BK Percision 20mhz Model#2120 Scope - Page 1
Forum section: electronics / repair

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 08, 2016, 02:56:59 am
content: I had to sell my Rigol DS1054 to pay bills and this scope had a nice fall and need work before .. So either I have no scope or try to repair the BK scope which is what I am trying to..Right now I am getting all kinds of issues with a stable signal and the bnc connectors are pretty rough and should be cleaned or replaced .. Oh the coil came loose from the crt and not sure what its called but us there a right or wrong way to glue it back into placeSo I have alot of work ahead of me ..I have no manual or schematic right now and will post pics if you everyone wants me too ..What would cause this ??

author: poot36
author_rank: Frequent Contributor
timestamp: January 08, 2016, 06:17:49 am
content: It looks like the Z axis blanking is not working properly. Do you have pictures of the coil that is now loose on the CRT? Almost all scopes use electrostatic deflection and not a magnetic yoke for deflection. It could be a degaussing coil but I doubt that. Check all socketed components for looseness, all solder joints for cracks, and that all connectors are securely attached.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: January 08, 2016, 06:47:01 am
content: Thinking the coil is the trace rotation coil? If so just put it back where you can rotate the trace horizontal effectively.

author: Biff383
author_rank: Regular Contributor
timestamp: January 08, 2016, 06:51:11 am
content: Try adjusting the probe.

author: tautech
author_rank: Super Contributor
timestamp: January 08, 2016, 07:55:15 am
content: User Manual:https://bkpmedia.s3.amazonaws.com/downloads/manuals/en-us/2120_manual.pdfService Manual:http://elektrotanya.com/b_k_2120_oscilloscope_sch.pdf/download.htmlhttp://bee.mif.pg.gda.pl/ciasteczkowypotwor/BK%20precision/

author: med6753
author_rank: Super Contributor
timestamp: January 08, 2016, 07:55:30 pm
content: Quote from: TorqueRanger on January 08, 2016, 02:56:59 amThat coil is for the trace rotation. You can glue it back onto the neck of the CRT.I also have a 2120 scope and I recently did a tear down.https://www.eevblog.com/forum/testgear/teardown-bk-2120-scope/msg822920/#msg822920There's a lot of noise on that trace. Plus it appears you have some blanking issues. I would start trouble shooting by checking all the supply voltages first and go from there.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 09, 2016, 04:34:16 am
content: @Med6753Thanks for the link and will have to check it out later... When gluing the ring does it need to be clock a certain way or it doesn't matter ?? Right now it apart its apart getting a good cleaning and new bnc connectors and plan on check the blackout circuit since it's only a couple components...The main reason for it being apart was to flatten the dent in front switch panel which came out pretty nice..

author: tautech
author_rank: Super Contributor
timestamp: January 09, 2016, 05:20:58 am
content: Quote from: TorqueRanger on January 09, 2016, 04:34:16 amOn P17 of this manual you will see the Trace rotation coil in the schematic:http://elektrotanya.com/b_k_2120_oscilloscope_sch.pdf/download.htmlYou'll need to carefully set the Trace rotation coil in place while powered on if there is no way to identify where it was before it shifted. Set the Trace rotation pot to mid way first and with a isolated push stick rotate the coils until the trace (no signal applied) is close to parallel to the horizontal graticule lines. Then mark the position of the coil, power down and glue in place. Power on when set in place and then make any fine adjustment necessary.

author: med6753
author_rank: Super Contributor
timestamp: January 09, 2016, 01:13:58 pm
content: TorqueRanger....what is this?https://www.eevblog.com/forum/beginners/bk-persicion-scope/msg172489/#msg172489Is that in fact the 2nd channel in the background? You never answered the question. If it is you don't have a blanking issue.Ya think it's time for some new pictures as to what you have now? The ones you posted in this thread are at least 3 years old.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 09, 2016, 03:26:15 pm
content: Quote from: med6753 on January 09, 2016, 01:13:58 pmOld thread and never got around to tearing the scope down for the repair or testing and it has gotten worst..Then I got the DS1054Z which was really nice to use but it had to go and now since I have no scope to use I figured it's time to wipe the dust off and finally fix it . Sorry I was working of a tow company working 24hr-5days and the days off I have custody of my son.. Oh I will update pics in a little bit ..Quote from: tautech on January 09, 2016, 05:20:58 amI will have to try it out and will post my results ..Quote from: tautech on January 08, 2016, 07:55:15 amThank you very much for the manualsQuote from: poot36 on January 08, 2016, 06:17:49 amI will post pics in a bit here and I will check all joints..

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 09, 2016, 03:27:33 pm
content: Quote from: Biff383 on January 08, 2016, 06:51:11 amI know the probes need to be calibrated but trying to fix main issue first..

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 10, 2016, 01:28:46 am
content: Quote from: med6753 on January 09, 2016, 01:13:58 pmAlso right now I have the unit apart and currently getting it back together.. I am not sure what channel or how its even configured and post pics later when the unit is done and hooked up to calibration. Oh I have a better camera and will be able to post better pics to help in repair..

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 10, 2016, 01:37:22 am
content: Also did some testing in the blankout circuit and everything was good for the couple parts I tested..

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 10, 2016, 06:34:58 pm
content: The coil I am talking about..

author: med6753
author_rank: Super Contributor
timestamp: January 10, 2016, 08:47:22 pm
content: That is the trace rotation coil. You can get an idea of it's correct position by checking out these 2 pictures. It doesn't have to be exact because you can adjust the trace after gluing it back onto the bell of the CRT.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 10, 2016, 09:51:01 pm
content: @med6753ThanksI will have test it and glue it later and hopefully will post pics of the problems in a bit..

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 10, 2016, 10:19:32 pm
content: Oh While a little work on the scope I found the bnc connectors are slightly to big to fit .. I was looking to pick some up from china on ebay.. Is that a good idea to use them on a scope or buy usa dealer?

author: med6753
author_rank: Super Contributor
timestamp: January 10, 2016, 11:26:29 pm
content: Quote from: TorqueRanger on January 10, 2016, 10:19:32 pmAre you replacing the BNC's because they are damaged or simply tarnished? If the latter I would try to clean/polish them. Mine show a little tarnish but work fine. No intermittent issues.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 10, 2016, 11:58:33 pm
content: Quote from: med6753 on January 10, 2016, 11:26:29 pmIn the fall they got messed up and needed to be replaced..

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 14, 2016, 03:21:25 am
content: Well I just filed down the bnc connectors I got and made them work .. I got it back together and tested the voltags on boards test points and all the voltages where within spec .. Also I will try to do more testing later and see what I can or failures .. But I need to look into finding the calibration manual for this scope ....

author: tautech
author_rank: Super Contributor
timestamp: January 14, 2016, 07:05:58 am
content: Quote from: TorqueRanger on January 14, 2016, 03:21:25 amAlready linked:http://elektrotanya.com/b_k_2120_oscilloscope_sch.pdf/download.html

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 17, 2016, 05:01:55 pm
content: I just got a chance to get it back to together and I some how manged to mix to connectors .. The led light up when switched on but nothing on the crt . Found the problem and fixed it but now I get just points of lights instead lines and half the crap don't work now wtf ...I am ready to take this to the dumpster... You guys got any help??I already check the power supply and the voltages are spot on but I can't check the high voltage ..

author: med6753
author_rank: Super Contributor
timestamp: January 17, 2016, 10:51:38 pm
content: Could you post a pix of what you have now?Go back and check your connectors again to make sure everything is plugged right. Hopefully your prior mis-connect didn't FUBAR something.Based upon your prior pictures your high voltage appears OK but you MIGHT have some open resistors in the focus divider circuit. But don't worry about that now. Just get the trace back.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: January 24, 2016, 04:26:05 pm
content: Update timeRight now I am snow in and am not going any where for a while (See Pic below)..But I have a little busy with work and trying to fix the scope ..Last time I guess I missed something but the scope is up and running .. The scope though is very jittery and can change wave form just by messing with knobs or such .. Also the brightness changes with certain knobs and I am loosing my mind trying to fix this .... I got signals from both channels for calibration of the probes but the I am still getting extra feedback in the background.Sorry everyone for changing up the game here but I placed a bid for $10+$14 shipped on a Tek 2215 scope and was not thinking ..But I got a surprise when he accepted the offer.. So I will have to see what happens and the scope looks pretty nice and it has a couple issues but will see if it arrives..I might keep working on the bk or donate it to someone local in NJ but will have to see how both scopes make out first..The listingFOR PARTS ONLY:You are purchasing a TEKTRONIX 2215 60MHz oscilloscope. Power on test only. Unit power on and display comes on.Item has some scratches on it from normal wear also the handle will not lock into place because theres a few plastic knobs broke off or bent. All buttons and knobs seem to be in working order beside the power button is stuck on.I would love to know how he is going to come out ahead here with shipping through Fedex ??Shipping: This unit will ship via Fedex Ground within 1-3 business days of confirmed payment. We are able to provide tracking numbers upon request. Please be aware that as this item is being shipped through Fedex

author: med6753
author_rank: Super Contributor
timestamp: January 25, 2016, 11:25:53 am
content: If you decide to give up on the B&K I might be interested in getting it as a parts unit. I see you are located in NJ. Where abouts in Jersey? I'm in New York about 75 miles north of NYC. Willing to pay cost of shipping if road trip is a little too far.I also see that you joined the Yahoo Tek group. You're in good hands with those folks.