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#1
03-03-2014, 11:47 PM
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Stupid stupid stupid
In a vain attempt to find a faulty cap on the sony I am working on I decide to try some cooling spray to see if I could cool different caps and watch for a change in the pic (light bars on the vert sides).
grab the dust off, invert can, pull trigger... opps.... Carpet stain cleaner fluid comes out, guess what...its conductive as hell. instant smoke and flames... dead set. 
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#2
03-03-2014, 11:54 PM
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anyway after seaching in vain for a smoke part (found one resistor that had gotten hot, thought it was it, but it was in the vert circuit and was ok), I decided to try trouble shooting.
same deal as when I 1st got the set, mains B+ ok but no flyback LV. start checking around the horz circuit and found the horz coupling trans did not have any B+ on the primary. Per the schematic its just connected to the 129v (mains b+). but Its open from the trans to the B+ hmmmm. start tracing the pcb and find a jumper that on the set is not a jumper but a resistor. Now in sams there is no resistor just a jumper, but I guess some smart engineer must have figured some goof would spray carpet cleaner on the pcb and mercifully put a low value low wattage resistor in place of the jumper. since I could not read the value on the charred remains (I missed it in the initial check out because it was so small and mounted vertically), I just put in a 1/8 watt 10 ohm in its place. after cleaning the pcb with a non conductive spray cleaner and blowing it all dry, I fired (sic) it up and back to working (well but for the vert bars on the ends), again. that was fun and educational.
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#3
03-04-2014, 05:37 AM
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That was probably on of sony's great fusable resistors.
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#4
03-04-2014, 09:15 AM
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Quote:
Did you look into the screen source electrolytics. A lot of times they cause strange looking faults in the raster.
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#5
03-04-2014, 09:40 AM
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A year and two months ago I had replaced three transistors and a bunch of electrolytics in a set and wired it all up ready to go with several DVM's hooked into critical voltage points. Started right up with 5 volts in the startup circuit and then good B+ and then ZAP and smoke and dead. The HV cable had slipped out of the CRT and fell down in the HV section of the board and I had thought it had been clipped into the CRT securely. That set is still sitting waiting for me to cool off.
__________________
Reece Perfection is hard to reach with a screwdriver.
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#6
03-04-2014, 09:51 AM
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Quote:
my play is to scope the K's of the CRT and see if there is something going on there. I want to isolate the fault to either the kine bias,sweep or HV. I think its the kine bias as there is no distortion in the image that shows thru. I hope scoping the pins of the crt will show the defect at the horz rate.
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#7
03-04-2014, 10:45 AM
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That was my first Sony color set. I got it used in the mid-70's. There was no set, that could compare, color and picture-wise. 
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#9
03-06-2014, 09:23 AM
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not likely, I have not lost a patient yet
it was pretty traumatic when happened but I got lucky and did not destroy anything hard to replace, AND I learned a big lesson never will spray something until 1st having test fired somewhere safe.
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#10
03-06-2014, 08:23 PM
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It is nice to hear that your set survived this near-catastrophe. In the surface-mount world, at least, zero-ohm resistors are common. They are marked "000" on top, typically. I do not remember if I have seen any non-surface-mount equivalents.
__________________
Chris Quote from another forum: "(Antique TV collecting) always seemed to me to be a fringe hobby that only weirdos did."
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#11
03-06-2014, 09:06 PM
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This is why I hate working on SS equipment, one oops and it can be a catastrophe.
When I was fixing my Sony I had several oops moments when I thought I'd blown something up.
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#12
03-07-2014, 07:56 AM
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Quote:
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Linear Mode
