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#1
11-16-2019, 10:39 PM
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Still waiting on C2D to come in. I was doing some work in the power supply tonight.
I've got a new issue. It's my fault. I won't get too into it, I did something stupid trying to check a component and learned my lesson. Blew out R119, M1, C1, and X1. X2 still looks okay, but X1 is now measuring 0 ohms regardless of the polarity. The set blows M1 immediately upon power up. I disconnected the 270V line between C2A and L34 and it still blows, so I know the problem is in the voltage doubler circuit with X1 and X2. R119, M1, and C1 are now replaced. R119 is now 3.9 ohm 10 watt, and M1 is a 2.5A 250V fast blow fuse. I also took the opportunity to install M2 as it's listed in the schematic, so I'll have that extra protection. I'm not sure what diode to get to replace X1. Any suggestions? I'm trying to decide if I should go ahead and replace C103 while I'm at it.
__________________
To keep your tubes running smoothly, make sure to dust underneath the glass as well. 
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#2
11-16-2019, 10:41 PM
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__________________
To keep your tubes running smoothly, make sure to dust underneath the glass as well.
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#3
11-16-2019, 11:04 PM
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Quote:
https://www.amazon.com/MIC-Silastic-...s%2C358&sr=8-4 not affiliated, jr
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#4
11-20-2019, 11:57 AM
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Portacolor sets are somewhat prone to tin whiskers in the pots...I had one which had the AGC pot dead shorted to ground via a tin whisker. The set had ZERO reception and it took some time troubleshooting the dead IF to trace it back to the AGC and then the pot...if a whisker developed on a pot connected to B+ or boost it could make the set really unhappy.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#5
11-20-2019, 12:45 PM
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Here's a video where I took some measurements on R5. https://www.youtube.com/watch?v=aBqK...ature=youtu.be
Could this be tin whiskers? How would I go about correcting that?
__________________
To keep your tubes running smoothly, make sure to dust underneath the glass as well.
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#7
11-20-2019, 07:15 PM
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Quote:
That being said, if I do need to replace this, does anyone know what replacement part I'd be looking for? Obviously I'll check Moyers with the part number first, but assuming they don't have a replacement.
__________________
To keep your tubes running smoothly, make sure to dust underneath the glass as well.
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#8
11-20-2019, 09:52 PM
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My standard process for tin whisker infested pots is to remove, and dismantle the pot take a toothbrush then fine sandpaper to the metal parts clean everything with a good control cleaner and paper towels, reassemble the pot, check resistance and range with rotation between all terminals and also case metal, and if all is good reinstall.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#9
11-21-2019, 09:17 AM
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Quote:
One thing I am sort of wondering about, and I can get pictures of this if you need it: I'm noticing that the pot doesn't have the standard three lugs. Instead, it has one that goes to C2D/the main PCB, and two that connect to ground. That matches the schematic just fine, but since this is unusual, is there anything I should be watching out for as I disassemble?
__________________
To keep your tubes running smoothly, make sure to dust underneath the glass as well.
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#10
11-21-2019, 10:06 AM
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Quote:
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#11
11-23-2019, 12:21 PM
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Okay, well I really went at it with the deoxit on R5. Not seeing any change.
Are we sure this can't be a HV problem? Or maybe a voltage problem? My HV to the CRT is still measuring between 7 and 10 KV. It should be around 15 per the schematic.
__________________
To keep your tubes running smoothly, make sure to dust underneath the glass as well.
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#12
11-24-2019, 11:44 PM
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You likely know this, but if not it merits saying: The portacolor is a hot-chassis set so to scope it without frying TV and or scope make sure to power the TV and ONLY the TV through an isolation transformer.
__________________
Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
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#13
11-25-2019, 10:00 AM
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Quote:
Does anyone have an image of what AC ripple looks like? I'm not sure what I'm looking for.
__________________
To keep your tubes running smoothly, make sure to dust underneath the glass as well.
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#14
11-25-2019, 09:55 AM
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Another sidebar/general comment. Are you keeping records of what you replaced and the outcome related to each one? It's getting tough to keep up with all the components you've replaced, and I want to make sure you're methodically tracking the cause-and-effect with each replacement/substitution so that you're not metaphorically chasing your tail in all this. Also, I'm pretty sure you are already doing this, but if not, be sure you're replacing one thing at a time (unless something is very, very obvious like a cascading fault that unequivocally fried multiple components).
Lastly, you may want to consider getting one of the relatively-affordable ESR capacitor testers. You can test caps in-circuit, and it could save you the hassle of shotgunning a lot of them (at least for the sake of diagnostics -- it's good practice to replace the electrolytics at this age).
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#15
11-25-2019, 11:05 AM
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Quote:
You would see a 60 cycle component in the waveform. The more pronounced it is, the more ripple is present.
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