Hammond 25 Leslie Booster Amplifier

[petemoore01]

  I aquired one of these last night, and tried touching insulated probe to pins on inputs of tubes and got merely a very low level normal hum like the amp is on...none of the usual ''clicks'' that would normally be produced from the speaker.
  It seems to be a power supply, and a 3 tube PP amp, two 6l6's PP and a 12au7 phase inverter. Just before the phase inverter is a volume control, I'm trying to gather info on what type [strength"] of input this output amp is expecting at it's ''input''...how to make it ''amp''.
  Usually, a 20w output of tubes will make some kind of connect-click when their input is probed with anything, I haven't gotten a peep out of it beyond the usual/normal/ barely audible hum of a quiet", idling amp.
  Before I delve into voltage readings and etc., I'd like to know what will feed the amp a signal it expects.
 

[blackcorvo]

You could try this simple signal generator:



"Ponta do Injetor" is where the output signal comes from. "Terra geral" is the common/ground connection.

Or you could get a cheap pocket radio and use the headphone output as your test signal.

[Suicufnoc]

If it's anything like my Leslies, it wants A LOT of input. We hooked up a little solid state practice amps output into one and that worked well.

[anotherjim]

From what little I've seen, the Leslie amps are intended for strong input, even from an existing amplifier speaker output. And yes, the input goes right to the phase splitter. I've seen "optional" dummy load resistors (8ohm) included in the design, presumably to keep the driving amp happy if that is also tube.
But a solid state amp won't mind not having a speaker load, so like Confucius said, that's a good try.

[PRR]

Such a pretty schematic:


For FULL output it wants 36V at 6L6 grid. The 12AU7 has gain of 15. So it wants 2.4V peak 1.8Vrms at the 10K pot for full output.

[antonis]

<off topic on>
Is the rectifier diode pair designed for  diodes of half PIV use..??
<off topic off>

[PRR]

Early Silicon diodes did not do high voltage; or their price/each rose faster than their voltage spec. It is not uncommon to find series diodes.