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2465 CRT Smoke

[email protected]
 

Greetings everyone,

I acquired a Tek 2465 last year. It had significant flicker on the CRT and a noisy fan, so I replaced all of the electrolytic caps on the power supply and rebuilt the fan motor...windings and all. It’s been working flawlessly for about a year…until today.

There I was. Enjoying the simple beauty of an amplitude modulated carrier wave pulsing out Van Halen’s ‘Right Now’ when I heard a pop, then a sizzle, followed by more popping and smoke pouring out of the front and back on the CRT side of the scope (and the fan discharge, of course). I shut it down (it was still working) and started an autopsy.

I’m not familiar with troubleshooting CRTs at all, so I simply discharged the anode and moved on to what I know. Since I was familiar with the power supply, I pulled it out for a look and discovered a blown resistor and X rated capacitor near the mains input. Admittedly, I should’ve replaced all the caps on the power supply.

Can anyone provide insight on what likely occurred? Did the CRT fail and cause the blown power supply, or did the blown power supply kill the CRT?! What is the typical CRT failure mode? How do I troubleshoot the CRT? Anything to know safety wise other than discharging the anode?

I happen to have 2 other non-working 2465’s that I acquired in the deal as parts donors. One powers up but has a fault that I’ve never looked into and I have no idea about the other.

Any help would be greatly appreciated.

-Dave
 

Dave,
The mains input filter caps seem to fail often without cause other than age. The amber RIFA caps are notorious.
--John Gord

On Mon, Sep 17, 2018 at 09:53 PM, <dharwood1980@...> wrote:


Greetings everyone,

I acquired a Tek 2465 last year. It had significant flicker on the CRT and a
noisy fan, so I replaced all of the electrolytic caps on the power supply and
rebuilt the fan motor...windings and all. It’s been working flawlessly for
about a year…until today.

There I was. Enjoying the simple beauty of an amplitude modulated carrier
wave pulsing out Van Halen’s ‘Right Now’ when I heard a pop, then a
sizzle, followed by more popping and smoke pouring out of the front and back
on the CRT side of the scope (and the fan discharge, of course). I shut it
down (it was still working) and started an autopsy.

I’m not familiar with troubleshooting CRTs at all, so I simply discharged
the anode and moved on to what I know. Since I was familiar with the power
supply, I pulled it out for a look and discovered a blown resistor and X rated
capacitor near the mains input. Admittedly, I should’ve replaced all the
caps on the power supply.

Can anyone provide insight on what likely occurred? Did the CRT fail and
cause the blown power supply, or did the blown power supply kill the CRT?!
What is the typical CRT failure mode? How do I troubleshoot the CRT?
Anything to know safety wise other than discharging the anode?

I happen to have 2 other non-working 2465’s that I acquired in the deal as
parts donors. One powers up but has a fault that I’ve never looked into and
I have no idea about the other.

Any help would be greatly appreciated.

-Dave
 

Yes, it is not likely to be the CRT, there is noting in there to smoke. If it cracks it can arc to something else, if you can get to the back of the neck just try moving it. Of course it should not move.

What did it smell like ?
 

It is animating when that happens, isn't it. Rifa caps are known as "delayed action smoke generators" for good reasons.

See images in

Repair techniques

On 17/09/18 20:48, dharwood1980@... wrote:
Greetings everyone,

I acquired a Tek 2465 last year. It had significant flicker on the CRT and a noisy fan, so I replaced all of the electrolytic caps on the power supply and rebuilt the fan motor...windings and all. It’s been working flawlessly for about a year…until today.

There I was. Enjoying the simple beauty of an amplitude modulated carrier wave pulsing out Van Halen’s ‘Right Now’ when I heard a pop, then a sizzle, followed by more popping and smoke pouring out of the front and back on the CRT side of the scope (and the fan discharge, of course). I shut it down (it was still working) and started an autopsy.

I’m not familiar with troubleshooting CRTs at all, so I simply discharged the anode and moved on to what I know. Since I was familiar with the power supply, I pulled it out for a look and discovered a blown resistor and X rated capacitor near the mains input. Admittedly, I should’ve replaced all the caps on the power supply.

Can anyone provide insight on what likely occurred? Did the CRT fail and cause the blown power supply, or did the blown power supply kill the CRT?! What is the typical CRT failure mode? How do I troubleshoot the CRT? Anything to know safety wise other than discharging the anode?

I happen to have 2 other non-working 2465’s that I acquired in the deal as parts donors. One powers up but has a fault that I’ve never looked into and I have no idea about the other.

Any help would be greatly appreciated.

-Dave
Chuck Harris
 

Your only mistake was likely just using the scope outside of the US.

At 120V, most of the filter parts on the input (mains) side of the scope
are rated adequately. At 240V, they tend to pop.

Replace the few RIFA caps, maybe the IEC power input filter/connector, and
the other burnt offerings, and your scope will be fine.

Or, if you are feeling lazy, just use the scope, until you feel like fixing
the input filter parts...

If the readout is turned on, the flicker in the CRT is normal. It is the
result of time sharing the CRT's beam to write the trace, the cursors, and
the display characters.

-Chuck Harris

dharwood1980@... wrote:

Greetings everyone,

I acquired a Tek 2465 last year. It had significant flicker on the CRT and a noisy fan, so I replaced all of the electrolytic caps on the power supply and rebuilt the fan motor...windings and all. It’s been working flawlessly for about a year…until today.

There I was. Enjoying the simple beauty of an amplitude modulated carrier wave pulsing out Van Halen’s ‘Right Now’ when I heard a pop, then a sizzle, followed by more popping and smoke pouring out of the front and back on the CRT side of the scope (and the fan discharge, of course). I shut it down (it was still working) and started an autopsy.

I’m not familiar with troubleshooting CRTs at all, so I simply discharged the anode and moved on to what I know. Since I was familiar with the power supply, I pulled it out for a look and discovered a blown resistor and X rated capacitor near the mains input. Admittedly, I should’ve replaced all the caps on the power supply.

Can anyone provide insight on what likely occurred? Did the CRT fail and cause the blown power supply, or did the blown power supply kill the CRT?! What is the typical CRT failure mode? How do I troubleshoot the CRT? Anything to know safety wise other than discharging the anode?

I happen to have 2 other non-working 2465’s that I acquired in the deal as parts donors. One powers up but has a fault that I’ve never looked into and I have no idea about the other.

Any help would be greatly appreciated.

-Dave
 

On Mon, 17 Sep 2018 12:48:35 -0700, you wrote:

Greetings everyone,

I acquired a Tek 2465 last year. It had significant flicker on the CRT and a noisy fan, so I replaced all of the electrolytic caps on the power supply and rebuilt the fan motor...windings and all. It’s been working flawlessly for about a year…until today.

There I was. Enjoying the simple beauty of an amplitude modulated carrier wave pulsing out Van Halen’s ‘Right Now’ when I heard a pop, then a sizzle, followed by more popping and smoke pouring out of the front and back on the CRT side of the scope (and the fan discharge, of course). I shut it down (it was still working) and started an autopsy.
Sounds like the X2 line bypass capacitors. These are notorious for
failing.

I’m not familiar with troubleshooting CRTs at all, so I simply discharged the anode and moved on to what I know. Since I was familiar with the power supply, I pulled it out for a look and discovered a blown resistor and X rated capacitor near the mains input. Admittedly, I should’ve replaced all the caps on the power supply.
Not necessarily, these are the specific capacitors. If you're in a
240 volt environment, these will fail more frequently than in a 120
volt environment. Certain manufacturer's input filters are notorious
for failing.


Can anyone provide insight on what likely occurred? Did the CRT fail and cause the blown power supply, or did the blown power supply kill the CRT?! What is the typical CRT failure mode? How do I troubleshoot the CRT? Anything to know safety wise other than discharging the anode?
Power supply should be fine. CRT should be fine.

I happen to have 2 other non-working 2465’s that I acquired in the deal as parts donors. One powers up but has a fault that I’ve never looked into and I have no idea about the other.

Any help would be greatly appreciated.
Try replacing those capacitors and do a general check. Look through
the archives for X2 capacitors for more background.

Harvey

-Dave
[email protected]
 

Gents,

Thanks so much for the initial advice. The general consensus seems to be that the CRT should be fine and I just need to take care of the power supply X2 bypass caps. Easy. I'll just finish the power supply rebuild job I half did last time. Lesson learned.

However, it really bothered me that I had observed so much smoke emerging from the case on the CRT side of the unit. If it were just the bypass cap, I would've thought the smoke would be drawn right out by the fan (which was still operating). For exploration purposes, I removed the shield from the board supplying the CRT. I found a fair amount of smoke residue on the inside of the shield outlining the big red component which looks to be potted in resin or something. I suppose voltage multiplier related? No visual damage to any board components, just what seems to be smoke residue.

Is this normal? Should I look into this more, or just repair the power supply and see what happens?

Thanks again for the advice. Learn something new each time I visit the forum.

-Dave
 

On Sat, Sep 22, 2018 at 12:00 PM, <dharwood1980@...> wrote:


Gents,

Thanks so much for the initial advice. The general consensus seems to be that
the CRT should be fine and I just need to take care of the power supply X2
bypass caps. Easy. I'll just finish the power supply rebuild job I half did
last time. Lesson learned.

However, it really bothered me that I had observed so much smoke emerging from
the case on the CRT side of the unit. If it were just the bypass cap, I
would've thought the smoke would be drawn right out by the fan (which was
still operating). For exploration purposes, I removed the shield from the
board supplying the CRT. I found a fair amount of smoke residue on the inside
of the shield outlining the big red component which looks to be potted in
resin or something. I suppose voltage multiplier related? No visual damage
to any board components, just what seems to be smoke residue.

Is this normal? Should I look into this more, or just repair the power supply
and see what happens?

Thanks again for the advice. Learn something new each time I visit the forum.

-Dave
Possibly just dirt and HV filth? Im pretty sure the "big red component" you are talking about is the HV CRT power supply.
 

On 2018-09-22 4:00 p.m., dharwood1980@... wrote:
Gents,

Thanks so much for the initial advice. The general consensus seems to be that the CRT should be fine and I just need to take care of the power supply X2 bypass caps. Easy. I'll just finish the power supply rebuild job I half did last time. Lesson learned.

However, it really bothered me that I had observed so much smoke emerging from the case on the CRT side of the unit. If it were just the bypass cap, I would've thought the smoke would be drawn right out by the fan (which was still operating). For exploration purposes, I removed the shield from the board supplying the CRT. I found a fair amount of smoke residue on the inside of the shield outlining the big red component which looks to be potted in resin or something.

So.. in short.. you found the smoking gum







-Dave
 

Aghhhh!!! That's terrible! :-)

On 9/22/2018 8:38 PM, toby@... wrote:
So.. in short.. you found the smoking gum
 

On Sat, 22 Sep 2018 12:00:28 -0700, you wrote:

Gents,

Thanks so much for the initial advice. The general consensus seems to be that the CRT should be fine and I just need to take care of the power supply X2 bypass caps. Easy. I'll just finish the power supply rebuild job I half did last time. Lesson learned.

However, it really bothered me that I had observed so much smoke emerging from the case on the CRT side of the unit. If it were just the bypass cap, I would've thought the smoke would be drawn right out by the fan (which was still operating). For exploration purposes, I removed the shield from the board supplying the CRT. I found a fair amount of smoke residue on the inside of the shield outlining the big red component which looks to be potted in resin or something. I suppose voltage multiplier related? No visual damage to any board components, just what seems to be smoke residue.

Is this normal? Should I look into this more, or just repair the power supply and see what happens?
Two things:

1) it kept on working.
2) those X2 capactors are across the AC line, effectively. Not only
do they smell bad (kind expression), but the amount of smoke produced
is close to a military tactical weapon.

Big component that is potted is likely the HV multiplier.

Replace capacitors with appropriately rated units that won't fail.
Clean off smoke residue where reasonable.

I'd then close it up and keep using it.

Much the same thing happened on a 7000 series scope.

Harvey



Thanks again for the advice. Learn something new each time I visit the forum.

-Dave
 

On Sat, Sep 22, 2018 at 12:00 PM, <dharwood1980@...> wrote:


For exploration purposes, I removed the shield from the board supplying the
CRT.
If there is too much carbon residue in there you'll have to clean it up. It throws off and destabilises the higher voltages there. The 91 or 99 % isopropyl will work, and actually lighter fluid. Even better is acetone but you have to test it in the plastic parts to make sure it does not dissolve them. Of course about everything is flammable so do accordingly.

If it is smoked up, don't put alot of hours on it until it is cleaned. If it arcs at all it can make a carbon track through or on the plastic and that is harder to deal with.
 

That "big red thing" is most likely the high voltage multiplier module.? All high voltage components attract air particles (like smoke) via electrostatic attraction.? Even normal operation often covers these high voltage components in black, soot like powder.? So that black residue may have been there all along and the exploding X2 caps only added to it.? The proper cure is to clean the residue (its partially conductive) and repair the caps.? The scope should be fine after that.

On ?Saturday?, ?September? ?22?, ?2018? ?02?:?00?:?39? ?PM? ?CDT, dharwood1980@... <dharwood1980@...> wrote:

Gents,

Thanks so much for the initial advice.? The general consensus seems to be that the CRT should be fine and I just need to take care of the power supply X2 bypass caps.? Easy.? I'll just finish the power supply rebuild job I half did last time.? Lesson learned.

However, it really bothered me that I had observed so much smoke emerging from the case on the CRT side of the unit.? If it were just the bypass cap, I would've thought the smoke would be drawn right out by the fan (which was still operating).? For exploration purposes, I removed the shield from the board supplying the CRT.? I found a fair amount of smoke residue on the inside of the shield outlining the big red component which looks to be potted in resin or something.? I suppose voltage multiplier related?? No visual damage to any board components, just what seems to be smoke residue.

Is this normal?? Should I look into this more, or just repair the power supply and see what happens?

Thanks again for the advice.? Learn something new each time I visit the forum.

-Dave
 

I forgot to mention, the black residue is usually easy to remove (I brush it away with a soft paint brush).? But a bit of alcohol or PCB cleaner will wash it off.? Take care not to wash it under or inside other parts.

On ?Saturday?, ?September? ?22?, ?2018? ?02?:?00?:?39? ?PM? ?CDT, dharwood1980@... <dharwood1980@...> wrote:

Gents,

Thanks so much for the initial advice.? The general consensus seems to be that the CRT should be fine and I just need to take care of the power supply X2 bypass caps.? Easy.? I'll just finish the power supply rebuild job I half did last time.? Lesson learned.

However, it really bothered me that I had observed so much smoke emerging from the case on the CRT side of the unit.? If it were just the bypass cap, I would've thought the smoke would be drawn right out by the fan (which was still operating).? For exploration purposes, I removed the shield from the board supplying the CRT.? I found a fair amount of smoke residue on the inside of the shield outlining the big red component which looks to be potted in resin or something.? I suppose voltage multiplier related?? No visual damage to any board components, just what seems to be smoke residue.

Is this normal?? Should I look into this more, or just repair the power supply and see what happens?

Thanks again for the advice.? Learn something new each time I visit the forum.

-Dave
 

Augh indeed! That was so terrible even the Roswell aliens facepalmed.
But the problem now is can this be repaired? If its of assistance I have a spare 'scope tube here which is surplus.Also a big box o' flybacks as mentioned before...
www.cwgsy.net/private/mandoline "Error 008472. Horrible bug encountered. $Deity knows what happened."

On Saturday, 22 September 2018, 21:07:31 BST, Adrian <Adrian@...> wrote:

Aghhhh!!! That's terrible! :-)


On 9/22/2018 8:38 PM, toby@... wrote:
So.. in short.. you found the smoking gum
[email protected]
 

Wow. Great thoughts. I had never considered electeostatic attraction of the high voltage. Of course!

I'll do a power supply repair and clean up the dirty high voltage areas and try it out. Unfortunately, work is sending me overseas for a week or so I'll post an update after I've had a chance to to the repair.

Many thanks!

-Dave
 

Hi Dave,

There's a 2465A for parts on eBay:

Cheers, Brian.
[email protected]
 

Gents,

Apologies for my delayed update. Unfortunately, work took me away for longer than expected.

As most of you expexted, it was just a power supply issue. I gave it the full work over this time with a good cleaning of the smoke residue near the CRT and the scope is right back in business.

Thank you all again for the helpful advice!

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