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I see Crate's Problem with the Palomino V32

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  • #16
    Since I've received a few PM's on this thread I thought I would post a PDF of the mod I performed on the Palomino for anyone who is interested. Even though a single 25 watt aluminum resistor can more than handle the cathode current of this amp, I went with two double valued units in parallel to increase the contact surface area of the resistance at the chassis metal bottom. I did this to improve heat rejection into the cabinet and away from the chassis internal area. It seems to work very well, as it dropped the temp around the controls and at the board significantly. Increasing the net value of the cathode resistors (as mentioned in the attachment) would probably help even more and extend the life of the tubes as well. The 25 watt resistors can be found on Mouser.com by searching the phrase "aluminum resistor" currently page 645 of their catalog:

    http://www.mouser.com/Search/Product...EYbTFjJwKbM%3d

    Barry
    Attached Files
    Last edited by bnwitt; 04-14-2009, 04:51 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.

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    • #17
      Originally posted by drewl View Post
      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.

      Yes I saw that. Switchable between 82 ohms and 53 ohms with an 82 ohm by itself or a 150 ohm in parallel with the 82 ohm. Probably would be a good setup for the palomino as well.
      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.

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      • #18
        Well theres more than one way to skin a cat. I installed this 115 vac fan on my last week. It blows partially into the chassic and partially into the tube area. I made a small vent on the back too. I also installed an on/off switch incase I wanted "silent running -otherwise it turns on with the power switch . Runs cools as a cucumber now! Bob

        "Reality is an illusion albeit a very persistant one " Albert Einstein

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        • #19
          Yep, that's another way to do it. Have you mounted a temperature probe above the power resistor near the controls to measure the temp there with the fan running?
          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.

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          • #20
            Not yet but I am curious. When I do i'll let you know. Bob
            "Reality is an illusion albeit a very persistant one " Albert Einstein

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            • #21
              OK with the fan off and a probe slipped into the back cover its about 137 degrees F. With the fan running it drops to about 103 F after a few minutes. I could have gotten it much cooler inside but I wanted to blow cool air into the power tube area too so only about 1/3 of the actually fan blows into the vent. bob
              "Reality is an illusion albeit a very persistant one " Albert Einstein

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              • #22
                Good thinking there! I have been somewhat interested in those amps, and this is good info if I happen to go about getting one eventually.

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                • #23
                  Well that's almost the exact temp drop I got with the resistor relocation, 30-35 degrees. So if the noise of the fan is objectionable it's the resistors, if not, the fan.
                  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.

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                  • #24
                    Each way has its merits. The fan allowed me to blow some needed air into the power tube area but introduces some noise and requires more moving parts. I aded a switch to disable it in case of recording or something.

                    The resistors add no more complexity are quieter but no additional cooling.

                    Both wouold be a really "cool" idea! Bob
                    "Reality is an illusion albeit a very persistant one " Albert Einstein

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                    • #25
                      I dunno, I accidentally left a V32 on at church and it ran idle for 2 weeks before we found it. The amp is in a plexi-glass box with contruction insulation on all sides, our worship leader's idea to keep stage volume down. Us musicians are totally against it but we can't talk him out of it. Anyway, that amp was fine afterwards, the guy who found it 'on' said he's never felt an amp cabinet as hot. I was planning on replacing the power tubes but it seems to be working AOK today. I agree heat is not our friend, maybe we got a 'one in 1000' amp.

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                      • #26
                        Crate V32 Palomino cathode resistor mod

                        So, if the the bias resistance is increased from 60 ohms to 75 ohms, what will the approximate % decrease in gain of the output section be?

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                        • #27
                          went with 2 150ohm resistors as per bnwitt's advice.
                          Clipped the old resistor and soldered jumpers right to what was left of the leads.
                          Work fast so you don't heat up the connection on the pcb and have your little lead come out.
                          Drilled some holes in the chassis and mounted the resistors out of the way.
                          Amp still sounds great, and I'll be much more comfortable at the gig!
                          Thanks, Barry!!!!

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                          • #28
                            Nice job there Charlie. I think your resistor location is better than mine since they aren't below any pots or sensitive components.
                            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.

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                            • #29
                              Actually...I thought it was kind of overkill...like putting them in the next county. But it sure couldn't hurt. And it was just plain easy having room to work. And now the whole chassis is a heat sink!
                              A very sensible mod.
                              Thanks again!!

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                              • #30
                                Why tack solder the wires to little leg stubs? I would remove the old resistors, clean the holes, and solder the wire right into the hole. They are plate through holes, you can solder them right as we see them in the photo.
                                Education is what you're left with after you have forgotten what you have learned.

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