GOM

My Ampeg fan started to make quite a bit of noise - not noticable when playing but a pain when at home practicing. Find out the fan voltage (and size) and have a look at [url="https://www.quietpc.com/acoustiproductsfans"]https://www.quietpc....stiproductsfans[/url] and see if they have an equivalent. I can't hear my fan at all now after having replaced it.

There should be a label on the fan giving the operating voltage. Have a look at http://www.quietpc.com/casefans

Those "thuds" are definitely something wrong with the amp ... it used to be called "motor boating" - no idea why - as Icastle said the most likely cause is the power supply coming up, overloading, going down and then repeating ad nausiam. Get it looked at by a tech.

First the easy part - yes, both test points need to be the same as the pots provide the grid bias voltage to the EL34s. Now the guess work ... there's a good chance that the 50W version only has a pair of EL34s instead of the 4 in the 100W. If that's the case and the cathode resistor is the same then the voltage would be half of the 75mV as you only have a standing current flowing through one valve rather than two. In a class A or AB amp the bias defines the point in the valve transfer function at which you switch from one side (of the EL34 pair) to the other. Basically if the bias voltage is too low you'll get distortion and if the bias is too high the EL34s will run hot(er) than they normally would. Would be nice to know what resistor value you have for R120 and R127 and what the HT voltage is (488v on the 100W). P.S. that 38mA is the standing current through EACH EL34.

Hmmm, sounds like the power supply might not be up to the job. What happens if you leave the Shimverb in and remove one of the other pedals?

I have exactly the same (3 hole fixing) bridge on my Deluxe PB which I'm just about to change for a Babicz FCH. (also changing the bridge on my Gibson SG for a Babicz). His Website is: http://www.fullcontacthardware.com/ and I bought mine from bestbassgear.com

Not rosewood but ... [url="http://www.thomann.de/gb/kala_u_bass_thumbrests.htm"]http://www.thomann.d..._thumbrests.htm[/url]