BK 2120 scope problem
I bought a 2120 from Ebay and it has a problem(Of course). The display shows the trace in about 1/4 inch square of the screen. It seems like it's working but the display size is too small. I have checked the output of the transformer and it seems within spec. I do have schematic, but not sure where to start looking. Any help is appreciated. Thanks.
-
-
Re: BK 2120 scope problem
Haven't gotten too far, only discovering what is not causing the problem. I had thought I was onto something when I disconnected the leads to the coil surrounding the CRT and nothing changed. I now believe that coil is responsible for trace rotation. Still unknown what can cause the screen to shrink to it's current tiny size. Unfortunately, I have no experience with video circuits. Mostly worked with audio equipment, cell phones, and power supplies. Any guidance would be appreciated. -
Re: BK 2120 scope problem
Contact the seller?Comment
-
Re: BK 2120 scope problem
It sounds like it is out of focus, and no horizontal deflection. Does the trace move or blink at really low sweep speeds, or is it in X-Y mode?
See this old post:https://www.badcaps.net/forum/showthread.php?t=15169
Schematic is here: http://elektrotanya.com/b_k_2120_osc.../download.htmlComment
-
Re: BK 2120 scope problem
The trace only moves about 1/4 of inch. The best I can get is a 1/4 inch line in center of screen. The focus and intensity adjust work. I need the trace to go completely across screen to see wave form. When I turn off scope the trace will dance to the left half of the screen, leading me to believe the CRT is good. It's like trying to view the world thru a pinhole.Comment
-
Re: BK 2120 scope problem
I would guess the power supply voltage is low for the CRT deflection.
Take a multimeter and measure the PSU voltages. The +140VDC, +260VDC rails have test points, and +24VDC, +12V, +5V.
The high voltage -1.9kV you need a HV probe to measure.
It is set up for the right line voltage 115V/230V?Comment
-
Re: BK 2120 scope problem
I did read correct voltages at 140 and 24v test points. I had a critical malfunction when attempting to read 2KV without HV probe and consequently I need to get a new DMM. I will post when I get a new meter and verify the voltages. Thanks.Comment
-
--- begin sig file ---
If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.
We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.
Please do not post inline and offsite as they slow down the loading of pages.
--- end sig file ---Comment
-
Re: BK 2120 scope problem
it was an old Radio Shack. had it for about 20yrs. Gave me an excuse to get a new one. Ordered an Extech MN16A. Kinda cheap, don't have the money for a Fluke at this time.Comment
-
Re: BK 2120 scope problem
Ok, I got new meter and tested all the voltage test points and the 240v is only 25v. I checked back at the transformer and only getting 130vac. I am thinking the transformer is the culprit. Now I just have to locate a new one. Any suggestions?Comment
-
Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
-
Re: BK 2120 scope problem
My bad, I will go back and check the components. Thanks much!Comment
-
Re: BK 2120 scope problem
I think I got it now. I am getting 25v out of BD501 and 140v out of BD502. I will order new rectifier. Will post with results.Comment
-
Re: BK 2120 scope problem
You need to measure the DCV between the two legs of the filter cap C503 for the top power supply, it should have (as you indicated 130VAC reading) 130VAC * 1.414 = about 183VDC.
So check the rectifier but I would suspect bad C503.Last edited by budm; 06-21-2015, 09:04 PM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
-
Re: BK 2120 scope problem
Yes, I ordered the cap also. No Eparts stores around here, Radio shack was the last to go about 6 months ago.Comment
-
I have an LG Plasma TV 60PM6700 for the past ~12 years.
In the last ~3-4 months I have been having some issues.- Problem: It started with random picture disappearing (sound still worked).
Frequency: Happened about once a week.
Solution: Had to turn off TV wait a few seconds before turning it on again. - Problem: Then it got worse and the TV started to shut down and when turning on the no picture just sound.
Frequency: Happened about once a week.
Solution: Had to turn off TV wait about 10-20 seconds and turn it on again to solve. - Problem: TV shuts down
- Problem: It started with random picture disappearing (sound still worked).
-
When I assembled dreamcast I mistakenly fastened long bolt and It resulted in
cutting tiny trace.
This tiny trace(Total width of white coating is 5.5mm) is between R337,R343 and IC101 and it is covered with white coating in the below screenshot.
Firstly I tried to bridging tiny broken trace with my own eyes...But it is totally impossible..So a week ago, I ordered G1200 Digital Microscope and I magnified this tiny broken trace with it.
But It seems that It is really very tiny trace So I plan to order 0.1mm coper wire from aliexpress in order to bridging... -
i have a problem with thinkpad X1 carbon gen 2 "LMQ-1MB 12298-2 48.4LY26.021"
The laptop was turned off because the MOSFET was not transmitting voltage. After checking it turned out that the gate pin on the MOSFET was the problem, because it was producing an inappropriate voltage. and it was discovered that the problem was with the Think engine, so I decided to reprint each pin, and finally the mosfet could work properly. However, there is another problem, even though the voltage has been supplied to the laptop, it still won't turn on, there isn't even an LED indicator. After double... -
PC Specs:- CPU: Ryzen 5 1600
- GPU: GTX 1080 Palit JetStream
- MOBO: ASRock ab350 PRO4
- RAM: Crucial Ballistix Sport 2x8GB 3000MHz (XMP 2.0)
- PSU: XFX 650W (don't remember what model)
- OS SSD: ADATA SP920
- OS: Windows 10 21H2
Problem description:
Hi. I have a problem that has been going on for some time (2-3 years). It's hard to explain what it really is. Sometimes, my computer stops playing music, stops videos (starts buffering on youtube), there is no sound in games and when I minimize the game window and return to the game there is a black screen with window borders... -
Good morning,
I have a problem with Lenovo T580, which after error code 0288 suggests a problem with the display. I checked the display and it works on another laptop. I replaced the display cable with a new one. I programmed another BIOS (downloaded from this forum) and I still have the problem of a dead display - there is an image via HDMI, and the system does not detect the built-in LCD at all. The problem appears to be hardware. What can I check to confirm or disprove this? I found many threads on the Internet related to this problem 0288, but without specific solutions. Please advise....
Comment