Scope is Dead

[sr1200]

I tried posting over the weekend when i was sitting in front of the thing, but kept getting a server error   Anyway, my scope died, kind of.  It sill powers up but the screen has gone kaput!  it kinda just Its VERY old, and I have to assume that theres a CRT in there or some kind of tube thats driving the screen, I will get the make and model a little later today.  Do all scope use the same kind of tube for the display? and are they still available generally?  I guess without a make and model its kinda tough to answer.  Ill repost in a couple hrs with the info on it.

 

[s2udio]

Most likely the EHT supply gone awol......
The CRT's tend to fade slowly rather than die quickly.
BTW be carefull, about 5-10kv+ in there when working !!!

 

[sr1200]

This scope is about 30 years old if its a day.  And the line would kind of conk out, id slap the side, it would come back then just kind disappear again.  Now, its just gone and no amount of smacking the side is bringin her back lol.  Im heading to the shop now, ill get some more info.  Thanks

 

[sr1200]

Ok we have a Leader LBO-502.  Im gonna open her up tomorrow. Ill post some pics of the autopsy.

 

[PRR]

> the screen has gone kaput!

Cracked? Smoking? Psychedelic? Blank?

The most-likely cause for "blank" is someone turned Brightness too far.

I think the mice get in at night and turn it.

On triggered-sweep, putting signal in channel 1 while the 'scope is displaying ch 2 will give "blank". So will too-small signal or too-dull trigger sensitivity.

The CRT never dies. My pre-WWII DuMont's CRT, found in trash, worked good.

The Leader is not old.... or in another view, it was aging as soon as the warranty ran out. My Leader had sagging voltages. "+12V" tended to be 10V or 11V. However it always gave a trace after 10 or 20 minutes.

There's a dozen other things. As s2udio says, the hi-voltage can fail. So can the blanking. There's less-high voltages on the CRT gun. The Leader is a royal pain to work inside; if your troubleshooting skills are thin, I would not suggest much internal poking.

Just a wild chance: Fold two towels and put them on the bench. Set the 'scope face-down on the towels. Lift 2 inches, and drop (while guiding!). CRTs can get loose dirt in the gun, which shorts it. A slam can knock it loose, and if it falls to the faceplate it can lay down there forever no problem. This hardly ever works, but it is something to try.

 

[sr1200]

Here are some pics (hopefully they show up)
I've banged prodded smacked and shook, still a blank screen HOWEVER, i did notice 2 things after i took the case off.  Then the Trig light lights up, i hear a little knocking sound (never heard that before) also, when i turn the unit OFF, for a split second i see a really faint dot at the center of the screen.  The inside of the unit is amazingly clean for something thats been sitting in a cold damp garage for years.

(pretty christmas lights that flicker up and down)

 

[s2udio]

HOWEVER, i did notice 2 things after i took the case off.  Then the Trig light lights up, i hear a little knocking sound (never heard that before) also, when i turn the unit OFF, for a split second i see a really faint dot at the center of the screen.

First point of call PSU section then Deflection/eht and flyback section.
Schematic would help.
Look for hot resistors(discouloured high wattage) and dry joints around them.
Hmmmm .....Got the 510/511 somewhere i think ?.
Or here
http://www.eserviceinfo.com/downloadsm/28249/leader_lbo510-511.html
Can't be a vast amount of difference ?
Shame to trash it !

 

[sr1200]

So to resurrect this dead horse of a topic... i visited my local repair shop, and it turns out they're lookin to sell a few scopes... they have a couple of these HP scopes that were phenominal (goes up to 100Mhz) has 4 inputs (can display all 4 at once) has memory and snapshot ability etc etc.  Hes askin like $500/scope.  (probes not incl)  I figure i'd probably blow around that much to get a decent scope anyway.  If anyone is interested in picking one of the others up let me know might be able to arrange a buy/ship thing.

 

[mjk]

$500 seems to be the right price to pay for a really nice used scope for audio work.

Thought I'd point out that the Tek TDS200 series lightweight slim profile scopes are starting to come up on ebay in the $500 range also. I just picked up a TDS 220 (2 channel 100 MHz) for $500 and free shipping to replace my recently deaded 2430A storage scope. The digital scopes are great at glitch capture.

 

[millzners]

So to resurrect this dead horse of a topic... i visited my local repair shop, and it turns out they're lookin to sell a few scopes... they have a couple of these HP scopes that were phenominal (goes up to 100Mhz) has 4 inputs (can display all 4 at once) has memory and snapshot ability etc etc.  Hes askin like $500/scope.  (probes not incl)  I figure i'd probably blow around that much to get a decent scope anyway.  If anyone is interested in picking one of the others up let me know might be able to arrange a buy/ship thing.

I've got one of those 'ol boys laying around here somewhere.  I actually had two but gave one of them away.  They're nice, kind of huge, but they're work horses and more than adequate for audio.  $500 is a little bit more expensive than you'll see for them on evilbay, but without shipping charges/damage to worry about, plus you know it works...  You could do a lot worse. 

If they let you pick which one you take home, find one with a brighter screen as they tend to get dim over the years, and look at the pins/knobs on the BNC input connectors on the front as they tend to get wore off especially on channel 1; those are both issues I've seen with that specific scope.

 

[sr1200]

All the units are pristine, and the screens are great (brightness adjustment works VERY well) these things have VERY little wear on them with the exception of a little dust from sitting on the shelf for a while.  Still has the manuals and bags of what look like ground clips.

 

[bruno2000]

I have a couple of Tek 2445B scopes that I love for audio work.  Saw one go on the "bay" for $200.
Best,
Bruno2000

 

[Samuel Groner]

We have one of those HPs at work, and I would not pay $500 for it. It is an early digital scope, and neither particularly user-friendly nor fast or otherwise powerful. For general audio work, a great analogue scope (as the mentioned Tektronix 2445B, or the faster 2465B) is cheaper to get and more useful, IMHO.

Samuel

 

[mobyd]

We have one of those HPs at work, and I would not pay $500 for it. It is an early digital scope, and neither particularly user-friendly nor fast or otherwise powerful. For general audio work, a great analogue scope (as the mentioned Tektronix 2445B, or the faster 2465B) is cheaper to get and more useful, IMHO.

Samuel

A big +1 on Tek 2445s and 2465s. I have one of each and the only problem I have ever encountered is that if the fan fails, it's not long before you end up replacing a pile of dried up electrolytic caps in the PSU. Not a difficult job but annoying and preventable.
M

 

[sr1200]

Thanks for the heads up on this, much appreciated.

 

[user 37518]

I also agree with getting a new scope: heres my 2 cents, you can get used analog scopes for scraps on e-bay, i recently bought a Tek 2235 with a calibration certificate for around 250 dolars on e-bay, and thats considered expensive compared to what most other used Tek scopes are being sold on e-bay. So my suggestion, sell it for parts on e-bay, and get a used Tek.

 

[abechap024]

For what its worth, I had trouble with my analog scope and replaced some of the HV caps (that had dried out) and now it works great. I would say troubleshoot your old one.