I'm taking the monitor out of my Blast to clean everything, so I want to discharge it. I have a high voltage probe from BK Precision. I connected the ground clip to the metal on the chassis and put the pointed tip under the anode, but didn't get any reading on the probe or hear anything. I assume it's already discharged, I read somewhere that the Blast monitors have a bleeder circuit to discharge automatically. It's a Nanao 2930, I don't see a manufacturing date anywhere. I've had it off for a while, I think March 24 was the last time I powered it up. Think it's safe? I'm just worried I'm not getting the probe in far enough or something. Does this look okay? Any other tips to ensure it's discharged?
- Thread starter tDRG
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- blast city discharge nanao
I've "discharged" my Blast monitor a few times and have never heard a "pop". To be fair, I'm using the screwdriver with heavy wire and alligator clips method, so I can't measure residual voltage on the anode. Don't know if there is a bleeder resistor, but I would assume if you short the anode to the grounding strap on the CRT, it should be safe. Personally, after removing the anode cap, I always "discharge" again just to be safe.
Cool, thanks. I don't think it pops with the probe anyway, it should be more of a hiss. Yeah, I've heard that you should touch the anode cap to the metal on the chassis a few times after taking it out too to make sure it's completely discharged.
Surprisingly, I also have one of those Makvision 29" (27" actual) flat tubes and that thing gives a loud crack when discharging it. First time made me jump and almost pissed my pants.
Now I'm ready for it...
For what it’s worth I’ve done it a handful of times on Blasts and didn’t ever get a pop.
Given no pop, I usually try and lightly pry the anode cap out with my screwdriver (wired to metal frame), then discharge again after the cap falls off.
Given no pop, I usually try and lightly pry the anode cap out with my screwdriver (wired to metal frame), then discharge again after the cap falls off.
thegreathopper
Professional
That won’t make any difference to the charge in the tube which is the bit that holds the charge.
What he said.
MS9, MS293* all have bleeder circuits. I've removed the anode with bare hands like a minute after I've pulled the plug on it. No charge. However, what has caught me is that when I go back to put the anode back on like 30 minutes after, I get a proper zap from the tube.
I don't know how long the chassis has to be connected to remove all residual charge from the tube, but it's likely a good few hours.
MS9, MS293* all have bleeder circuits. I've removed the anode with bare hands like a minute after I've pulled the plug on it. No charge. However, what has caught me is that when I go back to put the anode back on like 30 minutes after, I get a proper zap from the tube.
I don't know how long the chassis has to be connected to remove all residual charge from the tube, but it's likely a good few hours.
So it's expected to not see any voltage when attempting to discharge after leaving the cab unpowered for over a week, but there will still be a charge in the tube after removing the anode cap? Can that charge be released by inserting the probe into the hole? I'm just going to wipe it down with a wet paper towel and simple green, I'm not going to put it under a hose.
thegreathopper
Professional
Thats what I do, touch the hole where the anode attaches a few times with a minute or so gap until there’s no more spark or more often a small audible click.
If you have had it unpowered for a week, there won't be any charge left in the tube.
You can hose the tube if you want to, just let it dry fully (like at least a full day if you have the yoke attached). Don't scrub the back side too much as you can remove the graphite coating that's there to ground the outside of the tube.
I never wash the chassis, but some (crazy) people here do.
You can hose the tube if you want to, just let it dry fully (like at least a full day if you have the yoke attached). Don't scrub the back side too much as you can remove the graphite coating that's there to ground the outside of the tube.
I never wash the chassis, but some (crazy) people here do.
Sounds good, I'll give the back a gentle wipe but won't go crazy. Thanks.
Any idea what causes the most smell? The inside of the cabinet smells, but the smell isn't noticable around it. But after I had it turned on for a few hours, the smell lingered in the room for a few days. I assume it was exhaust being blasted from the fan on the PSU, not something like the grime on the monitor as it heated up or anything. I'll focus on cleaning the inside of the cab and hopefully that will get rid of it.
Any idea what causes the most smell? The inside of the cabinet smells, but the smell isn't noticable around it. But after I had it turned on for a few hours, the smell lingered in the room for a few days. I assume it was exhaust being blasted from the fan on the PSU, not something like the grime on the monitor as it heated up or anything. I'll focus on cleaning the inside of the cab and hopefully that will get rid of it.
Yeah, I've spent the day working on the area behind the marquee. The magic eraser is getting brown after even hours of scrubbing, so the inside will probably take a while. Still haven't taken the monitor out, are there any connections to remove on the 2930 besides the 3 in the front?
Nope, those are it.
it can be a PITA to get the monitor out if the bolts are not aligned. The bolts have a cut on one side. Make you sure you align them before you put the monitor back. It's by far the dumbest design decision on the Blast. Hate it with a passion.
it can be a PITA to get the monitor out if the bolts are not aligned. The bolts have a cut on one side. Make you sure you align them before you put the monitor back. It's by far the dumbest design decision on the Blast. Hate it with a passion.
JohnRambo'sKnife
Champion
Maybe I am a lucky idiot or that everything I have worked on has been mid 90s or later, but I have never discharged a tube and I have worked on maybe 20+. I always wear proper insulated gloves and have worked some commercial electrical in my younger years. I have been shocked once or twice by backfeed on neutral, but never by a tube. I am more worried about adjusting the geometry while the set is live.
Alright, finally took it out. Don't think I necked it, so I'll call it a success. Does the anode cap look okay? It came out when I stuck the discharger under it after taking the monitor out, a bit easier than I thought it would.
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JohnRambo'sKnife
Champion
Looks fine to me. Maybe wipe up a bit of the dirt/dust.
Cool, thanks! Yep, that's the plan. Chassis was cleaned and recapped, so I don't think I'll hose the whole thing down, just wipe the monitor with a bit of simple green and leave the gunk on the yoke/neck alone.
JohnRambo'sKnife
Champion
I would just wipe with dry towel/paper towel. You don't want to remove the coating on the back of the tube, just get any dirt off since it is accessible.
