Tek 465B
in [Repair]
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From: bg on 8 Nov 2007 03:30 Both channels on the verticle front end are damaged. One dual FET follower is a definite (Q1297). It is tek part number 151-1090-00. I haven't seen one yet using google. Is there a replacement or two discretes out there that will work? I noticed that the pinouts for the chip following the dual FET (U1290), are incorrect. Doing a diode test on the chip, there are several pins mislabeled. The external circuitry seems to go to the pins as shown on the schematic, but the internal circuitry ohms out to different pins. This would only be an issue if you ohm out the chip like I did to see if the chip was bad. If anyone is interested, I can post what seems to be the correct internal circuitry. bg
From: Jim Yanik on 7 Nov 2007 15:59 "bg" <bg(a)nospam.com> wrote in news:fgt74f$idp$1(a)news.xmission.com: > Both channels on the verticle front end are damaged. One dual FET > follower is a definite (Q1297). It is tek part number 151-1090-00. I > haven't seen one yet using google. Is there a replacement or two > discretes out there that will work? They would have to be matched,else you get an offset. check this out; http://www.sphere.bc.ca/test/tek-parts/tekparts2.html it appears they have some 151-1090's for sale. they also cross ref to a "2N5911 family". > I noticed that the pinouts for the chip following the dual FET > (U1290), are > incorrect. Doing a diode test on the chip, there are several pins > mislabeled. The external circuitry seems to go to the pins as shown on > the schematic, but the internal circuitry ohms out to different pins. > This would only be an issue if you ohm out the chip like I did to see > if the chip was bad. If anyone is interested, I can post what seems to > be the correct internal circuitry. > bg > > the 155-0078-xx is used in a lot of different scopes,several 7000 series plug-ins,too. -- Jim Yanik jyanik at kua.net
From: bg on 9 Nov 2007 01:29 Jim Yanik wrote in message ... >"bg" <bg(a)nospam.com> wrote in news:fgt74f$idp$1(a)news.xmission.com: > >> Both channels on the verticle front end are damaged. One dual FET >> follower is a definite (Q1297). It is tek part number 151-1090-00. I >> haven't seen one yet using google. Is there a replacement or two >> discretes out there that will work? > >They would have to be matched,else you get an offset. > >check this out; >http://www.sphere.bc.ca/test/tek-parts/tekparts2.html >it appears they have some 151-1090's for sale. >they also cross ref to a "2N5911 family". > >> I noticed that the pinouts for the chip following the dual FET >> (U1290), are >> incorrect. Doing a diode test on the chip, there are several pins >> mislabeled. The external circuitry seems to go to the pins as shown on >> the schematic, but the internal circuitry ohms out to different pins. >> This would only be an issue if you ohm out the chip like I did to see >> if the chip was bad. If anyone is interested, I can post what seems to >> be the correct internal circuitry. >> bg >> >> > >the 155-0078-xx is used in a lot of different scopes,several 7000 series >plug-ins,too. > >-- >Jim Yanik >jyanik >at >kua.net Thanks Jim. I had already been to that site and didn't see it the first time, even with my glasses on! Offset is the issue I am having. bg
From: Jim Yanik on 8 Nov 2007 15:29 "bg" <bg(a)nospam.com> wrote in news:fgvkea$n3d$1(a)news.xmission.com: > > Jim Yanik wrote in message ... >>"bg" <bg(a)nospam.com> wrote in news:fgt74f$idp$1(a)news.xmission.com: >> >>> Both channels on the verticle front end are damaged. One dual FET >>> follower is a definite (Q1297). It is tek part number 151-1090-00. I >>> haven't seen one yet using google. Is there a replacement or two >>> discretes out there that will work? >> >>They would have to be matched,else you get an offset. >> >>check this out; >>http://www.sphere.bc.ca/test/tek-parts/tekparts2.html >>it appears they have some 151-1090's for sale. >>they also cross ref to a "2N5911 family". >> >>the 155-0078-xx is used in a lot of different scopes,several 7000 series >>plug-ins,too. >> >>-- >>Jim Yanik >>jyanik >>at >>kua.net > Thanks Jim. I had already been to that site and didn't see it the first > time, even with my glasses on! > Offset is the issue I am having. > bg > > I've seen the input BNC connector cause DC offsets! seems it absorbs contaminants and becomes a weak "battery". -- Jim Yanik jyanik at kua.net
From: bg on 9 Nov 2007 07:07 Jim Yanik wrote in message ... >"bg" <bg(a)nospam.com> wrote in news:fgvkea$n3d$1(a)news.xmission.com: > >> >> Jim Yanik wrote in message ... >>>"bg" <bg(a)nospam.com> wrote in news:fgt74f$idp$1(a)news.xmission.com: >>> >>>> Both channels on the verticle front end are damaged. One dual FET >>>> follower is a definite (Q1297). It is tek part number 151-1090-00. I >>>> haven't seen one yet using google. Is there a replacement or two >>>> discretes out there that will work? >>> >>>They would have to be matched,else you get an offset. >>> >>>check this out; >>>http://www.sphere.bc.ca/test/tek-parts/tekparts2.html >>>it appears they have some 151-1090's for sale. >>>they also cross ref to a "2N5911 family". > > >>> >>>the 155-0078-xx is used in a lot of different scopes,several 7000 series >>>plug-ins,too. >>> >>>-- >>>Jim Yanik >>>jyanik >>>at >>>kua.net >> Thanks Jim. I had already been to that site and didn't see it the first >> time, even with my glasses on! >> Offset is the issue I am having. >> bg >> >> > >I've seen the input BNC connector cause DC offsets! >seems it absorbs contaminants and becomes a weak "battery". > > >-- >Jim Yanik >jyanik >at >kua.net I replaced the channel 1 connector, but plugged in one of the power connectors backwards. So I blew one of the dual fets and the other one seems to have a leakage problem. There is DC on the gate lead right after the attenuator. The 1 meg resistor in the attenuator output isn't low enough to pull the gate to 0 volts. Out of the circuit I can't measure anything abnormal with the FET but in circuit the DC is there. BTW , you are a great weath of info for these tek products. bg
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