Wanted NT2701 Neotec Chassis without burn hole.

[tommyinajar]

 Hi
I got a 27 neotec monitor free. The guy bought it and plugged it in when it was 5 degrees and snowing out, and promptly saw smoke and fire. I was going to * attempt * to fix the chassis, but after some consideration I think I might just look for a new one. There is a black hole where C419,C420, and a Jumper wire is (or was). The traces look like they might still be there but no pcb under them. I was going to see if I could jump the traces, and buy some caps, but there is also a darkening by the ac in on some diodes too. I'm thinking I'll  just find a different one. Pictures in a bit for all you sadists.

[lilshawn]

it's a common issue...it's mostly when those caps dry out and go bad, there is a transistor in between that burns up.

with the schematic and some patience it's possible to rebuild the area.

the transistor is responsible for turning the power on and off for the low voltage sections (12 volts/5 volts) when the monitor is powered down. the increased load of bum capaicitors causees it to get hot until it fails (spectacularly)

[tommyinajar]

I'm assuming the transistor is Q402 (bu4530al)?

The transistor looks ok, but I've got to pull it and test it.

I d/l the schematic and the value for c420 isn't listed, C419 is "PMP 102J.1.6KV" Those are the two caps that look crispy. And "J" is gone, (jumper wire?)

The traces are still partially there but the board is gone underneath. I'm going to desolder the parts off tonight probably. I wish I had a good pcb to look at.

[ed12]

hi
c419 and 420 are both high voltage cap's 1.6kv is normal
they will be silver tatalium
they control the width ie wide or normal
c420 must be in the circuit
q402 is your horz width driver transistor

ed

[lilshawn]

hmmm, actually no, q301 was the one i was talking about.

that, sir is a new one for me. wow.

it's interesting because the board is burned...but not the traces adjacent. (the trace is actually bridging the open space)

yes j is a jumper wire. That must have been the source of the fire. it could have gotten a tiny bit of corrosion on it and instead of being a wire it started to act as a tiny resistor, heating up like a toaster element. (corrosion causing the normally zero resistance to become a small resistance, causing heat)

i can't tell from your picture, but i'd be interested to find out where that jumper connected to...something up the line may have shorted causing the wire to burn up. I wish the schematics had a solder side map.

tell you what, i'll try to get out to the shop sometime tomorrow and see if i have a 2700 series chassis there. If I do, i'll grab some hi res photos of the solder side of that area...it will make rebuilding the one you got there a little easier. (unless someone here has one they can do now)

[ed12]

hi
it's just what i c

ed

[tommyinajar]

Cool some pics would be helpful I hope!

 I have to clean it better when I get the burnt parts off. The hole(s) are looking to be larger now than at first glance-

 There is really nothing left of the jumper wire, unless it melted down flat and looks like a trace. I was just going off the parts placement diagram. "J" marking on board has melted away.

It's funny the guy bought it from a local shop, they had it on all day and it worked and looked flawlessly. He left it outside in his truck in winter overnight, brought it in, plugged it in and ZAP! That's the most damage to a monitor pcb I've seen. Guess he had actual flames...

[ed12]

hi
and yes
bad new's

ed

[MonMotha]

FWIW, inspect the neck of the tube carefully before you bother too much trying to repair the board.  This kind of sudden heat stress can easily crack the CRT glass, usually near the neck area, due to the rapid increase in temperature from the tube heaters.

[tommyinajar]

I dug the CRT out last night, no cracks anywhere or soot...but I thought it was a 27" it's a 25".So the chassis is probably a NT-2515C.  They look a lot alike. There are no pcb id numbers and no markings anywhere that I can see for a positive ID, but it came out of a Blitz. Took off some caps and L042 coil to clean , also the left over burnt part was a jumper wire not a trace.

[ed12]

hi
scrape off the burnt pc board
even if means making a hole,just do it..as u are removing :carbon tracking:
that's tech for it WILL short again,replace the cap i told u has to be there
if that jumper was a coil but if it came to u with a jumper,no fear's put a jumper back in
replace the transistor,look the yoke over to c if there is a burn on it
if not most likely it got some mostiour in it
it is high voltage after all and will arch at any given chance
rember they are 1.6kv high freq cap's

ed

[tommyinajar]

I've got no idea where the jumper is supposed to be, I need a good top and bottom pic, or a solder diagram-  I've got one picture off a NT-2515C and it looks the same except for a few minor things,.