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 Post subject: Sony 5303 Micro tv vertical issue
PostPosted: Jul Mon 27, 2020 5:29 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2074
Location: Waukegan, IL
Recapped the deflection board on this tv. The lower quarter inch of the crt is lighter than the rest. Its like a quarter inch high band across the lower section of the crt is lighter than the rest of the picture.

I will add i left two of the original Alox capacitors in place. Once is acorss the vertical blocking transformer.

The band is hardly noticible most of the time, so i wanst gonna tear my hair out over it.https://m.facebook.com/groups/295773603 ... composer=0

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 Post subject: Re: Sony 5303 Micro tv vertical issue
PostPosted: Jul Mon 27, 2020 11:31 pm 
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Joined: Aug Thu 12, 2010 6:25 pm
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Location: Durham, NC
The Facebook link is a private one -- you have to be a member of the group to see it.

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Mark Nelson
A collector of TV signal boosters and UHF converters -- God help me!
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 Post subject: Re: Sony 5303 Micro tv vertical issue
PostPosted: Jul Fri 31, 2020 7:12 pm 
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Joined: Jan Thu 16, 2020 12:29 am
Posts: 645
Well the thing is to distinguish why the scanning raster is brighter at the bottom. It could be for two reasons, one that the CRT's beam current is altered in that zone for each field, which means there could be something wrong with the V retrace blanking applied to the CRT's grid-cathode circuit, or it could be brighter because the scanning lines are more crowded together in that zone due to a vertical scan linearity issue.


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 Post subject: Re: Sony 5303 Micro tv vertical issue
PostPosted: Jul Fri 31, 2020 9:51 pm 
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Joined: Apr Sat 06, 2013 2:18 pm
Posts: 541
Location: New Hampshire
Sounds like vert fold over at the bottom. First check the values & polarity
of your previous work. Then be sure to change ALL the electrolytic caps
you may have missed in the vert. Also be sure none of them were
supposed to be NP caps. Its been 40 yrs but I dont think there were any.
Usually vert fold over will go away when you shrink the pix & adj the lin.
Check resistors in the area of the vert controls last.

73 Zeno
LFOD !


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 Post subject: Re: Sony 5303 Micro tv vertical issue
PostPosted: Jul Fri 31, 2020 11:58 pm 
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Joined: Jan Thu 16, 2020 12:29 am
Posts: 645
Yes I agree, when the vertical scan linearity is very abnormal the scanning current turns around and drops to a lower value and the beam direction reverses, the lines not only crowd together, but the scan scan traces back over the previous scanned area looking like its folded over on itself.

The most difficult part of the vertical scan is the last part, this is where the current is the highest. It is affected by the shape of the drive waveform at the output transistor's base (it should be peaking up a little as shown in the 5-303 manual and not in fact be a linear sawtooth, the amp has positive feedback around it to get this correct) and it depends on the correct output transistor bias, and the output transistor being in good condition and the yoke coupling capacitor with a low ESR and normal uF value.


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 Post subject: Re: Sony 5303 Micro tv vertical issue
PostPosted: Aug Sat 01, 2020 3:47 am 
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Joined: Jan Thu 16, 2020 12:29 am
Posts: 645
Check with the scope, the drive waveform to the output transistor and the collector voltage.


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