Hammond M-100 AO67-3 amp

[Organfella]

At the risk of showing my ignorance I am asking an elementary (I suspect) question here. Elsewhere I have asked if anyone can assist with schematics for this amp but it appears that no one can. This leaves the impression that these model amps were either not used that often in later M-100 models, or any other model for that matter. The amp came out of an M-100 case without front legs, so apparently one of the later models. I scrounged the amp from the trash heap of parts as the cabinet was cannibalized for building a VPO (a project that turned sour on the brave attempter).

Now I have checked the amp visually and found no obvious blown components or other signs of failure, other than that someone had relieved it of the entire tube compliment. The power cord was in tatters and I replaced it. Also got a full set of tubes and want to test it but here is my question:

Where are the signal input connections? I want to try and connect it to a radio receiver just to see if it still works. The assembly apparently incorporates the pre-amp and expression pedal but the line filter connections had been snipped off right at their base so I cannot see the color codes. If I know where to connect the input wires I may be able to check the amp. Absence of schematics does not help either...

Maybe I am talking rot so please forgive the ignorance - but do go ahead and help me!

Thanks.

Nico

[enor]

The schematics for the AO-67 are in the M-series service manual, which you can easily find online.

It's not _that_ much different from an AO-29.

[peterb_2795]

Hi Nico,

I have an AO-67 and they are almost entirely the same as AO-29, but with additional power supply to feed an external reverb unit. Notwithstanding, I also have previously connected my amp up to bench test (in my case to an iPhone). I used the dry A channel tab to connect signal to and the GN/B tab to connect ground to. See photos below. Also, I attach an AO-67 schematic with connectors, valves and electrolytics highlighted. The A channel tab connection is at the top of the schematic off centre to the left.

You can also find a similar hookup at StefanV webpages at: http://www.stefanv.com/electronics/r...ground-up.html

Please do ensure that you have a load on the amp before powering up.

Cheers,
Peter

[Organfella]

Thanks nor and Peter. I want to connect an 8ohm speaker and perhaps a CD Player for the input. Peter do you mean I need to connect the input player before powering the amp?

Nico

[peterb_2795]

No, not really needed, but I *do* mean make sure that you have an output load (speaker in this case) connected before powering it up.

Cheers,
Peter

BTW: whilst I enjoyed listening to a bit of music played through the amp, it has none of the fidelity that I get through my normal hi-fi gear ... but I did enjoy the ambience of the glowing valves as I had a quiet glass of vino in a semi lit room ... lol

[Organfella]

BTW: whilst I enjoyed listening to a bit of music played through the amp, it has none of the fidelity that I get through my normal hi-fi gear ... but I did enjoy the ambience of the glowing valves as I had a quiet glass of vino in a semi lit room ... lol

Thanks Peter. I don't really want to use the amp for anything else than for what it was originally intended, the M-100 organ. I own two of these and really just want to see if this spare amp still works. I also have quite a few other amps, one from an ancient radiogram and from which the power supply was pilfered. That unit is still installed in a beautiful cabinet with the radio receiver. Need to figure out the inputs on that one too.... Too many gadgets to play with but what fun!
Nico