ins & outs
became popular sets switched to switching supplies. They
cost more than a hot chassis but less than a power transformer.
You need a cold chassis to hook things together, including test
equipment.

Most small sets up til the mid 80's were hot. Most high end sets
& consoles were cold with power transformers til abt 1980.
The more you spent the more likely you got a cold set.

More if you need it.........

73 Zeno

[maxhifi]

Originally Posted by Jon A.

Some are biased against hot chassis solid-state sets just because, well, they're solid-state. As for hot chassis tube sets, I've never heard a peep against them because of that. It's about preference, not superiority.

You have now! Especially in a tube set, which requires more frequent service, it is nice to know your life is not in jeopardy just by touching the chassis. Cold chassis sets are safer to work on, and don't require a cumbersome isolation trabsformer.

[Rod Beauvex]

I had always though a switching PSU was considered hot. Now I know different.

I vaguely understand how tube hot chassis works. I just thought that sort of thing didn't apply to SS.

[andy]

...

[dieseljeep]

Originally Posted by maxhifi

You have now! Especially in a tube set, which requires more frequent service, it is nice to know your life is not in jeopardy just by touching the chassis. Cold chassis sets are safer to work on, and don't require a cumbersome isolation trabsformer.

I was always biased, toward a transformer power supply, in a vacuum tube set. I always considered it to be a higher quality model.
It seemed funny that Muntz, being one of the lowest priced sets, used full power transformers until around the 1955 model year.

[zeno]

Originally Posted by Rod Beauvex

I had always though a switching PSU was considered hot. Now I know different.

I vaguely understand how tube hot chassis works. I just thought that sort of thing didn't apply to SS.

On a switcher the primary side is hot, thats where most the PS
parts are. Regulation comes by sampling the cold side through
an isolator or sampling a separate winding. It can get confusing
what you have. There was even a Panasonic that had 3 grounds.
Others prob did it too. Over the years all the power supply variety
kept you on your toes & kept things "interesting".

For servicing best to use isolation always. I will admit for 35 yrs+
I never did unless plug-in test equipt was used. Only got one
really bad shock, lots of CRT's discharges "SNAP !" , tingles & a few ZZZT's. But play it safe..........
Last thing is when you get to SS sets know what you got & which
ground to use while troubleshoosting.

73 Zeno

[Jon A.]

Originally Posted by maxhifi

You have now! Especially in a tube set, which requires more frequent service, it is nice to know your life is not in jeopardy just by touching the chassis. Cold chassis sets are safer to work on, and don't require a cumbersome isolation trabsformer.

Normally I wouldn't know if a chassis is hot or cold unless I saw a sticker on it indicating this. Until I get an isolation transformer I suppose I'll just have to reverse plugs if my meter shows voltage between the chassis and ground.

[rrrhre2s]

Another Possibility that the set has a full-wave rectified power supply with 4 diodes in a bridge configuration. Placing the chassis ground at about 70 volts above ground regardless of line cord plug polarity.

rrrhre2s

[rca2000]

MOST often...modern sets that have an SMPS power supply are 'cold" chassis, other than the primary side of the power supply. This has been pretty much the standard since the late 1980's or so--as sets with AV I/O connectors became popular. It IS possible to have AV connectors and such with a hot chassis, BUT it then becomes a big deal , using a bunch of either isolating networks using either transformers or optocouplers for EVERY connector, in or out. With a cold chassis-isolation is not necessary.

Now...there IS a type of SMPS out there...that is NOT isolated,known as the "buck converter", but it is not often used anymore. Zenith did use it on the 9_516 chassis.

Pretty much if you see an SMPS transformer on the chassis in the power supply...thee set IS isolated. Especially if it has multiple AV in/outs .

Also, since SMPS sets tend to be less power hungry than those with a hot linear regulator--most al sets these day are SMPS powered and cold. I have NEVER seen a flat panel with a hot chassis. Hot inverters yes--but chassis NO.

Now--Sony did NOT often use a cold chassis, into the mid-1990's or so--it was common to see a hot chassis with a bunch of isolation networks on the AV board, often ceramic-covered..But finally--they went to cold SMPS supplies...done the "Sony way"..with difficult to keep repaired ckty that was VERY finicky and delicate.

I have always been partial to cold chassis...and ALWAYS will be. Be it a tv, amp, radio or stereo chassis.