The AM Forum

Hola!

Anyone have the quad 807's direct coupled audio driver diagram? I'd like to build one up for my 4X1 rig.  So far I haven't been able to locate a schematic on the web.

Thanks!

Tom, K1JJ

Hi Thom,

I sent a copy of it to your email,  both the 807 driver and solid state driver versions.  

You might also look at the quad of 807s used for audio drivers in the RCA BTA-1M series.  Very similar.

73,
Rick

Thanks much, Rick!

Gee, that was painless after all my searching around... ;D

I wonder what the plate and screen voltages are?  I just see connection tags on the three schematics.
If you have the newer 1M 807 series diagram, please send it too. Maybe it has some improvements?

Bill/IFR:  I see there is a pair of p-p separate xfmr windings used to drive the first set of 807's. What did you do to eliminate that driver xfmr.... use a tube phase splitter circuit of some kind?

Tnx.

T

More GATES email is in your inbox....  Let me know if you want the data on the BTA-1M, I will not clutter your inbox if it is not desired.....

Tom,

In that circuit the 807 plates require 600 VDC, and the bias supply must provide about -280 VDC. There are two independent 6.3 VAC filament supplies required as well; one for each pair of 807s. For some reason, I thought the PSU was a bit more complicated or specialized for this unit, but I rechecked my schematic this morning and that is not the case. It is actually very simple and straighforward.

I'm glad that you were able to get the schematic of the BC-1G audio driver. As I had indicated previously, I have the schematic here, but it would have to be redrawn to make it legible and scannable, etc. I just did not have the time to do it in the very near-term.

I may make use of the BC-1G audio driver board assy I have here as well. Honestly, I'd probably prefer to wait for the 'QIX FET version, based upon the technical advantages of that design, but nothing beats at least eliminating the audio driver xfmr.....!!! And I do like to use tubes in my rig!!

73,

Bruce

Tom, Please email me a copy I would like to see it

<There are two independent 6.3 VAC filament supplies required as well; one for each pair of 807s. >

When I first looked at this circuit I wondered how they got around the problem that the cathode voltage or the 807 used as a cathode follower to drive 833s exceeded the tube spec for filament-to-cathode voltage.

Then I saw the solution when I found the whole schematic.

They use a dedicated winding for filaments of the two cathode driver tubes, don't ground it, and let it float.

Will do, Frank.

A coupla guys sent out the complete manual - so have everything now.

(Thanks much Rick/KHK and Terry/PFY!)

Maybe they will post it here so everyone can see it.  I don't know if there are restrictions, so will hold off for now.

T

Schematics were from the BAMA mirror site, so I will share just the schematics here.  The manual is rather large, best to get that directly from BAMA.

Here is my offering that is used in my Westinghouse MW-2 shortwave Transmitter.

The main difference is that the Westinghouse uses 100 henry reactors in the voltage amplifier and cathode follower stages rather than an RC network. I believe the GE I KW BC transmitter also had this arrangement. Many AudioFools also use chokes instead of resistors. If anyone has an interest in a clearer picture of this amp schematic, just email me and I'll send it out direct via email. This system requires 400 volt positive and a 400 volt negative source.       

I am working on the solid state audio driver  8)   What I'm doing is actually building one so there's a "real" unit to test with.  No, it will not be anything to look at - this is a test prototype.  Once the circuit is verified and tested, the next step will be a PC board assuming there is sufficient interest to cover the cost of the board creation..

The unit is designed to withstand tube arc-back, grid to cathode shorts and other hazzards without damage.  The unit features independent bias adjustment, and will produce at least 450 volts P-P.  I may in fact make it develop 500 volts P-P, or even a bit more.  This should be sufficient for just about any modulator tubes.

Two voltages are required - plus and minus 250 to 350 volts DC or so.  This is most easily done using a single power transformer with a bridge, and the center tap at ground, capacitor input filters (simple).  If tubes requiring a lower P-P voltage are used, a lower power supply voltage may be used.

Regards,

Steve

Steve,
Floating source driver with a pulldown to - rail?

Steve
 Count me in on a board.
                                        Mike
                                      KAØARA

me three ;D ;D ;D

Count me in for one of these boards also.