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Peavey XR 696F - I made a booboo

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  • #46
    OK I can't find Q106, an SDS-7204 this side of the pond!

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    • #47
      Originally posted by jondoe View Post
      OK I can't find Q106, an SDS-7204 this side of the pond!
      I see 7204 spec'd as a 300V 10mA NPN transistor, but I have no idea why you would need such a high voltage rating for Q106, since it is on a 25V rail. There should be many TO-92 NPNs will work there. If the pinout is oddball you can bend legs around to reorient them. I'm sure someone will correct me if I'm wrong.

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      • #48
        Seems like quite a meaty transistor!

        I found this Peavey transistor cross reference document;
        Peavey_Transistor_Cross.pdf

        It recommends a 2N6557 or MPS-U10, both of which I also can't source for anything less than the price of a kidney. Would it be advisable to also change Q117, so there are a pair of new transistors?

        Thanks!

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        • #49
          Originally posted by jondoe View Post
          Seems like quite a meaty transistor!

          I found this Peavey transistor cross reference document;
          [ATTACH]56006[/ATTACH]

          It recommends a 2N6557 or MPS-U10, both of which I also can't source for anything less than the price of a kidney. Would it be advisable to also change Q117, so there are a pair of new transistors?

          Thanks!

          Dang - wrong part - deleted
          Last edited by nickb; 11-21-2019, 07:24 AM.
          Experience is something you get, just after you really needed it.

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          • #50
            Originally posted by nickb View Post
            RS have them in packs of 100 for £8.80 for 100 https://uk.rs-online.com/web/p/products/8051129/

            You won't have to worry abut running out of them!!!!! Ever!
            Nick, that's a 6517 rather than 6557, is that what you meant?
            Originally posted by Enzo
            I have a sign in my shop that says, "Never think up reasons not to check something."


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            • #51
              Originally posted by g1 View Post
              Nick, that's a 6517 rather than 6557, is that what you meant?
              No I didn't mean that but I see what happened. I searched for the required part and it brought up the wrong one (nearest lexical match- how dumb is that?) and didn't spot it. Well spotted - thanks. Updated post.

              Can't find a decent cross for the moment. If I get time I'll try later.
              Experience is something you get, just after you really needed it.

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              • #52
                Originally posted by nickb View Post
                No I didn't mean that but I see what happened. I searched for the required part and it brought up the wrong one (nearest lexical match- how dumb is that?) and didn't spot it. Well spotted - thanks. Updated post.

                Can't find a decent cross for the moment. If I get time I'll try later.

                Thanks Nick, I'm glad it was well past the 8pm order cut off when I saw this last night

                Would the following be a suitable replacement?

                https://uk.rs-online.com/web/p/bjt-b...stors/7613701/

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                • #53
                  Originally posted by jondoe View Post
                  Thanks Nick, I'm glad it was well past the 8pm order cut off when I saw this last night

                  Would the following be a suitable replacement?

                  https://uk.rs-online.com/web/p/bjt-b...stors/7613701/

                  No, that will fry. The best I came up with was an MJE340 but the pinout is wrong and it's a bit slow. Might work at a push.
                  Experience is something you get, just after you really needed it.

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                  • #54
                    Originally posted by nickb View Post
                    No, that will fry. The best I came up with was an MJE340 but the pinout is wrong and it's a bit slow. Might work at a push.
                    Just curious why you think this needs a 20W transistor?

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                    • #55
                      Originally posted by glebert View Post
                      Just curious why you think this needs a 20W transistor?

                      It doesn't, but it 's the best I could find for the moment that would not evaporate.
                      Experience is something you get, just after you really needed it.

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                      • #56
                        The originals are 10w parts, that is why the little MPSA would burn.

                        We can deal with the legs in different order by turning the part sideways.

                        I still have a few 6557 as well as a coupl MPSU10, but in similar parts, I usually just find a TO220 from my stock.
                        Education is what you're left with after you have forgotten what you have learned.

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                        • #57
                          Originally posted by Enzo View Post
                          The originals are 10w parts, that is why the little MPSA would burn.
                          To educate me, I don't understand how a 300V 10mA rated transistor can be a 10W device, that sounds to me like 3W or less, but I can't find any info other that that on these parts. I have never looked at one in person to know how big, etc. In this specific case, the max voltage C-E would be less than 115V, and the current should be less than 10mA (per original part spec), right? The MPSA part at 625mW might then be at risk of burning up, but 10W seems overkill.

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                          • #58
                            The Peavey suggested replacement 2N6557 is a 2W part, were the originals just very over spec'd for some reason?

                            I just found this CEN-U10, it's a direct replacement for the MPSU10, which itself is a recommended alternative part on Peaveys list. It's a little expensive per unit and a 16 week lead time on Mouser It's look like the MJE340 and hoping it fits in around the heat sinks!

                            On closer inspection the one I removed from the amp was actually an MPSW42, which looked factory!

                            Click image for larger version

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                            Last edited by jondoe; 11-21-2019, 11:06 AM. Reason: realised the one that came out was a MPSW42

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                            • #59
                              Originally posted by jondoe View Post

                              I just found this CEN-U10, it's a direct replacement for the MPSU10, which itself is a recommended alternative part on Peaveys list. It's a little expensive per unit and a 16 week lead time on Mouser It's look like the MJE340 and hoping it fits in around the heat sinks!
                              Amplifiedparts has the original in stock and looks like they ship internationally. https://www.amplifiedparts.com/produ...7204-300v-10ma

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                              • #60
                                Well I'll be damned, after looking through ebay I found some new old stock MPSW42 (10 of them), which come out at the same price as the SDS 7204 after you take shipping into account. I've ordered those

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