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I see Crate's Problem with the Palomino V32

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  • I see Crate's Problem with the Palomino V32

    Now that I have run through this Crate Palomino V32 amplifier I can see why Crate discontinued the model and dumped them on the market. This is the first amplifier I have ever seen where the controls got so hot you could hardly touch them. This amp is a fire waiting to happen.

    I have seen some internet posts where the amps were returned with defective pots. Of course mine had a broken Middle control pot I was trying to find in another thread. I ended up disassembling it and popping it back together internally. I'm sure it had separated the wiper assembly from the metal shaft due to heat and the different expansion coefficients of metal and plastic.

    When this amp has been running for about 30 minutes with no signal, the pot control knobs are so hot they almost burn you. This is especially true for the ones in the middle of the control panel. Also, the Tolexed back panel is very warm and the upper cabinet around the vent is very warm. I pulled the back panel back off after seeing this and the 10 watt 60R power tube cathode resistor was the source of the heat. It was so hot you could have steamed water on it. Way too hot to touch. But of course you know I did it anyway. I need to get one of those infrared heat probes.

    I guess I have two options. Increase the resistance of the cathode resistor, lower the tube output and change the tone of the amp. Or, replace the single cathode resistor with two 125R 10 watt units in parallel to reduce the heat being generated. I think a cabinet fan might be in order for this amp as well. Man you could bake bread in this thing.

    In the picture attached you can see the resistor is directly under the middle pot that separated.
    Attached Files
    Last edited by bnwitt; 02-12-2009, 08:08 PM.
    Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

  • #2
    Originally posted by bnwitt View Post
    Or, replace the single cathode resistor with two 125R 10 watt units in parallel to reduce the heat being generated.
    As the dissipation would be the essentially the same, wouldn't the total heat being generated still be the same just spread out better?

    Comment


    • #3
      Yes. what would change is the surface area of the resistance. I was planning on installing them raised off the board separated and adding a cabinet fan to circulate air around them. The other option would be to build an array of heat sink type resistors down on the vent louvers at the bottom of the chassis and run a wire to them from the board. I'm trying to get the heat away from the pots and out of the chassis. Thoughts?

      Maybe two 150R 25 watt wire wounds down on the louvers. Move the heat down and increase the resistance from 60R to 75R
      Attached Files
      Last edited by bnwitt; 02-12-2009, 09:07 PM.
      Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

      Comment


      • #4
        Funny, we have a power supply product that uses those gold power resistors as a battery warmer!
        Anyway, you could mount one of those to the chassis to dissipate the heat.

        Comment


        • #5
          Hard Data

          Ok, for jollies I decided to take some thermistor temperature readings inside the chassis with it closed up. I hooked the amp up to a dummy load and strummed a guitar with the volumes cranked for about 30 minutes pausing like in between songs every 3 to 4 minutes.

          I took one reading in the center of the chassis about 1" away from the resistor. 135 degrees F

          I took a second reading near the mid pot at the top of the chassis. 130 degrees F

          Then I strapped the thermistor to the cathode resistor itself to get an idea what it's and the surrounding board temp was.
          219 degrees F. Like I said earlier, you could boil water on it.

          With that kind of heat it's like jiffy pop popped pots. No wonder the white plastic wiper assembly separates from the pot shaft.
          Attached Files
          Last edited by bnwitt; 02-12-2009, 11:12 PM.
          Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

          Comment


          • #6
            SO get an aluminum resistor and mount it off the pc board. On the end of the chassis maybe or even outside the chassis.
            Education is what you're left with after you have forgotten what you have learned.

            Comment


            • #7
              Originally posted by Enzo View Post
              SO get an aluminum resistor and mount it off the pc board. On the end of the chassis maybe or even outside the chassis.
              Yep that's my plan. I'm going to get two 120R aluminum units, parallel them and mount them both to the chassis with heat sink goop. That should fix the issue.
              Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

              Comment


              • #8
                And provide a handy little space heater.

                Comment


                • #9
                  Originally posted by drewl View Post
                  And provide a handy little space heater.
                  Ain't that the truth. Just like the Vox AC 30/6 with it's 4 EL84's and 50R resistor. Except in the Vox, the resistor wasn't gooped to a PCB. A bad situation made worse for sure.
                  Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

                  Comment


                  • #10
                    Had mine for 3 years and no problems except that it does indeed eat tubes! I measured the idle dissapation at around 13+ watts. I run Sovtek EL84M's in mine as they seem to be able to take it. Dont feel like bumping up the cathode resistor as its a hassle and then I might find the amps lost a bit of its mojo. The heat is expected as far as Im concerned with any amp that has this or an unsidedown orientation. Worried about the heat? Add a fan. bob
                    "Reality is an illusion albeit a very persistant one " Albert Einstein

                    Comment


                    • #11
                      Well I took the cathode resistor off of the board, replaced it with 2 each 120 ohm aluminum resistors in parallel bolted to the bottom vent area of the chassis, and the temp near the controls dropped 30 degrees. Whereas the single wirewound 60 ohm resistor ran 219 degrees on it's surface, the two 120 ohm resistors only ran about 120 degrees at their surfaces. I was going to add a fan but the one I bought was too noisey and I didn't need it after the resistor change.
                      Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

                      Comment


                      • #12
                        I think I might of experimented with a larger value resistor if I went as far as you did. I would be interesting to see(hear) if it sounded as good dissapating 11.5 or 12 watts. Well Im glad it worked out for what you were trying to accomplish ! Bob
                        "Reality is an illusion albeit a very persistant one " Albert Einstein

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                        • #13
                          Originally posted by rockon1 View Post
                          I think I might of experimented with a larger value resistor if I went as far as you did. I would be interesting to see(hear) if it sounded as good dissapating 11.5 or 12 watts. Well Im glad it worked out for what you were trying to accomplish ! Bob
                          Thanks Bob. As far as changing the cathode resistor and dissipation, it was a customer's amp and I didn't want to affect the tone. If it had been mine I would have lowered the ma a little. I was really surprised how much reduction there was in the temps inside the chassis just by moving the resistor(s) down to the vent area and using the heat sink aluminum body units though.
                          Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

                          Comment


                          • #14
                            Pretty "cool" way to cool things down! Me,well this thread has got me going on at least putting a fan in mine. Though it hasnt had any problems I imagine over time it may. Bob
                            "Reality is an illusion albeit a very persistant one " Albert Einstein

                            Comment


                            • #15
                              Vox got smart and made the resistor switchable on the newer CC series.
                              I always use my AC30 for cold outdoor gigs....it doubles as a hand warmer.

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