Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Stuff4bikes on March 24, 2022, 12:19:44 am
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I am getting and end rush of about 540v on 500v caps....
I am debating just strapping another identical cap with resistors as my solution. Problem is caps are 22uf
So my first cap would be 11uf correct? I do have a 3H choke between rectifier and first cap.
Second solution is to use two 100uf radial caps which would give me 50uf at the first cap...
And with the choke first it shouldn't effect my 5U4gb.
Sorry for the rambling but does any of this make sense?
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end rush.
Do you mean ‘in-rush’? (as in ‘startup surge’)
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Best is show a schematic or wich amp ?
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choke input supply, eh?
yes the more detailed a schematic (including resistance/impedance of your power transformer) you can provide the better
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Look at the first filter node off of the rectifier in this schematic https://el34world.com/charts/Schematics/files/Fender/Fender_super_reverb_ab763_schem.pdf (https://el34world.com/charts/Schematics/files/Fender/Fender_super_reverb_ab763_schem.pdf)
The resistors are for leveling the charge on each capacitor they also discharge the caps when you turn the amp off. This configuration solves your problem. The voltage doubles and the capacitance halves, so its easy to figure out what you need.
Notice too that the choke comes after the first filter node and after the plates in the Super. I have a 5F6a with a choke input though so it's doable. If you were using the choke upfront to drop voltage then by using caps in series on the first node you can make it acceptable with higher in-rush current/voltage surge.
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Problem is caps are 22uf .... So my first cap would be 11uf correct?
Second solution is to use two 100uf radial caps which would give me 50uf at the first cap...
Ahem .... why don't use a pair of 50uf radial cap .... they will result in a 25uf at the first cap ...
note that 22uf or 25uf, talking about E-caps is pratically the same value (due to % of tollerance)
Franco
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+++++++sorry meant to post this earlier today+++++++++++
++++++++i ordered 47uf 350v axial caps for this+++++++++++++
"In rush" sorry....540v on 500v caps...
Hammond AO-15 power transformer, ouput transformer, 5U4GB and a 3.5H choke.
That's the original power supply except I removed hammond's 15H choke and their capacitors.
3 X 22UF at 500v caps
I am using a Robinette type 5E3 board with a 5F2A preamp into a 5E3 output section running
Magnavox 6L6GA's. 7025 in V1 and a 6AN8 as the PI....
The amp is quiet and bottom end is not farty....my concern is that lowering my first cap filtering could effect
The bass response.
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...my concern is that lowering my first cap filtering could effect
The bass response.
If you usually play the amp with the Volume control turned up 75% then sure.
If you play the amp with the Volume below 50% then probably not.
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...my concern is that lowering my first cap filtering could effect
The bass response.
If you usually play the amp with the Volume control turned up 75% then sure.
If you play the amp with the Volume below 50% then probably not.
I don't really play....amp is for a buddy who plays live with Marshall's so this amp will probably get turned up. just to be safe I think I should wait for the new caps.
Thanks for everyone's help....