[TechAssist] Re: 2nd REQ TA...NAP HD2717C101 27B800, no video..(wasvertical prblm)

Have you seen this tip:
Symptom:  Dim raster with faint colored bars from top to bottom. No 
response to changes of video, no menu or graphics on the screen.
Cause:  The beams in the CRT are deflected into the CRT neck and scatter 
at random across the screen.  This is caused by either a loss of Minus 
13.5 volts to IC500 (vertical out) or IC500 itself.
Cure:  Check and replace as needed; R420, D409, C419, IC500.

Or this one:
SYMPTOM:  Open R420 or R445 with no apparent reason.  These resistors 
act as fuses in the plus and minus 13 volt supplies to the vertical 
output circuit.
CURE:  Replace original .33 watt, 1 ohm MF with .5 watt, 1 ohm MO 
resistors.  Use ONLY 4835 116 57109.
TIP:  If one of these resistors fail replace both with the above part.
*******************************************************************************************************************
Since 1972
Jim Myers
Telrad Electronics
Fort Wayne, Indiana


Intrepid Video Support wrote:
> Going with a fresh post on this one. I still can't find the problem.
> First thing, I found the resistors and diodes for the 13 (-/+) lines bad, 
> replaced those and shorted
> vertical IC.
> Then, I had raster that was red with retrace, found the RED video IC bad on 
> CRT board. Also, R50
> open..replaced, then back to no video.
> I've tried three more vertical out IC's all OEM and NTE, still no video. With 
> the NTE in, I get some video
> very top of screen about 1/4 inch across.
> On IC271, 46/47, voltages were about a volt low and wave forms were low p-p, 
> replaced IC..no fix.
> Wave forms in/out of SAW filter are OK.
> On pin 1 over vertical yoke, which comes from pin 5 of vertical wave form 
> shows about 50 vpp, very high.
> Pin 6,7 of vertical show low pp voltage.
> I've went over and over my traces solder, replace the resistors and diode 
> with OEM numbers, went over the
> CRT board again.
> If I remove the vertical plug, I do get a horizontal line and the power LED 
> flashes. I checked the yoke
> and it is about 1 ohm off from one on another set.
> I have the schematic of this section, but am not sure what is causing these 
> wave forms to vary.
> I put in another Philips IC and the wave forms are even farther off.
> Any other ideas before I scrap this set...I've done many of these B8 for the 
> same problem and have never
> had this type of trouble,
> Thank you.
> 
> Jeff Dougherty
> Intrepid Video TV/VCR
> 263 S Front St
> Steelton PA 17113
> fax...717-564-4952
> www.intrepid-video.com www.tech-repair.net
> 
> ----- Original Message ----- 
> 
> 
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