Hibernated Hammond M-101 Gone Quiet

[Composer]

My Hammond M-101 sat in a room for a few years unused after I moved house.

I recently removed, flipped over and re-screwed in the four transport bolts, connected the organ to the mains and turned the organ on in the correct way.

The amplifier seems to be making a quiet hum (it's alive), but when I set tabs, turn up the volume pedal and play keyboard keys, no sound comes out.

I opened up the back. All valves are glowing happily, except perhaps the amplifier's 6AU6 and the 12AX7 valves - difficult to tell, as those valve are encased in aluminium covers.

I note from the amplifier (chassis at the bottom on the left as I look in the back), that the 5U4 valve is missing. I once had the organ repaired by an engineer and he never commented on that missing valve, so I assumed that it does not need to be there?

Please could anyone give me hints as to what the problem might be, so that I can get my beautiful Hammond working again?

With kind thanks in advance.

[enor]

My Hammond M-101 sat in a room for a few years unused after I moved house.

I recently removed, flipped over and re-screwed in the four transport bolts, connected the organ to the mains and turned the organ on in the correct way.

The amplifier seems to be making a quiet hum (it's alive), but when I set tabs, turn up the volume pedal and play keyboard keys, no sound comes out.

I opened up the back. All valves are glowing happily, except perhaps the amplifier's 6AU6 and the 12AX7 valves - difficult to tell, as those valve are encased in aluminium covers.

I note from the amplifier (chassis at the bottom on the left as I look in the back), that the 5U4 valve is missing. I once had the organ repaired by an engineer and he never commented on that missing valve, so I assumed that it does not need to be there?

Please could anyone give me hints as to what the problem might be, so that I can get my beautiful Hammond working again?

With kind thanks in advance.

The 5U4 definitely needs to be there, unless the organ has been converted to a solid state rectifier (a bunch of diodes) sometime in the past. Not impossible, people sometimes do that.

[Composer]

Thanks Enor. I'll check this, though he organ was working before without the 5U4 present. I can't see a bunch of added diodes, though these may be inside the amplifier casing which I've not yet opened.