Hello, steemians, and welcome to da workshop, eh!
My friend Adam brought several amplifiers to me in August to work on for him, among them was a 1972 Fender Bassman 100 head. This is one of the early master volume heads that Fender produced in the 1970s. Some people really liked them and some people hated them because they weren't the same as the early 1960s amps. Personally, I like them because you can get more variety of sound settings with the master volume than you can without it. Another criticism of the 1970s amps was that they were "too clean" sounding. That might be a legitimate critique of the guitar amps, but for a bass amp, you need the power and clarity to be heard in the mix. When I was playing live with the band that I used to be in, I had a 1974 model of this amp that I used. Even with 100 watts of power, it was hard to keep up with a 50 watt Marshall amp. It comes down to a matter of how much power is necessary to push bass frequency sound as opposed to the midrange of a guitar amp.
This is the amp.
With this particular bass amp, when it was brought to me to check it out, it was unknown if it worked or not, and the power tubes were not in the amp. The first thing I did was to pull the chassis out of the cabinet so that I could inspect the wiring and the parts to see if everything was the way it's supposed to be. All of the parts in this amp are original, no replacements or modifications were found, except possibly the power cord. That thing is a lot longer than they normally are.
Everything looked ok on the inside of the chassis.
The power supply capacitors are mounted under a cover on the top of the chassis, so I pulled the cover off to take a look at them.
There was no broken wires or burnt parts under the cover, but I noticed that a couple of the capacitors were starting to leak a little bit, not usually a good sign. These things can leak in the same way as a battery, and then they don't do what they're supposed to do. You can see the leakage on the end of 2 of the capacitors. These are the original capacitors from the factory in 1972, so it's pretty impressive that they're still in this good of condition.
I decided to test the amp and see if it worked, as nothing seemed to be bad enough to cause it to blow a fuse. I found a set of power tubes for it in my tube stash and put them in, and gave it a test. It actually sounded better than I expected. I expected it to have a lot of buzz due to the old and leaky power capacitors, but it was fairly quiet, all things considered. After discussing the situation with Adam, he decided that it would be a good idea to put new power supply capacitors into the amp, for reliability if the amp was being used. He buys and sells these amps, so it's a good idea to have them in good working order when they're sold.
I had to order the parts, so the amp was put aside for a few weeks until I had both the parts and the time to get the job done. I finally was able to get back to the amp a few days ago and finished the rebuild.
I put the amp back together and tested it again to make sure everything was working right. After blasting out my eardrums and scaring all the cats, I decided that the amp was good to go. :-)
Here's a look at the back of the amp. When Adam brought me the amp, there was no back panel on it, so that's why it's missing here.
Well, that's all I have for this post, I hope you found it interesting!
Thanks for stopping by and checking out my post, eh!
Feel free to leave a comment if you would like.
