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Grundig TV Dead

 
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PostPosted: Mon Dec 08, 2008 12:42 pm    Post subject: Grundig TV Dead Reply with quote

Hi,

I have a Grundig 28wf100 CRT tv thats a few years old.

Last week it turned itself off and now won't turn back on again.
The LED on the front blinks green, but nothing else happens.

I have the service manual for the TV, but need somebody to tell me if it can be fixed, and how?

Do I need to replace something on the boards, or is it just a case of re-soldering some components?

Thanks,
Eoin
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LJ



Joined: 09 Dec 2008
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PostPosted: Tue Dec 09, 2008 6:48 pm    Post subject: Reply with quote

Check horizontal transistor, if it's shorted, release the Tr, then turn on the TV, when the green lamp blink check B+ fly back, it sould be 120 - 135 Vdc, if 0v or more then 180 Vdc, repair the regulator first.
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PostPosted: Wed Dec 10, 2008 8:51 am    Post subject: Reply with quote

Thanks for the reply.

I'm going to ask some silly questions now.

Would you know off-hand where the horizontal transistor is located (PSU, video, RGB)?

By release the Tr, you mean remove it from the board?

Where is the B+ fly back and the regulator?

I have the technical manual for the TV, but it has only circuit labels.

Thanks,
Eoin
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jts1957



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PostPosted: Wed Dec 10, 2008 11:58 am    Post subject: To (maybe) clarify what LJ told you Reply with quote

All this assumes you have some means of measuring resistance and voltage. How much experience desoldering/soldering have you had? Still want to try? Regulator (in Power Supply) provides B+ (usually 120 - 140 volts) through a winding in the Flyback to the Collector of Horizontal Output Transistor (flyback has thick red wire connected to "bell" of picture tube). Horizontal (3-leaded, Collector - Emitter - Base) Transistor should be secured to (usually) a fairly large metal "heatsink" near the flyback in the Horizontal deflection circuit. Start with set unplugged!
Test it first by putting meter leads (meter set to "diode" or "ohms") across base/collector, then base/emitter, then emitter/collector (one lead on base the other on collector, etc.). You should only get a "shorted" reading base to emitter (reads secondary of driver transformer &/or internal resistors). If collector to base &/or collector to emitter read "shorted," you only have to disconnect (float, either by cutting or unsoldering) center lead (Collector) from where it's soldered to the circuit board. If they don't have any "shorts", then just measure DC volts without disconnecting collector.
Turn set on and set the meter to DC volts and measure between the "pad" you disconnected (or not) lead from and ground. Usually emitter is ground (or close enough)(Red lead to "pad"). Meter should read the value your service manual quotes (maybe slightly higher).
All this just covers ONE possibility!
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LJ



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PostPosted: Wed Dec 10, 2008 2:04 pm    Post subject: Reply with quote

Sound like you haven't experience, jts1957 explanation is right but remember if you haven't experience, be careful with high voltage.
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jts1957



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PostPosted: Wed Dec 10, 2008 2:53 pm    Post subject: Reply with quote

LG - Check your Private Mail (PM)!
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jts1957



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PostPosted: Wed Dec 10, 2008 2:54 pm    Post subject: Reply with quote

Sorry.

LJ - Check your Private Mail (PM)!
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PostPosted: Wed Dec 10, 2008 3:26 pm    Post subject: Reply with quote

Thank you so much for the detailed answer.
I'll have a go at it over the weekend.

I might not have experience of pulling a TV apart, but I'm willing to learn, and have done lots of work inside of computers, including how to measure voltages, ohms, amps and capacitance with my trusty multimeter.

The problem I have is that the technical manual has nothing but diode and resistor labels, and I'm finding it hard to match that back to what you guys tell me to check for.

But, again, thanks for the great answer, and I'll let you know if there is any outcome from my fiddling.

Eoin
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jts1957



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PostPosted: Wed Dec 10, 2008 6:25 pm    Post subject: Service manual Reply with quote

Service manual is in this forum's database. Horiz. Output is TL2 (BUH1015). +VB (B+) equals 133 volts. Flyback = TRL2.

If TL2 tests OK, be aware DC is approximately 133 volts but, as "LJ" reminded me, normal Signal component (AC high voltage) (IF there) is a high voltage. Could give you one heck of a shock if you're not careful with your probes/fingers. Not as bad as DC high voltage at CRT anode!
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PostPosted: Mon Dec 22, 2008 2:41 pm    Post subject: Reply with quote

Hi,

Had a look, but couldn't figure out which component was tripping out.

So, I dropped it into a repair guy for him to have a look.

Thanks again for the advice.

Happy XMas.

Eoin
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