BK Precision 1465 Help with Repair - Page 1
Forum section: electronics / repair

author: Ernest1
author_rank: Contributor
timestamp: March 16, 2020, 04:43:51 am
content: So I just got this oscilloscope a few days ago broken and initially it didn't have a horizontal line on the screen but it was displaying off to the left like in pic 1 and I fixed that by messing with the break out board thingy at the back of the crt in pic 2. I tested it out a bit afterwards and decided to clean it since it was working wellhttps://imgur.com/a/6NifQUT.I took apart and cleaned the front panel and all the knobs separately with alcohol electronics cleaner and Windex for the screen.This is where I think I broke it, I sprayed the bottom of the bottom boardhttps://imgur.com/a/Qfqv7Qgwith electronics cleaner and used a tooth brush to clean the dust off but while I was doing that I heard something hit the floor and I found this little solder nuggethttps://imgur.com/a/8m3Hi5Pwith dimensions L 3.5mm W 1.2mm and I thought nothing off it. When I turned on the oscilloscope the screen lit up but there was no line so I turned the knobs and the DC BAL pot to try to adjust it but all I can see is the screen brightens move up and down or left to right as if there was a line but the size of the screen and very dim. Video of the issuehttps://youtu.be/PCEoz5JpYlwI tried to find where it fell from and found a likely spot but it didn't change anything after jumping the traces, I also tested the resistance and voltage before hand to make sure doing that doesn't blow it up.This might not be the problem though, it may be something completly different, maybe a loose connection that I disturbed or a short somewhere?I have no idea how these oscilloscopes work internally so im reading a guide on fixing oscilloscopes from this forum but in the mean time if anyone has any suggestions or knows what can cause this kind of issue or help me isolate the problem, I would be very thankful.

author: Renate
author_rank: Super Contributor
timestamp: March 16, 2020, 01:30:59 pm
content: (Please keep this to a single thread.)Have you tried the "Ext" on the Sweep selector knob?You should be able to get it to a single point in the center of the screen (turn down the intensity so you don't burn the CRT).Have you tried all the sweep ranges? Try with the sync selector set to Line and make sure the TVH & TVV are off.Do you have (or can borrow) another scope to work on this?Three possibilities:The horizontal output is broken at least on one side or bad connection to CRT.The ramp generator is broken.The multivibrator that runs the ramp generator is broken.If the Ext sweep works correctly then the problem is #2 or #3.The sweep control has a lot of points that you can look at to see if anything is happening.

author: mzacharias
author_rank: Frequent Contributor
timestamp: March 16, 2020, 02:35:51 pm
content: Open resistor in focus circuit?(or bad solder connections in same area?)

author: Renate
author_rank: Super Contributor
timestamp: March 16, 2020, 06:39:04 pm
content: It wasn't clear if the vertical was working.Does the vertical position make the spot go up and down?Does the calibrator signal into the input make it change to two dots?It would be a little tricky, but if that works you could use this scope to troubleshoot itself.

author: Ernest1
author_rank: Contributor
timestamp: March 16, 2020, 08:10:08 pm
content: I tried selecting sweep on ext or rotating it around but that didn't do anything.https://youtu.be/Vj6wzM2Ucm8When I plugged the calibration signal in to the input It didn't do anything but when I set the sweep to 10ms I could see the screen flicker meaning witch means that it does see the signal but its not displaying correctly.https://youtu.be/gRBAN5gUDG4

author: Renate
author_rank: Super Contributor
timestamp: March 16, 2020, 10:06:03 pm
content: Oops, sorry, I was confused by the attached photo.mzacharias is quite right, your problem must be in the focus voltage.