BK Persicion  Scope  - Page 1
Forum section: electronics / beginners

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: December 17, 2012, 12:07:24 pm
content: I have Bk precision scope model 2120 that I bought used but I had some rework to do ...So I fired it up for it first voyage and got this (with pictures below) and not sure if this normal or if there anything I can do to fix it??I already know it needs some cal and clean up ...ThanksJAy

author: alanb
author_rank: Frequent Contributor
timestamp: December 17, 2012, 12:23:25 pm
content: Looks as if you need to turn down the brightness a bit. If your probe is hooked on to the calibrate terminal this is the type of display that you should get. The tops of the square wave should be flat. If this shot was taken with the probes in the 10x position you should be able to make the square wave square by altering the adjustment on the probe If it on 1x then it will be an internal adjustment to get it flat.Hope this helps.

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 17, 2012, 12:26:16 pm
content: If your problem is the (near) horizontal line, then first turn the brightness back so the square wave has the normal brightness.If the line is still there then there is something wrong with the circuit that should blank the display when the CRT sweeps back to the starting position... (it has a name which I can't remember right now).

author: ptricks
author_rank: Frequent Contributor
timestamp: December 17, 2012, 12:35:38 pm
content: I have the same model scope and that is not normal. It should be perfectly flat. The sweep line across the display should not be present , you might need to troubleshoot the blanking circuit.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: December 17, 2012, 12:38:31 pm
content: Quote from: ptricks on December 17, 2012, 12:35:38 pmOk wish I knew what that was ...

author: alanb
author_rank: Frequent Contributor
timestamp: December 17, 2012, 12:46:38 pm
content: QuoteSorry - I thought the horizontal line was the second channel.

author: ptricks
author_rank: Frequent Contributor
timestamp: December 17, 2012, 12:48:24 pm
content: The blanking circuit turns off the beam when it is swept back to the side of the CRT to start another pass, without it you get a line drawn on the crt.Normally I just tell people to try to troubleshoot something without the schematic but on scopes it is best to have the service manual. I don't have one I can send but if you search on the net you might be able to find one.Edit: The line shown, do you have the second channel enabled ? Mode switch should be set to CH1 and then no line should be visible.

author: ptricks
author_rank: Frequent Contributor
timestamp: December 17, 2012, 12:50:38 pm
content: Quote from: alanb on December 17, 2012, 12:46:38 pmIt is the second channel

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 17, 2012, 12:57:07 pm
content: Quote from: ptricks on December 17, 2012, 12:50:38 pmLOL, so I prepared this nice diagram of the blanking circuit for nothing?Well, then the question is what is wrong with the scope?

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: December 17, 2012, 01:17:47 pm
content: Quote from: PA0PBZ on December 17, 2012, 12:57:07 pmThank you so very much ...The problem was the intensity resistor was way out of spec .. I also changed 2 poly caps out because the casing was staring to fall off and the trace rotation pot was broken ...