This week @ Tech-tut (August 13, 2010)

There’s not a lot going on this week. I’m finishing up the second tube amp build. This evening, and probably at lunch, too, I’m going to finish the V1.3 changes. I intermittently changed some things that were not noted in the schematics prior to V1.3, and I need to change them back. I am going to make a video or two to post to Youtube to demonstrate the amp. Nothing beats seeing. Seeing is believing. I want to install a switch to change from pentode to triode mode like the AX84 project did, but I’m still debating whether or not it’s worth doing. I’ll probably do it, and if it doesn’t sound different, I’ll just be stuck with it.

I also had to add a DC cooling fan to blow in the cabinet because the LM317 cases get fiery hot. The temperature of the heat sink was over 180° F after an hour of playing. The chassis was around 150° F. That’s just too hot. The EL84 runs at about 350° F, but I’m pretty sure that temperature is acceptable for a power tube. I suspended a fan to blow on the heat sink to see how much noise it imposes on the amp, and there is none. I also checked to see how direct the air needs to be to keep it under 125° F. Direct it stays under 100° F, but I’d wind up sticking my hand in the fan every time I went to turn it off. I made a makeshift bracket from a scrap piece of 1/8″ aluminum sheet. I put a piece of vinyl to keep the fan from rattling on the bracket. A picture of this is certainly worth a thousand words.

BTW…I played the amp this morning at 7, and it sounds much better now that I changed the first preamp stage’s cathode bypass resistor to 2.7k. :) This makes me happy.

I spoke with Grayson Sigler about the micRo CNC router delivery, and they were running a little behind due to a family illness. I expect within another week or so I’ll be pulling hair out learning a new skill. I’m glad that Grayson and Lumenlab are happy to help. I have also sought help from Pcb-gcode.org and probably others. I want to gain as much knowledge and experience so I may also be of help in the future. You can expect that the CNC routing experiences will be heavily blogged and video logged.

Other than waiting for amp parts to arrive, everything is calm on the tech front.

“It’s more than just a project.”

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About robbie

I am an electronics enthusiest and a ham radio operator (W1RCP). I like to play with electronics. It's fun and educational. I looked forward to working in the engineering field in the future. I have a BS in Electronics Engineering Technology from DeVry University. I also have an Associate's degree in Marketing Management from Moultrie Tech, and a diploma in Electronics from MTC.

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