The AM Forum

I recently acquired a near mint G 50. The transceiver has all the original tubes in it from 1961. I don't have a button type mic plug so I have not tried it on the air yet.

What do you fellows know about this rig? Seems like the engineers decided not to use a voltage regulator in the oscillator which may have helped it to remain on frequency or limit drift. The modulator is a hysing type with no modulation transformer. It states in the operating instructions that you should not exceed a 5 minute old buzzard transmission otherwise damage would occur. It's for AM only, no CW. It has a spotter on it to determine where your at but that function does not work with the crystal in line. Did anyone ever do any mods on this and for what purpose? It uses a fused plug with fuses that are very hard to find. The power transformer runs very hot. I seen one on ebay minus the power transformer. Perhaps this is one of the weak points on this rig?

Any thoughts are welcome.

 

I've had several over the years. Top of cabinet became too hot to even touch after being on for half hour or more. Don't recall any weird fuses in the holder. Rig worked well but drifted all over the place after initial turn on. Don't recall any published mods for the rig other then maybe put a muffin fan on top of the case to draw away the heat. Parallel 6L6's in the audio put out some healthy modulation.

I have one (and its G 28 10 meter sibling).

Like Pete says, you can use the top as a hot plate.  It does drift but most of the vintage AM stuff on 6 meters has a wide receive bandwidth so it won't be too much of a problem.  You could always use a crystal for nets or an external VFO if drift is too much for your taste. 

I don't recall the transformer getting excessively warm on either of mine during restoration/testing.  Maybe bad filter caps or a bad coupling or bypass cap in the audio section of yours?  You could reduce the transformer load a bit by replacing the 5U4GB rectifier with SS plus a dropping resistor.  I did this to reduce transformer heating in my Hallicrafters SX-42 and 62 receivers but I didn't feel the need to with the Gonset.  The 15 watt rectifier heater load is a significant portion of the total steady transformer load.

The receive section is sensitive enough for my use and sounds good.

All in all a nice looking functional box.  The later Japanese stuff (i.e. TS-600, FT-620B, FT-625) will outperform it EXCEPT for the nicer transmit and receive AM audio.  They also won't keep you shack nearly as warm on a cold winter night.

I also have a G-50 and ditto the above remarks.  It runs hot, but that could be helped with a small muffin fan to help circulate some air through the cabinet.  It is all in all a great 6 M AM rig.  Back in the day, they were considered to be the Cadillac of rigs, since everyone was running only 10-15 watts and the G-50 would do about double that.  Mine puts out about 28-30 watts.  I use it to check into the local 6 M AM net and always get great audio reports.

73,  Jack, W9GT

I have a G-50 here as well.

To me the modulator was unacceptable, and after a few tries, I settled upon a satisfactory solution.

Here are the issues as I see them:

1.) Restricted frequency response (no lows)
2.) Unable to modulate > 50% without severe distortion, but does get better above 500 hz
3.) way too much heat

So items 1,2 go together much like they do with the Retro-75. With the G-50 the Heising choke must pass both the class A modulator current, and the 6146 RF amplifier current. The core saturates as you run up the audio. There is nothing you can do to overcome this without doing major surgery.

I've covered this before on AMFONE, but never much interest. The solution was to use a push pull audio output transformer where the HV goes to the CT, and the modulator to one side, and the RF amp to the other. So this way the magnetic fields in the transformer subtract, and if equal currents are on each side we have no net magnetic field. Now all the trouble goes away like the blink of the eye, and we can modulate fully and cleanly to < 100 hz and up to and beyond 5 Khz.

Addressing item 3, the heat, is easy too. Just cut back on the modulator cathode current when in receive, and add a fan.

Some info (pics, schematic, scope shots) here:

http://pages.prodigy.net/jcandela/G-50/

Jim
WD5JKO

Hi Terry,

I too have worked on a number of these G50s.  The radio is very effective for 6M AM.  As to the heat, the major issue is the rectifier.  You can solid state it and cut down on the heat quite a bit.  The TX audio is all pretty much typical Gonset.  The shared audio/mod xformer as noted here doesn't give lots of audio, but for 6M it is sufficient.  The T/R switch is frankly bad.  It swithes some 14 contacts just for PTT ;D and it is a cause of much aggrevation.  Pete VZR told me he replaced one with a 14 pole relay  ::)

A couple things you can do:
1. Keep the set screws on the PTT switch tight.  
2. replace the 6L6 bypass cap with a 100uF
3. The radio has receive hum (60 cycle).  I hate hum so I tracked it down after noting it on every one I worked on.  It is caused by the proximity of the audio xformer to the power xformer...they are next to each other and the audio xformer has no shield.  I knocked out the hum by adding a ferrous piece of metal(steel...copper will not work) between the xformers (about 3" square with a bent plate on the bottom or clips.  Then rotate the audio xformer about 45 degrees.  I use a scope to null out the hum when rotating the xformer.

The VFO drifts wicked until it warms up.  I use a crystal as everyone is on 50.4 anyway.

my .02..

Pete

Im another who had a G-50 for awhile in the early 90's....nuff said about its faults.
I might rate it as a Pontiac but certainly no higher as there was better available. The only Cadillac of the day was The Clegg twins Zeus and Interceptor which is what replaced the Gonset.

Carl

Carl,

I have a Zeus/Interceptor pair in the waiting to be restored queue.  Do you remember any particular cautions or bits of advice?

Did you have the allbander receive converter for the Interceptor?  Finding one has been difficult and I am curious if it is worth the expense/effort?

I actually have two Interceptor's (Interceptor and Interceptor B) and two Zeus transmitters (one still requires some work). When transmitting, don't diddle with the meter switch. You could blow the meter. Both of my tube Allbanders work great with the Interceptors. Besides the built-in speaker, you have the ability to tune the HF bands (with an attached antenna) at the flip of a switch. There was also a solid-state Clegg Allbander, AB-144, that was produced in the 70's. Great little unit, if you want to transform your 2 meter multimode or any 2 meter receiver, into a HF receiver.

Clegg AB-144 Allbander:

(http://amfone.net/Amforum/gallery/25_10_03_11_3_42_16.JPG)

I have the Interceptor B and havent done anything but touch up the alignment when I got it Roger.

For the Zeus I had a problem with the 4X150 driver plate showing color but dont remember the fix, it was simple anyway.

Besides the weight the PS/Modulator unit is loaded with electrolytics that were replaced. The blown ballast tube got the National treatment, a 6V6, and all is well. I picked one that was well below good on the Hickok 752A since only the filament is used.

The Zeus is so stable Ive used it down with the SSBers for ragchews and even goofing around in contests. I use the TS-830/HA-6 for receive down there altho the Interceptor is fine if there is only one station and minimal fading.

Oh, the original 811A's were soft so I stuffed in Svetlana 572B's that were very unstable in a 6M conversion; they are still there and run damn near cold.

I also did the usual component juggling to widen the audio in the low level stages and run the clipper very light unless Im weak or its noisy at the other end.

All in all its arguably the best of its era.

No converter, I have more than enough radios as it is.

Thanks guys, this input was great! I have saved all information that was submitted ;D ;D

  Jim, what push pull transformer did you use? Looks like a thirty watt transformer would work.

Another thing I noticed without an antenna hooked up is the amount of static that is heard on receive. Even on a dummy load the static is still there?

  I used a junk box special!

http://pages.prodigy.net/jcandela/G-50/New_Mod_XFMR.JPG

No idea of the ratings, but a 25 watter or larger should do. Now if you can find one with primary screen taps, then more options come to mind. Use the screen tap on one side for the 6L6 modulator as this is a form of negative feedback. The other idea is to use the screen tap to offset the turns ratio such that you can get > 100 upward modulation. Here you could connect the modulator plates to the screen tap on one side, and take the Rf B+ off the full winding on the other side. Not sure what the step up ratio will be, but if not too high, this could work.

Jim
WD5JKO