Gen. Radio Model 1931-A Mod. Monitor (monkey business)

[Superhet66]

Monkey swing thing.

It might be putting the cart before the horse but I grabbed this for future use anyway.
I'll have it in my possession Friday pm.

Physically it's very clean. 

I'm starting to regret not grabbing a cheap, nice, 72" high rack not far from me . I never thought I would be accumulating rack based BA gear.

I won't ask any Q's just yet but I'm curious if anyone has worked with one of these  as a Jockey / BC tech./ Mad scientist...                                       
                                             
                                                          73          DJ

[w1vtp]

I was watching that beautie.  So you're the lucky dude.  I'm going to have to paw through my manual archives and see what I missed

[Mike/W8BAC]

I used to own one. I traded it to Paul/VJB a few years ago when I upgraded to an REA. They work fine and are built to last a long time. I hope you got a manual with it. A drum inside has to be turned or tapped for your frequency range. That's not hard at all. Some testing with a scope will tell you if it's working right. Good luck.

Mike

[Superhet66]

I was watching that beautie.  So you're the lucky dude.  I'm going to have to paw through my manual archives and see what I missed

The Mad Scientist!  

Hello Al,
I couldn't resist. I drive right past the person that was selling it once a week.
I hope I didn't step on any toes.
Any info would be appreciated  
From looking around, people seem to like working with them. (I like how they move the coil thru the field to get it in range.)
I think this comes with the lower freq. range set, 0.5 to 8 MHz, the other covers 3 to 60 MHz. I'll know more once I pick it up.

Thanks mike, you posted while I was tapping away here.

 
Fine job on the new digs over there bye the way!
                  
                                                 73   DJ

[WBear2GCR]

uh-oh... he's in trouble now!!

Now all that is needed is a rig to sit under it in the rack?

                          _-_-bear

[Jeff W9GY]

Had one at the little BC station I worked at in the 60's.  The thing never missed a beat in the three years I was there.

[Superhet66]

It's a relief to hear input from guys who worked with this monitor, thanks
( Mike, Jeff )

uh-oh... he's in trouble now!!

Now all that is needed is a rig to sit under it in the rack?

                          _-_-bear

I have one!    , I just need to plug the Weller in and put my thinking beenie on.

The Yazoo 101 will be my pal for a while. A PS filter cap / bleeder set is on it's way.
It may not solve the soft hum but it's a quick upgrade from the 30yo caps in there now.

I picked up a nice garage sale score. A 1950's grey metal table with a rubberized top. (I have a heavy lug to ground the steel table.) I grounded my other shop table after a 220v punch to the elbow.
I will be dragging the equip out of the bedroom and into the spare room here.

A few hundred pounds of BA gear in the budoir is not considered sexy by most YLs. In fact it can act as a form of birth control 

                                                                         DJ

[w3jn]

That thing is sweet - I have one - but it needs a pretty healthy RF drive to be able to set the munkey swing to the 100% cal level.

[N2DTS]

I used one for many years, before I got the rca/belair mod monitor.
One advantage it has is you can set the carrier level to 50% and read up to 200% modulation.

The disadvantages are, it needs to be retuned for different bands, it takes some drive, and I am not sure about the audio quality out of the unit (don't remember).
I gave mine to WA3JVJ who still has it.

Big power hog, but cool looking and reliable.

Brett

[W3GMS]

It's a fine piece of vintage gear.  I use one with my 1941 Gates 250C1. 
I am sure you will enjoy it.
Regards,
Joe

[steve_qix]

I own one, and have fixed many others back in the days before solid state mod monitors.

In its stock form, the mod meter only reads to 110% (if you set the carrier level properly).   However, a modification we used to do was to remove the meter face and re-do it to read to 130%, and then recalibrate the meter to read correctly.

As I recall, it takes about a watt of power to run it.

[W3SLK]

I have an old Triplett Modulation Meter I got off of ED, N3GreatWattEmitter, that uses an 82 tube, (since replaced with a 1n34). Strange though. You adjust your coupling for 50% carrier and that is it. The only problem is no tuned circuits. It all depends how well you couple to the RF.

[WA3VJB]

Yes ! As Mike mentioned, he sent along to me a 1931-A.

Glad this latest one has (also) gone a good home !

You noticed the selectable coil assembly in there? Upper left in the underside shot. It's a tuned front end that takes the 1931-A right through 40 meters. I'd be surprised if you found the "shortwave" version, they are as rare as the Gates HF-1.

Gorgeous lighted meters, you'll enjoy just watching it.

General Radio marketed their units in collaboration with several broadcast transmitter manufacturers.  

As a result, the 1931-A can be found today in Raytheon Brown, General Electric metallic green, Collins metallic gray, and the large-grain "texture" gray that General Radio used on this and their sound meters, Variacs, and other instruments and devices.

Trying to see what paint you may have on there; the shot of the percentage meter suggests it's the GR paint scheme.

These were very popular before the FCC changed measurement standards to match the permitted 125% modulation level, with overshoot to 133%.  Many of them remained in the equipment rack even after they were "replaced," to deliver air audio from the transmitter out to the radio station's front office, sales department and in many cases the studio headphone off-air monitor.

I have to think many of them also have been jettisoned by corporate owners who don't want equipment around that's not type-accepted.

[Superhet66]

Thanks for the history, Tech and reviews. Some mentioned it was a Watt Hog.
Does the 1 watt drive tell the whole story or is there additional "lossyness"?
I'm still doing my homework here.
I would not modify the meter face but I like the idea of 130% range. I could be non-destructive and make up a clear overlay and calibrate accordingly.
The finish is black w/ an alligator like satin wrinkle finish.
It will sit in its' foam capsule until I have a suitable home for it and I'm familiar enough not to hurt it.
                                                      Tanks,  D
 

[steve_qix]

I think a watt is fairly accurate on the broadcast band.   I can't speak to the other bands, however.  On the meter face - right, no reason to actually modify the original face.  I put a removable overlay over the original meter face and it worked like a champ.

These modifications (to make the unit read accurately to over 125% modulation) were made to units in use at the time (during the early '70s) at broadcast stations when I was a consultant.  It was surprising how many there were and in use at that time.

Regards,

Steve