833A (GU-48) Amp
- pre65
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#1141 Re: 833A (GU-48) Amp
I can't see at the moment, but I think I use 2 x 100W R1 (.1R ?) resistors and capacitors.
So, they are in the filament positive lead, and the caps are not across the filament.
Is that "bad" ?
So, they are in the filament positive lead, and the caps are not across the filament.
Is that "bad" ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
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#1142 Re: 833A (GU-48) Amp
I would say, no.
That's what I was thinking of.
So I'm not sure it needs improving.
That's what I was thinking of.
So I'm not sure it needs improving.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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#1143 Re: 833A (GU-48) Amp
How did Paul / Nick heat theirs? (Open question)
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#1144 Re: 833A (GU-48) Amp
Switched mode, I put a tube current sink (crude shunt reg) at end of power supply on the 5v rail of the filament power supply which prevented it from cutting out when faced with the cold 833a filaments.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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#1145 Re: 833A (GU-48) Amp
If I hadn’t done the above I would have used ac heating and injected the hum into the grid per S Bench which is how my last amp I brought to Owston was heated.
My next amp will be very simple and low powered, probably a 10 driven by a 5687 cf volt amp would probably be a cascade of 76’s or 27’s or similar. All ac heated and hum corrected with S Bench.
My next amp will be very simple and low powered, probably a 10 driven by a 5687 cf volt amp would probably be a cascade of 76’s or 27’s or similar. All ac heated and hum corrected with S Bench.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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#1146 Re: 833A (GU-48) Amp
I came across two filament chokes on Ebay, they are 2.5mH @ 12.5A.
I was "watching" them for a few days, then got a message saying the seller had reduced the price by 40%, so I purchased them.
They will go into the box of bits for the big rebuild.
Message for Nick. Some time ago I was chatting to you about augmented cathode follower drive for the 833a, and you thought you might still have a couple of PCBs for the circuit. Did you ever find them ? If so I'll send you some beer vouchers.
I was "watching" them for a few days, then got a message saying the seller had reduced the price by 40%, so I purchased them.
They will go into the box of bits for the big rebuild.
Message for Nick. Some time ago I was chatting to you about augmented cathode follower drive for the 833a, and you thought you might still have a couple of PCBs for the circuit. Did you ever find them ? If so I'll send you some beer vouchers.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#1147 Re: 833A (GU-48) Amp
I will have a look.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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#1148 Re: 833A (GU-48) Amp
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- pre65
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#1149 Re: 833A (GU-48) Amp
The filament chokes were delivered this morning, not a bad service from Latvia.
I'm going to rethink the way this amp is constructed as the total weight is likely to be backbreaking.
I'm going to rethink the way this amp is constructed as the total weight is likely to be backbreaking.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
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#1150 Re: 833A (GU-48) Amp
Separate modules?
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#1151 Re: 833A (GU-48) Amp
He already uses separate output transformers...it'll be just like giant Lego.
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
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#1152 Re: 833A (GU-48) Amp
Modules, that sounds good.andrew Ivimey wrote: ↑Mon Nov 11, 2019 3:02 pm He already uses separate output transformers...it'll be just like giant Lego.
Are you still travelling round the world Andrew ?
Been in the "shed" lately ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- andrew Ivimey
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#1153 Re: 833A (GU-48) Amp
The shed is seriously damaged.
I've just booked a flight to Beirut!
I've just booked a flight to Beirut!
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
#1154 Re: 833A (GU-48) Amp
I think back in the day when I made them I hadn't got my head around eagle PCB software so used a package that didn;t produce gerbers. As such I don;t think I got any spares made. However it would be simple enough to copy the circuit on the paper about augmented cathode followers. Not as simple as populating a PCB, but not that hard. I used ACF-2 in the following doc. You could use a depletion mosfet in the tail of the LTP.
https://www.desmith.net/NMdS/Data/955_A ... lowers.pdf
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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#1155 Re: 833A (GU-48) Amp
Thanks Nick.
On that ACF2 circuit is
A) The input direct from preamp ?
B) The output to 833a grid ?
And, what would be a good way to configure a +450v / -400v power supply ?
On that ACF2 circuit is
A) The input direct from preamp ?
B) The output to 833a grid ?
And, what would be a good way to configure a +450v / -400v power supply ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)