MartyStrat54
Well-Known Member
I was busy yesterday when I posted the above info. I did want to tell you that there is more to this installation. Most importantly you will need some rubber washers that go between the grille and the fan. This will isolate the fan unit and prevent excessive "whine" from the fan. I use four, 8/32 type bolts. These are small enough in diameter to go through the holes in the Marshall grille without any drilling. Put the head on the outside and the nut and lock washer on the inside.
You will need to drill a small hole in the bottom of the chassis. You will have to have the chassis pulled to determine where you can make the drill hole. It is best to make the hole oversized and then install a rubber grommet in it. Then you can pass the power cable through this hole over to the power switch. One wire will go to ground and the other goes to the "ON" switch. Make sure it is the right connection. You want the fan to come on when the switch is turned on.
I usually use stranded 16 gauge wire and that is plenty big for this application. I try to use just the right length of wire so that the excess just hangs without touching anything. (Attaching the wire to the grille may transfer fan noise.
Most of these fans have bare soldering terminals. You will want to use heat shrink tubing on these connections to prevent any possible shock from occurring. There may be some other little tweaks I do, but that depends on the individual amp. Sometimes I try different rubber washers to get the quietest mount. If your fan is below 35dB, that is really good and quiet. Let me know if you tackle the job. Just remember, these type of fans now come with a noise listing. Any fan of the proper size will do, just pay attention to the noise rating.
On a side note: If you had all four tubes replaced with YJ's, the heat problem would be a lot less than with EL34's in place. I notice that the YJ's have quite a long base to them and of course the EL84 is a much smaller tube and therefore it puts out a lot less heat. I do not think you would even need a fan if you were running a quad of YJ's with EL84's.
Marty
You will need to drill a small hole in the bottom of the chassis. You will have to have the chassis pulled to determine where you can make the drill hole. It is best to make the hole oversized and then install a rubber grommet in it. Then you can pass the power cable through this hole over to the power switch. One wire will go to ground and the other goes to the "ON" switch. Make sure it is the right connection. You want the fan to come on when the switch is turned on.
I usually use stranded 16 gauge wire and that is plenty big for this application. I try to use just the right length of wire so that the excess just hangs without touching anything. (Attaching the wire to the grille may transfer fan noise.
Most of these fans have bare soldering terminals. You will want to use heat shrink tubing on these connections to prevent any possible shock from occurring. There may be some other little tweaks I do, but that depends on the individual amp. Sometimes I try different rubber washers to get the quietest mount. If your fan is below 35dB, that is really good and quiet. Let me know if you tackle the job. Just remember, these type of fans now come with a noise listing. Any fan of the proper size will do, just pay attention to the noise rating.
On a side note: If you had all four tubes replaced with YJ's, the heat problem would be a lot less than with EL34's in place. I notice that the YJ's have quite a long base to them and of course the EL84 is a much smaller tube and therefore it puts out a lot less heat. I do not think you would even need a fan if you were running a quad of YJ's with EL84's.
Marty