Radio Preppers

General Category => Technical Corner => Topic started by: cockpitbob on October 19, 2016, 09:20:41 PM

Title: Found my first kit radio: 42 year old 5-Tube AM
Post by: cockpitbob on October 19, 2016, 09:20:41 PM
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.

(http://i120.photobucket.com/albums/o170/cockpitbob/SAM_2337_zpsojzqdzqp.jpg) (http://i120.photobucket.com/albums/o170/cockpitbob/SAM_2337_zpsojzqdzqp.jpg)

Beautifully clean inside.
(http://i120.photobucket.com/albums/o170/cockpitbob/SAM_2342_zpsgkqpubve.jpg) (http://i120.photobucket.com/albums/o170/cockpitbob/SAM_2342_zpsgkqpubve.jpg)


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.
(http://i120.photobucket.com/albums/o170/cockpitbob/SAM_2339_zpszy5zlruh.jpg) (http://i120.photobucket.com/albums/o170/cockpitbob/SAM_2339_zpszy5zlruh.jpg)

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
Title: Re: Found my first kit radio: 42 year old 5-Tube AM
Post by: gil on October 20, 2016, 03:49:42 AM
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..

Gil.
Title: Re: Found my first kit radio: 42 year old 5-Tube AM
Post by: cockpitbob on October 20, 2016, 10:06:17 AM
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.
(http://i120.photobucket.com/albums/o170/cockpitbob/usa_Graymark_kit_510_AA5_poster_zpspxxlcllb.jpg)