I have an Orange AD200B with the most frustrating hum I've ever come across. It might be something easy, but I'm at my wits end and could use some more minds.
It sounds like a ground hum to me, but I'm not positive.
-Controlled by master volume (goes away when master down)
-Can remove first tube and it's still there
-Can ground the input of the master and it's still there????? This one is confusing the crap out of me (checked the pot).
-Every ground in the amp checks out with a meter.
-of course tried all tubes
-Replaced E-caps, except the power tube plate ones (could it possibly be those and have it be controlled by the master vol?)
The part that drives me nuts is that I can ground the input of the master and it's there still, but if I ground the output (or just turn it down) it goes away. Am I crazy for thinking this is weird?
Any insight would be fanstastic!
Thanks
Orange AD200B hum
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Orange AD200B hum
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Stevem
- Posts: 4985
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Orange AD200B hum
Looks like this amp uses a ton of failure prone slip on connectors!
Is the ground for the heater winding good?
Try to nail down if it's 120 HZ D.C. power supply hum, or 60 HZ hum?
Is the ground for the heater winding good?
Try to nail down if it's 120 HZ D.C. power supply hum, or 60 HZ hum?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Orange AD200B hum
Did you find a solution? I have exactly the same problem.
Thanks for any advice.
Thanks for any advice.
Re: Orange AD200B hum
Ok, I allready figured out what was that. If you have same issue check heater supply. Especially R48 and R47 (100R resistors in AD200B mk3). They caused the heater to be unbalanced. Measure heater voltage and then check voltages between heater and ground.
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Stevem
- Posts: 4985
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Orange AD200B hum
When those 100 ohm hum balance resistors go bad its due to a shorted output tube.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Orange AD200B hum
Thanks for the responses.
So... I had to put this amp off to the side for a minute because it was frustrating me so much.
In a VERY SAD twist of fate an amp I built from scratch, which I have successfully built before, (completely different but with 4x6550) has THE EXACT SAME PROBLEM.
The heaters on my amp are run from the mains transformer and also from a separate 6.3 transformer and they don't match exactly... so I'm really hoping you are on to something.
Was your issues with the heaters controlled by the master volume?
That's the part that really gets me, why would it only be effecting the first two preamp tubes?
I can't for the life of me figure out bewteen 60-120hz. It's more of a buzz and doesn't seem to match up directly with either, but if I had to guess I would say 60hz.
So... I had to put this amp off to the side for a minute because it was frustrating me so much.
In a VERY SAD twist of fate an amp I built from scratch, which I have successfully built before, (completely different but with 4x6550) has THE EXACT SAME PROBLEM.
The heaters on my amp are run from the mains transformer and also from a separate 6.3 transformer and they don't match exactly... so I'm really hoping you are on to something.
Was your issues with the heaters controlled by the master volume?
That's the part that really gets me, why would it only be effecting the first two preamp tubes?
I can't for the life of me figure out bewteen 60-120hz. It's more of a buzz and doesn't seem to match up directly with either, but if I had to guess I would say 60hz.
Re: Orange AD200B hum
I just checked the Orange.
The heater setup has a center tap, but right near where the connector to the lamp goes are two brown-black-brown resistors R48 and R47.
I can't find them on the schematic and they measure at just under 1M, one side is to ground. A major clue.
I have to go to work, but I'm at least optimistic at this point (but also WHAT THE HELL).
The heater setup has a center tap, but right near where the connector to the lamp goes are two brown-black-brown resistors R48 and R47.
I can't find them on the schematic and they measure at just under 1M, one side is to ground. A major clue.
I have to go to work, but I'm at least optimistic at this point (but also WHAT THE HELL).
Re: Orange AD200B hum
Totally missed this where you named the resistors!
I'm very hopeful this is it. Thanks so much.
Why would they not have these on the schematic?!...ARG
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mikeydee77
- Posts: 3
- Joined: Thu Dec 20, 2018 8:07 am
Re: Orange AD200B hum
Thank you for posting this thread. It helped me massively today while scratching my head over an AD200...
Mike
Mike