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Supercharging a V8

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  • Boy am I glad I came back to this thread. Thanks for the continued input, Verne!









    Quote Originally Posted by Verne Andru
    View Post

    I did manage to snag another V8 and have run it in stereo with the other one. Sounds great!




    Congratulations on picking up another! I was on the lookout for ya but didn't see too many MIAs...

    Comment


    • Ended up buying a 12" Celestion greenback, and a 12" Celestion G12H, will have both inside one 2x12 cabinet, and the Palomino driving them as a 'head'.



      I resolved to making the speaker cab stereo/mono capable. The wiring requires two Mono 1/4" jacks coming out of the speaker cabinet, and a DPDT switch that lets you switch between 2x12" in parallel to one jack (4 ohm), or two independent 1x12" channels, one to each jack (8 ohm each).



      This way, I can use a Mono configuration to drive both speakers together, or I can switch to Stereo configuration and split it up, to drive each speaker independently per jack (in which case I would connect the head to the specific L or R channel depending on which speaker I want to use...



      Diagram: (source: LINK)





      Verne: I still think that switching from Stereo to Mono (i.e., from 4ohm to 8 ohm) via a switch while the amp is ON is *not* a safe thing to do. Comments?









      Quote Originally Posted by Verne Andru
      View Post

      Nope. I do it all the time with no issues. Trick is to be quick about it.




      Comment








      • Quote Originally Posted by Preacher
        View Post

        Boy am I glad I came back to this thread. Thanks for the continued input, Verne!



        Congratulations on picking up another! I was on the lookout for ya but didn't see too many MIAs...




        I appreciate the thought and thanks. There don't seem to be many of these around anymore - either on eBay or CL. Frankly if they made 500 total I'd be surprised. I tried a couple sellers on CL and finally found one who would ship, but only after there was no interest from his local community. It's mint and I got it for $100 plus $35 shipping. The second one does sound much better than how my first sounded before the mods so there does appear to be some variance from one to the next.









        Quote Originally Posted by gnolivos
        View Post

        Verne: I still think that switching from Stereo to Mono (i.e., from 4ohm to 8 ohm) via a switch while the amp is ON is *not* a safe thing to do. Comments?




        It comes down to understanding what's going on in the circuit. The output section runs through an output transformer so what goes to the speaker is somewhat isolated from what's going on inside the amp. The danger comes in putting an incorrect load on the transformer for a period of time. In most cases this will cause the transformer to overheat which usually causes the transformer windings to melt and short before any damage happens to the circuitry driving it. As long as you're just changing things by flipping a switch I don't see how you can cause any damage - unless the switch shorts. But if you are nervous, simply turn the amp off, make your change and turn the amp back on again. Bear in mind it gets pretty hard on the tube since you are causing them to heat/cool/heat.



        Question: Has anybody done any of these mods?
        <div class="signaturecontainer"><div align="center"><a href="http://www.VerneAndru.com" target="_blank">VerneAndru.com</a> | <a href="http://www.oKee.com" target="_blank">oKee</a>.<a href="http://okee.com/WebApp/Downloads/420-001-Comic_Book_Sampler.pdf" target="_blank">ComX</a> | <a href="http://www.danedetto.com" target="_blank">Danedetto Guitars</a><br />
        <br />
        <font size="1">- ---==&lt; <a href="http://www.VerneAndru.com" target="_blank">V</a> &gt;==--- -</font><br />
        </div></div>

        Comment


        • Which mods specifically?









          Quote Originally Posted by Verne Andru
          View Post

          Question: Has anybody done any of these mods?




          Comment


          • Any of them? I guess what I'm asking is -> is it worth my time to work up a consolidated schematic with all the mods. If no one's doing them, then it's not really an issue.
            <div class="signaturecontainer"><div align="center"><a href="http://www.VerneAndru.com" target="_blank">VerneAndru.com</a> | <a href="http://www.oKee.com" target="_blank">oKee</a>.<a href="http://okee.com/WebApp/Downloads/420-001-Comic_Book_Sampler.pdf" target="_blank">ComX</a> | <a href="http://www.danedetto.com" target="_blank">Danedetto Guitars</a><br />
            <br />
            <font size="1">- ---==&lt; <a href="http://www.VerneAndru.com" target="_blank">V</a> &gt;==--- -</font><br />
            </div></div>

            Comment


            • I'm certainly WANTING to do the mods. I think if you could find the time to consolidate them in one 'post' that would be awesome. I think I have a good idea of what to do, but it took a good while to read through!

              Comment


              • Here's a little teaser for you guys... progress on the 'mini plexi' cabinet I am building with V8 guts. I am also having a 2x12 cabinet built, with Celestion speakers.







                And the speaker output on the back:

                Comment


                • ^^ Looking good.
                  <div class="signaturecontainer"><div align="center"><a href="http://www.VerneAndru.com" target="_blank">VerneAndru.com</a> | <a href="http://www.oKee.com" target="_blank">oKee</a>.<a href="http://okee.com/WebApp/Downloads/420-001-Comic_Book_Sampler.pdf" target="_blank">ComX</a> | <a href="http://www.danedetto.com" target="_blank">Danedetto Guitars</a><br />
                  <br />
                  <font size="1">- ---==&lt; <a href="http://www.VerneAndru.com" target="_blank">V</a> &gt;==--- -</font><br />
                  </div></div>

                  Comment


                  • Yeah, I would dig the schematic for sure. I think I got the basic idea of what you did but so far I've just done the C12 & C9 lift. But thanks for all the work you've put into it documenting this far.

                    Comment


                    • Verne,



                      Would you be able to provide us with correct procedure to drain the capacitors in this amp? I already have built a wire with 10Kohm @ 5W ceramic resistor. One side needs to be clamped to ground (chassis), but for THIS AMP, what is the recommended point to drain the caps? You cannot really reach under the caps on the V8 without removing the board, so I am trying to find a good spot that you can reach on the TOP of the circuit, to tap into. Some people seem to even prefer downstream after the resistors etc....



                      What do you recommend?

                      Comment


                      • Nice one. It's looking good dude.

                        Comment


                        • Pin 1 on V1 to ground, no resistor.



                          This board holds a fairly serious charge, so be sure to test with a meter to make sure it's dead before you start mucking.
                          <div class="signaturecontainer"><div align="center"><a href="http://www.VerneAndru.com" target="_blank">VerneAndru.com</a> | <a href="http://www.oKee.com" target="_blank">oKee</a>.<a href="http://okee.com/WebApp/Downloads/420-001-Comic_Book_Sampler.pdf" target="_blank">ComX</a> | <a href="http://www.danedetto.com" target="_blank">Danedetto Guitars</a><br />
                          <br />
                          <font size="1">- ---==&lt; <a href="http://www.VerneAndru.com" target="_blank">V</a> &gt;==--- -</font><br />
                          </div></div>

                          Comment







                          • Pin 1 on V1 to ground, no resistor.



                            I'm going to assume V1 is one of the tube sockets... at Pin #1. But which tube?



                            Also, do you normally remove the tube to get to PIN1, or do you make contact at the base of the socket on the other side... I think you can access them through there, not 100% sure.



                            And yes, I did look at the schematic!

                            Comment








                            • Quote Originally Posted by gnolivos
                              View Post

                              I'm going to assume V1 is one of the tube sockets... at Pin #1. But which tube?



                              Also, do you normally remove the tube to get to PIN1, or do you make contact at the base of the socket on the other side... I think you can access them through there, not 100% sure.



                              And yes, I did look at the schematic!




                              I hope you don't take me for a jerk for what I'm about to post, but it needs to be said, so bear with me.



                              This is one of the main reasons why it's difficult discussing this stuff on an internet forum. Particularly with the V8, we're dealing with dangerous voltage levels that need to be treated extremely seriously.



                              What I posted above makes perfect sense to anybody who has a rudimentary understanding of what they are doing. Your question indicates this does not include you. No disrespect meant.



                              At this point I would ask you to find a tech in your area who can explain these things to you and show you the proper procedure for draining capacitors - something that goes beyond where to connect wires. It involves what to wear, how to stand, what to do and what not to do.



                              If I go any further I run the risk of a major misunderstanding, which could lead to you being physically harmed, which I do not want and do not want to be held responsible for.



                              Please understand I'm not being a jerk, just watching out for your and my well-being.
                              <div class="signaturecontainer"><div align="center"><a href="http://www.VerneAndru.com" target="_blank">VerneAndru.com</a> | <a href="http://www.oKee.com" target="_blank">oKee</a>.<a href="http://okee.com/WebApp/Downloads/420-001-Comic_Book_Sampler.pdf" target="_blank">ComX</a> | <a href="http://www.danedetto.com" target="_blank">Danedetto Guitars</a><br />
                              <br />
                              <font size="1">- ---==&lt; <a href="http://www.VerneAndru.com" target="_blank">V</a> &gt;==--- -</font><br />
                              </div></div>

                              Comment


                              • Verne,



                                Totally understand. In fact, I kind of knew this is where you were going to come back... But I tried as a last resort.



                                I did a ton of research and did find some useful info on youtube etc, but I agree, getting someone to show you in PERSON is the way to go. I'll try to find someone to do that.



                                Thanks for all your help so far!!!

                                Comment



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