Post by thread:[EE]: Transistor replacement

HI all My old Tek 7704A scope encountered a sudden problem last night. The display suddenly (and permanently) shifted over to the right and compressed a bit. After a few measurements and tests, I narrowed the problem down to the horizontal driver board, one of the horiz diflection plates just sits at 50V. As it turns out, the transistor which drives that line (marked Q95) has a collector emitter short. I'd love to replace it, btu I don't know what an equivalent or suitable part would be. The original part number is 151-0270. This is followed by the number 718 (after a space). There is also a large letter F on the can (I guess Fairchild?). It is a PNP transistor in a TO-5 or TO-39 can. Anybody have an idea what would be a good replacement? Secondly, any ideas why this type of failure happens? Overvoltage? I don't have a service manual, unfortunately, so I don't know what voltages are supposed to be supplied to this board. It has only one voltage supply connector (the others are small coax signal lines), and it has 6 pins. The voltages I measure on them are 0,-50,0,-14.9,+14.8,+153.7 in that order. Do these sound correct or could it be that the 153.7 should be +50? I want to make sure that the failure is really confined to the transistor and not somthing in the power supply which had the secondary effect of killing the transistor. Thanks for any help you can give, Sean -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

part 1 2601 bytes content-type:text/plain; charset=us-ascii There is a company in Canada called Sphere (or something like that, Sphere is part of the name). They have a wonderful cross reference of Tek semiconductor numbers to industry standard. I think they also sell some Tek IC's and semiconductors. If you get in a real bind, I may have an old 7704a parts mainframe at home that may still have the horizontal driver intact (I know, a lot of "mays"!!). Scott Sean Breheny <shb7@CORNELL. To: spam_OUTPICLISTTakeThisOuTMITVMA.MIT.EDU EDU> cc: Sent by: pic Subject: [EE]: Transistor replacement microcontrolle r discussion list <PICLIST@MITVM A.MIT.EDU> 06/26/01 01:59 PM Please respond to pic microcontrolle r discussion list HI all My old Tek 7704A scope encountered a sudden problem last night. The display suddenly (and permanently) shifted over to the right and compressed a bit. After a few measurements and tests, I narrowed the problem down to the horizontal driver board, one of the horiz diflection plates just sits at 50V. As it turns out, the transistor which drives that line (marked Q95) has a collector emitter short. I'd love to replace it, btu I don't know what an equivalent or suitable part would be. The original part number is 151-0270. This is followed by the number 718 (after a space). There is also a large letter F on the can (I guess Fairchild?). It is a PNP transistor in a TO-5 or TO-39 can. Anybody have an idea what would be a good replacement? Secondly, any ideas why this type of failure happens? Overvoltage? I don't have a service manual, unfortunately, so I don't know what voltages are supposed to be supplied to this board. It has only one voltage supply connector (the others are small coax signal lines), and it has 6 pins. The voltages I measure on them are 0,-50,0,-14.9,+14.8,+153.7 in that order. Do these sound correct or could it be that the 153.7 should be +50? I want to make sure that the failure is really confined to the transistor and not somthing in the power supply which had the secondary effect of killing the transistor. Thanks for any help you can give, Sean -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads part 2 3865 bytes content-type:application/octet-stream; (decode) part 3 154 bytes -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

At 02:27 PM 6/26/01 -0400, Scott F. Touchton wrote: >There is a company in Canada called Sphere (or something like that, Sphere >is part of the name). They have a wonderful cross reference of Tek >semiconductor numbers to industry standard. I think they also sell some >Tek IC's and semiconductors. > >If you get in a real bind, I may have an old 7704a parts mainframe at home >that may still have the horizontal driver intact (I know, a lot of >"mays"!!). If you go that route, replace both transistors at the same time. That way, their gain will be more closely matched, and you won't end up with a non-linear sweep. Given the opportunity, I'd set up a similar circuit on the bench, and select a matched pair. -- Dave's Engineering Page: http://www.dvanhorn.org I would have a link to http://www.findu.com/cgi-bin/find.cgi?KC6ETE-9 here in my signature line, but due to the inability of sysadmins at TELOCITY to differentiate a signature line from the text of an email, I am forbidden to have it. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> -----Original Message----- > From: pic microcontroller discussion list > [.....PICLISTKILLspam@spam@MITVMA.MIT.EDU]On Behalf Of Scott F. Touchton > Sent: June 26, 2001 11:27 AM > To: PICLISTKILLspamMITVMA.MIT.EDU > Subject: Re: [EE]: Transistor replacement > > > > There is a company in Canada called Sphere (or something like that, Sphere > is part of the name). They have a wonderful cross reference of Tek > semiconductor numbers to industry standard. I think they also sell some > Tek IC's and semiconductors. > Try http://www.sphere.bc.ca/test/index.html for their on-line catalog of used test gear and parts. They also have links to sources for service manuals on this page - Sean may find his TEK 7704A scope. Lyle -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Hi Scott (and others), Thanks for the really quick reply. I checked out Sphere's site,but this part number (151-0270) is not listed, it goes from 0269 to 0271. Argh! I might very well be interested in buying the horizontal driver board from your parts 7704A. Please let me know if you would be willing to do that. I did notice on their web site, though, that they say that old tek service manuals list equivalent part numbers for many of the parts. If anyone has a 7704A manual and can check that number for me, I'd greatly appreciate it. Unfortunately, Sphere doesn't have any 7704A manuals. I'd appreciate any further suggestions, too. This is a really bad time for me to have my scope go, too, since I am finally in the midst of working on that wireless communications tutorial for microcontrollers that I mentioned back in March. Thanks! Sean On Tue, 26 Jun 2001, Scott F. Touchton wrote: {Quote hidden}> > There is a company in Canada called Sphere (or something like that, Sphere > is part of the name). They have a wonderful cross reference of Tek > semiconductor numbers to industry standard. I think they also sell some > Tek IC's and semiconductors. > > If you get in a real bind, I may have an old 7704a parts mainframe at home > that may still have the horizontal driver intact (I know, a lot of > "mays"!!). > > Scott > > > > Sean Breheny > <shb7@CORNELL. To: .....PICLISTKILLspam.....MITVMA.MIT.EDU > EDU> cc: > Sent by: pic Subject: [EE]: Transistor replacement > microcontrolle > r discussion > list > <PICLIST@MITVM > A.MIT.EDU> > > > 06/26/01 01:59 > PM > Please respond > to pic > microcontrolle > r discussion > list > > > > > > > HI all > > My old Tek 7704A scope encountered a sudden problem last night. The display > suddenly (and permanently) shifted over to the right and compressed a > bit. After a few measurements and tests, I narrowed the problem down to > the horizontal driver board, one of the horiz diflection plates just sits > at 50V. > > As it turns out, the transistor which drives that line (marked Q95) has a > collector > emitter short. I'd love to replace it, btu I don't know what an > equivalent or suitable part would be. The original part number is > 151-0270. This is followed by the number 718 (after a space). There is > also a large letter F on the can (I guess Fairchild?). It is a PNP > transistor in a TO-5 or TO-39 can. Anybody have an idea what would be a > good replacement? > > Secondly, any ideas why this type of failure happens? Overvoltage? I > don't have a service manual, unfortunately, so I don't know what voltages > are supposed to be supplied to this board. It has only one voltage supply > connector (the others are small coax signal lines), and it has 6 pins. > The voltages I measure on them are 0,-50,0,-14.9,+14.8,+153.7 in that > order. Do these > sound correct or could it be that the 153.7 should be +50? I want to make > sure that the failure is really confined to the transistor and not > somthing in the power supply which had the secondary effect of killing > the transistor. > > Thanks for any help you can give, > > Sean > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Sean Breheny wrote: > > HI all > > My old Tek 7704A scope encountered a sudden problem last night. The display > suddenly (and permanently) shifted over to the right and compressed a > bit. After a few measurements and tests, I narrowed the problem down to > the horizontal driver board, one of the horiz diflection plates just sits > at 50V. > > As it turns out, the transistor which drives that line (marked Q95) has a > collector > emitter short. I'd love to replace it, btu I don't know what an > equivalent or suitable part would be. The original part number is > 151-0270. This is followed by the number 718 (after a space). There is > also a large letter F on the can (I guess Fairchild?). It is a PNP > transistor in a TO-5 or TO-39 can. Anybody have an idea what would be a > good replacement? Hi, I had a look at the service manual for a tek 7844 scope. Looking at the schematic for the horizontal amplifier there is a tranisisor that drives the left plate. The reference for this is Q1920. This has the tek part no of 151-0270-00 (no mention of 718). This is then described as "Transistor: Silicon, PNP, sel from 2N3495" Maybe this is of some help? Mike -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

2N3495 = 120v 0.1A 0.6w >150MHz replacements 2N2634, 2SA712 It's a fairly standard looking deflection transistor. :o) -Roman mike oneil wrote: {Quote hidden}> > Sean Breheny wrote: > > > > HI all > > > > My old Tek 7704A scope encountered a sudden problem last night. The display > > suddenly (and permanently) shifted over to the right and compressed a > > bit. After a few measurements and tests, I narrowed the problem down to > > the horizontal driver board, one of the horiz diflection plates just sits > > at 50V. > > > > As it turns out, the transistor which drives that line (marked Q95) has a > > collector > > emitter short. I'd love to replace it, btu I don't know what an > > equivalent or suitable part would be. The original part number is > > 151-0270. This is followed by the number 718 (after a space). There is > > also a large letter F on the can (I guess Fairchild?). It is a PNP > > transistor in a TO-5 or TO-39 can. Anybody have an idea what would be a > > good replacement? > > Hi, > I had a look at the service manual for a tek 7844 scope. Looking at the > schematic for the horizontal amplifier there is a tranisisor that drives > the left plate. The reference for this is Q1920. This has the tek part > no of 151-0270-00 (no mention of 718). This is then described as > "Transistor: Silicon, PNP, sel from 2N3495" > Maybe this is of some help? > > Mike > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

"Alan B. Pearce" schrieb: > > no of 151-0270-00 (no mention of 718). This is then described as > > "Transistor: Silicon, PNP, sel from 2N3495" > ^^^^^ > > Roman replied > >2N3495 = 120v 0.1A 0.6w >150MHz > >replacements 2N2634, 2SA712 > > >It's a fairly standard looking deflection > >transistor. > >:o) > >-Roman > > Sounds like Tek selected it for 160V or greater Vce seeing he reckoned it > had 153 Volt rail. Yes, this is possible. Most probably they were selected in pairs of equal beta, remember that we are talkind about DC-coupled diff amps here. Greets Jochen Feldhaar DH6FAZ > > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

>Yes, this is possible. Most probably they were selected in pairs of equal >beta, remember that we are talkind about DC-coupled diff amps here. >Greets >Jochen Feldhaar DH6FAZ Granted, but by the time you get to the output stage, I suspect that these are really only level shifting to drive the deflection plates, and transistor beta spreads are designed out by careful feedback arrangements. In view of it operating at a voltage greater than the manufacturers Vce rating I would think that this would be the primary selection criteria, with possibly a minimal test to remove outliers in the beta spread. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

remember too that a good deflection driver (as in a CRO) uses negative feedback, so the transistor curves and beta are not a critical as you might think. I would just replace it with the next one up in voltage ratings (whatever I had in stock) and see what happened. :o) -Roman Alan B. Pearce wrote: {Quote hidden}> > >Yes, this is possible. Most probably they were selected in pairs of equal > >beta, remember that we are talkind about DC-coupled diff amps here. > >Greets > >Jochen Feldhaar DH6FAZ > > Granted, but by the time you get to the output stage, I suspect that these > are really only level shifting to drive the deflection plates, and > transistor beta spreads are designed out by careful feedback arrangements. > In view of it operating at a voltage greater than the manufacturers Vce > rating I would think that this would be the primary selection criteria, with > possibly a minimal test to remove outliers in the beta spread. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

"Alan B. Pearce" schrieb: > >Yes, this is possible. Most probably they were selected in pairs of equal > >beta, remember that we are talkind about DC-coupled diff amps here. > >Greets > >Jochen Feldhaar DH6FAZ > > Granted, but by the time you get to the output stage, I suspect that these > are really only level shifting to drive the deflection plates, and > transistor beta spreads are designed out by careful feedback arrangements. > In view of it operating at a voltage greater than the manufacturers Vce > rating I would think that this would be the primary selection criteria, with > possibly a minimal test to remove outliers in the beta spread. > Hello Alan, the part about the feedback is not correct IMHO, there is no feedback from the deflection plates to earlier stages. The trick is done by current sourcing and AC compensation. The HAMEG 1007 featured a trigger view showing the actual trigger point out of the peak rectifier, and we were joking for months before it started to give accurate results. Also the paired beta was necessary in the X final amplifier for best linearity using the X magnifier... Greets Jochen Feldhaar DH6FAZ > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

As there is one transistor that is still operational, why not remove it and measure its characteristics. Then substitute a pair of modern transistors with similar characteristics. My apologies if this has already been suggested, I have only been half following the thread. Chris Carr > "Alan B. Pearce" schrieb: > > > >Yes, this is possible. Most probably they were selected in pairs of equal > > >beta, remember that we are talkind about DC-coupled diff amps here. > > >Greets > > >Jochen Feldhaar DH6FAZ > > > > Granted, but by the time you get to the output stage, I suspect that these > > are really only level shifting to drive the deflection plates, and > > transistor beta spreads are designed out by careful feedback arrangements. > > In view of it operating at a voltage greater than the manufacturers Vce > > rating I would think that this would be the primary selection criteria, with > > possibly a minimal test to remove outliers in the beta spread. > > > > Hello Alan, > the part about the feedback is not correct IMHO, there is no feedback from the > deflection plates to earlier stages. The trick is done by current sourcing and > AC compensation. The HAMEG 1007 featured a trigger view showing the actual > trigger point out of the peak rectifier, and we were joking for months before it > started to give accurate results. Also the paired beta was necessary in the X {Quote hidden}> final amplifier for best linearity using the X magnifier... > > Greets > Jochen Feldhaar DH6FAZ > > > > > -- > > http://www.piclist.com hint: The list server can filter out subtopics > > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Hi all, Thanks for the help, especially the cross reference to 2n3495. I actually found a site on the web (not Sphere but I can't remember the URL offhand) which did cross-ref the 151-0270 to 2n3495. I then ordered some replacements last night from mouser(actually NTE288s which are the suggested NTE replacement). Just for the heck of it, I plugged in a regular old 2n4403 and it is working fine right now, although I know that probably wouldn't work under all conditions, right now the Vce is only about 60V, and the 4403 is rated to 80. I will make the proper replacement when the transistors arrive tomorrow. I will probably do a few rough tests to get a pair which is a matched as I can out of the several I ordered and then replace both transistors. Thanks again and I will be sure to ask for further help if I need it, Sean -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

part 1 2245 bytes content-type:text/plain; charset=us-ascii Glad you got it working... sorry to be out of touch, been out of the office. If you ever need any replacement parts for it let me know. I have a complete 7704 hanging around for spare parts (even have additional CRT). The only defective part seems to be the power supply... but thats probably just a power transistor that I am too lazy to track down. (I have a 7834 and a 7623 pretty much in the same shape... and a 535, 535a, 545, 547, 5440, 503......................) Welcome to Touchton's Home for Wayward Scopes! That's the last time I'll root through the basement! Scott F. Touchton 1550 Engineering Manager JDS Uniphase Sean Breheny <shb7@CORNELL. To: EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU EDU> cc: Sent by: pic Subject: [EE]: transistor replacement microcontrolle r discussion list <PICLIST@MITVM A.MIT.EDU> 06/27/01 05:31 PM Please respond to pic microcontrolle r discussion list Hi all, Thanks for the help, especially the cross reference to 2n3495. I actually found a site on the web (not Sphere but I can't remember the URL offhand) which did cross-ref the 151-0270 to 2n3495. I then ordered some replacements last night from mouser(actually NTE288s which are the suggested NTE replacement). Just for the heck of it, I plugged in a regular old 2n4403 and it is working fine right now, although I know that probably wouldn't work under all conditions, right now the Vce is only about 60V, and the 4403 is rated to 80. I will make the proper replacement when the transistors arrive tomorrow. I will probably do a few rough tests to get a pair which is a matched as I can out of the several I ordered and then replace both transistors. Thanks again and I will be sure to ask for further help if I need it, Sean -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics part 2 3296 bytes content-type:application/octet-stream; (decode) part 3 144 bytes -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Sean, Tek is based here in Portland, OR and there is a wealth of resources for all their scopes available but I've lost contact with most of them... First, Tek's service department's phone number is/was 503-627-6640. One source of manuals is/was Seattle Manuals Plus (?) 206-531-8031. The next guy has manuals and possibly some parts but he definitely knows who to contact. I bought service manuals for my 465B and DM44 from him about 6 years ago. He's retired from Tek and his name is Dean Kidd at 503-625-7363. Note, this is Oregon which is PDT so consider that and the fact he's retired if you call. Fumbling through my notes I found one more name. I think he's another source of manuals. His name is Ed Matsuda and his number is/was 619-479-0225. These numbers may be stale but if Tek's service department can't help, try Dean Kidd. Hopefully he's still around... Finally, and this is a `long-shot'... Tek part numbers are normally consistent so I looked in my 465B manual and found 151-0271 which is a Motorola SPS8236 PNP device. It `may' be that the 151-0270 is a similar NPN device. I haven't checked the web. Good luck! - Tom At 01:59 PM 6/26/01 -0400, Sean Breheny wrote: {Quote hidden}>HI all > >My old Tek 7704A scope encountered a sudden problem last night. The display >suddenly (and permanently) shifted over to the right and compressed a >bit. After a few measurements and tests, I narrowed the problem down to >the horizontal driver board, one of the horiz diflection plates just sits >at 50V. > >As it turns out, the transistor which drives that line (marked Q95) has a >collector >emitter short. I'd love to replace it, btu I don't know what an >equivalent or suitable part would be. The original part number is >151-0270. This is followed by the number 718 (after a space). There is >also a large letter F on the can (I guess Fairchild?). It is a PNP >transistor in a TO-5 or TO-39 can. Anybody have an idea what would be a >good replacement? > >Secondly, any ideas why this type of failure happens? Overvoltage? I >don't have a service manual, unfortunately, so I don't know what voltages >are supposed to be supplied to this board. It has only one voltage supply >connector (the others are small coax signal lines), and it has 6 pins. >The voltages I measure on them are 0,-50,0,-14.9,+14.8,+153.7 in that >order. Do these >sound correct or could it be that the 153.7 should be +50? I want to make >sure that the failure is really confined to the transistor and not >somthing in the power supply which had the secondary effect of killing >the transistor. > >Thanks for any help you can give, > >Sean ------------------------------------------------------------------------ Tom Handley New Age Communications Since '75 before "New Age" and no one around here is waiting for UFOs ;-) -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics