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63 Ampeg B15NC re-cap

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  • #16
    Originally posted by bob p View Post
    you just solder them in and flip the switch?
    Actually, yes. And I've had a problem on two occasions with this. Because I didn't re-form the caps I can't know if they were just bad caps (others reported similar problems with the brand/model) or if it was poor inventory management on the part of the supplier. It doesn't matter though because I had other reasons to change brands. I buy new caps for each build and HOPE that they will be fresh enough. No problems with the brand I've been using for the last three builds.

    I can't imagine a repair tech that keeps inventory re-forming every electrolytic cap prior to installing it in a repair.?.

    Your method is certainly ideal. Admirable even. I don't think it negates suspecting OLD caps or their ability to be re-formed though.
    "Take two placebos, works twice as well." Enzo

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "If you're not interested in opinions and the experience of others, why even start a thread?
    You can't just expect consent." Helmholtz

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    • #17
      Chuck, my experience is that DIY building and repairing gear involves different types of inventory management.

      If you build to order you can custom order parts as needed, and if you deal with exclusively new caps you can probably get away with not reforming, but you will still experience cap failures because reliability just isn't what it should be. when those failures occur you're left re-ordering and re-waiting for parts to arrive

      If you're repairing with an "I can fix it today" ideology then you're forced to keep some parts in stock because people don't like to wait for custom orders of basic parts. caps sitting on shelves is a reality in that context.

      reforming caps isn't the huge asspain that some people make it out to be. At the bare minimum all that you need is a variac and a standby switch. And the willingness to spend a few moments walking over to the amp between other tasks and tweaking a knob. If you want to get more sophisticated, it's no big deal to have a breadboard setup where the caps drop into your reforming jig and get the treatment before being placed in-situ.

      it sounds a lot harder than it really is.
      "Stand back, I'm holding a calculator." - chinrest

      "I happen to have an original 1955 Stratocaster! The neck and body have been replaced with top quality Warmoth parts, I upgraded the hardware and put in custom, hand wound pickups. It's fabulous. There's nothing like that vintage tone or owning an original." - Chuck H

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      • #18
        I "pre form" all electros.Its not a "re-form" if its not old caps,I would never re-form an old cap,if theres a doubt,just replace it.I dont keep a big supply on hand but I do have about a dozen various values.I have a "jig" set up connected to a power supply with voltage and amp meters.I can do about 10 caps at a time.I am not saying its 100% necessary,but its the way I learned and old habits........

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        • #19
          I've got a 1963 B15N that I have been restoring. The amp itself works fine though the cabinet needs a lot of work. The power transformer was replaced prior to my ownership of the amp. It works fine but I'll replace it with the vintage correct one eventually. The amp works fine with today's wall voltages btw. I didn't check the heater voltages but I am sure it is just fine. The original power transformers in these were not quite up to snuff and they often fail eventually. Fliptops sells a replacement that is a little uprated if you needed one.

          Greg

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          • #20
            Originally posted by soundmasterg View Post
            I've got a 1963 B15N that I have been restoring. The amp itself works fine though the cabinet needs a lot of work. The power transformer was replaced prior to my ownership of the amp. It works fine but I'll replace it with the vintage correct one eventually. The amp works fine with today's wall voltages btw. I didn't check the heater voltages but I am sure it is just fine. The original power transformers in these were not quite up to snuff and they often fail eventually. Fliptops sells a replacement that is a little uprated if you needed one.

            Greg
            Thanks Greg! I finished the re-cap & power plug, turned it on unloaded and promptly blew the fuse. Looks like I'll be needing that Fliptops PT. Nice site BTW.

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            • #21
              Originally posted by frankeg View Post
              Thanks Greg! I finished the re-cap & power plug, turned it on unloaded and promptly blew the fuse. Looks like I'll be needing that Fliptops PT. Nice site BTW.
              Wait a minute! Disconnect the PT secondaries. Does it still blow the fuse? If not there is a problem other than the PT downstream.
              "Take two placebos, works twice as well." Enzo

              "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

              "If you're not interested in opinions and the experience of others, why even start a thread?
              You can't just expect consent." Helmholtz

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              • #22
                Originally posted by Chuck H View Post
                Wait a minute! Disconnect the PT secondaries. Does it still blow the fuse? If not there is a problem other than the PT downstream.
                Will do Chuck but all the tubes including the rectifier were removed prior to power up and I checked the hum balance circuit & lights on the heater circuit (no shorts). The power cord was replaced with 3-prong and the ground switch & cap were disconnected. I could have nicked the new power chord when I stripped it and will check that too. Thanks for the feedback! I'll let you know. fg

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                • #23
                  You can disconnect the primary wires of the transformer from the mains wiring in the chassis. Now fire it up. If it still draws current, you have a problem in the mains wiring. If it stops, then the transformer or beyond is at fault.
                  Education is what you're left with after you have forgotten what you have learned.

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                  • #24
                    The wire I nicked on the new power cord was the ground wire. I restripped it this time using an exacto knife and a heat gun (very clean). I removed all secondaries and turned it on. The fuse blew immediately. Safe to order a new PT? BTW, should I suspect the retifier tube (original GE) is bad as well? I have no means to test it other than leaving it in there which I'm a little worried about.

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                    • #25
                      Provided the PT is hooked up correctly (more on this) with all the secondaries floating there shouldn't be any current draw. So if this can be confirmed then your PT is drawing current sufficient to blow the fuse by itself (= bad). But as far as I know you have no awareness that this amp ever worked. So unless you're certain about the PT lead designation you cannot know if someone else messed that up before it came to you. And it would be very easy to leave it that way when installing the new power cord because, well, why would you question it before now? But I would be certain about the PT lead designation and that it's hooked up correctly. If it is I'll say the PT is bad.
                      "Take two placebos, works twice as well." Enzo

                      "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                      "If you're not interested in opinions and the experience of others, why even start a thread?
                      You can't just expect consent." Helmholtz

                      Comment


                      • #26
                        I have a 1967 B15N in for repair right now and the heater winding is shorted. If I leave it connected the fuse would blow immediately if I wasn't using my light bulb current limiter/variac. When the heater winding is disconnected, then the PT works fine and the light bulb is dim as it should be. This is with no tubes installed too. The amp was worked on by someone prior to my seeing it and some of the work is shoddy, but everything is wired correctly.

                        This kind of thing seems to happen with the vintage B15 series...the PT seems like it is right on the edge of providing what the amp needs. It sounds like the PT in yours is dead also from your description but be sure to investigate all the particulars that Chuck and the others mentioned before assuming the PT is bad.

                        Greg

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                        • #27
                          Originally posted by bob p View Post
                          As Chuck says, the filament voltages on a 115 VAC amp running at 125 VAC should still be within the 10% tolerance band for 6.3 V heaters, but why push the limits? If it were me I'd just plug the amp into a bucking transformer to bring the mains voltage down to a safer area for the amp. If necessary, google for RG Keen's "Vintage Voltage Adapter."

                          Chuck, I don't have incandescent light bulbs to use in the current limiter any more. We have CFL lamps and LED lights. When I'm dealing with old caps I reform them with a variac. Rather than recommending light bulb limiters, I think we need to get with the times and start recommending current limiting resistors. At least they're still available.
                          No, you NEED the PTC propertry no standard resistor will give you.
                          Use these which have red hot Tungsten filaments, what the Doctor ordered:



                          Juan Manuel Fahey

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                          • #28
                            Originally posted by soundmasterg View Post
                            I have a 1967 B15N in for repair right now and the heater winding is shorted. If I leave it connected the fuse would blow immediately if I wasn't using my light bulb current limiter/variac. When the heater winding is disconnected, then the PT works fine and the light bulb is dim as it should be. This is with no tubes installed too. The amp was worked on by someone prior to my seeing it and some of the work is shoddy, but everything is wired correctly.

                            This kind of thing seems to happen with the vintage B15 series...the PT seems like it is right on the edge of providing what the amp needs. It sounds like the PT in yours is dead also from your description but be sure to investigate all the particulars that Chuck and the others mentioned before assuming the PT is bad.

                            Greg
                            If the fuse holds with the filament winding disconnected, that would likely indicate that there is a short after the transformer and not a transformer failure. What is the AC voltage across the filament winding when disconnected?
                            "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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                            • #29
                              Originally posted by The Dude View Post
                              If the fuse holds with the filament winding disconnected, that would likely indicate that there is a short after the transformer and not a transformer failure. What is the AC voltage across the filament winding when disconnected?
                              You know, after I read your reply I realized what I said was incorrect. This amp has been sitting around for close to a year since I first looked at it. The owner was going to buy a new PT and get it to me, and I have been waiting for him to do so. Since it has been awhile the details of the amp's malfunction were foggy in my mind. The current limiter light bulb glows with all of the PT secondary wiring disconnected, and also with everything connected, which indicates a shorted transformer. Sorry to lead anyone astray! Hopefully the owner will get the PT soon so I can get this amp out of my garage!

                              Greg

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                              • #30
                                Just to follow up and properly close this thread: It took about a month to get my new PT (Heyboer) from Fliptops which I promptly installed along with all new electrolytic caps and a 3-prong power cord. Works and sounds great! In fact, an employee from the local music store that I did this for and is a very good Bass player, said it is the best sounding amp he ever played through! Of course I can't take credit for that since I just replaced parts but it was real nice to hear! As my reward, the owner gave me a 74 Fender Super Reverb to restore. Life is good and I'm having fun with it! I'm retired and this keeps my mind active. Thanks to all for sharing your thoughts! fg

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