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I fired up a BF Deluxe Reverb the other day built in a Hammond Organ chassis using the transformers. My goal was to build the vibrato channel with only one input, and no reverb or vibrato circuit. Here is my schematic with the power supply omitted : http://www.whiteghostshivers.com/ima...eak/deluxe.pdf
Here's the stock AB763 for reference : http://vintagefenderamprepair.com/wp...-schematic.pdf
I was intent on building the vibrato channel because of the extra gain stage. I've got 420VDC on the plates and everything else checks out down the line, except for the fact that when I turn up the volume pot or the tone pot, I get ~50V drop at the plate on only one side of the OT/6V6 plate. The tone becomes quite harsh as the amp breaks up, as well. I did a lot of troubleshooting with some help on the AX84 forum, and couldn't quite figure out where all that power was dissipating. I ended up yanking the extra gain stage before the PI, rendering the amp basically a DR normal channel, or just the "Deluxe Amp" normal channel(without the 47n coupler or 220K mixer). This is what I cut : http://www.whiteghostshivers.com/ima...luxe2stage.png
Amp sounds really good now, and the voltage drop issue went away.
I'm still interested in implementing the extra gain stage in the vibrato channel, though. I've done a lot of reading on the net and found a few folks that have put together the normal channel w/ no verb, vibe, but no success stories of replicating the vibrato channel. I figure my woes revolve around some loading that the vibrato channel "sees" from the rest of the stock AB763, that I don't have. Without it, it seems its overwhelming the PI . I don't have a full working knowledge of what exactly that triode is doing, as I'm assuming it's not just another normal gain stage.
Has anyone got any ideas on how to implement that gain stage in my build, without building up the complete reverb and vibrato circuits? I of course could be totally wrong about my "loading" theory. Thanks, J
Here's the stock AB763 for reference : http://vintagefenderamprepair.com/wp...-schematic.pdf
I was intent on building the vibrato channel because of the extra gain stage. I've got 420VDC on the plates and everything else checks out down the line, except for the fact that when I turn up the volume pot or the tone pot, I get ~50V drop at the plate on only one side of the OT/6V6 plate. The tone becomes quite harsh as the amp breaks up, as well. I did a lot of troubleshooting with some help on the AX84 forum, and couldn't quite figure out where all that power was dissipating. I ended up yanking the extra gain stage before the PI, rendering the amp basically a DR normal channel, or just the "Deluxe Amp" normal channel(without the 47n coupler or 220K mixer). This is what I cut : http://www.whiteghostshivers.com/ima...luxe2stage.png
Amp sounds really good now, and the voltage drop issue went away.
I'm still interested in implementing the extra gain stage in the vibrato channel, though. I've done a lot of reading on the net and found a few folks that have put together the normal channel w/ no verb, vibe, but no success stories of replicating the vibrato channel. I figure my woes revolve around some loading that the vibrato channel "sees" from the rest of the stock AB763, that I don't have. Without it, it seems its overwhelming the PI . I don't have a full working knowledge of what exactly that triode is doing, as I'm assuming it's not just another normal gain stage.
Has anyone got any ideas on how to implement that gain stage in my build, without building up the complete reverb and vibrato circuits? I of course could be totally wrong about my "loading" theory. Thanks, J