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Champ 600 Point-to Point Rewire! The first One?

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  • #16
    You could add an external speaker jack that way or if you used a tip shunt jack & wire the amps output to the tip & sleeve connectors & wire the internal speaker to the tip shunt & sleeve you would never run the risk of operating the amp without a load in the circuit. Just a thought.
    Hey you... Yeah you kid... Ya wanna buy some "Magic Beans"?

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    • #17
      Use the vintage speaker... a 5 watt SE can take the slight impedance mismatch without any issues & a lot cheaper than a new Weber 6" alnico... which are out of stock AGAIN!
      Hey you... Yeah you kid... Ya wanna buy some "Magic Beans"?

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      • #18
        Originally posted by macpgh View Post
        ... I didn't know what it was at the time either, but later found it was a early 50's fender delux & the first to go with 9 pin pre-amps. I was hoping to liberate it before they trashed it, but no such luck this time. They blew the speaker & gave it to somebody else.
        Ha ha... good stuff...
        I also had an interesting experience when taking some trash to the dump and following a small open bed pickup truck with a pile of construction debris.
        My wife said " that guy's old suitcase is about to fall off his trash pile".
        To which I quickly screamed in a hysterical girly voice.... "that's not a suitcase it's a F*** tweed Vibrolux.
        I pulled him over and asked if I could have it... of course he didn't care, who'd want it, it was some old broken tube thing.
        Recapped all it needed was two new power tubes and a rectifier. The speaker was fine.
        I just don't run into things like this anymore.
        Bruce

        Mission Amps
        Denver, CO. 80022
        www.missionamps.com
        303-955-2412

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        • #19
          Another Champion 600 rewire

          Been following this post for awhile & figured it was time to post some pretty pictures of my Champion 600 rewire job. I opted not to install a 5Y3 like Mandopicker did so I just built a bridge out of 1N4007's. Sounds quite tasty though but a bit more input gain than I was expecting. I'm waiting on some 5751's & 12AT7's I ordered to tame it a bit. I also replaced that awful tan velvet grille cloth with a piece of Striped Oxblood & will post final picture after I finish recovering the cabinet in Blonde Nubtex.





          Hey you... Yeah you kid... Ya wanna buy some "Magic Beans"?

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          • #20
            Looks great.

            Try adjusting your power resistors between filter caps to reduce gain a bit. This will lower the voltage at your preamp tubes plates.

            FYI: I now use a 5V4 and have beefed up the filter caps to 40uf, 33uf, 33uf, and the cathode resitor in my bias assemply to 100uf x 150 volts.

            All that with the alnico weber and it is a real killer...even connected to a 1 x 12" or a 2 x 12". A real fun project.

            The adjustable bias is really easy to add and is extremely useful.

            Congrats!
            Mandopicker

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            • #21
              Nice work. Looks like you moved the output jack and installed a fuse holder in that hole. Did you relocate the Output transformer? You use the power tube location for the rectfier. Where is the best place to put the power tube where it will not interfere with the speaker magnet. Is that an issue?

              I am modding one. I do not have the cab and speaker on hand. Only the chassis.

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              • #22
                Originally posted by macpgh View Post
                I would suggest that you put in a 1/4 jack female & then wire the stock speaker to the amp chassis with a 1/4 male. That way you'd be able to run a different speaker cabinet & use the unit as a head....
                It's great fun to play a Champ through a big 4x12" speaker cabinet.

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                • #23
                  Thanks. You are correct in that I used the original output jack for the new fuse location. The current OT is an upgraded version from Mojo, but also fits the original foot print. I have used Hammond 125ESE and slightly smaller in other Champ 600 chassis, but each required a new position. Position of power tube can be tricky, so just visualize where everything will line up. To do this, you should remove everything from the chassis to prepare for the rebuild anyway.

                  For fun, I decided to remove all of the fiberboard and try rebuilding it again using more point to point techniques. I'll have to say that is was great fun and made for a REALLY bullet proof amp in the end. Sounds excellent with the increased filtering and the overkill of DC Heaters. (I just had to do it. A great sounding amp with no flabby-ness when cranked.

                  I just love it and it makes a great bedroom amp played through ALL pedals.

                  Click image for larger version

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                  Click image for larger version

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                  Mandopicker

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                  • #24
                    Here's mine:

                    I'll send more and better pics frm my other computer later.


                    Originally posted by Mandopicker View Post
                    Thanks. You are correct in that I used the original output jack for the new fuse location. The current OT is an upgraded version from Mojo, but also fits the original foot print. I have used Hammond 125ESE and slightly smaller in other Champ 600 chassis, but each required a new position. Position of power tube can be tricky, so just visualize where everything will line up. To do this, you should remove everything from the chassis to prepare for the rebuild anyway.

                    For fun, I decided to remove all of the fiberboard and try rebuilding it again using more point to point techniques. I'll have to say that is was great fun and made for a REALLY bullet proof amp in the end. Sounds excellent with the increased filtering and the overkill of DC Heaters. (I just had to do it. A great sounding amp with no flabby-ness when cranked.

                    I just love it and it makes a great bedroom amp played through ALL pedals.

                    [ATTACH=CONFIG]15810[/ATTACH]
                    [ATTACH=CONFIG]15811[/ATTACH]
                    Attached Files

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                    • #25
                      I Pretty Much Bogarted Your First Design

                      Really only one best place for the Power Tube. Next one I'll do with a Full Wave SS Rectifier and keep the power tube where it is.
                      Attached Files

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                      • #26
                        Looks great. The SS Rectifier would give you some extra space.

                        Another cool version I made was taking the Champ 600 and wiring it up like a Valve Jr. (using an EL-84) Same p-t-p method as nost recent 600 incarnation, but included a Master Volume, and an adjustable tone control, and bias. This one totally sounds differnt and is very loud. I used a 125CSE as the Ot and it required a compleltey new location. A blast to run both using stereo effects pedals. A real big soiund.

                        That said...would you agree that the amp sounds quite a bit better than the stock version after the operation.

                        * I forgot to suggest that, from my experience, the stock 470 ohm 5w bias resitor runs the 6V6 way too hot. Some might disagree, and suggest that lowering the B+ voltage using zeners between the HV CT and ground is a better method. I have done it successfully, but short of having these parts, finding the best value to keep the 6V6 happy is a good idea.

                        Infact, you might discover that what might be needed is something more than twice that size. Easy enough to calculte the optimal value and bias setting given the amount of Plate voltage measured at pin 3 of the 6V6 in a simple calculation. The adjustable bias I use...(1 x 1k 3 watt pot + 200 ohm 5 w reistor in series) will get you every possibility in between. The weber bias calculator is a helpful tool to get you in the ball park.
                        Last edited by Mandopicker; 10-21-2011, 11:17 PM. Reason: More helpful info...
                        Mandopicker

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                        • #27
                          Originally posted by Mandopicker View Post
                          ...For fun, I decided to remove all of the fiberboard and try rebuilding it again using more point to point techniques. I'll have to say that is was great fun and made for a REALLY bullet proof amp in the end....
                          David,
                          Congratulations on your rebuild. I think that true point to point wiring is an art form and, when done correctly, it is sturdy and reliable. There are cons of course such as more labor intensive for initial build and repairs, higher skill level and planning required. Works out well for a Champ 600 though.
                          Cheers,
                          Tom
                          Last edited by Tom Phillips; 10-22-2011, 05:47 PM.

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                          • #28
                            David, will you share your fixed adjustable bias mod component list?

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                            • #29
                              It is actually an adjustble bias design by using a resistor and a pot in series with the cathode of pin 8 on a 6V6. I have used a fixed bias setup, but not a my Champ 600 builds. This is different and requires a few more parts. Fun to do both and have the bias type switchable.

                              For my Champ 600, getting good quality pots of high enough wattage value is a bit tricky. I have used 200 ohm value pots with anywhere between a 470 ohm and 820 ohm 5 watt resistor depending upon what is required to get the tube running happily based on plate voltage etc.

                              Though after experimenting a number of times, I found that using a 1K 3 watt pot in series with a somewhat low value 5 watt resistor (200 ohm 5 watt) works well and with no failures to date. This allows me to dial in a fairly wide range to accomodate a 6V6 or even a 6L6 if a larger OT is used. For fun I sketched out a design that works well for me.

                              I hope it helps and good luck.
                              Click image for larger version

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                              Mandopicker

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                              • #30
                                Thanks for the clarification. I'd thought you did fixed bias, and I wondered why I saw the things I saw like the big cathode resistor. Gerald Weber has a plan in his book, Tube Guitar Amplifier Essentials , for fixed adjustable bias for the Champ that I am going to use on another build.

                                Does the negative feedback circuit have any correlation on the grounding side with the 220K resistor (or anything else other than ground)?

                                IOW, when I connect the 220K resistor to my fixed bias circuit, I think I can just run the 1.5K resistor (negative feedback circuit) to ground on its own.

                                Is that correct?

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