This is my first post (pretty sure). I love this forum, I love browsing through everyone's comments / build pics and learning where I can! Anyway... I have bought myself a AC15C1, It already has a UK made Alnico Blue speaker which is a win.. I'm wanting to play around with some mods, most of the mods I've found are pretty straight forward and I am fairly confident doing them myself. I can solder fine. There is one however which I'am a little cautious on... Adding the choke. Alot of people seem to rave about the results. Problem being, from what I understand is that it raises the B+ voltage from 300V to 330V (ish) causes the tubes to pack it in. Is there anyway to tame this B+ back to a voltage that isn't going to destroy my tubes? My mate has a choke in his and he just "wings it" with tubes (sometimes they last weeks, sometimes days), however it does sound really good. Any help is greatly appreciated, thanks in advance
I would imagine that voltage increase would be the result of not choosing the correct choke values?
Most Vox are 15 henry but DCR and mA ratings vary widely. Either increase the choke specs; leave in any sag resistors or add; or put a reverse zener diode on the CT to reduce voltage.
Not sure what the schematic looks like for this amp.
Yeah I tried to find a schematic to post, but couldn't find anything. I'm 99% sure my mate runs a 10HY @100mA Choke. I'm thinking I will get a 15HY @100mA and try that. If the voltages are still to high then try a 20HY. Thanks for your input, appreciate it
vox_boy wrote:Yeah I tried to find a schematic to post, but couldn't find anything. I'm 99% sure my mate runs a 10HY @100mA Choke. I'm thinking I will get a 15HY @100mA and try that. If the voltages are still to high then try a 20HY. Thanks for your input, appreciate it
Look at the DC resistance of the choke ... that's what is going to drop the voltage ...
vox_boy wrote:Yeah I tried to find a schematic to post, but couldn't find anything. I'm 99% sure my mate runs a 10HY @100mA Choke. I'm thinking I will get a 15HY @100mA and try that. If the voltages are still to high then try a 20HY. Thanks for your input, appreciate it
Look at the DC resistance of the choke ... that's what is going to drop the voltage ...
Ah okay thanks for that! So just to be clear..... the DC resistance of the choke should match the resistor its replacing?
You might want to go with an AC-30 choke, they're rated close to 500 DCR at 100mA. You could also try and increase R72/73. Wouldn't be a bad idea to increase screen R's to at least 470R to 1kR.
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