The AM Forum

 

   Trying to fix a WRL Globe Champion 300. The problem is that I've lost filament voltage only to the initial stages of the Speech Amp. There is no filament voltage for the 6AU6, 12AX7, 6AQ5 and the 6AL5. I've checked the tube sockets, cleaned them and looked for a bad solder connection on the filament string and re-heated  the string, however still no filament voltage. Any suggestions?

Thanks Tim
WB8UHZ

Filament feed to the speech amp section is controlled by a switch on the audio gain control, make sure the gain is turned up and if so check for a bad switch section on this control.

 Thank you. That switch seems to work OK when testing with a volt/ohm meter but I'm thinking if I can find one just replace the switch entirely and see if that fixes the problem. What do you think of just bypassing the  switch?

Yea, just jumper around it and see what happens. If the fils light up, replace it. If you don't use the Champ on CW, the switch of no use.

  Thanks

  I'll jumper it and see but it works using a VOM.

Some champs had a seperate switch below the mic gain.  Some had the switch built into the mic gain POT.

Make sure one tube does not have a dead short in the speech amp by yanking tubes out.

C

 Thanks, yes I have tried other tubes as well but still no filament voltage.

Are the filaments lit on the 2E26, the 12AU6, 6CL6?  If so and the wire from that switch beind where the mic gain pot is attached, you may have an open or missing wire connection to where it terminates.

  Jim

Thanks. The 2E26, 809, 6CL6 all have filament voltage but they are supplied by a different tap on the transformer. The speech amp filaments are for the 6AU6, 12AU7, 6AQ5 and 6AL5, none of those light up.

You probably just answered your own question.  A different tap on the xfmr.  Have you tried to measure the filament voltage on the other tap?  It's possible that the xfmr filament winding is open.

Fred

Has the transformer been replaced with a non standard version.  In the standard version there are two 6 volt windings, one for the 809s and the other for the rest of the tubes.  The finals are supplied by a 12 volt winding.  The diagram shows the 6 volt winding in question supplying the 2E26, 6CL6, the 6AU6 in the VFO and the 12AU7 keyer.  Following that is the switch for the audio section on the same winding and the tubes you don't have filament supply on.

If you have a different transformer then that won't be the case and you should measure the voltage on the winding supplying that switch.  If nothing is present then you have a bad transformer or the wire supplying it is disconnected.  You can remove all the tubes in the audio section and used your ohm meter to measure from that switch to each connection for the filament supply on each tube in the audio section. 

From what I am reading, you may have the wire from the switch to that series of tubes either disconnected or missing.

If the transformer is original it is possibly a broken wire at the switch which I believe then goes to the 6AU6. It was on by one strand on the last one I worked on and then broke off during a QSO but the rig was standing on end and easy to see.

Carl

Yo'


   4X150's are a sweet sub fer the AX-9909's.
"Cheap flat sockets"1. make it the way to go.

1. T195 Mod deck.

/Dan

No need to modify the rig.  You can use the Tungsram OS51 ( 6083 or PE1-100 ) tube which is a direct drop in replacement Tube.  They are not expensive and plentiful.  Output power is about the same.  Maybe a tad less.

C

5894

7094. Only one is needed.

I have two sets of spare AX9909 tubes so probably have enough for at least the rest of my time with my Chump 300.

Out of curiosity, does anyone know if the 7094 requires a different socket than the AX9909? I realize the plate lead needs to be move, and possibly other rewiring.  But I'm having trouble figuring out if a different physical socket is required.

The 7094 has also reached almost dodo bird status and didnt do very well in the HT-41. Not one of RCA's better ideas.

While a pair of 5894's will do well a pair of 7854's will be better along with their Motorola numbered equivalent which I dont remember offhand.

Carl

Tim WB8UHZ, has used/run the Globe Champion 300 transmitters for many years.

Hopefully he'll get back to the forum/list here, and let us know if he got the filaments lit up on those tubes or tracked down the original problem that he had asked about with that transmitter.

Al VE3AJM

The Motorola part numbers are 97-136-A01 and the generic number is Amperex 8643.  They have a more roubust  plate structure and higher rated HV (750 if memory serves).  I have a pair in my Champ and they work very well.  The 5894 does fine also but the HV rating is about 600 volts.  The 5894 will be ok in the Champ with the normal duty cycle a ham uses.

Thanks Jim. I just wish the 300 I had here last year didnt already have a half assed 813 conversion when my customer got it. Took a lot of work to get it sorted out as well as efficient on 10M. I already had a couple of NIB 7854's and the Motos also but the sheet metal had all been hacked away.

Carl

What a shame Carl, I suppose some previous owner had an 813 and didn't want to buy something else.  The 5894/8643 is a very easy conversion.

I was able to turn up three 7094s by just mentioning on the air that I was looking for one. I've seen at least a half dozen at fests since. Yea, they're not common, but not impossible to find. If you get two, you'll have a lifetime supply for use in the Globe Champ.

Condition and price?

 

    Thanks for all the comments. I found the problem with the GC 300. The Gain switch was bad. I had 6 vots on once side of the switch but not on the other. Both sides of the switch must have the voltage. Of course there was no voltage on the filaments of any of the tubes in the speech amp, those noted. What I have done so far is jump the switch and the filaments are on and using the rig and enjoying it again.

Thanks 73 Tim
WB8UHZ

Two were new and with very late date codes. One was used but worked FB. Some of the ones I've seen at the fest did appear to be well used.

The way I would approach the mod is to look for a 7094. If one is found in good condition for an reasonable price, go for it. Otherwise, I'd move on to the other options mentioned here. The good thing is that there are more than a few good options.

I managed to get some spares for use with my Viking I or 32V2, or finding a Globe Champ tx. That was back in the day when the 4D32 tube was extremely hard to find at a reasonable price, and I managed to find some new Cetron 7094s with a military sticker on the side of the tube box at a more reasonable price.

I always thought they were a cool tube, right from reading about their use in that 200 watt transmitter in the ARRL Handbook from the late 50s, after the run of the Chambers 813 transmitter in the Handbooks, and with Steves letter to ER magazine about using them in his Globe Champion.

Al VE3AJM

The 7094 was RCA's attempt to update the 813 but it certainly was not very rugged in the few commercial products that used it. All the ones Ive seen the past few years at hamfests were in the $100 range for NIB and not much less for used ones which I didnt trust. At online tube bandits they are around $200 each....dont know how many sell at that price. The same sources have the 7854 at around $75, still not cheap.

In a Champ at half the voltage the 7094 sounds like a lifetime swap.

I went on vacation this week and on the trip picked up a long wanted Globe Champion 300.  It is in the back seat of my car until I get back home to Texas in a week.  I have not opened it up yet but the prior owner has told me the final AX-9909 tubes are missing plus the 809 modulator tubes.  The rig has not been operational in over 25 years and it looks abused.  I know I am going to have to have a replacement dial cover for the VFO replaced as it is beyond use as it is so cloudy you can't read the vfo markings.  I sure hope the iron is OK.  I am suspecting the transmitter may have to be stripped and rebuilt from the ground up, but I sure hope that is not the case.  I got it FREE, so I can't complain and now have some wiggle room to invest money into the restoration.  This is not going to be some simple one week restoration project and not for the faint of heart!

As bad as the girl looks right now,  I'm excited about obtaining it and eventually getting it on the air again.  I think I have found a source for some 8643 tubes for a mod and I am hoping I can find some 809 modulator tubes.  (I don't know what is necessary to swap 809s for 811s bias wise.)

I see Motorola used the 8643 tubes and they tied the plates together with a round top heat sink anode connector with two holes drilled in it to accept the anode pins.  I'm thinking of finding some aluminum round bar stock and trying to make a couple anode connectors this way.  if anyone has some used Motorola ones for 8643,  I'd sure be interested in obtaining them from you.  I know the 5894 tubes had smaller diameter anode pins but maybe the spacing is the same and I could just drill those out bigger if ones for 5894 tubes were available.

Anyone have any 809s they could part with or know how to use 811s instead?

Lee, w0vt

Just plug in the 811s and run them zero-bias. They do draw more filament current. If you are concerned, put in a separate fil tranny for the 811s.

Thanks, Steve.  that is easy enough!

Lee, w0vt

Hi Tim,
Nobody mentioned the 4D32. I have a transmitter with a 4D32 in it( Viking 1-1/2) I am running 1000 volts on the tube. I am using a highly modified Globe King 500 modulator deck as the modulator. The 4D32 still has 150 watts outpoot after 11 years of service. About 40 years ago I worked on a Globe Chump. I put a 7094 in the PA. It worked very well,,,, When you could buy them over the counter. I have a Globe Chump that I have been planning on modifying for the last 25 years or so. The Tank circuit in the chump is rather light duty. It is comparable with something you would find in a DX 100 or other 100 watt transmitter. I would not trust it with anymore power than it already has to deal with. I have already stuffed a Globe King 500 mod transformer in to it. The 809s may give way to a pair of 811s., A push pull audio driver, and one 4D32.The Three diode ultra modulation circuit shall be employed. The modulation capabilities of the chump are on the edge. Years ago it was carrier power that sold transmitters. A carrier does not do the talking ,the modulator does. When it is said and done I will probably pass it along. I have enough 100-150 watt transmitters. In closing; if the Philament power switch on the gain pot is crapped out . Just remove it. Get the philament wiring away from the audio gain port to avoid the possibility of hum pick up.
Tim WA1HnyLR

Any relation to the philamentdelpha orchestrator?

Well, Philament is an elegant way of saying filament just as microphonium is for microphone, De Tim WA1HnyLR

No, philodendron.

Tim,
I am about to restore a 300 Champ too.  I'd be interested in getting a description of the cabinet paint job coloring and texture from you if your transmitter has an original cabinet finish on it.  I don't know much about Globe Champ finishes.  I can't tell or know if mine is original but I suspect it is not original.  It appears to be painted with a flat silver paint of some kind.  it is not a hammertone, sand or wrinkle finish.  There seems to be no BLUE or GREEN look to the silver.  How does this compare to yours?

Lee, w0vt

I'd be interested in knowing from you experts if it would help to parallel or strap on some more capacitance to the oil filled filter cap in the high voltage power supply?  I think the oil cap is 6 uF if I recall correctly.  Seems kind of marginal to me.

Lee, w0vt