Gates bc-1 question(ss..)

[KI4OWV]

Finally started digging around in the old Gates broadcash trans I recovered to see what I had to work with and found a few suprises. First - the schematic don't match. The Gates BC-1-T I downloaded from bama appears to have sweep tubes in the modulator - mine has 807's. It looks like two more 833's were added after the factory build (4 total) in the pa. Extra wiring is obvious. Gates bc-250 originally? (transmitter has only Gates on front for id. No id plates) Has a switch for 250-1000 watts inside the frt. door. (added with factory "kit" maybe?)  Basically I need suggestions as to what schematic I need. I intend to restore to operating condition on B/C BEFORE any "tweekin". Suggestions?

[KL7OF]

I'm not sure if your BC1 is a T model.......I know that the Gates BC1-G has 2- 807 rf drivers, 4- 807 Audio drivers (2 driving another 2 as cathode followers) , 2-833 modulator tubes, and 2-833 final tubes.......Can you post a picture?    Steve

[k4kyv]

The early BC1-T used 6BG6 sweep tubes.  They are basically 6L6's with plate cap out the top, designed for early tube type TV's.  Gates later changed to 807's.  They released a retrofit to convert existing 6BG6 audio and rf drivers to 807's.  It includes a complete new circuit board for each.  Better quality - the original sweep tube board was brown bakelite.  The 807 version was glass-epoxy.  There were some minor changes to the circuit, in addition to the different tube sockets.

When they first came out with the rig, the sweep tubes were very cheap, but as the older TV's were replaced with newer models, those old sweep tubes became more expensive than 807's, so Gates changed over to the cheaper tube.

[WA3VJB]

Don's got it right, examples of the BC-1T (1957-1962) can be found with  807 and 6BG6.
Those outfitted with 807s can be considered later in the production run, or else retro-fitted. Some have brown bakelite boards, and the glass boards to which Don refers would subsequently be found throughout the production run of the BC-1G (1962-1973 +/-)

My brother retrieved a "T" from an undergound telephone company equipment vault a few years ago as WOL in Washington DC prepared to move to a new transmitter site.  That example of the transmitter had the brown 807 boards installed, but still with the transmitter was a set of brown 6BG6 boards that the station had pulled out but saved.

[KI4OWV]

I'll try to get a few pics up mon. The mod board is green epoxy. The two added final 833's have the filament wiring done in high-tech 12ga white single-strand hard copper. This thing is also severly js'ed with non-factory wiring all over the place. The whole thing ain't complicated - just gonna be time consuming to restore to factory config. Hey Don KYV - caught your qso with the nova scotia op with the 45 watt ranger last night. Sweeeet! 73 Max

[k4kyv]

The two added final 833's have the filament wiring done in high-tech 12ga white single-strand hard copper. This thing is also severly js'ed with non-factory wiring all over the place. The whole thing ain't complicated - just gonna be time consuming to restore to factory config. Hey Don KYV - caught your qso with the nova scotia op with the 45 watt ranger last night.

So you say two more 833A's were added to the rf final, to make it a total of 6 (4 for the rf and 2 for the modulator)?

I received the Nova Scotia station almost 100%, except for a few QSB's.  Some interesting discussion of low power AM broadcast stations I noticed the time I was up there, but he says don't exist anymore.  Ran about 50 watts carrier, and used wire antenna supported by wooden poles, much like you might see in a ham setup for 160.  He mentioned knowing someone who has one of those 50w transmitters he is considering converting to ham use.

[KL7OF]

I would ask the same question as Don....Does your TX have 6 833s?   If so, I wonder how the plate supply has been modified....... not to mention the filament supply.....

[KI4OWV]

OK guys-  I finally got around to digging in the old Gates with the good weather AGAIN since I had it stored away from the shack. What I found was it was originally a BC-250T (I found a factory sticker that had fallen to the bottom) that appears to be upgraded to a -1. It has the 250-1000 switch inside the front door that appears to be a factory-type mod (or kit). It has (4) 833's and appears that at least 1 was js'ed in or rewired with residential-type solid copper 12 ga. wire. I was inspecting it for hidden or unseen problems and found that the shaft and roller was missing from the PA load inductor . The Mod boards use 807's (I have two). The best board is white with some heat damage around the two large resistors between the upper 807's. I understand these resistors should be remote-mounted off of the board on terminal strips to protect the board and doubled in power handling capacity  - correct? Another problem - The two high-voltage solid state rectifiers that I was supposed to get (from a B.E.) never materialized. The HV rect"s are 8008's correct? Even though the blue glow is nice I have no desire to use mercury-vapor rectifiers. I need a useable schematic and values for the parts for  solid-state replacements if anyone has any ideas. I don't want to risk experimenting with the almost-new hv trans in this beast. The LV rect's I have already found solid-state replacements for. I am preparing to get it out and give it a bath and buffing  / touch-up before it goes into the shack and will take pic's before and after clean-up and before Iron installation.  Paul/vjb has expressed desire for a story on the recovery and as soon as I get the pic's I'll try to get one written and submitted. Be watching - It is very comical in a National Lampoonish way. I also need a copy of the manual and correct schematic for this trans. I will be glad to pay for this plus a roller-inductor, solid-state rectifiers, or parts to complete mine. Any one who has experience with one of these,has parts or wishes to comment feel free to post. Hope the spring weather holds! 73 - -KI4OWV(at)yahoo.com

[WA3VJB]

I've received a sales brochure on the BC1-T.
It refers to the "heavy" 6BG6 like an 807. (sales talk)
Posted here with some narrative from the source.
Many thanks, Larry.The 1-T I am using also has a factory installed CONELRAD kit in it!  The first one I have ever seen.  It was amazing!  It switched the plates of the 833's to a separate tank circuit, lowered the power to 250 watts, and switched the grids of the 833's to a separate oscillator driver circuit mounted in the same box as the separate tank circuit!  Most of us had separate low power transmitter to use on CONELRAD.

Larry W7IXZ

[k4kyv]

I've received a sales brochure on the BC1-T.
It refers to the "heavy" 6BG6 like an 807. (sales talk)

Speaking of "sales talk" I still get a chuckle out of the sentence in the BC1-T owner's/service manual that says "Congratulations.  You are now the owner of the finest transmitter money can buy"! 

[KI4OWV]

Thanks to everyone who replied especially by email. Don (kyv) what do you use for HV rect's in your BC-1? Thanks Larry (IXZ) for the info. Do you have any ideas on the shaft and roller for the PA load inductor? Mine does not show any signs of arcing just looks like it was robbed for parts. I do have a Harris MW-1 solid state transmitter that has the inductors intact and may be able to use for replacement. I also need the sheet-metal cover for the meters on the right side of the case if anyone has one lying around. Still need info on building the solid-state replacements for the 8008 HV rectifiers. New cost of these are prohibitive @ 150.00-175.00 per pair! I did find new 8008's for 17.00/ea @ aes and may have to go that way. Any info or comments pls post or email direct to KI4OWV(at)yahoo.com. Thanks guys! 73 - KI4OWV - Max Poston

[k4kyv]

I use solid state plug-in replacements in mine.  Eliminates the filament transformer, leaving enough room to shuffle chokes around to replace my very talkative mod reactor with a potted one that does not vibrate with modulation.  The solid state replacements were already in mine when I got it, but no-one had removed the filament transformer.

The 8008's can be replaced with 872-A's, if you have a source of those on hand.  Exact same tube, just a different socket.  Is it the original MV tubes or the solid state replacements that cost $150-175 a pair?

I had a pair of 866A solid state  replacements on hand, and put those in my 1-T as well.  I replaced the 5R4 bias rectifier with solid state diodes, and use the freed-up octal socket to hold the 6AS7G DC amplifier that provides protective bias to the 833A's,allowing the final to work on CW.

So my BC1-T has all solid state rectifiers, but everything else in the transmitter is still hollow state.