Tube Amp Archive

Hi Mark, Your words were heard and I did ask for a reverse Zener but it was an old Philips one and I must admit that it did not have the prefix of "R" on it. I will get another and try it. I will also use your suggestion Tom. Thanks again,
Peter

Hi Mark, As far as a heat-sink goes I have a good "L: Shaped piece of thick aluminium and a fined type heatsink all with white paste so it should not be a heat problem I will get some alligator clips and try and measure the Current. I will find a 50w 100v and try that though, That should be big enou...

Well I connected a 75Volt 20watt zener to the centertap on the primaries and it dropped about 30 volts for a minute or so and then failed. it now has continuous polarity through the diode. Maybe a 50watt will do the trick.

Thanks TM,
"Any one else want to way in on this method"

Hi Mark Thanks for the reply, infact thank "all" of you for your replies. The power transformer has its own 60V tap so that should be unefected. This amp started as a stock 50Watt Ceriatone OTS, then I modded it to a HRM and then further mods led to adding the 2 extra sockets and installing 4 x 6V6 ...

I only have a 68 v 20 Watt Zener and was thinking I could just lower voltage to the 4 x 6V6 Tubes

Yes of course, Pin 6 is the screen, not the Plate and that's what needs lowering. Thanks...

Hi Tom, I am using Tungsol 6V6GT at the moment. I founs a supplier but I have to check that it is the correct polarity. In my case I am not wanting to lower the voltage across the pre amp tubes, only the 4 x 6v6 Tubes so I am thinking of conecting a 68v 20w Zener from the wire comming of of the 20uF...

Thanks Tom, I tried Mouser and that 56 volt and 100 volt Zeners are not available on line. I will search out some other suppliers. It seems that the high power Zener is the way to go though instead of the low watt mosfet design

Thanks Bill So I can use the first option as per link http://www.aikenamps.com/Zener2.pdf using mosfet or try the 56v 50w Zener. I have 480volts DC at pin 3 and idealy would like to drop 100v and make this switchable so would a 100v100w zener be ok? What is the safest and best option, Thanks in adva...

Thanks for the link, That is a good start. A bit technical for my tiny brain but I think I can nut it out in time. So 2 different approaches to this problem.
Regards
Peter

Hi All, I have modded my 50 watt Dumble to a HRM and then gone further with adding 2 valve sockets and running 4 x 6V6 tubes. I have it Biased low as I am getting 480 Volts across pin 3 and earth (Tube installed). Can any one out there show me by way of illustration how to lower the plate voltage. I...