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Ampeg PF-50T Humbuster

#81
JimmyM said:
See, guys? Told you that they knew already but nobody believes me!

:p
Click to expand...

See my response above ^^.

The shorter version:

My experience last November emailing LOUD about this major problem with an otherwise great amplifier proved fruitless. YMMV.

So, sure, they know (knew) about it JimmyM. They're just not going to do anything about it. They suggested I should feel free to do the mod and void my warranty (not that I needed their permission). So, I did. It was about 10 minutes of trivial bench-time.
 
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#83
SirMjac28 said:
Mine is still dead quiet without any mods is it broke? :)
Click to expand...

I guess we would have to define dead quiet.

I occasionally have my bass and amp in the living room for use while composing. I live out in the country. It's very quiet in my house in general. Even more so in the middle of the night.

Sometimes I'll get up around 3:00am to get some snacks out of the fridge. On a few occasions I'd do that and see that I inadvertently left my bass amp on. I could walk right up to it and I would not know that it was on except for the purple pilot light.

Before I did the mod I could hear that the amp was on from down the hall before I got to the living room.

I have no reason to believe that my hearing is super-human. :)
 
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#87
Doner Designs said:
Thanks everyone for the advice via this thread and the various links. I got the mod done today with supervision and assist from my son who is an engineer. It works as advertised. There is now zero audible 60 hz hum and no audible degradation of the tone when playing. Also am now able to adjust the bias properly whereas I had previously set it in a position that minimized the hum. Posting pics here for anyone who had trouble seeing the detail in the bertr photo. Got the parts from Mouser.

By the way, I found the secret sauce that makes this amp sound so good - it contains a flux capacitor. Really - upper left in the first full size picture. No idea what that is doing there. Maybe the name of the company that makes the boards for Loud Tech.

View attachment 2968755

View attachment 2968748

View attachment 2968748 View attachment 2968749 View attachment 2968750 View attachment 2968751 View attachment 2968752 View attachment 2968753 View attachment 2968754 View attachment 2968741 View attachment 2968747 View attachment 2968746 View attachment 2968743
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I wonder if Yamaha will keep the flux capacitor on the board.
 
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#89
basstamer said:
It would be great if someone from LOUD would chime in on this!
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Issues are seldom admitted to, everyone would want their amp fixed and that costs. Recalls are only issued if there is a safety issue. Service centers might have a tech note describing how to bring an issue up to date if there were a fix. Revisions, for one reason or another are common with all companies.
 
#90
beans-on-toast said:
Issues are seldom admitted to, everyone would want their amp fixed and that costs. Recalls are only issued if there is a safety issue. Service centers might have a tech note describing how to bring an issue up to date if there were a fix. Revisions, for one reason or another are common with all companies.
Click to expand...
I understand the constraints of running a business. I just have a very sentimental attachment to Ampeg as it was the first amp I ever got back in the 60's. And, yes, it was a B15N. And, yes, it was dead quiet. :)

I guess I see the PF50T as being a very worthy successor to the Ampeg line if they would just make this one design change. I'm not expecting them to mod everybody's amp, but, for their sake, I'd like to see them rev this board going forward. That's all.

I got mine last November. Maybe they've changed the board since then, or, maybe not?
 
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#91
basstamer said:
I guess we would have to define dead quiet.

I occasionally have my bass and amp in the living room for use while composing. I live out in the country. It's very quiet in my house in general. Even more so in the middle of the night.

Sometimes I'll get up around 3:00am to get some snacks out of the fridge. On a few occasions I'd do that and see that I inadvertently left my bass amp on. I could walk right up to it and I would not know that it was on except for the purple pilot light.

Before I did the mod I could hear that the amp was on from down the hall before I got to the living room.

I have no reason to believe that my hearing is super-human. :)
Click to expand...

I live alone and I hate any noise with a passion I'm almost anal about it. I'm running this amp with an Ampeg Portaflex PF-115LF so I'm not sure if not having a tweeter has something to do with it? Also, mine isn't a year old so maybe they corrected something?
 
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#94
SirMjac28 said:
I live alone and I hate any noise with a passion I'm almost anal about it. I'm running this amp with an Ampeg Portaflex PF-115LF so I'm not sure if not having a tweeter has something to do with it? Also, mine isn't a year old so maybe they corrected something?
Click to expand...

The problem is power line related hum, 60hz in north america, 50hz in some other regions. Any tweeter related noise would be more about high frequency hiss.

You’d have to open the amp and check the board revision with others. But the problem could have been a component issue or even a batch of transformers. In that case, it wouldn’t have required a board revision.

Since your amp is quiet, I wouldn’t worry about it. You can always have a service center perform the mod for you if you feel that it can be improved.
 
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#95
SirMjac28 said:
Now I'm thinking I got a bad one? :)
Click to expand...
Not sure what you mean by a "bad one"?

If you have been playing the amp, and enjoy it, it's a good one.

I think the point of this thread is about discovering an improvement on an already great design. I mean, the breakup on this thing is fabulous! I love the ability to get somewhere between the B15 and SVT sound that I can do with this amp.

I've gotten gigs as a result of this amp that I otherwise probably wouldn't have gotten.
 
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#96
basstamer said:
See my response above ^^.

The shorter version:

My experience last November emailing LOUD about this major problem with an otherwise great amplifier proved fruitless. YMMV.

So, sure, they know (knew) about it JimmyM. They're just not going to do anything about it. They suggested I should feel free to do the mod and void my warranty (not that I needed their permission). So, I did. It was about 10 minutes of trivial bench-time.
Click to expand...
So what's the problem then? You're all set. And by the way, LOUD no longer owns Ampeg. Yamaha does.
 
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#97
basstamer said:
Not sure what you mean by a "bad one"?

If you have been playing the amp, and enjoy it, it's a good one.

I think the point of this thread is about discovering an improvement on an already great design. I mean, the breakup on this thing is fabulous! I love the ability to get somewhere between the B15 and SVT sound that I can do with this amp.

I've gotten gigs as a result of this amp that I otherwise probably wouldn't have gotten.
Click to expand...
I was kidding and I love this little beauty
 
#98
beans-on-toast said:
The problem is power line related hum, 60hz in north america, 50hz in some other regions. Any tweeter related noise would be more about high frequency hiss.

You’d have to open the amp and check the board revision with others. But the problem could have been a component issue or even a batch of transformers. In that case, it wouldn’t have required a board revision.

Since your amp is quiet, I wouldn’t worry about it. You can always have a service center perform the mod for you if you feel that it can be improved.
Click to expand...
Knowing my luck Beans it would instantly become noisy:)
 
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#100
For Yamaha people interested in modding the PF50T at low cost:
- Do not change the board (yeah!! Money saved!)
- Change R128 in the manufacturing process with a 3.9k resistor instead of 680R (see tracing of MNATS page 1 of the current thread)
- When mounting the board in the chassis, have the person doing the assembly solder a 100uF 100V from back of the diode to ground.
Done.
 
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