Kikusui cos5040 scope - Page 1
Forum section: electronics / repair

author: welpester
author_rank: Contributor
timestamp: June 11, 2017, 12:49:45 pm
content: HelloI have cos5040 scope and i am not really experienced on analog stuff (my experience comes mostly from digital side). Problem with the scope is that channel 2 have no trace at all. Channel 1 works fine after i cleaned all connectors from boards. Before cleaning channel 1 trace just fade slowly away time to time and then suddenly comes back. I tried to find service manual, but no luck. Schematics i managed to find, but thats all.So can someone help me?edit: Little more information. On dual channel mode channel 1 trace shows fine, but in add mode there is no trace at all. Could it be that somehow ch2 signal is way too high or low?-welpester

author: tautech
author_rank: Super Contributor
timestamp: June 12, 2017, 09:07:20 pm
content: Welcome to the forum.Can you provide a link to the schematics you have ?

author: welpester
author_rank: Contributor
timestamp: June 13, 2017, 08:50:01 am
content: https://elektrotanya.com/kikusui_cos5040_sch.pdf/download.htmlThis is where i got it.When page loads, there comes little link below preview picture where you can download it. You have to wait approx. 30sec (before there is ...processing...)-welpester

author: tautech
author_rank: Super Contributor
timestamp: June 13, 2017, 09:09:41 am
content: Quote from: welpester on June 13, 2017, 08:50:01 amOK, thanks. Got slow connection and this file is 45.5 Mb so I probably won't come back to you tonight and I've got stuff to do tomorrow. But I will be back.

author: welpester
author_rank: Contributor
timestamp: June 13, 2017, 09:51:20 am
content: Big thanks at this point!-welpester

author: tautech
author_rank: Super Contributor
timestamp: June 13, 2017, 09:57:33 am
content: So normally we'd look for V values on the schematic at various test points but there aren't any.So the only option is to follow the signal path and compare readings with Ch 1.Have you access to another scope ?An appropriate signal input can be the probe Cal or some DC value, just make sure both channels are set the same and measure/compare at the same point in the signal path for each channel.First point I would check is R115/215 as FET inputs can be damaged by overvoltage inputs.Then junction of R114 and R120/R214 and R220 and so on............

author: Electro Detective
author_rank: Super Contributor
timestamp: June 13, 2017, 10:01:25 am
content: Not sure if it's any help, but I have the cos 5060 model (nice CRO btw) and these are the links for related fileshttp://www.kikusui.co.jp/manuals/index_e.php?GROUP=COS&skip=20http://www.kikusui.co.jp/manuals/index_e.php?GROUP=COS&skip=0I think the cos 50xx series are either the same circuit paths or very close in buildBest of luck sorting it out

author: welpester
author_rank: Contributor
timestamp: June 13, 2017, 11:02:05 am
content: Thanks for quick reply!I have access to another scope and sig-gen too. I try to do as you suggest.i'll be back in few hours-welpesterQuote from: tautech on June 13, 2017, 09:57:33 am

author: welpester
author_rank: Contributor
timestamp: June 13, 2017, 11:04:53 am
content: Thanks!I have downloaded cos5040 user manual from there. I think that they are not offering service manual for my scope.-welpesterQuote from: Electro Detective on June 13, 2017, 10:01:25 am

author: guenthert
author_rank: Frequent Contributor
timestamp: June 13, 2017, 12:05:27 pm
content: I got a COS5060 of which one channel's vertical amplifier was playing tricks on me -- or so I thought. I opened it, didn't see anything obviously wrong (nothing burnt or smelly). Since there is no fan its pretty clean inside despite its age. While in it, I sprayed some contact cleaner on the contacts of the buttons and potentiometers of the front panel, turned them a bit in the hope to remove any dirt, closed the device again and that was it -- works fine again.As far as I understand, it's quite common that user interface elements are the cause of malfunction on devices of this age (30+ years). Might be worth a shot to attempt to clean them again.

author: welpester
author_rank: Contributor
timestamp: June 13, 2017, 01:13:15 pm
content: Thanks.I will try that too.-welpesterQuote from: guenthert on June 13, 2017, 12:05:27 pm

author: Electro Detective
author_rank: Super Contributor
timestamp: June 13, 2017, 02:24:43 pm
content: I emailed Kikusui Support about 6 months ago out of curiosity and they advised me there were no PDF service manuals available for this model.That said, if you can find a re-badged version of these oscilloscopes, perhaps someone has scanned a hard copy to PDF ?Check for sticky, dry switches and contacts first,and a few gentle taps on the boards, you may get lucky...before bringing out the big guns

author: eighty-one
author_rank: Newbie
timestamp: June 13, 2017, 06:50:16 pm
content: I had the lower frequency COS5020, which had a couple of problems.One of the defects was no trace on channel 2, which turned out to be the input fet 2SK107. Curiously, it seemed OK out of circuit, but when probed, there was no waveform coming out.I suggest You open the scope and gently probe / compare the two inputs with an oscilloscope (having no generator, I connected the two inputs to the cal output). This shouldn't be too hard to accomplish, as if its in any way similar to the 5020, the channels should be nearly identical in layout and staggered one on top of the other.Of course, I shouldn't tell You that there is high voltage inside and You should take precautions poking around!When working, the kikusui had a very tektronix-que feel to it and I sometimes miss it (had to sell one, and the lower bandwidth scope lost, leaving me with a higher bandwidth soviet benemoth).regards

author: welpester
author_rank: Contributor
timestamp: June 13, 2017, 07:14:32 pm
content: Hi and big thanks to everyone who involving this.Here is what i found so far:Vertical mode CH2, Volts/div rightmost position, pulled out, red knob clicked left to clock four?timebase .2 sec /div, coupling ACTrace is definitely there because when i turn intensity to full, trace seems to be there but out of screen (top).If i pull position knob CH2 it switches to bottom, but still out of screen.Measurements done so far:Both channels fed by same signal and for u102 and u202 pin 9 on both, signals are almost equivalent.Other pins on that chip are not so equivalent. Pin 9 there is 1.5v difference.Here is what i had done so far, but more tomorrow-welpester

author: tautech
author_rank: Super Contributor
timestamp: June 13, 2017, 07:52:55 pm
content: The only pins that matter are 1 and 5 (outputs) but it looks like a differential output. Be sure the Variable for both channels is set to Cal (off).

author: Electro Detective
author_rank: Super Contributor
timestamp: June 13, 2017, 10:13:05 pm
content: Found the email from Kikusuiit might be worth following up for someone with a sad Kikusui scope"Regarding the COS5060TM, this model is very old model.So unfortunately we finished support this model.However, we can provide the service manual of COS5060 to you.Please let us know if you need it.Thank you for your understanding.Best regards,Daisuke Tezukadaisuke@kikusuiamerica.comKikusui America,Inc.2975 Bowers Avenue, Suite 307Santa Clara, CA95051Toll-Free:1-877-876-2807Phone:408-980-9433 ext.108Fax 408-980-9409"Excellent straight up reply and options

author: welpester
author_rank: Contributor
timestamp: June 14, 2017, 09:56:18 am
content: Few days ago i sent mail to kikusui and now get ansver that they do not have service manual available such an old model as mine.So i asked if i can get service manual for cos5060. Waiting for their answer now-welpesterQuote from: Electro Detective on June 13, 2017, 10:13:05 pm

author: welpester
author_rank: Contributor
timestamp: June 14, 2017, 06:26:38 pm
content: Hi.I finally managed to do some measurements with my other scope and here is result so far.Feed: 32kHz sine wave to ch1 and ch2measured: u102 and u202, ca3086 chip pinsCh1 pin 9 signal level 29mV, DC-offset 0VCh1 pin 1 signal level 41mV, DC-offset 5,13VCh1 pin 5 signal level 41mV, DC-offset 5,14VCh2 pin 9 signal level 29mv, DC-offset 0VCh2 pin 1 signal level 12mV, DC-offset 6,44VCh2 pin 5 signal level 18mV, DC-offset 4,62VI tried to adjust balance and offset trimmers on ch2, but there is no much effectto "huge" difference on levels regarding to ch1.Can those passives surrounding u202 chip cause this or wich could be most obvious tocause this?maybe it is that u202 wich is broken?-welpester

author: welpester
author_rank: Contributor
timestamp: June 15, 2017, 07:30:53 am
content: Got answer from Kikusui and they have no manuals for 5000 series.How old Electro Detective your email was?-welpester

author: stj
author_rank: Super Contributor
timestamp: June 15, 2017, 02:35:56 pm
content: here:https://www.elektrotanya.com/kikusui_cos5040_sch.pdf/download.htmlandftp://helpedia.com/pub/temp/service_manuals/bee.mif.pg.gda.pl/ciasteczkowypotwor/Kikusui/KIKUSUI%20COS%205040,%20COS%205041%20Instruction.pdf

author: welpester
author_rank: Contributor
timestamp: June 15, 2017, 04:59:06 pm
content: Thanks for links, but i alredy have those files. Manual that i need is Service manual.-welpesterQuote from: stj on June 15, 2017, 02:35:56 pm

author: stj
author_rank: Super Contributor
timestamp: June 15, 2017, 05:07:27 pm
content: top link is the schematics, that's about as close as you will get.

author: welpester
author_rank: Contributor
timestamp: June 15, 2017, 05:52:31 pm
content: I am slowly understanding that...-welpesterQuote from: stj on June 15, 2017, 05:07:27 pm

author: welpester
author_rank: Contributor
timestamp: June 16, 2017, 01:57:48 pm
content: Hi.I am planning to replace U202 chip (ca3086), but it seems to be obsolete. Equivalent nte912 also seems to very hard to get. So, does anyone here own those chips and would like to sell me two of them?-welpesteredit: I suddenly managed to found it! Jameco sells them.

author: welpester
author_rank: Contributor
timestamp: June 18, 2017, 01:26:13 pm
content: HiI soldered u202 out of the board and measured it as broken (2 of 5 transistors are dead)-welpester

author: stj
author_rank: Super Contributor
timestamp: June 18, 2017, 01:40:40 pm
content: if you have a component tester then you can make one.it's just a bunch of matched transistors.

author: welpester
author_rank: Contributor
timestamp: June 18, 2017, 01:58:22 pm
content: Quote from: stj on June 18, 2017, 01:40:40 pmDon't mind to try to find matching pair... Ordered 2 pcs of ca3086 chips. Should arrive on next week.-welpester

author: welpester
author_rank: Contributor
timestamp: June 30, 2017, 08:46:04 pm
content: HiI changed u202 chip and now it works. Thanks for helping me-welpester

author: tautech
author_rank: Super Contributor
timestamp: June 30, 2017, 08:52:31 pm
content: Quote from: welpester on June 30, 2017, 08:46:04 pmCool, well done.The old follow the signal path trick.For completeness post a pic of the unit showing some waveforms.

author: welpester
author_rank: Contributor
timestamp: June 30, 2017, 08:54:56 pm
content: Quote from: tautech on June 30, 2017, 08:52:31 pmI take few pics tomorrow and post here.-welpester

author: welpester
author_rank: Contributor
timestamp: July 01, 2017, 09:01:29 am
content: Photo 1Two phase sifted sine waves

author: welpester
author_rank: Contributor
timestamp: July 01, 2017, 09:09:29 am
content: Photo 2Am modulated sine wave

author: Electro Detective
author_rank: Super Contributor
timestamp: July 02, 2017, 02:11:19 am
content: Great news welpester !..good guys win again