The AM Forum

I just had one of these amps come into my shop. Has anyone had any experience with one? I'm going to pair it up with a 5100b.  I've never seen a full wave bridge power supply using 816's before. I can't get one of the 816's to fire. It has filament voltage and ac from plate transformer. I've played musical tubes same results on one socket. So the issue is not the tube, I've checked out the socket too I'm stumped. The schematic is on BAMA. I'm just about ready to solid state the supply.

73 N8QPC

Hey bud...

Nice amp.

If it's not the tube or socket, have you checked the plate lead?  Maybe an (open) intermittent connection inside a plate cap???

Just a thought..  If it's not the tube, socket or voltage, not much left.

Chris in San Diego says Hi, by the way...  Your name came up talking about a Desk Kw or some such thing.

--Shane

Nice amp for a pair of 813s.  Lot of heat and light for about 600 watts.  An SB 200 will about do this in a lot less space and cost.  Those 816s are difficult to find and may not last long.  I had an LPA 1 and had lost of trouble with them flashing over.

Using the internal power supply in the 1000A restricts it to 375W input power while operating AM.  Take into account the efficiency being around 30% would give you around 112 W output.  Also, you would need to reduce the output power (~20W)from the 5100 to restrict the drive so as to not run more than the 375W input.  When considering all of that, you would not be gaining much over the B&W as a stand alone. 

Regards,
Joe, W3GMS   

it has an unusual fil xfmr ... 3 windings ... sounds like one may have poor internal connection .... are the fil voltages measured under load ?

The filament voltages were ok. I lost my patience and rebuilt the supply solid state with a new plate transformer. I also got rid of the 8 filter caps for single oil filled. It made more power than it would stock I believe.Any how it's  done and gone.
Thanks for the advice. 73 N8QPC