Found my first kit radio: 42 year old 5-Tube AM

Started by cockpitbob, October 19, 2016, 09:20:41 pm

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October 19, 2016, 09:20:41 pm Last Edit: October 20, 2016, 10:08:15 am by cockpitbob
I was going through my massive piles of boxes in the basement and found a gem in one.  In high school electronics class we all built a kit AM radio.  The Graymark Model-510 5-tube AM.  Apparently it's based on a fairly standard design my Dad referred to as "the all American 5 tube" design.

I have no memory of how much the kit cost or if the school provided it then, but the new-old stock kits seem to be going for $300 on eBay.

I took a risk with the capacitors and just plugged it in.  It still works after 40 yeas of sitting in a box!!!!
It takes about 30seconds to warm up.  And "warm-up" is the right term.  The top of the radio feels uncomfortable warm on one side. ;D
It seems just a little deaf, so I'm trying to find the manual for it so I don't have to do an alignment without guessing.

Beautifully clean inside.

It's all point-to-point wiring.  No circuit board!  I did pretty good soldering back then, though my dressing the wires wasn't very artistic.

So, if an EMP takes out all my transistor based stuff, I've got an all tube receiver.  Of course with the grid down I have no idea how I'll power it since it needs high voltage to run the tubes  :o


Very nice Bob! Does it plug in the 110V grid power directly? Power supply is the  main reason I haven't built a tube radio yet..



October 20, 2016, 10:06:17 am #2 Last Edit: October 20, 2016, 10:10:11 am by cockpitbob
Yeah, it's AC powered.  I found a schematic for it.  I haven't found a manual, but the 5-tube AM is such a common design I've found old and modern articles on how to do the alignment.
There's no chance of powering it from batteries.  It's a hot chassis rig! :o  Note the 5 tubes' filaments are in series directly across the AC power line (lower right corner) and V1 is rectifying the AC, so it's got 170Vdc inside!

But it works!  I was listening to part of the $h!t show, I mean Presidential debate on it last night while I was looking for more info on it.