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  • Source for AB power transistor

    I posted this same request over at the PM forum, so forgive me if I seem a little desperate. I have this AB power transistor number, but have been unable to locate a cross reference or source to purchase same. The number that I believe to be AB's is 245D00031E. Since the device came from A CMC Servomate SM1, I have the schematic and it is listed as component Q7 bearing their part number 29782LG. I know there are some real electronic guru's here so, I may have a better chance at success with you guys.

  • #2
    Custom Part Number

    AB doesn't make power trans, I can just about guarantee you that. What they do do is to buy a large lot and have their own custom number and logo printed on them.

    Keep checking for a cross ref. trans that well fill the bill or just plain break down and call AB and talk to their service techs. If by any chance they have discontinued the use of that particular part they will be more then happy to give you a replacement (stock) part number

    But....

    In the past I had this problem with Motorola SCRs which were very rugged and well made. The problem was there were no more of these Motorola SCRs available. The replacement held up electrically, performed beautifully, BUT did not have the same heat dissipation characteristics of the original.

    Simple fix, I had to ad a fan to the power amp is was in and the thing worked fine
    Last edited by JoeFin; 09-13-2007, 12:02 AM.

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    • #3
      That is absolutely an Allen-Bradley in-house part number, and bears no relation to any other numbers, as far as I can determine.

      Failing getting the part from them, the only recourse is to reverse-engineer it, looking at the schematic and usage of the part to derive the requirements for a suitable substitute.

      In these days, when bipolar transistors are getting rare, especially in the TO-3 case, that might be challenging.

      A glimpse of the schematic might prompt some more questions and get to a sub......

      What kind of circuit is it from? Something that is potentially a switching type drive or power supply? Or a "linear" type circuit? The latter will be easier to cross, as switching bipolar transistors 'went away" longer ago than linear.
      1601

      Keep eye on ball.
      Hashim Khan

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      • #4
        So far everything I have tried has come up empty, including Allen-Bradley (now part of Rockwell Automation) parts department. AB has created a "case number" and will have technical support research the part number and call me back if they can find out anything about it.

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        • #5
          Post the part of the circuit it is found in. It may be possible to cross-reference it. If it's an old germanium transistor you may be SOL but if it's simply a common NPN or PNP switching power transistor and the voltages are known there may be many substitutes including the ubiquitous 2N3055. If it is in a balanced analog circuit then it may still be substitutable but should be swapped out in pairs.

          Just be warned - without seeing the circuit it is in it is not possible to know with any certainty that it is even a transistor. It could easily be an SCR or even a diode in sheep's clothing.

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          • #6
            Here you go. Note that the "transistors" in the top half are numbered from left to right as Q5,Q6,Q7,Q8,&Q9. The bad transistor is Q7.

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            • #7
              That is a common NPN switching transistor. The only voltages shown are +12 so it may simplify things. I'll see if I can wrangle up an available replacement and perhaps others can be looking too.

              Edit: As it happens, the 2N3055 transistor just might be a good substitute. It is a hardy switching/Audio transistor and has a very long pedigree. Q7 in your circuit is running complementary to Q12 so I'd be tempted to change them both at the same time. A fundamental nature of switching transistors is that they saturate quickly so have few power dissipation issues, and that they have low vce levels which is the voltage drop across the emitter/collector junction. Anyway, it's available, or was, at radio shack and worth a try.
              Last edited by dp; 09-13-2007, 03:49 AM.

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              • #8
                If it's NPN in a TO3 case a 2N3055 will often replace it. I have a handful of them in my parts stock. They should still be available.
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  If you look closely at the circuit, it is rather interesting. Things may not all be as they seem......
                  It looks as if there might be a need to see what is off to the right before making a final decision on what the voltages really are. The 12 V is not the supply for the part in question. A 2N3055 and maybe even a 2N3773 would likely not be a good choice.

                  The value of R102 is a hint, along with the value of C39.
                  1601

                  Keep eye on ball.
                  Hashim Khan

                  Comment


                  • #10
                    Here is what is to the right of the portion displayed prior. It is a 90vdc servoamplifier capable of delivering 12amps continuous and 20 amps peak (if any of this helps)

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                    • #11
                      Another interesting thing to note: Other transistors in the circuit, such as Q6, Q8, and Q9, have more "standard" 2N-style numbers. This suggests that Q5, Q7, Q10, and Q12 are indeed special in some way. Just a thought.

                      -Mark
                      The curse of having precise measuring tools is being able to actually see how imperfect everything is.

                      Comment


                      • #12
                        I spent some time with CMC tech support today and learned the component is no longer available. He indicated that when last sourced, it was a "darlington" component (is this a mfg?) and that it is a "fast-switching, cascoding" type of transistor, NPN in a T03 case. He felt the 29782LG number would be the best one to try and match, although he did give me the last CMC number (X18-19246). Using the LG number sort of makes sense, since the adjacent transistors have numbers like "2N5322". He also stated it was being used in a "push-pull" configuration and it does look like the 2 transistors together are operating between the 100vdc circuit. I'm concerned about just how difficult this may turn out to be. He made the comment something like "well, you said yourself, this is over 20 years old" like I'm supposed to scrap a nice running Hurco over a single transistor? I've got some other leads, regarding old servo amps, that I'm working on.
                        Last edited by Jim Caudill; 09-14-2007, 12:29 AM.

                        Comment


                        • #13
                          Originally posted by Wirecutter
                          Another interesting thing to note: Other transistors in the circuit, such as Q6, Q8, and Q9, have more "standard" 2N-style numbers. This suggests that Q5, Q7, Q10, and Q12 are indeed special in some way. Just a thought.

                          -Mark
                          It could be that what makes them special is that they are matched sets. I used to get matched transistors from TRW for hi-power RF amplifiers I manufactured. That matching resulted in new part identification. They were batch matched meaning I could grab any two transistors and be assured they were sufficiently identical in the important areas as to be interchangeable.

                          Comment


                          • #14
                            Originally posted by Jim Caudill
                            I spent some time with CMC tech support today and learned the component is no longer available. He indicated that when last sourced, it was a "darlington" component
                            Interesting - it isn't drawn as a Darlington but that is often the case. It does make it difficult to reverse engineer old electronic equipment when the components are not off the shelf. Darlington transistors are actually two transistors in a single chip. They share the collector terminal but the emitter of the input transistor is wired directly to the base of the ouput transistor in a common emitter configuration. It reduces the drive current needed to saturate the output transistor. It remains a three-wire device. In switching circuits these are often matched sets.

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                            • #15
                              Ooooh, I may be able to help here. My stepdad once had a company that used matched transistors, and I sold his transistor curve tracer for him on Fleabay.

                              One thing stepdad gave me was a couple of ziplock bags full of TO3 transistors that had been characterized for hfe and breakdown voltage. These were used in parallel (hence the matching) in a 160v, many-hundreds-of-amps power supply. They may just be rated beefy enough for your use. If the stars align properly, it would be no problem for me to pick 4 (matched spec units) out of the bag and perhaps trade you something for them.

                              I'll check the specs on them when I get home.
                              The curse of having precise measuring tools is being able to actually see how imperfect everything is.

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