beginners luck advice needed

[ampdummy]

I recently acquired an old hammond AO35 with the intention of starting a new hobby. Before making any changes I thought I'd would see if the amp was in working condition. I hooked a speaker and plugged my guitar in .The amp powered up and sounded O.K. for a little while then the volume gradually faded out to nearly nothing. I turned it off and let it cool down for a couple of hours ,when I powered it up again I get a pretty loud hum and very weak sound.Any suggestions will be appreciated.Also when you touch the strings on the guitar the hum gets stronger i.e just touching the strings not actually playing. I went into this expecting a challenge and must admit I get a little stubborn(my wife say's obsessive)when faced with problems such as this .Thanks in advance

[Amp Kat]

I would say change the tubes and the caps and it should be fine. Then again I've never worked on one of these.

[ampdummy]

beginners luck

I fooled around with it today,checked some grounds and input jack and got most of the hum out. Same thing happened with volume stated out fine and faded after a few minutes.I think I'll try some more tubes. I replaced the two ax7's with new didn't make any difference. It also has 2 EL84's and a 5Y3GT.I think it's probaly a good first project for a beginner.I was really suprised at the sound.My plan is to get it working properly if possible, and then start investigating what mods would be beneficial. I open to any and all advice. Thanks

[stokes]

Filter caps would be a good place to start.

[ampdummy]

ao-35

I replaced caps and got the amp working. I need to know where would be the best place for a volume pot. Pardon the dumb questions,I guess everybody's gotta start somewhere.I'll say this,this is a pretty addicting hobby.

[stokes]

What kind of tubes do you have in that?I cant find a schem for it.If you have a dual triode as the first preamp tube,I would say to replace the resistor from the grid to ground on the second stage with a 1meg pot.If you can point us to a schem,I am sure you could get plenty of opinions on some circuit mods that would sound better for guitar use.

[ampdummy]

volume pot forAO-35

It's got a jan 5751,12ax7,two EL84's and 5Y3GT.It was an amp for reverb in an organ and had two small bulbs as volume limiters,which I removed and installed a 1/4 jack for input. I really appreciate the help.

[stokes]

Okay,putting the 1meg as I described will work.

[ampdummy]

Thanks. There's schematics at www.captain-foldback.com... I may want to do something in the way of tone pots,but I'm going to stick to one thing at a time, that way I can fix my screw ups more easily. I appreciate you guys responding to such basic questions.

[stokes]

Okay,looking at the schem.,R6 would be the place to put the volume control.Just look at a Champ schem and wire the 1m pot the same way in place of that 1m resistor.

[ampdummy]

Thanks again for your help, I was kinda stumped.Nothing was making a lot of sense. Sometimes you look at something so hard you can't make heads or tails of it ,now things are starting to click.I'm pretty impressed with this little amp,I've got a good enough grip on things now and got in reasonable working order, so now I can move on to tweaking and mods and really screw things up.