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Thread: I see Crate's Problem with the Palomino V32

  1. #1
    Senior Member bnwitt's Avatar
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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 Thumbnails Attached Thumbnails p2120003.jpg  
    Last edited by bnwitt; 02-12-2009 at 09:08 PM.
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  2. #2
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    Quote 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?

  3. #3
    Senior Member bnwitt's Avatar
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    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 Thumbnails Attached Thumbnails 25w-resistor.jpg  
    Last edited by bnwitt; 02-12-2009 at 10:07 PM.

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    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.

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    Senior Member bnwitt's Avatar
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    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 Thumbnails Attached Thumbnails p2120004.jpg   p2120006.jpg  
    Last edited by bnwitt; 02-13-2009 at 12:12 AM.

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    Senior Member Enzo's Avatar
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    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.

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    Senior Member bnwitt's Avatar
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    Quote 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.

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    And provide a handy little space heater.

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    Senior Member bnwitt's Avatar
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    Quote 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.

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    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

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    Senior Member bnwitt's Avatar
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    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.

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    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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    Senior Member bnwitt's Avatar
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    Quote 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.

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    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

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    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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    Senior Member bnwitt's Avatar
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    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 Thumbnails Attached Thumbnails palomino-cathode-resistor-mod.pdf  
    Last edited by bnwitt; 04-14-2009 at 05:51 PM.
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    Senior Member bnwitt's Avatar
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    Quote 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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    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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    Senior Member bnwitt's Avatar
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    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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    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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    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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    Senior Member trevorus's Avatar
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    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.

  23. #23
    Senior Member bnwitt's Avatar
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    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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    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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    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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    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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    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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    Senior Member bnwitt's Avatar
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    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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    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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    Senior Member Enzo's Avatar
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    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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    I don't doubt that you could be right.
    I'm not an electronics guy, but I've done a lot of soldering on automotive stuff and easy electronics...mostly guitar wiring; so, at least I know how to drive a soldering iron.
    I'm not at all familiar with circuit boards and didn't want to risk screwing anything up by cooking it. I just don't know their properties...how easy it is to ruin something.
    This seemed like the safe way...and I was too lazy to remove the whole board to do it from the other side where the rest of the solders are.

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    I recently bought one of these crate palomino 32 amps ..it ran a little hot so I replaced the 60ohm resistor with a 82 ohm resistor.(25 watt aluminum case)..I cant hear a difference in the tone or drive and the amp runs very cool ..no need for a fan...I am also going to add a 600 ohm resistor in parallel with the 82 ohm and a spst switch so I can switch between 72 or 82 ohms...did not want to go lower than 60 ohms to help prolong the life of the tubes...

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    I have the similar v3112 v30. It also ran very hot. I got a little ac desk fan that I put in the bottom of the amp and aim upwards. It helped immensly. I wonder if my tubes will last longer now?

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    Hello all,

    I was very excited to find this thread a couple weeks ago. Iíve had a Crate V3112 since 2006. I will play this amp until it dies, and then Iíll try and find another one to replace it. I love this amp. Itís always been very hot, I have a small 4Ē fan I keep on the floor behind it. But it does seem to eat tubes. I tonight I did the resistor mod. Now that itís done, I canít say I notice a difference in overall temp. I was hoping I can get some input from you guys.

    I replaced the stock 60 ohm resistor with this 75 ohm one:
    71-RH02575R00FE02

    Mind you, I know zilch about electronics. The stock one was 1%, the replacement is 5%, which is better from what Iíve read.
    Going from 60 to 75 ohms means less heat, right?
    The stock resistor was 10 watts, the new one is 25 watts. I donít know what difference this makes, so if someone could explain it, Iíd appreciate it.

    Once back together, I let it warm up a bit and played it Ė it sounds as fabulous as always. (I have a Tone Tubby speaker, which really rocks). I initially left the back cover off. The new resistor is very cool, I can put my finger on it, no problem. I donít have the ability to measure the surface temp, but itís nothing like 200 degrees thatís for sure. However, the knobs are still quite warm. They were never so hot that I couldnít touch them, but they are still as hot as they used to be. With the cover off for a while, it seems to me that itís the tubes themselves that are the source of most of the heat. Running my little fan keeps the whole amp as cool as a cucumber.

    So anyway...
    Iíd just like some confirmation - did I pick the correct resistor?
    What did I accomplish, electronically speaking, by going from 60 ohm to 75?



    Last edited by guitarfish; 09-24-2011 at 03:40 AM.

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    Interesting. Your pots have plastic shafts. My V32 has metal shafts(US model)..... Im not sure a change going from 60 to 75ohm will make that much of a difference really. With the 60 ohm mine idles at around 13.5 watts diussapation. I was planning on trying something around 100 ohms but never got around to it. Being mounted off the board will help I imagine though.Bob
    "Reality is an illusion albeit a very persistant one " Albert Einstein

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