Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dpm309 on January 23, 2015, 09:50:22 am
-
I had a request to put an on-off switch in 2 Egnater amps. One is a Tweaker 88 and the other a Vengeance Head. The owner says the fans are too noisy and I advised him they are there for a reason. I am hesitant to do this as I do not want to be responsible for and damage to these amps. I am I correct or would it be OK to perform this mod? Also, does anyone know where I can find schematics for these?
Thanks,
Dan
-
Violating any Warranty may be an issue. Anyway:
The logical solution is to reduce voltage to the fan to get it to run slower. Then there's less whooshing noise. If the fan is 120VAC use equal dropping resistors on both legs of the fan's power supply. Alternatively, replace a 120VAC fan with a brushless 12VDC fan. Run the DC off the heater supply, using a rectified branch off the heater supply. Yes, this may make the heater winding run hotter, but there's a fan! This runs the 12VDC fan at about 9VDC, which is fine. Note that if you drop a fan's voltage supply too low, it won't be able to start spinning, and so will burn-out; so feed it as least 75% of its rated voltage, and make sure it starts reliably.
It doesn't take much air motion to cool an amp, so slower air speed is fine and less noisy.
-
> the fans are too noisy
PLAY LOUDER!!
Agree that if the designer felt a fan was needed, despite the obvious annoyance, then it surely IS needed.
Sometimes they are over-size, and I have slowed fans. Even to half-voltage, for network gear over-designed to survive an A/C failure in a desert hut but now loafing in my office. But I would be real wary of doing this for someone else.
-
Thanks for the input. I agree with PRR and do not want to bear the responsibility of damage to these amps. Fan noise on these amps seems to be an issue that Egnater needs to address.
Dan