voltage checks


Not many exciting build pictures today, folks, mostly a verbal report.

First, several posts ago I shared a little addendum about the hand tools that you’ll want to have for this build. There’s one additional tool that you’ll need to purchase or borrow for this phase of the build: a digital multimeter. It’s typically a little box, battery operated, with two probes attached by wires, one red and one black. The one I use, below sells for just shy of $12 at Fry’s.com.


You can measure all sorts of electrical values with this gizmo, but for our purposes there are two really important things you can do with this magic box.

First, throughout the build, and especially the wiring phase, if you want to be certain that something you wired is really connected, you can set the meter to measure resistance (Ohms), touch the probes to the beginning and end of the part you want to test, and see if the numbers on the meter readout jump around. If they do, you’re in good shape. If not, it’s time for head scratching and troubleshooting.

Getting back to our build, with all the interwiring done, it’s time to begin to check our wired connections against the tables and diagrams in the assembly manual. This can be a tedious process, because at this point you have wires running every which way underneath those PCB’s, and following the path of a single, black wire, for example, can be difficult. This, again, is where the impedance function of your multimeter can help you to test your connections.

At this stage of the build, we finally get to install our fuse in its little compartment in the IEC power cord connector. No tubes are installed in their sockets yet; we still have the amp upside down and the bottom cover removed.

We flip the power switch and hope nothing starts to smoke. It doesn’t – awesome!

Then we use our meter to check that the voltage across the fat pins of the 300B tube sockets is 5V DC… and it is!

More voltage checks to come, after which we’ll install all the tubes except for the rectifier and we’ll see if they light up when we switch on the amp.

Until then…

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