Ampeg PF-50T Humbuster

[cdwthunderfoot]

Revisiting this, and using Bertr's previous post as a template. I'm going to de-solder and remove r128, solder in a 3.9k resistor in it's place, solder a 100uF 100V cap to the Anode side leg of D29 with the other leg of the cap being soldered to ground. I did want to clarify something regarding the cap. If I'm using a polarized capacitor what side should be soldered to ground? + or - ?

 

[beans-on-toast]

If I'm using a polarized capacitor what side should be soldered to ground? + or - ?

[+] goes to ground in a power tube bias circuit.

If the polarity is backwards, it can explode. Be careful to get it right.

 

[JimmyM]

Forgot to mention in here that I got my amp back a couple weeks ago and this mod rocks! Thanks to all the electronics whizzes who geniused it up.

 

[keyofnight]

Forgot to mention in here that I got my amp back a couple weeks ago and this mod rocks! Thanks to all the electronics whizzes who geniused it up.

I think I'm gonna have this mod done too. Just out of curiosity, how much did your tech charge for it?

 

[JimmyM]

I think I'm gonna have this mod done too. Just out of curiosity, how much did your tech charge for it?

$45.

 

[beans-on-toast]

$45.

Did you finially get your ‘69 SVT repaired? Changing a pot is a much bigger job because of all that has to be disassembled.

 

[JimmyM]

Did you finially get your ‘69 SVT repaired? Changing a pot is a much bigger job because of all that has to be disassembled.

Not yet.

 

[button]

Just wanted to chime in - I had this mod done by Revamp in Los Angeles and am very pleased with the result. The amp is dead quiet now and still retains the original tone. I paid somewhere around $100 for the mod.

 

[SactoBass]

I wonder if Yamaha will keep the flux capacitor on the board.

 

[keyofnight]

Alright, folks. I did the mod myself, and it is fabulous. Everything is really quiet now. Eerie quiet.

 

[MrCash]

Looks like these are now coming from the factory with the mod.

No more Procrastination! (An interesting small valve head story)

 

[JimmyM]

Looks like these are now coming from the factory with the mod.

No more Procrastination! (An interesting small valve head story)

Right...they've been doing that for a good while now, but it's always nice to get more confirmation.

 

[basstamer]

Looks like these are now coming from the factory with the mod.

No more Procrastination! (An interesting small valve head story)

Good news! This was such an easy, inexpensive, and important fix.

 

[Doner Designs]

Right...they've been doing that for a good while now, but it's always nice to get more confirmation.

Is the factory mod the same?

Impressive.

 

[JimmyM]

Is the factory mod the same?

Impressive.

I'm the wrong guy to ask about that, but as far as I can see, yes.

 

[bobcruz]

Yamaha ownership already showing benefits?

 

[JimmyM]

Yamaha ownership already showing benefits?

LOL! No, the Yamaha stuff isn't out yet. As far as I can tell, it's been ongoing for a few months at least, and that would mean these are the last of the LOUD-made 50T's.

 

[Martin Beer]

Yep, that's me in the thread linked. My Pf-50t is one of the last of the LOUD units, which there are some nice clearance deals on. The mod appears the same as Bertr's method on this thread, except the additional resistor is positioned differently (they lifted r128 instead of the diode leg), and the added capacitor goes to a different ground trace. But electronically, it's the same.

 

[MrCash]

Yep, that's me in the thread linked. My Pf-50t is one of the last of the LOUD units, which there are some nice clearance deals on. The mod appears the same as Bertr's method on this thread, except the additional resistor is positioned differently (they lifted r128 instead of the diode leg), and the added capacitor goes to a different ground trace. But electronically, it's the same.

View attachment 3166997

Do you remember what revision your board was please?

 

[MrCash]

LOL! No, the Yamaha stuff isn't out yet. As far as I can tell, it's been ongoing for a few months at least, and that would mean these are the last of the LOUD-made 50T's.

Does this mean the end for the pf20t and pf50t? Or are they just going to be somewhat revised?