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Understanding when a transistor swap is or is not appropriate

Discussion in 'General Electronics Discussion' started by tryppyr, Dec 6, 2013.

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  1. tryppyr

    tryppyr

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    Oct 22, 2013
    If you've been following my thread on repairing the oscilloscope, you know I'm more than a little confused and frustrated by the difficulty in knowing what parts can be swapped for other parts presumed to have failed. Fundamentally, it's a problem of cross-referencing one manufacturers part numbers with others, until you get to one that can be readily obtained.

    Here's an example. In order to repair the ailing 48V rail, I want to replace the 4 transistors in that rail. The HP part numbers are:

    1853-0080
    1854-0071
    1854-0215
    1854-0358

    Of those, I could only find a cross-reference for the 1854-0215 (which is a standard 2N3904). The others don't seem to cross reference, which left me feeling I had no choice but to buy expensive replacement parts from vendors that specialize in obsolete replacement parts. Yet something in me screams that if I only knew how to cross reference this I could get a 67 cent replacement part instead of spending $5 for the one from the obsolete parts vendor (and incur the annoying wait time).

    Another unrelated example. I bought a semiconductor grab bag full of of Motorola HEP parts. I did the research on those and found that three of them (HEP-S0019, HEP-S0031 and HEP-F2005) are deemed equivalent to the 2N3906. That, in and of itself, isn't too surprising. But the question lingers why make so many variations of the same thing if they are functionally equivalent? Are there situations in which they aren't functionally equivalent?

    One of the pieces from the grab bag (HEP-F9003) comes up in the cross reference documents as a silicon diode, not a transistor. Uh... okay... so maybe they put it in a three legged package for a reason that escapes small brains like mine?

    I'm finding that datasheetarchive is helpful, but not always. I find that the sites trying to get RFQs out of you are useless. Some sites that want to sell you stuff CAN offer hints as to the replacement parts (e.g. VETCO), but that information isn't always reliable.

    Are there other sources of information I could reference? I hate asking specific cross reference questions every time I hit a dead end on Google.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Take a look at the sticky post in the datasheets section. I'm sure I have linked to some sources of cross-referencing.

    When I was working on an old HP plotter, the service manual helpfully included a section cross-referencing many of the HP part numbers to OEM part numbers (I'll see if I still have it, although it was pretty old).

    Hmmm... Can't find that, but I do have a copy of what (I think) the thread I suggested will point you to. Just in case they're not available, I'll include them here if I can.

    OK, I think they've been resampled as I uploaded them, and I have a couple of other files too large to upload. PM me your email address and I'll send all I have to you.

    I hope I have something which might help. It may still be worth checking the links as it is possible that these lists have been updated.

    (Why didn't I remember these before now???)
     

    Attached Files:

  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Let's see how good they are:

    1853-0080 = 2N4888 2N4888(SEL)
    1854-0071 = CP4071 CP4071 CP4071
    1854-0215 = 2N3904 2N3904 2N3904
    1854-0358 =

    I have checked 5 different references for these. I don't know how independent they are, but they seem consistent at least.

    The last one is not mentioned. Can you double check you have the number right?
     
  4. tryppyr

    tryppyr

    228
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    Oct 22, 2013
    Yes, 1854-0358 is the number for Q8. Described as follows:

    Transistor NPN SI PD=310MW FT=60MHZ
     

    Attached Files:

  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Unfortunately firefox crashed after I had posted lots of useful information.

    Let's see if I ca recreate it...

    The 1854-0358 may have been a Motorola part with a Vcebo of 100V and an Ic(max) of 250mA

    This document
    on page 6-7 lists the 1854-0358 as a possible replacement for the 1854-0350. That sounded good until I found (here) that the 1854-0350 was equivalent to a 2N3724A, and the datasheet for that indicates a very different beast. Other stuff on page 6-7 indicates that the manual is an OCR version, finding a scanned (but not OCRed) version might be useful...

    However this sojourn into an equivalents dead end has yielded another source of HP cross reference information.

    (And I'm going to save now because it was at this point my browser crashed...)

    It hasn't crashed yet... http://www.hparchive.com/hp_PARTS.htm <-- at least one of my lists comes from here

    This document lists the 1454-358, but only (and unhelpfully) as "TRANSISTOR". That PDF is a scan only and the pages are out of order, so it will take you some time to find page 108 -- it's about half way through. However it does list it as costing $1, so it's unlikely to be anything very special. (Incidentally, if anyone knows of a program which can rearrange pages in a pdf...)

    (Still hasn't crashed!)

    This page lists a number of scanned copies of some HP magazines which include cross reference information. I've only been through one of these!

    I think that's it now :)
     
    Last edited: Dec 7, 2013
  6. tryppyr

    tryppyr

    228
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    Oct 22, 2013
    Interesting site. I already had the cross reference document there, but not the catalogues. Thanks for sharing the links!

    As to rearranging pages in a PDF, I may be able to do it if the PDF isn't protected. I have Acrobat Pro.
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    But wait... There's more!

    I recall seeing a quoted value for HFE before my browser crashed, and I can't find it now. I recall it was bizarrely low (like 30) but quoted in such a way that I wondered if there was some OCR error. Maybe it's 300?

    And other sites suggest that an alternative name is SPS3626. This is listed as having 3 sources, one being Freescale (the others being HP and Agilent). And Freescale started out as a division of Motorola, so that matches with some speculative information above. Unfortunately SPS3626 doesn't lead Google anywhere interesting :(

    It seems to be a dead end. It is listed as a milspec device everywhere, so maybe somewhere there is something about it, but I can't find it. Sorry.
     
    Last edited: Dec 7, 2013
  8. tryppyr

    tryppyr

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    Oct 22, 2013
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Amazing! Thanks :)
     
  10. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
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    Nov 28, 2011
    tryppyr, I already told you what transistors to use for the transistors in the +48V regulator. You can use the same devices as the equivalent positions in the 120V regulator. See post #79 on the other thread.
     
  11. tryppyr

    tryppyr

    228
    1
    Oct 22, 2013
    For those, like myself, who prefer data they can manipulate to static data, I have converted the "Transistor - Diode Cross Reference - H.P. Part Numbers to JEDEC Numbers" data into an Excel spreadsheet.
     
  12. tryppyr

    tryppyr

    228
    1
    Oct 22, 2013
    For those interested, I received the parts from Tucker today. None were in original HP baggies. They were in pink baggies with the HP numbers on them. The numbers on the transistors were in two cases Motorola numbers that aligned with the HP numbers, and one just seems to be a JEDEC equivalent.
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    When you say Motorola numbers that aligned with HP numbers, do you mean they were labelled with something like "1854-0215", or that they have the part number from the equivalents list(s)?
     
  14. tryppyr

    tryppyr

    228
    1
    Oct 22, 2013
    I bought three transistors...

    1853-0080 (marked 713 3-080)
    1854-0071 (marked 4-071 212)
    1854-0358 (marked 2N5551)
     
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