Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Beckman Industrial 9020 - Poor focus with no adjustment

Status
Not open for further replies.

Affy420

Newbie level 3
Joined
Sep 17, 2019
Messages
4
Helped
0
Reputation
0
Reaction score
0
Trophy points
1
Activity points
36
Hi.

I've just bought myself an old scope (Beckman Industrial 9020) for a bit of DIY testing on some circuits I'm building with the kids.

Really nice bit of kit, and all seems to work, except the focus is shot (large disks visible instead of small dots for Ch1 and Ch2) and also the intensity knob makes a slight difference to the brightness.

Of the two issues, the main one is the focus as that prohibits the real use of the scope and I suspect that fixing this may bring the intensity into line.

It seems that the OPPOSITE problem was solved in March 2009 (ooops, over 10 yrs ago now!) where the OP had good focused, but no intensity/brightness control.
Previous thread link - https://www.edaboard.com/showthread.php?144350-Beckman-industrial-circuitmate-9020-oscilloscope

The fix had been proposed by Chris Williams (Chris56000 - https://www.edaboard.com/member.php?201035-Chris56000) who seemed to have detailed knowledge of the componentry and workings of the scope.

In a way, I'm reaching out to see if this fellow is still around (not too far from where I live in Birmingham, UK) and happy to assist.
Any other assistance would also be gratefully received!

Thanks
Affy
 

You almost certainly have an open circuit resistor somewhere around the CRT controls. Excessive brightness may also cause the focus defect, it may be pushing the CRT so hard that it can't actually produce more light but the electron beam is passing the focus anode so fast it doesn't have chance to converge the beam.

Brian.
 

Thanks betwixt.

I'll take a look, but concerned about the VERY high voltages I may encounter!
 

I'll take a look, but concerned about the VERY high voltages I may encounter!
To some of us those are quite low voltages, only 2KV!

Seriously, switch it off first and give it a minute or two to discharge capacitors then just start measuring resistances. Download the manual, the problem is almost certainly on page 43 in the bottom right corner (with it rotated so text is the right way up).
My first guess would be that one or more of R559, R560, R561 or R563 has changed value. If they need replacing, make sure you use high voltage rated ones.

Brian.
 

Thanks betwixt

I've opened her up and going in with a multimeter...
Not looking for HT voltages yet!!! just going to take your advice, allow it to discharge and then test resistances in the first instance.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top