Leader LBO-315

[JohnnyP]

My trusty little scope died a couple weeks ago, finally getting around to repairing it.

I know, I should have taken pics of it as I tore it down, but I figured I'm a genius and could figure it out.   

Got it all back together except for one EMI shield.  I emailed a photo of it to Leader to see if they knew where it went.  They opened up a couple they have in for service, but they are newer than mine and the shielding is different.

I bought it new in '89.  I have attached a couple pics.  I think.

[JohnnyP]

This thing is like a Chinese puzzle.  I tore it down again and figured out where the shield goes.

It can't be installed at the last minute.  It's invisible when everything's back together.

[JohnnyP]

Hooray!  All back together except for the cover, and it works.

The scope overheated and died on me a few weeks ago, so I took it in to Leader for repair.

They emailed a pic showing a burned spot on the power supply board, and said they have no spare power boards to replace it because the scope is too old.  See attached "BadBoard" pic from them.

I brought it back and let it sit until this weekend, when I decided I would remove the power board and have a look.

I cleaned it up then removed the four diodes where the burn mark was.  According to the schematics Leader was kind enough to supply, the diodes were the bridge for the 100v supply.  Eureka, one of them was shorted.

Simple problem to solve, but I made it way harder than needed by tearing it down  as far as I did.

I told my wife it would have made things a lot easier if I had taken pics, but then I wouldn't have learned as much.

[calin]

Nice work man !! enjoy it

You will laugh but last week or so I got an LBO-516 (100Mhz one with some really interesting display functions also) for 19$. It had a nasty ding on a side so I fixed it .. well .. with a hammer  .

What happened , no idea but i think somebody either dropped something on a side or the scope was dropped, maybe something pushed the thing or something on it .. whatever. The cover was touching the PCB inside and was making a short. Took the cover off .. banged the thing with a hammer and mallet to make it straight and viola .. one 100Mhz perfectly working scope.  I compared what it measures with an Agilent and .. ugh the dreaded Owon scope that Dave just "roasted" in a recent review and the oldie is spot on

Not to shabby for 19$

[JohnnyP]

Wow, good find.  Most people would hesitate to "waste" $20 on a scope that was obviously a piece of junk.

My scope was still running hot and the switching waveforms in the power supply were nasty looking, overshooting and double pulsing.  Found a bad 9v regulator IC, all good now.

The attached photo shows the switching waveform, looks like hash.  The bottom trace shows the 9v output is about 20v and pulsing.  Good clue it's bad.

The other photos show the waveforms after replacing the regulator.

Nothing spectacular, but it's all working again.  Was afraid it was a a basket case when I started.

[calin]

Yep .. good "waste". I love getting these oldies back to life .. the Leader was a truly easy fix .. I took the cover off .. push on/off button and it worked .. The hammer part came later.

I just bit the bullet this morning and i "wasted" another 73$ this time on a Fluke 8842A 5 1/2 digit multimeter ... "for parts not working" but with a live display and looking in decent shape . Can't wait ... hope is another "good waste" because these things sell over 300$ usually on ebay.

Here is a photo of the "dinged" LBO before hammer treatment ...

[HighVoltage]

JonnyP
These Leader scopes are somehow amazing in the built quality.
I still have the same one in use from time to time and touching the knobs is something special.
They do not make such high precision mechanical adjustments anymore in modern scopes.
Good old days.

If I remember right, Leader also made the LBO-316 at the time with a battery pack.
I used it a lot, until the small Tektronix 222 and the 222PS PowerScout came out.
Now they are all in a museum

[calin]

Yeap I love the Leader ... for some reason I like it more when I measure noise stuff. It is still going strong and stable no issue.

Recently I tried to get a Tek 475A back to life - got it off Craiglist for 25$ .. but darn after I got in to fixing the power supplies still .. dead CRT. I literally rebuilt the Low Voltage power supply just to find out that some hard handed idiot has probably tried to get the CRT out and it literally got the CRT neck broken in two. Talking about fine mechanics , you should see the time base selector on a 475 or a 4xx series Tek .. DAMN !! Now the Tek sits in the maybe some day pile waiting for a CRT.

BTW .. the Fluke 8842 meter was an extraordinarily good "waste" .. the meter was bang on and working like a champ. A bit of a faded display but bang on everywhere. I compared the thing @ work with the new 61/2 Agilent meter freshly calibrated and is just a count or two here or there - fantastic. After a good clean and some love is my go to bench meter now .. for 73$. Best deal I ever got on ebay I wold say. The build quality in these meters .. like a very precise tank . Nothing but top notch quality.

[HighVoltage]

Calin
Yes, the old Tek scopes had something special to them as well. Too bad, those days are over.

In regards to the Fluke 8842A, I had two of them in the past and they could not width stand, being in the near of high voltage measurements. Even when they were not hooked up to anything, the radiated noise from a spark discharge got them completely screwed up. I had the same problem with the really nice Philips Multimeter, the PM2535. Since I am doing a lot of high voltage measurements, I could not really use either of them. Interestingly, the Agilent 34401A can even be hooked up to the circuit that is producing the high voltage and it keeps measuring perfectly. I never had a Agilent 34401A fail on me with this kind of measurements. The same is true for the Leader scopes, they just work and work.

[calin]

Holly $@#t !! you are playing with some "HighVoltage" there if you managed to buzz out the meters

I measure mostly low voltage stuff anyways so the fluke is OK .. My greatest touch of HV  stuff was measuring the cathode voltage on the Tek i was trying to fix - 15KV.

What I like on the 8842 is the very high input impedance on the thing - you can measure many sensors directly without messing (loading) the signal .. on the low ranges is like 10.000 M ohm if I remember right. I wold love an Agilent .. especially the new ones are very nice. But for hobby budget that needs to be wife approved ... too bad not gonna happen soon ... I barely managed to get the 73$ approved