What to do with a pair MKIII'S

for Dynaco Mark II/III/IV and DIY PP monoblocks

What to do with a pair MKIII'S

Postby battradio » Sun Mar 03, 2013 4:17 pm

I traded for a pair of MKIII'S , that have a missing power transformer , I have two nice power transformers , the right size that are 390-0-390 , at 200 ma , 6.3 at 6 amps and 5.2 at 3 amps , but no bias winding .I have a pair of Poseidon driver boards that I plan on using , and was wondering , how much power out put it would loose with cathode bias , or should I just use a small transformer , like the one picture with 6.3 volts feed into the seconday , to get about 55volts AC for the bias circuit .
Image

The third choice is to use a choke input for the B+ and use 6B4G's inplace of the 6550's with cathode bias .

I will be using low noise diodes instead of a rectifier tube , and rectify the 5.2 volts to DC for the input tubes , and use 12AX7 & 12BH7 as the input tubes
Mark
Image
User avatar
battradio
KT88
 
Posts: 927
Joined: Tue Mar 10, 2009 12:58 am
Location: near ST.Louis MO.

Re: What to do with a pair MKIII'S

Postby DeathRex » Mon Mar 04, 2013 10:41 am

Backwards 15V transformer.
At first I wanted to be a ET. Now I are one.
User avatar
DeathRex
KT88
 
Posts: 1014
Joined: Wed Nov 18, 2009 8:13 pm
Location: Cortez, CO

Re: What to do with a pair MKIII'S

Postby EWBrown » Mon Mar 04, 2013 7:11 pm

The backwards 15V xfmr would deliverabout 46-48 VAC with the 15V side connected to 6.3VAC filament power, that should work well.
It is a "time-honored" method of generating bias voltage. With the backwards xfmr, you could use a full wave bridge for cleaner DC voltage ,
or just go with the standard half-wave rectification, either way is OK.

/edB
Last edited by EWBrown on Wed Mar 06, 2013 10:31 am, edited 1 time in total.
Real Radios Glow in the Dark
User avatar
EWBrown
Insulator & Iron Magnate
 
Posts: 6389
Joined: Wed Mar 19, 2003 6:03 am
Location: Now located in Clay County, NC !

Re: What to do with a pair MKIII'S

Postby Shannon Parks » Tue Mar 05, 2013 6:42 am

You can also use the Eiclone method, using - from memory so check the schematic - a .1uF 630V cap and a 27K, 3W resistor, half wave rectified.

Shannon
User avatar
Shannon Parks
Site Admin
 
Posts: 3764
Joined: Tue Mar 18, 2003 5:40 pm
Location: Poulsbo, Washington

Re: What to do with a pair MKIII'S

Postby TerrySmith » Wed Mar 06, 2013 8:50 am

The Eiclone method works well (Thanks Shannon!), I've used it in many builds.
T. Smith
User avatar
TerrySmith
KT88
 
Posts: 973
Joined: Sat Jan 31, 2004 12:51 pm
Location: Maryville TN


Return to poseidon

Who is online

Users browsing this forum: No registered users and 16 guests