Announcement

Collapse
No announcement yet.

5F6A Tweed Bassman Kit

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    The kit arrived today and everything looks great. Very nice cabinet and covering. I was worried about the chassis, since some folks have complained that the metal finishing wasn't the best quality. My chassis looks great - I'm in the metal biz and the plating looks fine. If you stick your nose up close, you can see that the steel wasn't polished perfectly smooth prior to plating. But, pull your head back a foot and it looks like a mirror. Graphics looks very good too. I upgraded the speakers to a set of Weber's Vintage Series 10A125. I also upgraded to a Heyboer multitap OT. I'd get started on the kit tonight, except I need a soldering iron tip and my Radioshack is closed for a while because of a local flood.

    Comment


    • #17
      Here's a question for the experts about the Weber power transformer. The secondary has two sets of high voltage taps. One set is a pair of red/white wires - 660V. The other set is a pair of red wires - 720V. The Weber schematic uses the 720V, and shows the lower voltage not connected. Is that correct? I'd like to get the "tweed bassman" B+ of around 470V. I plan to use a 5U4GB tube rectifier instead of the Weber copper cap.

      Also, there are two taps on the primary side of the PT, one is 120V and the other is 125V. I assume this is for adjustment of the B+ to the desired range. If all goes well, this amp should be making loud noise tonight.
      Last edited by Diablo; 11-08-2008, 08:23 PM.

      Comment


      • #18
        More questions...
        I have a Heyboer output transformer 18343 with 2, 4, 8 ohm taps and there was no wiring diagram included. The four wire colors are black, yellow, white, and green. Anyone know what's what? I've searched the web and Heyboer and Weber's sites and have come up with nothing.

        Comment


        • #19
          Originally posted by Chuck H View Post
          Steve, great rundown on the issues at hand. And thanks for backing me on the cap difference issue. When I said "I probably couldn't tell if you changed one or two caps" I was being liberal. I probably could actually. And I love polyester for some amps. But I don't use it because it changes tone depending on it's temperature. It's worth noting that cap construction (other than materials) can have a big impact on the tone also. So not all polyprops are created equal. Nor are the polyesters. I love Mallory 150's but I don't like the Torres Orange drop polyesters. No Offense. I like a big brash tone anyway so the 715's do a nice job and stay consistent with temperature. They're great for big overdriven Angus like tones and if used right, even sustainy leads (just consult the Trainwreck Express parts list) But for the ultra high gain SLO and Dual Recto stuff and the vintage Fender vibe polyester is king. I just can't take how an amp using them only sounds great for the first ten minutes. Or great, then OK, then like crap after you push it for one song. It's funny because when I used to play live I was using an amp I modded with polyester caps. I would actually look foreward to firing up my amp after break because I knew it would sound good again for a little while.

          No more. Nothing but polyproylene for me from now on.

          Chuck
          Chuck,

          I'm noticing something similar (thought it was my imagination) about my 5F6A-alike....sounds great for about 10 minutes, then starts to sound overly compressed. I wonder if it's the same thing....and WHICH caps should be changed (ALL??)

          Comment


          • #20
            Originally posted by Diablo View Post
            Here's a question for the experts about the Weber power transformer. The secondary has two sets of high voltage taps. One set is a pair of red/white wires - 660V. The other set is a pair of red wires - 720V. The Weber schematic uses the 720V, and shows the lower voltage not connected. Is that correct? I'd like to get the "tweed bassman" B+ of around 470V. I plan to use a 5U4GB tube rectifier instead of the Weber copper cap.

            Also, there are two taps on the primary side of the PT, one is 120V and the other is 125V. I assume this is for adjustment of the B+ to the desired range. If all goes well, this amp should be making loud noise tonight.
            Diablo,

            I built an amp that's essentially a 5F6A clone using the Weber PT you have. I used the 120V primary and the 720V Secondary wiring. With a 5U4GB I'm getting around 460-465V B+ (Tubes biased aprox 60% dissipation)
            "In theory, there is no difference between theory and practice. In practice there is."
            - Yogi Berra

            Comment


            • #21
              Thanks JoeM for the info on the PT. Your B+ is in the right neighborhood for me, so I'll hook mine up the same way. I'm still not sure about the Heyboer OT. If they used the same wiring code that Ted Weber lists for his OT, then I know what to do. But if they don't have the same color code, I may get smoke.

              Comment


              • #22
                Ted Weber shot me an e-mail and gave me the OT wiring code for the Heyboer. It's the same color codes as the Weber 18343. Hooked it all up, turned it on standby and all was good for about 30 seconds, then I saw smoke! I had wired the two main filter caps to the hot side of the standby switch and at least one of them burned up. I rechecked all the wiring and found nothing unusual. I replaced all the Chinese tubes with NOS, fearing that maybe one of them was shorted. I grabbed the 36 year old capacitor can that I had replaced in my Ampeg V4, and jumpered it into the 5F6A. I put this filter cap on the switched side of the standby. I also stuck in a new fuse - the only one I had was 6 amp. Put the amp on standby and it was fine. Checked the bias voltage at -50V, took it off standby and held my breath. It worked. Plate voltage right at 462V with a 5U4GB rectifier. Checked the bias current around 40mA on the GT6L6. Played it for about a half hour and all was still well. At that point I stuck in a pair of Phillips 6L6GWB and biased them at 35mA. I tried the amp using a 12AX7 and 12AY7 in V1, and it really makes a difference in the amount of grind. Once I order and replace the main filter caps, I'll shoot some pictures.

                Comment


                • #23
                  I can't say which cap/s might be responsible. It could even be a tube or resistor. Most resistors "derate" with high temperatures. A bad one could do it at moderate temps. The effect I've heard as it applies to polyester caps is just a general dulling or top end roll off and/or the bottom end gets weaker. The compressed thing you describe sounds like a power supply or tube issue. Check your electrolytics and try a tube swap. FWIW electrolytics derate too. This could include a derate in voltage rating and the ability to deliver the current needed. This usually would result in hum or a cap failure. Do a voltage test. Check voltages and bias when you flip the off standby. Then play the hell out of it for ten or fifteen min. Check all the same voltages again. Any changes?

                  Chuck
                  "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

                  "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

                  Comment


                  • #24
                    I finished up the amp and it sounds fantastic. Here are all the substitutions - not sure if they are an improvement over stock because I never tried it stock.

                    Speakers - Weber 10A125 Alnico Vintage Series in parallel
                    1.5K grid stoppers added to power tube sockets
                    Victoria-style presence circuit mod, 25K pot + 4.7K resistor +.1mfd cap
                    Safety diodes added to rectifier socket
                    RCA 5U4GB tube rectifier
                    Carbon comp resistors everywhere it made sense
                    Heyboer multitap output transformer running on 2 ohm tap
                    Two Illinois 100/450 caps in series for the main filters + two 220K balance
                    Mostly Sprague mylar and foil caps, one Cornell Dubellier and one oil/paper
                    NOS Phillips 6L6WGB, RCA 12AX7 in V2 and V3, 12AY7 in V1
                    Adjustable bias - 50KL pot in series with 39K resistor
                    Better chicken head knobs
                    Fender style pilot lamp

                    When I replaced the failed power caps, I put the new caps on the spare boards that Weber provides if you want to mount them in the Fender location. I left the two preamp caps on the mini board inside the amp.
                    If I had it to do again, I would sub in better quality tube sockets. These work, but I don't think they will last forever.

                    And here's the pictures.....http://s268.photobucket.com/albums/j...assman%205F6A/

                    Comment


                    • #25
                      Diablo,

                      When I built my 5F6A clone, I noticed Ted had a 56K resistor in the NFB loop, where the Fender schematics (including the RI) have 27K. I played around with various values and settled on 33k. You might consider experimenting here a bit and see what you prefer.
                      "In theory, there is no difference between theory and practice. In practice there is."
                      - Yogi Berra

                      Comment


                      • #26
                        You're right JoeM, thanks for pointing that out. I saw the same thing on Weber's schematic and I used the 27K resistor in the NFB loop, just like Fender. But, I forgot to list it in my mods list. This amp just begs to be played loud. It sounds like it's alive.

                        Comment


                        • #27
                          Today I hauled my amp over to two different guitar shops to get their opinions on the quality and tone. I told them I wanted to find out how it compares to other amps on the market and if I should do anything to change or improve it. The first shop sells Fenders and is the local music store that's been there for more than 3 decades. The owner is a pretty good guitar player, so I think his opinion is worth something. He liked the amp better than the original Bassmans, because it had a "tighter sound". The only issue he found was that the chassis was a little microphonic if you tapped on it while the volume was dimed....maybe the 12AY7 was microphonic? I slipped a 12AX7 in it for him to see which version he liked. He liked the 12AY7 better in V1, because it sounded warmer when cranked up. One thumbs up, and on to the Guitar Center. The GC guitar expert wasn't that much of a player, but he was very curious about what components were used in the build, type of wood, brands of tubes, types of speakers etc. After he played it for about 15 minutes, he told me it sounded very good. He wished the GC carried "high end" amps like that. He told me he thought it should be a $2200 amp. I told him I was interested in his feedback because I may want to build more to sell if they compare well to others on the market. His suggestions were to add a reverb and a master volume. I told him I didn't think the master volume was such a good idea, but have been thinking about a front end reverb unit. He liked the amp a lot, but told me he couldn't afford it. He shot some pictures of the guts with his cell phone, for his buddies. He asked if I could build other amps for his friends who wanted vintage stuff other than Fenders.....like HiWatt.

                          This weekend, I'm going to haul it over to the Victoria amp dealer to see how it compares. Into the lion's den.

                          Comment


                          • #28
                            They gave the amp a test drive at the Victoria dealer. He was a pretty good guitar picker armed with a Strat. He liked the amp and tone and said if I build another, do it the same way. To him, "it sounds like a Bassman". Without A/B ing it with the Victoria, he couldn't say if it sounded any different. They were pretty busy, so there was no time to A/B the two amps.

                            Comment


                            • #29
                              1.5K grid stoppers added to power tube sockets
                              Victoria-style presence circuit mod, 25K pot + 4.7K resistor +.1mfd cap
                              Safety diodes added to rectifier socket
                              Carbon comp resistors everywhere it made sense
                              Heyboer multitap output transformer running on 2 ohm tap
                              Mostly Sprague mylar and foil caps, one Cornell Dubellier and one oil/paper
                              NOS Phillips 6L6WGB, RCA 12AX7 in V2 and V3, 12AY7 in V1
                              Hi there!

                              Think you can give me some hints on replacements for my 5F6A?
                              I made the weber head model, using a homemade 2x12 with Celestion Blue's.

                              Tubes? Where to get them? What to get?
                              Caps? Thinking of Sprague Orange drops.
                              1.5k grid stoppers? Why?
                              Victoria-style presence? What does that do?
                              Heyboer OT, big difference?

                              //Jibe

                              Comment


                              • #30
                                Originally posted by jibe View Post
                                Hi there!

                                Think you can give me some hints on replacements for my 5F6A?
                                I made the weber head model, using a homemade 2x12 with Celestion Blue's.

                                Tubes? Where to get them? What to get?
                                Caps? Thinking of Sprague Orange drops.
                                1.5k grid stoppers? Why?
                                Victoria-style presence? What does that do?
                                Heyboer OT, big difference?

                                //Jibe
                                Tubes - Phillips 6L6WGB from ebay...about $45/pair. You could also try new issue Tungsol 5881 for around $30/pair. The 6L6WGB is same as 5881 designation - small bottle 23 watt. I'd get the power tubes first and see how you like 'em. Next, get a 12AY7 for V1. Try ebay..about $20.

                                Caps...Sprague Orange drops or maybe try those Sozo mylar film and foil caps from Weber. I haven't tried either in the Bassman, but I do have old mylar film and foil in there, so I'd lean towards the Sozo caps.

                                The 1.5K grid stoppers can prevent oscillation and shouldn't impact the tone in a negative way.

                                The Victoria presence circuit just gives a quiet non-scratchy pot.

                                Heyboer OT - I don't know if it's an improvement over the Weber OT, since I never tried the Weber. Heyboer builds the transformers for MOJO, general opinion is good.

                                I don't want to send you on a wild goose chase. For all my changes from the stock kit, I never tried it stock, so I can't honestly tell you that these changes are an improvement. All I can say is the amp sounds very nice.

                                Comment

                                Working...
                                X