Author Topic: Adding a cooling fan to an Enforcer Head  (Read 2912 times)

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Offline Watson

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Adding a cooling fan to an Enforcer Head
« on: January 17, 2014, 10:04:15 pm »
Why?
I have an early SUNN Enforcer amp head that lacked the front grill. Playing it long and loud definitely heats it up so I added an after market grill. The passive cooling was fine but since I had an extra 12vdc computer case cooling fan I thought it would make sense to add it. In case anyone else might feel the need I took a few shots of the process. I didn't want the fan to always run so I also added a thermostat switch so the fan would only run when it was really needed. Here's the materials list for the addition of the fan.

Schematic and changes
Below are images of the relevant area of the Enforcer schematic and then a 2nd view showing the planned changes.

Parts List
From Amazon.com
$5.20 - Syba SY-CAB65007 3 Pin Female to 2 x 3 Pin Male Connectors Fan Power Extension Y Cable (7.75 Inches) - click here
$9.75 - Thermostat Switch - Circuit On At 100°F and Off At 85°F - Large Flange - click here
$1.59 - spade-type wiring terminal connectors - click here

From Radio Shack
$1.79 - RadioShackŪ +12V Fixed-Voltage Regulator 7812 - click here

From TigerDirect.com
$7.99 - Masscool BLD-12025V1 Blue LED 120mm Ball Bearing Case Fan - click here

From Hanson Hobbies
Futaba J Servo Connectors - click here
« Last Edit: January 19, 2014, 10:17:09 am by Watson »

Offline Watson

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Re: Adding a cooling fan to an Enforcer Head
« Reply #1 on: January 17, 2014, 10:06:39 pm »
STEP 1: Make 12vdc available for the fan
The Enforcer amp doesn't have an internal 12 volt supply but it does have a 15vdc supply coming off the power transformer. So you need to add a 12 vdc voltage regulator in order to power the cooling fan. A 7812 voltage regulator takes the 15vdc from the existing +15vdc regulator and provides a constant 12vdc output. Remove the power supply PCB from the Enforcer amp head.
« Last Edit: January 18, 2014, 04:06:13 pm by Watson »

Offline Watson

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Re: Adding a cooling fan to an Enforcer Head
« Reply #2 on: January 17, 2014, 10:08:28 pm »
STEP 2: Drill the mounting holes for the regulator and the fan socket wiring
Mount the 7812 regulator to the factory power supply pcb by drilling a hole adjacent to the legs of the 7815 regulator.  The hole for the input leg needs to be drilled in the circuit run where the output leg of the 7815 is located so that the output of the 7815 can be used as the input to the 7812. The ground leg (middle leg) of the 7812 is mounted in a hole you need to drill in the rather large circuit run used by the ground of the 7815. For the output leg of the 7812 regulator, drill a third hole in the large ground circuit run (see pictures). Adjacent to the output leg hole you need to drill a second hole that will be used for the lead going to the thermostat. 

In order to isolate these two holes from the ground circuit, use a graver tool or an x-acto knife to cut a channel or "moat" around the two holes. This will fully separate and isolate them from the Enforcer's PCB ground circuit run. You are basically creating an island with two holes in it.  One hole is for the output leg of the 7812 and the other hole is for the + lead that will be going to the thermostat switch. It isn't the prettiest modifcation but it is effective and by chossing this location you can avoid unecessary wiring and the existing runs are right there to provide the "easy" input and ground connections.

One more hole is now drilled into the Enforcer PCB. This hole is for the negative lead going to the socket that the fan will plug into. It is drilled near the "island" you created in the ground PCB circuit run (see picture). 
« Last Edit: January 18, 2014, 04:33:23 pm by Watson »

Offline Watson

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Re: Adding a cooling fan to an Enforcer Head
« Reply #3 on: January 17, 2014, 10:14:57 pm »
STEP 3: Mount the regulator
Next go ahead and mount the 7812 regulator and solder it in place. You only need 1 of the 2 female 3-pin sockets from the y-cable so cut one socket free from the Y-cable assembly leaving the wire as long as possible. That leaves you with the other female socket and the male plug, neither of which is needed so cut those off and leaving just the wire. Discard the severed socket and plug. I bought the Y-cable as a convenience since it had the already wired socket I needed and some extra wire.  In the remaining hole that was drilled in the +12 volt island, solder one end of the red 6 inch loose wire and on the other end of the red wire solder an 18-22 gauge female spade terminal connector. This end will plug onto the thermostat switch once it is mounted in the Enforcer chassis.

Finally, solder the loose end of the black wire attached to the 3-pin female socket into the hole that was drilled into the ground circuit run on the PCB. On the red lead also attached to the 3-pin socket, solder another 18-22 gauge female spade connector.  This end will attach to the other end of the thermostat. You can cut off the yellow wire as it is not needed.

One last wiring task is to cut the red & black wires attached to the 3-pin socket about midday in their length.  I attached Futaba J 2-pin crimp connectors to the cut wires and this will allow the PCB board to remain removable after the socket and the thermostat are mounted. Again, see the pictures and the need will be obvious.
« Last Edit: January 18, 2014, 04:37:27 pm by Watson »

Offline Watson

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Re: Adding a cooling fan to an Enforcer Head
« Reply #4 on: January 17, 2014, 10:17:19 pm »
STEP 4: Mount the thermostat switch
About an inch from the edge of the power supply PCB, mark and drill a 1" hole in the Enforcer's chassis.  See the pictures for orientation. I used a stepped drill bit commonly available in hardware or automotive stores for making various sized holes in sheet metal. I choose the location in the chassis that is right next to the "business" end of the PCB where the 7812 regulator was just mounted. Using the thermostat as a template I also drilled 5/32" holes for mounting it to the chassis. Then cut a gasket (optional) from sheet cork or other gasket material and then mounted the gasket/thermostat so the sensor end is facing out toward the vacuum tube side of the chassis. Now you can plug the two red wires with their spade connectors into the two male lugs of the thermostat.
 
« Last Edit: January 18, 2014, 04:38:22 pm by Watson »

Offline Watson

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Re: Adding a cooling fan to an Enforcer Head
« Reply #5 on: January 17, 2014, 10:18:39 pm »
STEP 5: Mount the 3-pin fan socket
Just one more fabrication task to do.  Drill a 5/16" hole near the thermostat and using a small file, enlarge it to be a rectangle into which the 3 pin female connector fits snuggly. Then go ahead and install the 3 pin female connector socket into the chassis from the PCB side of the chassis so it is facing out towards the vacuum tube side of the chassis. Mix some 5-minute epoxy and run a bead around the socket (PCB side of course) in order to cement it in place.

Although you could hard-wire the fan, by installing this socket the fan will also be easily removable when you need to perform amp maintenance. A little time now will be appreciated the next time you have to change tubes or adjust the bias.
« Last Edit: January 18, 2014, 04:43:03 pm by Watson »

Offline Watson

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Re: Adding a cooling fan to an Enforcer Head
« Reply #6 on: January 17, 2014, 10:20:26 pm »
STEP 6: Put things back together
Now you can mount the Enforcer power supply PCB back onto the chassis, plug the two red wires into the thermostat switch (either side, it doesn't matter) and plug the red/black fan socket leads back together.  The wiring part of the 12vdc power supply addition is complete.
« Last Edit: January 18, 2014, 04:44:39 pm by Watson »

Offline Watson

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Re: Adding a cooling fan to an Enforcer Head
« Reply #7 on: January 17, 2014, 10:21:47 pm »
STEP 7: Mount the fan
I chose to use a fan I had on hand and it was slightly taller than the chassis to inside cabinet dimension of the Enforcer cabinet so I routed a shallow trough for the fan to sit it.  I made the trough just deep enough that when the fan is put in place it is wedged snugly between the inside of the head cabinet and the chassis. The trough was wider than the fan's width and I used this fact to aid it securing it. I cut a small strip of hardwood an screwed it into the trough in a fashion that allows it to serve as a retainer for the fan. The fan is captured between the hardwood strip and the cabinet securing it quite well. I had some ebony lying around so I used it since it is black already and pretty much blends in with the cabinet.
« Last Edit: January 18, 2014, 04:04:25 pm by Watson »

Offline Watson

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Re: Adding a cooling fan to an Enforcer Head
« Reply #8 on: January 17, 2014, 10:22:30 pm »
STEP 8: Plug in the fan
The location of the fan was chosen to be right behind the power tubes and the fan oriented so it is blowing towards the rear of the head which then draws fresh air through the grills in the front of the amp head and across the tubes and out the back. The cord on the fan is plenty long enough to comfortably route under the transformer and then plug into the socket that was mounted in the chassis.
« Last Edit: January 18, 2014, 04:04:01 pm by Watson »

Offline EdBass

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Re: Adding a cooling fan to an Enforcer Head
« Reply #9 on: January 18, 2014, 11:14:53 am »
Nice! One the most comprehensive DIY's on this site, well done Watson!
However I'm not exactly sure why one would feel the need to put a fan in an amp that was engineered to be convection cooled though. All of my tube amps get quite toasty after a few hours, and I'm convinced they start sounding (and smelling...) better as they get hot; usually by the last set they are both literally and figuratively "cookin'".
I've never played with an Enforcer, do Enforcers have a chronic overheating issue?

Offline Watson

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Re: Adding a cooling fan to an Enforcer Head
« Reply #10 on: January 18, 2014, 11:27:42 am »
Mostly done because I can. I have only owned this one Enforcer and don't personally know another owner.  I absolutely love this amp and typical of SUNN, it has gigantic power and output transformers. I also recently re-tubed it with KT66s instead of the 6L6GCs it was equipped with.

When I got this one, I noticed it had been used pretty hard and heated as evidenced by the slight warped cabinet top it sports. Combine that with an extra blue LED cooling fan from my last PC build, luthier skills, some electronics skill and one 19 year old left at our address who plays the bajeebers out of it and viola...a nice minor winter project is born.

To your point...I seriously doubt it needs it but I can't sit still and it does look cool when the fan kicks in :-)

Offline EdBass

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Re: Adding a cooling fan to an Enforcer Head
« Reply #11 on: January 18, 2014, 11:40:59 am »
Mostly done because I can. I have only owned this one Enforcer and don't personally know another owner.  I absolutely love this amp and typical of SUNN, it has gigantic power and output transformers. I also recently re-tubed it with KT66s instead of the 6L6GCs it was equipped with.

When I got this one, I noticed it had been used pretty hard and heated as evidenced by the slight warped cabinet top it sports. Combine that with an extra blue LED cooling fan from my last PC build, luthier skills, some electronics skill and one 19 year old left at our address who plays the bajeebers out of it and viola...a nice minor winter project is born.

To your point...I seriously doubt it needs it but I can't sit still and it does look cool when the fan kicks in :-)

Absolutely excellent reasons as far as I'm concerned Watson! Again, nicely done!