[ForSale-Swap] FS: 1930's Rack Rig Project

Sat Jan 10 14:35:31 EST 2009

Sure sounds like a lot of fun Don...have one of those, similar, in my basement waiting for rebuild, traced the owners back to WLW engineers here in Cincinnati, uses a pair of RK-20's in the Final, RK-31's in the modulator and weird Fan (outside of cabinet mounted) meters, 10 of them in total...good luck.

73, Tim K8WBL

"I Need Mo Powa, Cap'n!"

--- On Fri, 1/9/09, Don Merz <n3rht at yahoo.com> wrote:

From: Don Merz <n3rht at yahoo.com>
Subject: [ForSale-Swap] FS: 1930's Rack Rig Project
To: forsale-swap at mailman.qth.net, "Glowbugs" <glowbugs at piobaire.mines.uidaho.edu>, "BASWAPLIST" <baswaplist at foothill.net>
Date: Friday, January 9, 2009, 8:31 PM

FOR SALE: $150 Rack Rig--Originally 50T in Final. This is not shippable--it's in a 6 foot rack. Pick-up only in Pittsburgh, PA.

This rig came to me in pieces. The steel front panels had been attacked by acid from leaking lead-acid batteries and rusted where the acid ate off the paint. he whole rig was allowed to weather in bad storage and has some surface rust on chasses, panels and brackets. All that being said, it is still a worthy restoration project. Read on.

The 50T rig has six 19 inch panels, from the top: Antenna Tuner, RF Final, Exciter, Modulator, Medium Voltage PS and High Voltage PS. I replaced the top 4 panels with new ones, cut and drilled exactly like the old ones. I polished the Crowe knobs and Triplett meters. I replaced the open relay rack with an enclosed rack on a wheeled stand. I stopped there and have done nothing to electrically restore it. But it looks great!

The antenna tuner has been hacked up pretty good. It has one missing cap and one bad thermocouple ammeter. The wiring is a mess. If you want to use this, it will need completely rebuilt.

The RF final deck is single-ended with a 50T and designed for plug-in coils. The coils must have been home-wound--the 5-pin jack bar does not look commercial. 3 meters: Grid MA 0-100, Plate MA 0-300, and filament volts 0-15. Two caps are grid tune and plate tune. A pilot lamp is connected to the filament transformer. The wiring is mostly intact and/or restorable. The coils I have are junk and probably not original to the rig. There is no 50T final tube. But I may have some RCA 808s--see below.

The exciter is a 6C5 xtal osc driving a 6L6 (doubler?) pushing an 807 (buffer?). Output of the 807 is link-coupled to the 50T final with sloppy wiring. 2 meters are switchable among all 3 stages 0-5MA grid current and 0-200MA plate current. Each stage uses plug-in coils. The 6C5 and 6L6 use plastic Hammarlund-style coils. The 807 uses the same unknown 5-pin jack bar as the 50T final. Two pilot lamps indicate filament power and ???maybe xtal current? I think all three tubes are there. The wiring is mostly intact and/or restorable.

The modulator is designed or 4 2A3s, 1-56 and 1-57. None of these tubes are present. The mod TF is Thordarson 7D84 which is designed for 801 to 3 different load taps with max Dc thru secondary of 200MA. The interstage TF is Thordarson 6422 which is designed for coupling PP 2A3s to 800, 830B or RK-18 grids. A third TF is Thordarson 4304 which is a 1:3 ratio TF for coupling a single tube audio stage to a PP audio stage. The wiring is mostly intact and/or restorable. 

The medium voltage PS deck supplies all filament power and uses 2 5Z3 tubes to supply some other voltages. It also has some questionable power switching. Has some loose wires and looks altogether pretty suspicious. Probably needs a complete rebuild. 

The HV PS uses 3 83V tubes in parallel. The centerpiece is a Thordarson T-7127 TF which is 825-0-825 at 250ma. This TF my be okay. There are 2 chokes and a filament TF that look to be in bad shape. One cap is an Aerovox, but the other is weird and may even be home made. There is some push-button/relay gizmo that is broken and two rheostats which are both disconnected. I think this deck is junk.

I had some ideas for rebuilding this TX, as follows:

Antenna Tuner: The Stancor Hamannual 3rd ed has a similar tuner and that could be used as a guide to rebuild this one.

RF Final: The 1939 ARRL Handbook has a single ended final that would work with RCA 808, Eimac 35T or 35TG or Taylor T-55. This would use B&W TVL coils, though BC-610 coils could probably be adapted and might fit in the space available.

Exciter: Restore it as-is. A very similar exciter appears in the Stancor Hamannual 4rd ed.

MV PS: I think this is restorable and useable pretty much as-is. 

HV PS: Replace with another one built from scratch to provide needed voltages, probably solid state.

I have all my notes, copies of various circuits that might be useful and so forth to go with the rig. 

Your winter project awaits!

$150 pick up in Pittsburgh, PA. 
Don Merz
412-735-4959
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