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April 2013 "The Retro-Shield" Article by David Goodsell

Posted: Tue Mar 26, 2013 6:36 pm
by BobCochran13
This is a very interesting project. I wish there was another article discussing how to work with vacuum tubes. I am not sure about doing this project, but supposing I do, I see that MDB Ventures has 12K5 tubes by different makers. I'm not sure which one to pick or how to get a coil for it -- or even what a coil looks like for these tubes. I'm also not sure how the photos of the tube and some of its components in the magazine assist with actual assembly of the tub onto the circuuit board for this project...Thanks for any comments or suggestions...Bob Cochran

Re: April 2013 "The Retro-Shield" Article by David Goodsell

Posted: Tue Apr 02, 2013 12:13 pm
by dgoodsell

Glad you found the article interesting. It does not matter which 12K5 you purchase, they all should work. The oscillator coil(L1) can be purchased from Antique Electronic Supply for $8.95. Be sure to also buy the $0.95 S-T9304 Oscillator Adjustment Tool set.

To mount the tube socket, I used a pair of 3/16" x 3/4" long hex spacers. The other components are located near their connection points, as shown in Figure 8 of the article.

Here is how I would build this project:
1. Buy all the components.
2. Place them on the circuit board in the locations shown in Fig 8. Move them around to fit.
3. Drill the mounting holes where needed.
4. Do the Gnd Bus, using #20 tinned copper wire.
5. Using the schematic as a guide, wire up the RF Osc section, which includes the tube. Be careful not to damage the delicate oscillator coil.
6. Do the RF Monitor section.
7. Lastly, tackle the Audio Amp section, which is pretty crowded.

I'm here for any other questions.

Good luck.