Sanyo CE21A2 TV arcing in tube neck between anodes at switch-on
 

Hi all,

I have a 21" Sanyo TV set (Philips tube) which, when switched on,
starts up very briefly and arcs once between the anodes visible in the
long uncovered tube neck. The line stage shuts down so quickly that it
appears not to start-up at all, but clearly it is doing in order to
provide the voltages required for the single arcing. The set then just
stays in standby mode with the front LED blinking 3 times in a row
repeatedly.

I cannot find blink codes for the front LED, but I can assume it's in a
protection mode (unless anyone knows differently?) and need to find the
reason for the arcing. Initially I had found that R666 - bad omen or
what - (8R2 5W) lifted out from its intact solder joints.
Fibreglass-pen treatment to the legs of the resistor and resoldering
put that right, but did not affect this fault. The resistor is a
surge-limiter in the feed to the line-output transistor (or HOT, if you
prefer that terminology). Maybe this is coincidental or a clue as to
what may have happened to cause this arcing.

The line-output transistor and its internal diode is fine and so is the
snubber capacitor, so they're ruled out as causing excessive-voltage
from the flyback. I'm not sure what to do next... LOP transformer or
tube defective? I know Philips have been having tube problems for a
while now, already written off a 32" one with internal leakage causing
a protection fault.

Thanks all,
James

PDF service manual for this set/chassis available to download he

http://www.spiritworldcentral.com/files.php

HandyMan wrote:
Hi all,

I have a 21" Sanyo TV set (Philips tube) which, when switched on,
starts up very briefly and arcs once between the anodes visible in the
long uncovered tube neck.

is the power supply Ok? the B+ line not too high?
-B

Sorry, I should have said.

The B+ line is spot on for its standby voltage. Of course, the line
stage stays on for such a short time that I can't check the B+ voltage
in the 'On' state, but if the standby voltage is right, I can only
assume it drops to the correct level when the line stage pulls some
current.

On 2 Oct 2005 08:19:18 -0700, "HandyMan"
put finger to keyboard and composed:

I have a 21" Sanyo TV set (Philips tube) which, when switched on,
starts up very briefly and arcs once between the anodes visible in the
long uncovered tube neck. The line stage shuts down so quickly that it
appears not to start-up at all, but clearly it is doing in order to
provide the voltages required for the single arcing. The set then just
stays in standby mode with the front LED blinking 3 times in a row
repeatedly.

Could it be that the focus and G2 voltages are too high? If so, then
this may be due to an open resistor in the bottom end of the
screen/focus block on the FBT.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

Likely the picture tube is bad. Unlikely, a crt rejuvinator
MAY save it, but not likely.

On Sun, 2 Oct 2005 19:52:38 -0230, "Skype_man"
wrote:

Likely the picture tube is bad. Unlikely, a crt rejuvinator
MAY save it, but not likely.



I've seen several recent Philips CRTs that were so gassy the necks
glowed. They must be having some manufacturing problems.
Andy Cuffe

-- Use this address until 12/31/2005

-- Use this address after 12/31/2005

Thank you everyone for your replies.

Well, since this message was posted, I noticed arcing from a part of
the tube bowl (top-right corner) where glass has been knocked out to
the dag, with a long crack emanating from this damage right to the seal
between tube bowl and front glass screen.

The arcing at this point only happens once every 10 or so switch-ons,
so I hadn't seen it before.

I assume air has got in and the arcing is because there's now no
electron beam flow from the cathodes due to air resistance and
impedance and so the EHT, with no electron beam current to sate it, is
seeking a point of lower potential and finding it in the form of the
grids and cathodes. This is only a theory though, since I have not come
across a CRT with air in it before. Anyone know for sure that this
effect would occur if the tube was absolutely full of air?

Thanks again for your kind help.

Best regards to all,
James

Andy Cuffe wrote:

I've seen several recent Philips CRTs that were so gassy the necks
glowed. They must be having some manufacturing problems.
Andy Cuffe

It's caused by Taco Bell commercials.

--
PB
"Fresh windows units enter the internet backwards, bent
over & naked, screaming “Don’t infect me! It will take
me more than 12 minutes to download the security
packs!”-anonamin

Plague Boy wrote:
Andy Cuffe wrote:
I've seen several recent Philips CRTs that were so gassy the necks
glowed. They must be having some manufacturing problems.
Andy Cuffe

It's caused by Taco Bell commercials.

Don't knock 'em. They're the only real example of truth in advertising
today. They begin and end their commercials with "Dung!"

--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.