4600 no picture p317 interface board

jacklick

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After recapping monitor it was working fine for like the 5 min I had it in cabinet. Then started playing blind so brought back to bench.

Swapped in known good p317 and it worked fine so know the issue is there.

Read the flow chart and some threads. Turn up screen and get white raster with retrace.
tested TR201 and TR202 good but replaced them anyway to be 100%. Still no pic.
Tested VR201 good but swapped out just to be 100%. Still no pic.

Can't test zd201 (easily at least) but guess I could pull it from working board. Calls for a 6.8v 1/2 watt zener. Looks like 1n754A or 1n5235B would be replacements.

I also have a 1n4732 which is 4.7v. Guess I could recheck the caps too.

Other thoughts?
 
Swapped the zeners and the good p317 still works so has to be something else. Will still probably order some just to have on hand.
 
In my experience it's often the black level pot VR201. Fiddle with the pot and see if the picture comes and goes.
 

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just some more documenting as I was just measuring in ckt and comparing to my working x0149 p317 board.

I got to r205 which measured @ 1.2k in ckt on bad board compared to correct 100k for working board. <<this seems strange

I then tested r224 and r220 out of ckt on bad board and realize my non-working board (version x0150 p317) has these resistor values swapped.

schematic shows r224=1k & r220=680 and you can see by band colors, on my left board in pic below, that they are swapped. Wonder why they did that on the x0150 boards?

Also note in the pic that the x0149 p317 board (right) has r206 mislabled as r200 (note the pic blow is same as above but with red circling resistors in question)

for later reference...easy resistor color code calc.
https://www.digikey.com/en/resource...version-calculator-resistor-color-code-4-band
 

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I got to r205 which measured @ 1.2k in ckt on bad board compared to correct 100k for working board. <<this seems strange

pulled and tested tr203 bad. replaced with new 2n3904. r205 now measures correctly @ 100k in ckt.

Unfortunately, still no joy.
 
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pulled and replaced both x201 and x202. Assuming you can test these with normal diode test, they tested bad. replaced with 1n4148. Feel free to jump in if this wrong.

Still no joy and symptom has not changed. will keep pulling and testing parts I guess. tested tr210 good but may replace just in case.
 
pulled and tested good tr207-209. note you can at least test base>collector here in ckt.

tested tr204-206 in ckt bad. These are PNP; E>B and C>B can be tested in ckt. Pulled them and they all tested bad out of ckt as well. replaced with 2n3906.

Fired her up and have picture now. Whoo-hoo! Crazy all these parts went bad after a cap kit?

But something not 100% on the sync ckt. picture is half off screen when sync'd, horz centering pot seems to throw it out of sync. Could it be related to parts I used for x201 & x202 or maybe r224 and r220 being opposite from my other p317. Will post a pic or something next.
 
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Ok all finished. No sync issue after all. I was messing with using positive sync from TPG and forgot to move it back to negative sync.

not bad for a tube that fails low cut off test on restorer, had a broken blue cut-off pot on neck board, and plenty of burn. hopefully the next 4600 I have to fix will be easier now.
 

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