Nanao MS8 monitor killed with 240v

good job OP

That is nice work.

Did you ever find out what went wrong with that outlet?

assuming it was right at some point, the only thing that really could have happened is someone put the neutral side of that plug's wiring into the opposite leg of the incoming 240v inside the breaker box...

I don't think there is any scenario where both legs/hots should be inside that 120v recepticle.
 
I'd consider the one in your pics to be a 26SU.

Sometimes labelling on the chassis can be all over the place, but I'd typically say:
26A = original brown PCB variant
26SG = green 100v variant, power connector is hard wired
26SU = green 120v variant, power connector has a header

There's other differences between the SG and SU, but if you look at the PCB colour then the type of power connector it should help tell you which variant it is.
 
Thanks all, I wish I had taken pics of the chassis while I had it out. I'll have to snap some from inside the cab so I can tell the owner which cap kit to get ordered.
 
Well I celebrated too soon.

I had this on for about an hour after getting it back running. I noticed the HOT was getting pretty warm considering it was mounted on it own heat sink. After about an hour it went blank and the F902 was blown again.

I figured it was the cheap(ish) HOTs I bought off ebay that were crappy so I ordered the cap kit and a D1880 from APAR to ensure I'd get a legit one.

Just did the cap kit and installed the APAR HOT and fuse blew immediately and new HOT is shorted again.

I should have know I don't get that lucky.

Going to double check everything I checked before but since the 240v went trough the yoke coil I'm wondering if it melted some of the insulation and its shorting. It'd be weird that I had such a good image when it was working though..

Can anyone else with one of these monitors check their horizontal yoke ohms for me? (I know ohms and henrys are not the same)

.6-.8 seems super low to me....

C96D876F-EDF6-44C3-A3B5-7261C00ED3AC.jpeg

3EF37D38-0982-409C-ACBD-0D89169C8206.jpeg
 
I'm thinking this chassis is headed for the trash. I can't keep blowing $9 HOTs on it.


Is there any common HOT shorting things on these chassis to look at?
 
Do you have a correct B+ (92V) at the fuse F902? I mean fuse off circuit and bulb attached to the fuse holder (VR side) and ground (TP2), not what you did above.

If you do, put the fuse back in, HOT off circuit (and yoke disconnected from chassis) and lift R543A and R543B from the PCB and see if you get a good stable B+.
 
Do you have a correct B+ (92V) at the fuse F902? I mean fuse off circuit and bulb attached to the fuse holder (VR side) and ground (TP2), not what you did above.

If you do, put the fuse back in, HOT off circuit (and yoke disconnected from chassis) and lift R543A and R543B from the PCB and see if you get a good stable B+.


I will check.

When you say "HOT off circuit" do you mean the HOT out of the circuit by leaving the yoke disconnected?
 
With the HOT out of the circuit I should be able to test it off the tube correct? (like other chassis)
 
Yup, no tube. Put the chassis on your bench and power it with an ISO transformer.
 
Do you have a correct B+ (92V) at the fuse F902? I mean fuse off circuit and bulb attached to the fuse holder (VR side) and ground (TP2), not what you did above.

If you do, put the fuse back in, HOT off circuit (and yoke disconnected from chassis) and lift R543A and R543B from the PCB and see if you get a good stable B+.


I did this and the fuse on my isolation transformer blew immediately. Any thoughts?



This is how I wired it up:

2F64EE66-CB28-40A7-961F-4D7FD7FB733E.jpeg

Light bulb leads on the Fuse clip and TP2 ground.
 
There must be a faulty part in the power circuit (parts numbered 9XX). I'd start by checking the voltage regulator Q901.
 
assuming it was right at some point, the only thing that really could have happened is someone put the neutral side of that plug's wiring into the opposite leg of the incoming 240v inside the breaker box...


This is totally what happened.

This is also exactly how you get a 240V outlet in your home (for stuff like your electric dryer/stove/etc). You normally just use a different physical outlet, that a 120V plug won't plug into.

A home breaker box has multiple phases of 120V going into it. All of the 120V outlets in your house get one of those phases, plus neutral. 240V outlets instead get two 120V phases that are out of phase (instead of one 120V and one neutral).

In fact, you can easily 'make' a 240V outlet out of two separate120V wall outlets, if you know they are out of phase (which you can easily test for.) There's a company that makes adapters specifically for this purpose. I've used them:


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You probably already did it, but someone at that storage facility should be notified. They also probably have some bullshit statement in your lease preventing it, but they really should be responsible for damage to your stuff, as a result of their electrician (or more likely some other idiot) fucking up.

That totally sucks. At least it wasn't a more valuable game.
 

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Do you have a correct B+ (92V) at the fuse F902? I mean fuse off circuit and bulb attached to the fuse holder (VR side) and ground (TP2), not what you did above.

If you do, put the fuse back in, HOT off circuit (and yoke disconnected from chassis) and lift R543A and R543B from the PCB and see if you get a good stable B+.


I don't think this is the correct way to hook up a bulb.
I replaced the power transistor Q901, lifted R543A & B and hooked up the bulb per this and tried it again. Instantly blew my isolation transformer fuse and fried another Q901.
 
...

Can anyone else with one of these monitors check their horizontal yoke ohms for me? (I know ohms and henrys are not the same)

.6-.8 seems super low to me....

I have the MS8-26SU at .64 Ohm (H) and 42.6 (V) [0.45 mH (H) & 78.3 mH (V)]

I don't know of any drop in replacements, but I would check the transformer on the chassis ac line to see if it came open from the excess voltage.
 
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