Warning on ext. speakers with CTC185 chassis

[Jeff Strieble]

Greetings!

I was nosing around on this group awhile ago and came across a
warning that should and must be heard, if you haven't heard it
already. The RCA CTC-185 XL-100 TV is a great set, once the issues
with the solder joints around the on-board tuner are corrected (I've
had one now for almost four years; it has a great picture, like a
picture postcard, on cable in my small town, even though I've already
had the RF port replaced--the technician resoldered everything around
the tuner when he put back the tuner cover after completing the
repair--haven't had any trouble with the tuner or EEPROM since, and
these repairs were made at least two years ago).

However, this set is not, I repeat not designed for use with external
loudspeakers connected directly to the audio output. The reason is
that the CTC185xx series is a hot chassis design; if the speaker leads
are shorted to ground for whatever reason, extremely serious damage to
the set will occur which will cost at least the original purchase
price of the set to repair. Moreover, anyone who comes in contact with
the speaker frame or terminals and ground will receive a severe
electrical shock and could even be electrocuted. If you want to use
external speakers with this set, run the audio output of your VCR
through an external amplifier and speakers, or else send that output
to a wireless headphone set such as are sold at Radio Shack. (I use
the audio output from my cable box and run it through my Aiwa
bookshelf stereo. Wonderful sound, especially when I listen to the
music channels on Comcast digital cable or music programs on PBS,
etc.)

Kind regards,

Jeff Strieble, WB8NHV
Fairport Harbor, Ohio USA

 

[Art]

Another Great Thompson Design, Eh, Jeff?? May I presume that GE/RCA have
issued a service bulletin regarding this fact via the GE/RCA tech service??
If not, have you called and asked them why they haven't?? Because this is a
lethal customer fault that should be at least addressed on the service level
if at not via a notice generated by the manufacturer.
"Jeff Strieble" <jeffhs@ameritech.net> wrote in message
news:98360ebb.0311110200.6e1fce63@posting.google.com...

Greetings!

I was nosing around on this group awhile ago and came across a
warning that should and must be heard, if you haven't heard it
already. The RCA CTC-185 XL-100 TV is a great set, once the issues
with the solder joints around the on-board tuner are corrected (I've
had one now for almost four years; it has a great picture, like a
picture postcard, on cable in my small town, even though I've already
had the RF port replaced--the technician resoldered everything around
the tuner when he put back the tuner cover after completing the
repair--haven't had any trouble with the tuner or EEPROM since, and
these repairs were made at least two years ago).

However, this set is not, I repeat not designed for use with external
loudspeakers connected directly to the audio output. The reason is
that the CTC185xx series is a hot chassis design; if the speaker leads
are shorted to ground for whatever reason, extremely serious damage to
the set will occur which will cost at least the original purchase
price of the set to repair. Moreover, anyone who comes in contact with
the speaker frame or terminals and ground will receive a severe
electrical shock and could even be electrocuted. If you want to use
external speakers with this set, run the audio output of your VCR
through an external amplifier and speakers, or else send that output
to a wireless headphone set such as are sold at Radio Shack. (I use
the audio output from my cable box and run it through my Aiwa
bookshelf stereo. Wonderful sound, especially when I listen to the
music channels on Comcast digital cable or music programs on PBS,
etc.)

Kind regards,

Jeff Strieble, WB8NHV
Fairport Harbor, Ohio USA

 

[Leonard Caillouet]

This is incorrect in a number of ways. The speaker or other external
grounds on any television made for the US market is not "hot" unless the set
is in need of repair. Not even Thomson would do this. Any competent
technician can confirm this and likely does as part of any repair. Even if
there were a problem that caused the speaker ground to go high and it was
shorted to ground, the damage would likely not cost anywhere near the
original purchase price of the set to repair.

The frame on nearly all speakers is not connected to the speaker terminals
at all. The speaker terminals go to the voice coil, via a crossover network
if there is one.

If the set is used with a single pair of 8 ohm speakers connected properly
to the external connections there is no hazard if the set is working
properly and has not been tampered with or otherwise modified from the
original design.

Leonard Caillouet

"Jeff Strieble" <jeffhs@ameritech.net> wrote in message
news:98360ebb.0311110200.6e1fce63@posting.google.com...

Greetings!

I was nosing around on this group awhile ago and came across a
warning that should and must be heard, if you haven't heard it
already. The RCA CTC-185 XL-100 TV is a great set, once the issues
with the solder joints around the on-board tuner are corrected (I've
had one now for almost four years; it has a great picture, like a
picture postcard, on cable in my small town, even though I've already
had the RF port replaced--the technician resoldered everything around
the tuner when he put back the tuner cover after completing the
repair--haven't had any trouble with the tuner or EEPROM since, and
these repairs were made at least two years ago).

However, this set is not, I repeat not designed for use with external
loudspeakers connected directly to the audio output. The reason is
that the CTC185xx series is a hot chassis design; if the speaker leads
are shorted to ground for whatever reason, extremely serious damage to
the set will occur which will cost at least the original purchase
price of the set to repair. Moreover, anyone who comes in contact with
the speaker frame or terminals and ground will receive a severe
electrical shock and could even be electrocuted. If you want to use
external speakers with this set, run the audio output of your VCR
through an external amplifier and speakers, or else send that output
to a wireless headphone set such as are sold at Radio Shack. (I use
the audio output from my cable box and run it through my Aiwa
bookshelf stereo. Wonderful sound, especially when I listen to the
music channels on Comcast digital cable or music programs on PBS,
etc.)

Kind regards,

Jeff Strieble, WB8NHV
Fairport Harbor, Ohio USA

 

[John Del]

Subject: Re: Warning on ext. speakers with CTC185 chassis
From: "Art" stuby45@massnet1.net
Date: 11/11/03 5:43 AM Eastern Standard Time

Another Great Thompson Design, Eh, Jeff?? May I presume that GE/RCA have
issued a service bulletin regarding this fact via the GE/RCA tech service??
If not, have you called and asked them why they haven't?? Because this is a
lethal customer fault that should be at least addressed on the service level
if at not via a notice generated by the manufacturer.

Wow, where have you guys been? Hot chassis designs have been around forever
(including old tube radios). There is nothing wrong with this low end design
as long as people with no brains stay out of them.


John Del
Wolcott, CT

"Nothing is so opportune for tyrants as a people tired of its liberty."
Alan Keyes

(remove S for email reply)

 

[JURB6006]

Ummm, I've worked on a few of these and I seem to remember an STK 730 chopper
based SMPS. This set <u>should not</u> have a hot chassis.

Is it possible the original poster made an error and meant a CTC175 ?

I could be wrong, this is from memory. In any case I don't recommend using
external speakers on anything not designed for them. I don't know how much of
this is going on now, I haven't really paid attention but I remember alot of 16
or 32 ohm speakers in TVs over the years. Even a tinny little 8 ohm inside the
TV might have 7 ohms DC resistance. When you hook a "real" hi fi speaker to it,
the impedance curve can waste those wimpy little outputs.

I seem to remember sets (was it the CTC140 ?) in which the only change made for
the premium sound was bigger, lower impedance speakers. The chips were the
same.

JURB

 

[Jason D.]

On Tue, 11 Nov 2003 09:19:14 -0500, "Leonard Caillouet"
&lt;lcailloNOSPAM@devoynet.com&gt; wrote:

This is incorrect in a number of ways. The speaker or other external
grounds on any television made for the US market is not "hot" unless the set
is in need of repair. Not even Thomson would do this. Any competent
technician can confirm this and likely does as part of any repair. Even if
there were a problem that caused the speaker ground to go high and it was
shorted to ground, the damage would likely not cost anywhere near the
original purchase price of the set to repair.

The frame on nearly all speakers is not connected to the speaker terminals
at all. The speaker terminals go to the voice coil, via a crossover network
if there is one.

If the set is used with a single pair of 8 ohm speakers connected properly
to the external connections there is no hazard if the set is working
properly and has not been tampered with or otherwise modified from the
original design.

The key:

If using insulated external speaker wire permently attached through
the non-insulating speaker case and other end insulated male plug.
Also made in a way the TV outputs is female connector with NO metal
exposed.

But people don't listen, and use outputs to drive amp or unsafe
speaker sets that where dangers comes up.

The rules states that all inputs and outputs must be electrically
isolated from line power, if power cord has ground pin plug it goes to
cold side. The neutral &amp; hot wires stays inside the hot side behind
isolating device.

Inputs &amp; outputs for user signals with hot chassis:
Can be optisolators, isolated power transformers, signal isolation
transformers, even isolate most of chassis with isolated hot/cold
flyback done this way.

This CTC185 chassis is hot chassis through and through and micro is
programmed to have no i/o option since this is a low end chassis even
has jungle IC is same one for CTC197 &amp; PTK195.

Cheers,

Wizard

Leonard Caillouet

"Jeff Strieble" &lt;jeffhs@ameritech.net&gt; wrote in message
news:98360ebb.0311110200.6e1fce63@posting.google.com...
Greetings!

I was nosing around on this group awhile ago and came across a
warning that should and must be heard, if you haven't heard it
already. The RCA CTC-185 XL-100 TV is a great set, once the issues
with the solder joints around the on-board tuner are corrected (I've
had one now for almost four years; it has a great picture, like a
picture postcard, on cable in my small town, even though I've already
had the RF port replaced--the technician resoldered everything around
the tuner when he put back the tuner cover after completing the
repair--haven't had any trouble with the tuner or EEPROM since, and
these repairs were made at least two years ago).

However, this set is not, I repeat not designed for use with external
loudspeakers connected directly to the audio output. The reason is
that the CTC185xx series is a hot chassis design; if the speaker leads
are shorted to ground for whatever reason, extremely serious damage to
the set will occur which will cost at least the original purchase
price of the set to repair. Moreover, anyone who comes in contact with
the speaker frame or terminals and ground will receive a severe
electrical shock and could even be electrocuted. If you want to use
external speakers with this set, run the audio output of your VCR
through an external amplifier and speakers, or else send that output
to a wireless headphone set such as are sold at Radio Shack. (I use
the audio output from my cable box and run it through my Aiwa
bookshelf stereo. Wonderful sound, especially when I listen to the
music channels on Comcast digital cable or music programs on PBS,
etc.)

Kind regards,

Jeff Strieble, WB8NHV
Fairport Harbor, Ohio USA

 

[Jason D.]

On 12 Nov 2003 00:12:46 GMT, jurb6006@aol.com (JURB6006) wrote:

Ummm, I've worked on a few of these and I seem to remember an STK 730 chopper
based SMPS. This set <u>should not</u> have a hot chassis.

Is it possible the original poster made an error and meant a CTC175 ?

CTC175 &amp; CTC185 are like in concept but design not same and is hot
chassis. CTC176 &amp; 177 uses STK730-xxx is true hot/cold chassis due to
SMPS transformer and allows i/o capablity.

I could be wrong, this is from memory. In any case I don't recommend using
external speakers on anything not designed for them. I don't know how much of
this is going on now, I haven't really paid attention but I remember alot of 16
or 32 ohm speakers in TVs over the years. Even a tinny little 8 ohm inside the
TV might have 7 ohms DC resistance. When you hook a "real" hi fi speaker to it,
the impedance curve can waste those wimpy little outputs.

I seem to remember sets (was it the CTC140 ?) in which the only change made for
the premium sound was bigger, lower impedance speakers. The chips were the
same.

If true, that's interesting.

JURB

 

[RonKZ650]

Ummm, I've worked on a few of these and I seem to remember an STK 730 chopper
based SMPS. This set should not have a hot chassis

It's definately a hot chassis, and I mean HOT. Some sets if you accidently
ground the hot chassis it does minimal damage, not the CTC185. Ground the
chassis on it and immediately the board is burned, ICs burned as well as the
filiments in the CRT burned out. Yes, it is a hot chassis.