On 2017/07/06 10:04 PM, wrote:
On Friday, July 7, 2017 at 12:48:26 AM UTC-4, John Robertson wrote:
On 2017/07/06 8:20 PM, rickman wrote:
wrote on 7/6/2017 3:32 PM:
On Thursday, July 6, 2017 at 2:47:59 PM UTC-4, Jeroni Paul wrote:
wrote:
https://na.suzohapp.com/pdf/service_...vp2_manual.pdf


https://na.suzohapp.com/pdf/service_..._schematic.pdf


B+ is 12v3, 12V and 24V good. i was thinking yoke, but they ohm out
good, and look like brand new. no physical damage. looks like a few
transistors are after the vertical ic, i'm looking at them now. not
real good at following this schematic, so any help is appreciated.

thanks

In the yoke there are two coils for vertical and two for horizontal
connected in series or parallel depending on the design, if in
parallel one coil connection could be broken. The coils are connected
together in the solder posts on the yoke, you may check there if some
wire looks loose.

thats a great idea, i didnt know the coils were doubled up. i will
check that for sure tonite. i was thinking of inverting the image,
there are solder pads for an inverted header on the chassis board, and
see what the image does. that would tell me if its the yoke or a
chassis issue. does that make sense?

I don't get why your idea is not good. If you can flip the drive signal
polarity the image will invert. If the problem is in the drive
circuitry the half that is working will swap with the half that loses
drive. If the problem is in the yoke the image will invert, but the
problem won't. No need for fancy testers or widgets. Or maybe there is
something I don't understand about this?


Great point Rick, that would indeed be a good test to see if the yoke is
linear or not.

John :-#)#


i soldered a header into the reverse position on the chassis, and gave it a try. it did the same thing as before, just inverted. now the bottom half of the screen has an image that compresses toward the center, a total collapse on the center, and no image in the upper half of the screen. does that rule out a yoke problem?

thanks


Based on Rick's points above I think we can rule out the yoke. Nice work
Rick and yourself for that test!

If you have a 'scope then now is a good time to check the outputs of the
LA7851's sawtooth wave generator. Also 'scope the output of the vertical
drive IC to is if it too is still a saw tooth or not. Should swing
pretty much the entire source voltage (24VDC?) if I am not mistaken...

John :-#)#
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