10L43 Predicta no hv

[DaveWM]

those voltages do not look to far out of line. Next you should check the 6DQ6 (not the plate of course).

you said something about drawing an arc at the plate of the 6DQ6? I have heard of drawing an arc at the plate lead of a 1B3 to see if HV AC is present. I prefer to use a HV prob a the 1B3 DC output (the metal tube socket).

Use a neon bulb held near the plate lead of the 6DQ6 (or anywhere near the fly) it should glow.

[DaveWM]

regarding predicta repairs,

To do it right requires a lot of hours

pull chassis, can do a through clean up of years of nasty gunk (esp if in a smoky enviroment) just so you can see what you are working on.

remove pcb from chassis

check for defects in traces and tube sockets

replace all film caps

hope the Networks are ok

clean and or replace bad pots

filter caps

and most importantly work around and correct prior hack repairs

There are not a lot of folks I would trust to do it right.

[DaveWM]

re read your post since the HOT is red plating we can assume no grid drive, but to be sure just get a quick reading there with the HOT in place.

You may end up needing a new HOT when all said and done as red plating can ruin a good tube.

Was there any notes regarding the chassis status after it was returned?

[whatadish]

no notes...he called me a couple times telling me he could fix it with a hammer. all the plastic dials were broken into pieces. A few caps were hooked into place because he said they were the wrong values. He replaced K7 but it is an old nos. Pin 6 of the k7 shows correct voltage, not sure if I trust an old nos one. Thx Jim for the pm, if anyone needs any bulk copying done i own a small copier company. I will stick the hot back in and do a quick check. Does the crt and yoke need to be connected...they were for my 6cg7 reads. Don't want to damage the crt as it looks and tests new. I did retest the hot and it is still quite strong.

[DaveWM]

yes yoke should be connected, its needed for the HV to work.
keep the brightness turned down just in case it comes on strong but does not have vert sweep etc.. to avoid a burn.

They are really not that hard to work on AFTER you get thru the learning curve on how to remove the PCB etc.

I like the modular construction since it takes up a min of bench space.

If it was on my bench I would do another base line test, then if still no go, do the full on pull the pcb up and make sure all caps have been replaced (film type), check traces closely, check tube sockets closely, leave the networks alone for now, try it out again.

On mine I found it fairly easy to remove 4 or 5 wire wraps and then you could unsolder from the stakes. Bob has done more, his technique of complete removal makes access that much easier, just depends on how comfortable you are working on it.

I have worked on a few, the much networks never gave me a problem, but that does not mean they never have issues, I just prefer to see if it will work with them in place before attempting to make my own. Some of them look like they could be checked if need be.

checking the HV with the neon is real quick and a fast test.

[whatadish]

okay then

[whatadish]

okay...good news, reasoning that because the grid had ac present I would likely be looking for a shorted cap. Sure enough found defective but NOS sprague .0047 video cathode bypass cap... just because it hasn't been used old is old and I should have checked it before installing it. Replaced cap and hot socket and violla got my -45v at grid and what do you know...full raster with snowy but good picture. Still no sound though...some audio buzzing. No redplating and a good 13.5 kv at anode. Any takers for the sound issue...6bq5 and output tranny test good. This had great audio before my buddy got a hold of it. My guess is that some people are a little timid about lifting that board...ground tabs are pretty fragile and heater grounds are directly connected to three of them. repaired a few foil pops while under there. time for some pizza and a Sam...then a little audio signal tracing. I love this site...pics to follow as soon as i remount the crt in its swivel.

[DaveWM]

keep at it audio I would start with a new detector tube, check voltages, look for broken tube sockets, check voltage on detector and audio out.

look for open quad coil, they have a pretty sharp peak so may be suffering from screwdriver drift.

[whatadish]

ugh...had a pretty nice picture for about ten minutes...went to start reassembly and lost hv again. completely removed board this time repaired a lot of foil pops and tears, repaired 5 or 6 traces...still no go on hot grid bias. Looks like tube sockets are next...most have broken pins. I need an outlet for 2 octals and 6 nine pin sockets. At least I know all trannys, coils, and crt are good. Alignment looked really good...I think the crt is new. Enough for this weekend though.

[whatadish]

do all 10L43 chassis have this cap..cant find it on this chassis...it is supposed to be on the terminal strip between the if shield and board by the AOT. The set was working for a short period so I assume it is possible to not have this component.

[DaveWM]

I presume the C42 is the predicta ref number? I show a C18 .1 uf in that location on the sams and the ones i have worked on have it.

[whatadish]

while I still have not figured this out I have gone through the circuit board as best as I can. I have traced all grounds and appear to be good, all tube sockets meter good too..interestingly enough I have encountered yet another issue I am hoping someone can help me with...the width control seems to be getting very warm. 280v on wiper(vr tests fine) 27 to 50v at other end at hot. I guess without understanding how the basic hot circuit works I was just hoping after going through the board again I would find something obvious. I checked and rechecked my stake connections. Almost impossible to solder without sanding them down. I just don't understand how just moving the chassis a couple inches caused such a huge failure when it had such a nice picture for a few minutes. B+ seems to have jumped about 30v too. I have found another working 10L43 chassis that I am hoping will help me troubleshoot this with my limited knowledge of tv circuits. In the meantime any help would be appreciated.

[Down Under]

> It's like, WHEN "they" drop that damn BOMB on IRAN soon, even p[eople in
> Tasmania, are going to eat a little crap!!!

After reading all of ROXX's crap, I'm amazed he's even heard of Tasmania. As an Australian, I found this quite funny, but I'm glad you won your case.

And good luck with the Predicta whatadish, you'll love it when you find the problem(s) and see that picture for the first time.

Cheers,

Adam

[DaveWM]

the width pot is a supply to the screen of the horz out.
if its getting hot is may be that the screen is pulling too much current.
If that is the case it may be that the plate of the horz out is not pulling current.
remove the horz out tube and see if you have B+ on the plate lead.
Its ok to check the plate lead IF the horz tube is out of the circuit.
This will check the continuity of the fly windings/damper circuit/choke coil, all of which supply the horz out plate lead. Make sure also that the damper filament is lighting, I had a predicta that would loose its HV unless I pressed on the damper tube sideways, turned out to be a bad filament ground stake that only effected the damper tube.

remember do NOT check the horz out plate lead with the tube installed, the strong pulses of a working horz sweep circuit could destroy a meter.

[DaveWM]

Originally Posted by whatadish

.the width control seems to be getting very warm. 280v on wiper(vr tests fine) 27 to 50v at other end at hot.

this is way off, should be about 175v at the screen.

sounds like you have lost the B+ to the plate lead of the Horz out (and the screen is drawing all the tube current).

see my prior post.