toshiba 35 " crt

[cashkennedy]

This is a late 90's 35" Toshiba crt, when its first turned on there is horrible pin cushion effects on the screen (see pics of menu, though it affects everything obviously). I assume there is a cap somewhere that has to warm up. What area is this cap likely located? board behind the electron gun? (I know nothing about crt's so just guessing)

Where should I be looking / testing with free spray / heat gun?

[stj]

Re: toshiba 35 " crt

you need a service manual.
full model number & chassis number would help.

[cashkennedy]

Re: toshiba 35 " crt

brand is toshiba
model is ce35d10
chassis tac 9410
manufactured july 1995

I would have figured crt's were becoming so cost competitive by the mid 90's that they wouldn't even give a shit to make a decent service manual.

[stj]

Re: toshiba 35 " crt

dont you believe it, there are great manuals for crt stuff.

[cashkennedy]

Re: toshiba 35 " crt

here are some closeups of the flyback transformer, I assume it would have to be something around it.

[Andrew F. Ali]

Re: toshiba 35 " crt

Test the big Filter cap and any other Hi-volt elect-caps in the Primary and Secondary power supplies. Test caps in the Horiz Osc and Output circuits including the Hi-volt Non-polarized caps as well.

[stj]

Re: toshiba 35 " crt

did you check for cracked soldering on stuff bolted to heatsinks yet?

[cashkennedy]

Re: toshiba 35 " crt

No I haven't checked for cracks, should I check / discharge anything other then the primary cap? before pulling out the mainboard to inspect it.

[stj]

Re: toshiba 35 " crt

depends, if your going to swing the boards out then no, but if yur going to totally remove the chassis then you probably should discharge the tube.

[cashkennedy]

Re: toshiba 35 " crt

below are some pics of the back of the board, the 2 major components that are attached to heatsinks are circled in red. Almost all of the major joints were held together by clips? before soldering, making it hard for me to really tell a dry joint, but I'm not any good at finding bad joints anyway.

There a couple of joins with flux / or paste residue next to them, such as the heatsinks.

There a bunch of hidden hand soldered after thought components under the tunner / logic portion of the set. Lots of marker / writing over the board, hopefully that's just internal testing and not that the board had a lot of errors originally.

When you say not to disconnect the tube without discharging, does that refer to the 4 thick wires that go to the neck of the tube, or what I assume is the degauss / thick wire running all around the back of set but not going into set, or the thick wire from the flyback transformer?

[stj]

Re: toshiba 35 " crt

it refers to the flyback read wire.
and the ground wire

[freakaftr8]

Re: toshiba 35 " crt

Could be bad B+ regulation. Check boost supply first. Primary capacitors. Horizontal pincushion usually relates to low B+. Use the old hairdryer method on filter caps.

[cashkennedy]

Re: toshiba 35 " crt

I tried heating various areas starting with the power supply primary, then secondary, then around the flyback, the back of that section, then the boards behind the electron gun, and finally the tuner area. Nothing did anything other then the tuner area made the sound not work for a few seconds, luckily worked again after I turned it off and waited a while.

I guess ill try some more serious applications of heat to the power supply and flyback board areas, but is there anything else that could be getting better after the set is on for a while other then something heating up?

[stj]

Re: toshiba 35 " crt

deflection control i'c(s) probably single sided and bolted to a heatsink
they often have a few small caps in front of them.

[cashkennedy]

Re: toshiba 35 " crt

would the deflection control be near the 4 thick wires that run to the neck (coil area of the tub) ? and how many pins is the ic likely to have? like 3? 8? 32?

[stj]

Re: toshiba 35 " crt

between 7 and 11 pins usually.

why dont you just put all the chip part numbers into a search engine to see what they do!

[momaka]

Re: toshiba 35 " crt

The joints on the component circled in red in the first picture in post #10 do look suspicious.

I think the simplest thing to do is to start by reflowing the joints on all larger and heat-sinked components. Also reflow the joints on all connectors. Bad solder joints may not be the problem, but it's good to do it anyways so then you don't have to guess.

The easiest way to reflow that many joints is to get some liquid or paste flux (or flux pen) and apply on all joints that you intend to reflow, then hit them with the soldering iron. You need not apply solder to the iron for every joint... just a tiny bit once in a while to help with the heat transfer.

And preferably do it with a 50-60 Watt iron. 40 Watts may just be enough, but you may struggle on some of the bigger joints with it (or take too long to melt the solder).