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Toppled over my analog oscilloscope. Now no display. (Hitachi V-1565)
Posted by AbsoluteCatalyst on 03 Dec, 2017 02:41 -
I screwed up and left my oscilloscope standing upright while I was learning how to use it. Predictably a family member bumped into it and toppled it over. When I picked it up I found that the CRT display no longer functions at all, even after turning it on and off. I'm praying that this might just be an easy fix, maybe something just disconnected internally, but my outlook is grim.
Ironically right before it fell, I finally got the hang of it.
I've checked the fuses under the power socket and I found them to be seated properly. I've also opened up the scope itself, checked almost all the connectors and found none of them In their sockets. I've also checked for continuity on the CRT's filament and between pins heater 1 and 2, so it seems to still be intact (this was suggested to me by someone on Reddit), and I'm assuming the power supply still functions correctly since the buttons and LED's for the front panel still work as normal.
There was nothing loose or broken inside of the casing either, and the CRT glass is intact.
If anyone can offer any advice or help on as to what to look for in a case such as this, or if anyone has gone through this before, I'd really appreciate your input!
This oscilloscope was an awesome gift from my girlfriend's father (same as the multimeter), and I genuinely really liked this scope. I'm really hoping I can figure out what broke and if I can repair it instead of just replacing it with a digital scope.
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Do you see any signs that anything else is functioning, such as front panel lights or anything else?
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Do you see any signs that anything else is functioning, such as front panel lights or anything else?
Yeah the small lights on the front panel still work. The buttons are also responsive (the TIME/DIV switch's "Auto" mode lights up when pressed, Selector lever still cycles through etc) -
Yeah the small lights on the front panel still work. The buttons are also responsive (the TIME/DIV switch's "Auto" mode lights up when pressed, Selector lever still cycles through etc)
Well ... unless you can verify the high voltage is present, it's possible that the physical shock has damaged the interior components of the CRT. Let's see who else has ideas. -
When you confirmed continuity between pins 1 & 2 of the CRT, was that with the CRT socket disconnected? ie., just the CRT heater by itself? Unfortunately, the electron gun assembly in a CRT is fragile and easy to damage especially with power applied because of the high temperature of the heater.
With any luck, it might be a problem outside the CRT. If you can't find a schematic look for a pinout of the CRT. You'll have to find some safe way to measure high voltages. The cathode and control grids should be something like minus 1-2 KV relative to circuit common. The deflection plates should be around 100 V. The PDA (Post Deflection Acceleration, probably a separate lead to the bell of the CRT) could be 3 to 10 KV.
Best o' luck,
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^ This.
Confirm that the CRT heater is intact, preferably by actually observing the glow in the neck of the tube when powered on. Needless to say, don't kill yourself by inadvertently bridging some HV with your body parts. To use the resistance measurement you must first unplug the socket from the CRT and assure that you are measuring the correct pins on the CRT itself. Beware, again, because parts of the scope can still retain a high voltage charge even when the scope is off and unplugged. -
Check the CRT anode connector and see if it's loose. If it has one of those aweful pin type anodes the pin socket in the connector fatigues and pops off. It may or may not go back on, replace it if it doesn't.
Other things to check from shock are board to board interconnects, they may have come loose or broken their solder joints. Also check for cracks on the traces, which may be microscopic and only detectable by testing. Poking around in it with something non-conductive while it's powered can help find these. -
This may seem like a silly comment, but have you checked all of the settings?
I am not familiar with the Hitachi V1565, but banks of interlocking push buttons sometimes all 'jump out' when subjected to shocks. Position pots, especially vertical, can catch one out
Regards, BT -
This may seem like a silly comment, but have you checked all of the settings?
I am not familiar with the Hitachi V1565, but banks of interlocking push buttons sometimes all 'jump out' when subjected to shocks. Position pots, especially vertical, can catch one out
Regards, BT
The pots maybe, but I don't know of any scope that just dies because all of the buttons are out, there should still be something on the CRT. -
Right.
Sorry for your bad luck with the scope
Unplug the scope from outlet
First i would check all the board inter connects leads front panel contacts PSU connectors etc etc.
Those can get dislodged by shock quite commonly.
Next check for any physical damage on the board (cracks chips etc) Twist boards carefully to reveal any hidden cracking (use care and not too much force)
After that do careful physical study of the structure paying attention of stress points (Especially case screw areas where the shock will have transferred to internal components.)
If all these steps show now damage you should progress to checking the voltages.
Plug the device and turn it on (do not do this unless you are aware of the dangers of high voltage and are comfortable progressing. Use care be aware
Use manual to find the voltage test points.
Go through full voltage testing of all boards
If all voltages are fine you should move to troubleshooting actual CRT what i believe is most likely culprit (do not skip the other steps as they will rule out other possible malfunctions)
Unplug power (not just turn it off)
Word of warning CRT's are dangerous best of times and study carefully what you can and cannot do with CRT's
Again do not progress unless you are sure you know what you are doing.
Make physical study of the CRT observe any outward physical damage do careful study with magnifying class or other suitable optical assist.
Again pay particular attention to the stress points (where case makes contact with the CRT and ESPECIALLY the neck that is the weakest point in CRT.
make sure neck board is attached well (again remember safety and checking the board is well seated can be done with plastic tool rather than touching it) use care !
Now all these steps might show no issue but as the reason of the malfunction was caused by concussive force it is possible if not likely CRT is internally broken
To verify this you will need some specialist equipment and a specialist.
Do not fool around with CRT's with power on or fiddle with the nipple
and i am not talking about the good kind.
Good luck keep us posted how you progress
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I was under the impression CRTs implode if cracked. Also the filament would have gone pop too if it vented.
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You might be able to sell it on eBay as "not tested
" for 100 USD
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I was under the impression CRTs implode if cracked. Also the filament would have gone pop too if it vented.
CRTs in analog 'scopes are much smaller than those in TVs, & hence, the air pressure on their surface is not near as great, also, the glass is proportionally thicker.
A crack will normally just ruin the vacuum, with no dramatic effects.
The very large RADAR CRTs which were commonly available surplus after WW2 were well known for implosions, as were some early TV CRTs, but small CRTs as used in ' scopes & TV CRTs made after the early 1960s are pretty much immune to such happenings, unless you work really hard to cause one. -
PM sent.
Also, check out Grumpydoc's teardown of the sister scope, v-1065. It's a good reference thread. -
Especially if it happens in the neck area, I've seen CRTs that had cracked necks but were otherwise intact, and the evacuation pip in the middle of the neck pins is easy to break. If it loses vacuum the filament will quickly burn out though, and if there's a visible getter in the neck it will change from silver to milky white.
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Especially if it happens in the neck area, I've seen CRTs that had cracked necks but were otherwise intact, and the evacuation pip in the middle of the neck pins is easy to break. If it loses vacuum the filament will quickly burn out though, and if there's a visible getter in the neck it will change from silver to milky white.
Yeah pretty much so.
It is not always obvious when small CRT is broken
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Thank all of you for your support and advice! Sorry I wasn't able to respond, finals week is coming along so I haven't had a chance to work on it as I would have liked, which kinda sucks.
I'll try out some of your suggestions soon and keep this thread updated!
Another thing I may have failed to mention was that despite receiving a resistance reading, I do not see the filament lighting up at all when on. (Or at least from what I could see with the metal shroud over it.)
The only thing that worries me though is that I've never truly worked with high voltages, and not that i'm intimidated about injury or etc, but more so I'm not sure if I have the right equipment and the last thing I want to do is destroy my fluke multimeter as well. (Another gift)
I've asked around acquaintances and even professors at my campus, no one knows how to deal with something like this. I'm completely out of luck with any outside help besides these forums, so thank you! -
Did you check the filament with the tube unplugged? Otherwise you're just reading the transformer.
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Sorry, Cyber Dragon - My post re the switches etc was not clear. In light of the assumption that the OP was fairly new to scopes, I thought that the trace could have been absent or 'hidden' due to switch positions.
50 years of using scopes, and 30 years with my 'go-to' old CRT model and I switched it on yesterday and - no trace. I'm ashamed to say I faffed about for a good 60 seconds before I found a trace !!
BT -
The V-1565 has an on-screen display, so even if the trace was "missing", the OSD characters would be present. There's also a boot-up sequence that displays during power on that is independent of the dial settings.
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This may seem like a silly comment, but have you checked all of the settings?
This was one of my first ideas, I also thought it might have just toggled or messed up a setting but sadly regardless of my settings nothing will display. I know when it reboots it goes through a "Calibration" self test which displays on screen, but this is completely absent now. On bootup, the buttons on the front panel still actually stay lit for a couple of seconds like as if it "thinks" it's still going through this test.
I am not familiar with the Hitachi V1565, but banks of interlocking push buttons sometimes all 'jump out' when subjected to shocks. Position pots, especially vertical, can catch one out
Regards, BTDid you check the filament with the tube unplugged? Otherwise you're just reading the transformer.
Was this the wrong way to read it? See the pins of the CRT tube on the bottom? That circuit board is normally plugged into it. Pins H1 and H2 are connected to my meter in this photo. (Note I took this off with my bare hands. Was I meant to get electrocuted at that point? Does that mean it no longer stores any charge in that case then?)Check the CRT anode connector and see if it's loose. If it has one of those aweful pin type anodes the pin socket in the connector fatigues and pops off. It may or may not go back on, replace it if it doesn't.
The anode seemed pretty well in place when I tugged on it. So did the board sockets themselves with the exception of the delay line which is a little loose on it's circuit board port but not enough to fall out on it's own, and still slides in fairly snugly.
Other things to check from shock are board to board interconnects, they may have come loose or broken their solder joints. Also check for cracks on the traces, which may be microscopic and only detectable by testing. Poking around in it with something non-conductive while it's powered can help find these.
I have some free time tonight after class that I'll be able to inspect it more closely. Someone also suggested that the power rails for the CRT may have been damaged.
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Without seeing the PCB I can't say how likely it is, but look closely around any heavy components like transformers, chokes or large capacitors, also look around the mounting points. It's not uncommon for equipment subjected to large G forces like this to get cracks in the PCB that can break traces and make it stop working.
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First, stick it on your Lab door:
then move on with the repair. -
This may seem like a silly comment, but have you checked all of the settings?
This was one of my first ideas, I also thought it might have just toggled or messed up a setting but sadly regardless of my settings nothing will display. I know when it reboots it goes through a "Calibration" self test which displays on screen, but this is completely absent now. On bootup, the buttons on the front panel still actually stay lit for a couple of seconds like as if it "thinks" it's still going through this test.
I am not familiar with the Hitachi V1565, but banks of interlocking push buttons sometimes all 'jump out' when subjected to shocks. Position pots, especially vertical, can catch one out
Regards, BTDid you check the filament with the tube unplugged? Otherwise you're just reading the transformer.
Was this the wrong way to read it? See the pins of the CRT tube on the bottom? That circuit board is normally plugged into it. Pins H1 and H2 are connected to my meter in this photo. (Note I took this off with my bare hands. Was I meant to get electrocuted at that point? Does that mean it no longer stores any charge in that case then?)Check the CRT anode connector and see if it's loose. If it has one of those aweful pin type anodes the pin socket in the connector fatigues and pops off. It may or may not go back on, replace it if it doesn't.
The anode seemed pretty well in place when I tugged on it. So did the board sockets themselves with the exception of the delay line which is a little loose on it's circuit board port but not enough to fall out on it's own, and still slides in fairly snugly.
Other things to check from shock are board to board interconnects, they may have come loose or broken their solder joints. Also check for cracks on the traces, which may be microscopic and only detectable by testing. Poking around in it with something non-conductive while it's powered can help find these.
I have some free time tonight after class that I'll be able to inspect it more closely. Someone also suggested that the power rails for the CRT may have been damaged.
I made this very quick and... crude... drawing showing how it actually fell.
I never received the handle with it so it fell bare on it's back. The red portion showing where the front panel was etc. Think that type of fall can destroy the neck? It wasn't actually that hard of a fall as I saw it slowly tilt over and then fall.
Dear OP i would suggest to follow the troubleshooting routine rather than randomly poking around.
The changes you find the problem in such complex equipment without any thought are slim.
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I don't think this scope has a troubleshooting guide. I've looked at the manual for the 1065 which should be similar and all it says is refer servicing to a technician.
I do have the 1065 schematics though, I'll try to find some voltages for the CRT circuit.