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k7000 19" screwy color behavior
snappleman:
I have no clue why they're not to spec but yeah they're all good and all factory so I ended up leaving them in. I've been researching a bit about K7000s and it seems pretty common to have factory mods or little differences here and there. If they had been somewhere "important" like the power supply or around the HOT I'd have changed them to match the schematic but they seem to be pretty isolated from any forms of danger.
On that C44 though, if you're not sure the flyback is good it might be smart to change that out as well.
MKFan4Life:
Ordered 2 polys with identical ratings for the C44 cap. The flyback was installed new a couple of years back when I stored the game here at home and was trying to figure out why the chassis went down (which ended up being the voltage regulator I replaced a year ago when I got the game out of storage to play some more).
I installed the new flyback since it was original to the chassis, and the old one had visible cracks. I hope it was not a dud flyback and caused all the stuff going on now. I heard there were some duds Bob Roberts sold in the past, and this came from him before he took that last break. I haven't heard anything about him in forever. Hope his health has improved.
:D
MKFan4Life:
--- Quote from: snappleman on August 19, 2021, 12:34:32 am ---I have no clue why they're not to spec but yeah they're all good and all factory so I ended up leaving them in.
--- End quote ---
Was curious and desoldered R7, R8, & R9 on my K7197. They all tested almost exactly 33K out of circuit. In circuit, they plop all the way down to about 7.9K. I also checked the color bands, and indeed, they are all 3 marked as 33K resistors. I don't look at bands much at almost 50 years old. I have a lot of trouble telling violet from gray or blue and sometimes think orange looks red. A good magnifying glass helps though.
I also tested R25, R26, & R27 which all tested differently in circuit than they were supposed to be valued at. Just like before, they all tested almost spot on when out of circuit when compared to the data from the WG specs. The color bands all denoted exactly the values the WG data lists.
Moral of the story: believe it when someone says parts test differently in circuit. Funny thing I noticed also, yesterday, I recorded the values of R25, R26, & R27 in circuit. Today, after pulling all 3 to verify their values, I put them back in, and all 3 gave totally different values than yesterday in circuit. At first, I was like, guess they haven't cooled down yet and the value is fluctuating. Then I waited about 15 minutes, and they never wavered from the new values.
The only thing I can think of is yesterday I had left the linearity coil out to test it, and left R98 & R99 each with a leg lifted to check their true value when I initially tested R25, R26, & R27. Those components altered the readings of the other 3 resistors in circuit I figure. I should know that. I studied several electronic courses working on a degree within the past couple of years, but calculating circuits was near the beginning of my courses, lol. Very rusty.
snappleman:
Thanks for doing the legwork, I feel better knowing that. But now I'm thinking I should be a bit more methodical about shotgunning parts that are out of spec, and given that I'm just an amateur at this I'll learn any lesson that comes my way.
snappleman:
Now that this chassis is mostly working (need to get the degaussing circuit fixed) I swapped on the matching k7000 yoke and it got the geometry even straighter and the convergence is still super nice. The next step is a bit tricky because having the chassis, isolation transformer, scart2arc and the switching PSU for that all in the TV case gets things very uncomfortably hot, and there's barely any room. So now after 20-some years in this hobby it's finally time I built my own Crapmame TV enclusure!
This is actually a big deal for me because my wife (girlfriend at the time) told me it was inevitable I'd build a Crapmame of some kind. It's taken 20 years but now it's time to make that a reality! 8) 8)
I figure I'll use some plywood to build a super bootleg box that houses everything and has a couple nice speakers in it, along with a couple 120mm PC fans on either side acting as intake and exhaust to keep things cool. I've built my own racks for studio outboard gear and they each weigh a solid 400+lbs each all loaded up and are still sturdy and standing after all these years, so I figure a CRT isn't gonna be too hard...