Vince:
Other than expensive flybacks, you should check the B+ regulation circuitry
to verify that it is indeed regulating at the correct voltages. Also, with
a variac on the AC line, vary the line voltage +/- 10 volts or so to see if
the B+ holds steady.
Check all the pcb solder connections around and near the high heat producing
components such as power resistors, diodes, semiconductors, ICs mounted on
heatsinks, and the flyback xfmr.
I would also ESR check all the electrolytics in the PS and in the Flyback
area and flyback derived B+ circuits..... no ESR meter?.... then the only
alternative is the more time consuming task of substitution and replacing
electrolytics.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


"Vince and Marge" wrote in message
I have a Daewoo color MdlDTQ-25S2FC Chassis CN-200A. The H.O.T. overheats
and then fails, need help on this, also I have Zenith SJ2726EW5, the
regulator {STR53041} overheats and fails, any ideas on either on of
thesse?
Vince.

On Fri, 8 Aug 2003 14:53:07 -0700, "Sofie" wrote:

Vince:
Other than expensive flybacks, you should check the B+ regulation circuitry
to verify that it is indeed regulating at the correct voltages. Also, with
a variac on the AC line, vary the line voltage +/- 10 volts or so to see if
the B+ holds steady.
Check all the pcb solder connections around and near the high heat producing
components such as power resistors, diodes, semiconductors, ICs mounted on
heatsinks, and the flyback xfmr.
I would also ESR check all the electrolytics in the PS and in the Flyback
area and flyback derived B+ circuits..... no ESR meter?.... then the only
alternative is the more time consuming task of substitution and replacing
electrolytics.
--

In this Daewoo, good news for you, problem isn't flyback, I know this
well CN-200a and 200i, fixed so many of those chassis...Replace three
100uf 35V caps. Two near vertical IC heatsink, one in middle of PSU
between rows of ceramic axial resistors.

There two more which is really responsible for shutting down after 1/2
hour or killing the HOT is two 1uF 160V caps in H. driver circuit.
Replace both with 1uF 160V or 200V. All caps preferably 105C
temperature rating.
Fly on daewoo wasn't the problem actually. The heat building in there
is excessive because chassis is tiny, crammed so tight that hot
components are cooking these caps to death and browning the PCB.

Zenith, you might have a bad tube overheating that STR-53041. Check
the two small capacitors in that hot side of switching power supply
first.

Get ESR meter if you're repairing for a living.

Cheers,

Wizard

Possible parts to check/replace:
Daewoo
Open C401 in horiz driver ckt. 1ufd/160V
Q402 D1880,Q804 C2500, Q805 E13009-2, 5A FUSE
If you have repeated failure of H.O.T. Add a 33 ohm 1/4 watt resistor
across the Base and emitter of H.O.T.

On 9 Aug 2003 09:48:28 -0700, (Danny) wrote:

Possible parts to check/replace:
Daewoo
Open C401 in horiz driver ckt. 1ufd/160V
Q402 D1880,Q804 C2500, Q805 E13009-2, 5A FUSE
If you have repeated failure of H.O.T. Add a 33 ohm 1/4 watt resistor
across the Base and emitter of H.O.T.

Actually there is another cap in horizontal circuit same specs, 1uf
160V. Change both, also few other caps sitting in hot spots like I
listed in other post. Every one I checked, they were bad, ESR is too
high or totally open.

Cheers,

Wizard

About 70% or so of all Zenith tv's and Citizen tv's made by Zenith
since around 1992 till now have defective picture tubes that cause
either a defective green gun giving you bright green screen or a G1
short causing the power supply to become defective:

http://www.iwaynet.net/~nesda/Zen90.html

either way 70% of them or so have a defective crt and many are only a
couple of years old,I tell the customer that an average tv should last
over 12 years and I give my customers Zenith's phone number and I tell
them to complain to them:

LG ELectronics
Alabama,USA
Ph:1-800-243-0000

I have had at least 100 customers call Zenith and complain about those
garbage crt's.

That is the official phone number for Zenith (1-800-243-0000),it used
to be for Canada as well but now Canada's # is 1-888-542-2623,it is
accessible in Cape Breton where you are at,and of course in Dartmouth
where I am at.