Adding a fan to a DC-3

What is the cleanest way to add a fan to a DC-3 combo? I suppose it wouldn't be hard to splice into the AC power after the AC receptacle, then add a new power cord with an in-line switch, then a 120VAC fan.

Is there an adaptor available to plug into the AC receptacle, then plug in the main power cord and new power cord for the fan into that adaptor? Where do you mount the switch?

It would be nice if I could wire a fan the would come on automatically, every time I turn on the main power switch. Can this be done, and where would I connect it, and to what voltage? If a DC fan is connected to a DC voltage, then maybe this can add noise to the amp?

Any advice is appreciated.

I just purchased a 50 caliber + that had a fan added at some point in its life. It was done very easily and cleanly just running power soldered from the main AC termination ponts inside the chassis through an small existing hole in the chassis. The fan was mounted in the bottom of the chassis just under the power tubes. It was about 5 inch standard type of cooling fan. I've seen those micro type fans mounted on the inside side of the chassis so the air moves across all the tubes. It doesn't look like rocket science. What I would suggest is some kind of cable disconnect when you pull the chassis out so you don't have to lug the fan with you.

Hope this helps.

TD

photogold said:

What is the cleanest way to add a fan to a DC-3 combo? I suppose it wouldn't be hard to splice into the AC power after the AC receptacle, then add a new power cord with an in-line switch, then a 120VAC fan.

Is there an adaptor available to plug into the AC receptacle, then plug in the main power cord and new power cord for the fan into that adaptor? Where do you mount the switch?

It would be nice if I could wire a fan the would come on automatically, every time I turn on the main power switch. Can this be done, and where would I connect it, and to what voltage? If a DC fan is connected to a DC voltage, then maybe this can add noise to the amp?

Any advice is appreciated.

Click to expand...

I added a 12vdc fan to mine. hooded up a 9 vdc wall wart to the internal switch and used industrial velcro to hold the adapter to the inside of the combo. Not as neat as a 120vac fan but real quiet and does a good job of keeping the chassis cool to the touch. Bob

I prefer 12 vdc fans. They are quieter and there is no extra noise carrying wires added to the amp. I power mine off the 6.3vac winding. Use 2 1n4007 diodes to rectify the ac to dc and a 470uf capacitor to smooth the voltage and you end up with around 8vdc. This runs the fans slightly slower but cuts down on some of the noise. I use 3 to 3.5 square brushless fans for this application. They work great and are extremely quiet. Just make sure to twist the wires tightly. This helps reduce any noise in the wiring.





Thanks
John

After doing BobR's bias mod I don't need a fan anymore.It runs at a nice even temp like my other tube amps.My neg bias is running at -14.3v and the amp seems quite happy there.
YAY BOB!! 8)
P.S. all my stock pile of tubes work fine now(no redplating)

bhsbhswarp said:

After doing BobR's bias mod I don't need a fan anymore.It runs at a nice even temp like my other tube amps.My neg bias is running at -14.3v and the amp seems quite happy there.
YAY BOB!! 8)
P.S. all my stock pile of tubes work fine now(no redplating)

Click to expand...

Very 'cool' -pun intended! John from Mansfield Guitars modified his bias kit after talking to Mesa directly. It seems they suggested changing the 120k to 100k and not worrying about the slight change to the PI bias. It was nice to know I came up with the fix Mesa themselves suggested!
Oh and John from Mansfield was very gratious to offer me an upgrade 100k pot and 22k resistor to use in mine. Bob

OK so I finally installed a fan on my DC-3, and it worked out very well. I found a 3" 120 VAC fan and I attached it to the back board of the cabinet so that it blows upward. I attached it with industrial strength velcro and a disconnect plug, so that it can be removed easily if needed.

It is hard to find an AC fan, but they do make them. 95% of the fans are 12 VDC. I did this before I saw the post from mansfieldguitars, otherwise I might have tried using a 12V fan. But the 120 VAC was probably easier to install, and with no need to build a little rectifier board. The fan has some noise but not bad. It is maybe as loud as the fan on my PC. I don't notice it at all when I'm playing at low bedroom volumes. And I don't hear any electrical noise through the speaker.

I didn't take a photo, but I accessed 120 VAC power by connecting to the white neutral on the terminal of the AC plug. I routed that wire around the side of the circuit board to where I connected the other wire to terminal terminal on the power switch (the terminal which has no power when the switch is open). Then I twisted both wires together and routed them across the front chassis, under the wires that connect to the tone pots. This keeps the wires away from touching the tubes. Then I used the existing vent holes to route the wires down into the cabinet. If anyone tries this mod, be sure that you have good soldering skills. You are working with 120 volts, so bad things can happen if a connection comes undone.

The chassis is now much cooler and the fan comes on whenever I turn the power switch on.

Ok then....???? Huh? Aint ckicking on those links! Bob

reported :mrgreen: