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Considerations when replacing GZ34 with 1N4007's

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  • #16
    Now what really makes me wonder, is the manual's instructions about adjusting the hum balance.

    Using a DC current meter at the speaker output - what??
    - Own Opinions Only -

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    • #17
      First I'll ask if anyone thinks there would be a benefit to having a standby switch so you can at least get the heaters warmed up before hitting the plates with B+ ?
      The biggest issue I see with SS rectifier is the price of 300B tubes. If the slow ramp-up of tube rectifier B+ is helping power tube life, you really need to emulate it.

      Now, to further flog the mort cheval, and incur the wrath of a sun god worshipper , why would they use a different vendor socket for the rectifier and preamp tubes? They're all octos. That's just bizarre. So it's not this particular 5AR4, and either of the 6SL7's have the same issue in the recto socket? The pins in the socket are still locked in place and have not broken free and got pushed out of place? I wonder if someone had done something funny (mod) with this unit to use some other rectifier or something.
      "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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      • #18
        I've had sockets where I've fitted the tube and had to push the pins from behind and they've moved a fair bit to give full engagement. When new the pins would have been fully secured though. I noticed that the Chinese wafer-type of transmitting tube sockets can be borderline - either the ceramic is too thick (or maybe the surface glaze) or the individual pin sockets are positioned too far off the underside.

        My own view is I'm reluctant to make a design change to an amp to get round a problem; the amp is tube rectified and this is not the issue, but the socket is. Converting the amp to SS rectification doesn't fix the problem - it sidesteps it through re-design and gives rise to other concerns. Just my own personal view.

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        • #19
          Is John L. Lumley alive? Can he be contacted and asked what the heck is up with this socket?

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          • #20
            Originally posted by g1 View Post
            First I'll ask if anyone thinks there would be a benefit to having a standby switch so you can at least get the heaters warmed up before hitting the plates with B+ ?
            The biggest issue I see with SS rectifier is the price of 300B tubes. If the slow ramp-up of tube rectifier B+ is helping power tube life, you really need to emulate it.

            Now, to further flog the mort cheval, and incur the wrath of a sun god worshipper , why would they use a different vendor socket for the rectifier and preamp tubes? They're all octos. That's just bizarre. So it's not this particular 5AR4, and either of the 6SL7's have the same issue in the recto socket? The pins in the socket are still locked in place and have not broken free and got pushed out of place? I wonder if someone had done something funny (mod) with this unit to use some other rectifier or something.
            I know we're all hindered from not seeing the physical photos of the Rectifier Tube socket, as well as the two Preamp tube sockets for the 6SL7 tubes. I assume like the rest of us have, that all three tube sockets are the same. Or is that NOT the case? I've not encountered LONG-PIN rectifier tubes, as what we're being told appears to be what's needed in this case. From the photo in the manual, all looks normal, as far as the three octal tubes in the photo. We really can't see any detail to suggest anything odd. No special added base to replace bad pins on the rectifier tube pin base is being used.

            I know this is going out on a limb, but, having had to re-solder octal tube pins periodically in hopes to restore the operational state of an output tube in a set of power tubes, many times with success, that lends credence to perhaps scavenging a set of pins from some bad octal tubes, or similar source, heating up the pins in the 5AR4, inserting a suitable contact lead, such as 20AWG buss wire, and trying to add additional pin length to what's on the tube. Obviously the full length of the second set of pins would be too long, but with careful slicing of pins with a Dremel fitted with carbide discs for slicing, one could cobble the extension of the pins on a good 5AR4 so the longer pins DO engage the socket terminals. Hard to really see if this would work, NOT seeing the physical tube socket as you have there. I too am bewildered with this problem-induced tube socket as has rendered this amp non-functional.

            Granted, adding a Standby Switch on the back of the amp out of sight would be a solution to the warm-up time, but would work, if there's no other solution. Creating a slow-ramp circuit to use rectifier diodes would be a lot of work.
            Logic is an organized way of going wrong with confidence

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            • #21
              Thinking more about your tube socket.....is it possible the socket contacts have been pushed out of their original detented positions as they appear to be on the preamp tube sockets? If the tube socket body is the same, I can't think how else the tube socket pins won't engage the sockets.
              Logic is an organized way of going wrong with confidence

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              • #22
                Originally posted by nevetslab View Post


                I know this is going out on a limb, but, having had to re-solder octal tube pins periodically in hopes to restore the operational state of an output tube in a set of power tubes, many times with success, that lends credence to perhaps scavenging a set of pins from some bad octal tubes, or similar source, heating up the pins in the 5AR4, inserting a suitable contact lead, such as 20AWG buss wire, and trying to add additional pin length to what's on the tube. Obviously the full length of the second set of pins would be too long, but with careful slicing of pins with a Dremel fitted with carbide discs for slicing, one could cobble the extension of the pins on a good 5AR4 so the longer pins DO engage the socket terminals. Hard to really see if this would work, NOT seeing the physical tube socket as you have there. I too am bewildered with this problem-induced tube socket as has rendered this amp non-functional.

                I would try extending the pins using the pins from a tube base like this.

                https://tubedepot.com/products/8-pin...base-only-deep

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                • #23
                  We can think of all manner of technician fixes to solve the immediate problem, but that overlooks the amp should not have the problem in the first place. I swear we are missing something.
                  Education is what you're left with after you have forgotten what you have learned.

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                  • #24
                    Originally posted by Enzo View Post
                    ......I swear we are missing something.
                    A picture.

                    "Yeah, well, you know, that's just, like, your opinion, man."

                    Comment


                    • #25
                      Originally posted by glebert View Post

                      I would try extending the pins using the pins from a tube base like this.

                      https://tubedepot.com/products/8-pin...base-only-deep
                      Wouldn't this give you the same length pins as we already have? Which are said NOT to engage the socket terminals.
                      Logic is an organized way of going wrong with confidence

                      Comment


                      • #26
                        Originally posted by nevetslab View Post

                        Wouldn't this give you the same length pins as we already have? Which are said NOT to engage the socket terminals.
                        My thought was to harvest the pins out of the tube base to make pin extenders. Don't know of it would work or not, as others as have said this all makes little sense without pictures.

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                        • #27
                          Oh no! THE SUN GOD! HE'S COMING!....

                          Oh hey, look, he's actually kind of cute.

                          These are all great responses, sorry for the delay time as it's been a crzy holiday weekend. I have a phone in my hands now, fully prepared to take some pictures and eat crow once we found out what I've overlooked! A couple takeaways;

                          1. It is the ONLY socket of this STYLE in this amplifier IIRC; the other sockets are much more traditional, this one is wacky: A floating octal base where pins travel through to a wafer type socket, ground rails attacked to chassis mounts.

                          2. I believe it is the "Wafer" type socket, at least on the pin fittings, which could account for the lack of depth due to manufacture mistake. The pins are not internal, but floating above the wafer socket. It's possible someone re-tensioned them incorrectly at one point?

                          3. I have also considered extending the leads, or even hardwiring the tube in. The customer is familiar with this sort of work and could be understanding, but it seems, for lack of a better word, "Janky". At first 1n4007 struck me as an elegant workaround but....

                          4. I think the consensus is that 1n4007 could be totally safe... or cause a lifetime of problems. So, now the we know the sun god is all talk, I'll try to solve the issue rather than to circumvent it... sometimes a weekend helps clear your head.

                          So I am heading into the shop soon, I'll take some pictures and we can see who was closest without going over. Thanks for all your expert attention and patience,

                          -Matt
                          Attached Files

                          Comment


                          • #28
                            Somehow I have this mental image: we are sitting in the back seat of the car, and our feet don't reach the pedals. We think of extending the pedals, or maybe extending our feet with heels. Or maybe making remote controls for the pedals. Maybe the car was built wrong? Lots of solutions xcept why are we not sitting up front?
                            Education is what you're left with after you have forgotten what you have learned.

                            Comment


                            • #29
                              Originally posted by Mr_bibbles View Post
                              1. It is the ONLY socket of this STYLE in this amplifier IIRC; the other sockets are much more traditional, this one is wacky: A floating octal base where pins travel through to a wafer type socket, ground rails attacked to chassis mounts.
                              2. I believe it is the "Wafer" type socket, at least on the pin fittings, which could account for the lack of depth due to manufacture mistake. The pins are not internal, but floating above the wafer socket.
                              Wafer socket - only seen them on super cheapo very obsolete gear. Sounds like a very dicey improvised setup. Not the kind of thing we would expect on a jewel like the Lumley. Maybe a repair done by a person who had a limited supply of parts and/or knowledge? Photos may help us decide.

                              3. I have also considered extending the leads, or even hardwiring the tube in. The customer is familiar with this sort of work and could be understanding, but it seems, for lack of a better word, "Janky".
                              "Janky" = Irish slang for "half assed." "That grease monkey put a janky fix on my motor, now it's totally banjaxed." Very appropriate!

                              Looking forward to getting the janky socket out of your banjaxed Lumley, and a proper one installed so you can listen to the indescribably awesome tone of a single ended 300B amp. Or so I've been told...

                              Speaking of Lumley, does anybody remember Enid Lumley? She was an Absolute Sound commentator who looked & listened to the world from a unique angle. For instance she reported a certain hi fi preamp sounded better when it was turned upside down. Good ol' Enid. Now who would think of that? Maybe she should right-side-up the preamp & listen whilst standing on her head and report on that. It's only fair. Of such things are snooty hi fi publications made.

                              This isn't the future I signed up for.

                              Comment


                              • #30
                                Somehow I have this mental image: we are sitting in the back seat of the car, and our feet don't reach the pedals. We think of extending the pedals, or maybe extending our feet with heels. Or maybe making remote controls for the pedals. Maybe the car was built wrong? Lots of solutions xcept why are we not sitting up front?
                                Ah how true this was.

                                SO back in the shop today, confirmed what I knew; the pins did not even REACH the little "grabbers" on the pin socket bottom, so tightening them would yield no results!

                                WHAT I DID NOT KNOW was that the eyelets holding the grabbers had become a little loose over time, letting the "grabbers" travel about a MM or two lower than they should, and the "grabbers" themselves were bent upwards slightly. So, carefully flattening the edges of the eyelet, the "grabbers" dropped back down a smidge, close but not perfect. Then I VERY carefully bent the "grabbers" down a little bit and re-tensioned them as I normally would any socket.

                                This was as humiliating as it was effective.

                                Looking back at last week, my landlord sold the property so I've been filling out housing applications all week, one of my best friends was moving to New York, my partner started a new job, our band coordinated our first show in 2 years, and our shop was finally returning to full 40 hours for amp work so I was already a bit stressed out and definitely absent minded... thank you guys for getting me "up in that front seat".

                                Here's a pic of the socket (after doing the eyelet press / re-tension):
                                Attached Files

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