a little help with a BC1-T Gates...

[KI4OWV]

Got the transmitter. Got the H/V worked out I think. Got 8 833's - 2 new. Lot of prob's with modulator and rf osc. I have'nt begun to sort out. How would this thing work if I drove it with a Drake T-4X With the audio mods? That would cure the vfo prob.  (the drake covers 160 as well as 75 and lower.) Instead of using 2  833's for the modulators to drive two finals what would happen if I rewired to 4 833's for the final rf pa's? Sounds good but would it work? 73 de KI4OWV - Max

[N8ECR]

Hey OM,  The drake should drive it ok, but be careful not to give it too much at first, just drive it right into the .01 cp on the 807's driver.  I would not try to make a linear out of the thing , would take all the fun out it, and cause you many head aches.  I have a BC1H and drive right into the 807 as said above with the power very reduced, a johnson ranger works even better as a driver, I guess I forgot to say that I have a resistance in series with the DX-100(non inductive type about 50 ohms, maybe a can-tenna will work here???) to absorb some of the power, you likely better do this as well.  Then your going to have to work on the output network and get into tune before giving it the HV, or the over load relays are going to kick the whole thing off right now.   A small audio amplifier(2 watts or less) with a 600 ohm output is all that is needed to modulate the transmitter.  You might want to catch up with Don Chester K4KYV he couldbe a great help to you , as he has one of those tranmitters

[W7IXZ]

I would try to get it operating as stock, it would be much easier.  If you wanted to drive it with the T4X as a modulated driver you would need to either bypass the 807's and change the 833's to class "B" linear, or change both the 807's and 833's to linear.  Much to much work.  The Gates series of transmitters are the easiest to get on 160, and only a few adjustments are needed.  The grid circuit will tune by just removing any padder caps, and the 833 tank is about as easy to do.  I have 4 Gates here, 3 are BC-1T's and one is a BC-1H.  One of the T's has the rare 6BG6 tubes as RF and audio driver tubes.  Do you have a diagram?  I had to change out a cap on the osc grid to get my crystal to oscillate, but now I use a Johnson 122 VFO to drive the osc stage and it works fine. 
Good luck.
Larry W7IXZ

[flintstone mop]

Hi Max
I have to agree with Larry.............
The TX should be no problem troubleshooting. It should play with little or no effort. I hope you have the manual or schematic. That helps a lot. Lottsa room in there to work. Be careful with the HV and the safety circuits, they may have been disabled.
Fred................I wish Santa would bring me a broadcast TX box   

[Tim WA1HnyLR]

Hnyello Max, I am intimately familiar with the Gates 1T It would be a total waste to make it into a linear amp. The problem you will run into is RF layout.Myself being of limited space if I had a 1T I would strip it down out of the cabinet carefully keeping the wire harnesses intact. I would rebuild the transmitter ito a six foot 19 panel width rackI would mount all of the iron on the floor of the rack . I would add a steel plate shelf or two above the first layer of iron for other power supply stuff. I would make use of the 807 cathode followeraudio driver. This is a very good audio sceme. The big problem with the audio driver board is that the 807cathode follower screen resistors change value and things melt down. make sure that the values are correct. I use a combintion of resistors to get the appropriate values at much greater dissipation than stock.The stock BC1T rf layout uses a fixed tank capacitor and a variable inductor for pa tuning. This inductor has too many turns to be used as a multiband transmitter. I would use the small fixed inductor that is part of the tank circut and go with a conventional pi net out. You could also use the roller inductor that was used for outpoot loading . It has more than enough inductance for 160 M . I would wind a seperate 40 meter series inductor with 3/8 copper tubing. 7-8 turns 3" diameter. Plate tuning and loading are accomplished by a vacuuuuuum variable cap--500Pf@10 Kv or better for tuning and a 2000Pf 3Kv for loading. You could use a 1000Pf cap and one of the .001 mica caps from the original outpoot network as  well. 833 tubes in parallel may be a bit problematic at 40 meters unless good attention to detail is paid with RF layout. Another alternative is to build an RF deck with a pair 4-400s in parallel. This will work well for multiband operation. If you are isistant about the use of 833 A s in the RF ,the stock 807 driver stage is a bit underpowered. It has been my experience in broadcast service that the transmitter has trouble making better than 100% positive modulation at full power. It does well at 250 watts. There is a tertiary winding on the modulation transformer that modulates the rf driver at a low percentage of modulation in order make full modulation.This system works well but the drive levels are still too low. If I were to bother with an onboard driver in the stock transmitter I would probably use a pair of very healthy TV sweep tubes like the 6LF6-6KD6 or the EL 509/6KG6will work well. You could also eliminate the driver stage and use a link coupled grid inpoot. A BC610 plate coil works well.You may have to tap down on one side for the grid connection. Use a dualsection air variable about 200Pf per section 2Kv spaceing. You could use a pair of DX 100 plate tuning caps tied together with a shaft coupling. You will need at least 100 watts of power to adaquatley drive the 833As. A DX100 would work OK . The power supply would have to be solid stated to get the voltage up a bit to make the drive. A viking Vallint would work very well for this service. BUT  the RF outpoot of either must be partially modulated by the tertiary winding on the BC1T mod xfmr. Simple take a piece of two conductor power cable. Run cable from terminal strip on mod xfmr  tertiary terminals to the accessory connector on back of Valliant wire in place of stock modulator hook up. Remove mod tubes from Valliant. I hope this tutorial has helped you out and others that read this post. Good luck De Tim WA1HnyLR