I see Crate's Problem with the Palomino V32

[charlie chitlins]

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.

[loanwolf]

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...

[nomadh]

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?

[guitarfish]

Hello all,

I was very excited to find this thread a couple weeks ago. I’ve had a Crate V3112 since 2006. I will play this amp until it dies, and then I’ll try and find another one to replace it. I love this amp. It’s always been very hot, I have a small 4” fan I keep on the floor behind it. But it does seem to eat tubes. I tonight I did the resistor mod. Now that it’s done, I can’t 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 I’ve read.
Going from 60 to 75 ohms means less heat, right?
The stock resistor was 10 watts, the new one is 25 watts. I don’t know what difference this makes, so if someone could explain it, I’d appreciate it.

Once back together, I let it warm up a bit and played it – 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 don’t have the ability to measure the surface temp, but it’s nothing like 200 degrees that’s for sure. However, the knobs are still quite warm. They were never so hot that I couldn’t 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 it’s 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...
I’d just like some confirmation - did I pick the correct resistor?
What did I accomplish, electronically speaking, by going from 60 ohm to 75?

[rockon1]

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

[guitarfish]

On the back, mine says "Designed and Mfd in the USA" and has the St. Louis address on it. No date of manufacture, however.

[Enzo]

The dissipation for a resistor is a matter of current through it tomes voltage across it. That is all. If it dissipates 3 watts it will do so whether the resistor is rated 5 watts or 25 watts. The difference is the heat will be spread a little more, so while the overall heat level in teh chassis won;t change, the intensity of the heat spot right at the resistor will lessen. And by mounting right on the metal chassis, you might get a little better heat flow out of the chassis.

Increasing the cathode resistor would tend to increase the voltage across it, which in turn would tend to bias the tubes colder. That would reduce the dissipation, ALL THING BEING EQUAL. However, when you drop the tube current, the B+ (high voltage supply) will also rebound some, meaning the voltage goes higher. That tends to counteract the change. So the difference will not be as pronounced as simple calculations might make you think.

The stock one was 1%, the replacement is 5%, which is better from what I’ve read.

Not sure where you would have read that. "Better" just means more suited to the application. Peanut butter isn't better than toothpaste. But peanut butter makes a better sandwich, and toothpaste is better for cleaning teeth. Hmmm, perhaps chunk style toothpaste...

1% and 5% are called tolerances. That means, how close to the stated value will the resistor be. So a 10% resistor is one that will be within 10% of its stated value. SO a 5% 100k resistor could be anywhere from 95k to 105k and still be a good part. A 1% 100k resistor would be anywhere from 99k to 101k. SO the smaller the percentage the tighter the tolerance, the closer the value. In guitar amps it rarely matter much, after all 50 years ago, those vintage Fender amps we love so much were made with 20% parts. Higher precision parts tend to be more expensive, but these days, even 1% resistors are cheap. I cannot imagine why a 5% part would be better than a 1% part.

[guitarfish]

Enzo, thanks for the explanation, and for straightening me out on the tolerances. I guess what I'm wondering is what, if anything, did I accomplish with this mod?

Ideally, I'd like less wear and longer life on the tubes. I can still run an external fan, I have no issue with that. FWIW, I also bought the 82 ohm version of this resistor, as someone else in this thread had installed one of those. I'm just not clear if it's going to make much difference.

Opinions, please.

[Enzo]

Tubes run cooler with less power dissipated in them. Power is current through the tube times voltage across the tube. SO since they tend to be interactive, you measure the new voltage across the tube and the current through it, and multiply. How much did the dissipation go down? That is what you accomplished.

VOltage across the tube means from plate to cathode. Or subtract whatever is at the cathode from the plate reading. The plate voltage itself tells us nothing. Since you know the cathode resistor, then you can measure voltage across it to calculate tube current.

[Mica]

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.

Hi, I own the V32 head and would like to install a fan. Can someone describe how to connect the fan to the power switch?

Thanks,
Kevin

[Mica]

Hi, I own the V32 head and would like to install a fan. Can someone describe how to connect the fan to the power switch?

Looking at my question I thought it was worth clarifying. I have a 5V fan that I was hoping to put in the amp, so I would need to find a source of 5V source to connect it to. I guess the easiest thing would be to get a 120V fan and then it could be connected to the switch.

[guitarfish]

Well, I installed the 82 ohm version of this resistor, and I am very satisifed with my amp now. While I can feel a reasonable amount of heat coming out of the top vent from the tubes, the knobs were just slightly warm after about 45 min of use, where they would normally be quite hot with the stock resistor. And this is with no fan running. With my little 4" floor fan, the amp is practically cold, which probably isn't desirable, I mean it is supposed to be warm. So in conclusion, I highly recommend the 82 ohm resistor.

Oh, and just to correct myself earlier in this thread, the stock resistor was 5%, and the replacement is 1% - I'd accidentally said the opposite.

[pdf64]

Regards installing a fan, great results can be obtained using a 12Vdc PC type fan, driven by ~9V from a rectifier on the 6.3Vac heaters. Can be mounted on a bracket using existing chassis holes, see Installing a fan in vintage Fender amps
I use a FWB rectifier and >220uF smoothing cap.

[Mica]

Thanks pdf64. I checked out the diagram and it looks simple enough. Is the 6.3Vac heaters the same as the terminals across the pilot light shown in the "Installing a fan in vintage Fender amps" link you provided. If not, can you describe how to locate the 6.3Vac heaters. As must be obvious I'm not an amp tech, but know enough about basic electronics to perform simple mods.

Thanks again,
Kevin

[pdf64]

Is the 6.3Vac heaters the same as the terminals across the pilot light shown in the "Installing a fan in vintage Fender amps" link you provided

Yes.
Bear in mind that the + & - outputs from the rectifier (whether it's a single diode or a full wave bridge File:RC Filter.png - Wikipedia, the free encyclopedia) can't be grounded to the chassis (so ignore the ground on the wiki link).