anyone has the JTM45/100 voltage chart for new stuff kt 66

frenchie · Post by **frenchie** » Fri Nov 02, 2007 1:43 pm

all is sayed int the title of the topic ...anyone can tell me ?

neikeel · Post by **neikeel** » Fri Nov 02, 2007 3:18 pm

sorry, only voltage readings I know of are these:

http://www.drtube.com/schematics/marshall/1959t-66.gif

these voltages (in circles) are spot on in my Metro 45/100

You could ask somone toopen theirs up and do a chart, I think Majorwatt might have one (a Super JH, I believe)

frenchie · Post by **frenchie** » Fri Nov 02, 2007 3:36 pm

so my question was kind of a really good one .......i already have this grid but ,on this one the pt delivers approx 560v and the tubes are gec .......so if i say voltages are a bit different with 490v and valve art i don't think anyone will contradict me.........

neikeel · Post by **neikeel** » Sat Nov 03, 2007 7:34 am

No I think it quite likely that the new amps have lower voltages.

It is my understanding that although they sound pretty good the newer KT66s cannot handle the same high voltages and even Marshall in their blurb acknowledge that the voltages in the amps they are producing will hammer the newer valves pretty quickly.

Suggest a poll of those who have had KT66s go pop, after how much running time and to check if was due to operator failure (ie wrong wire in wrong place etc

) or just failed.

I know Flames popped one on his first 45/100 after a few hours.

In fact I will post poll now

Flames1950 · Post by **Flames1950** » Sat Nov 03, 2007 8:20 am

My first set lasted maybe thirty hours, those were the GT KT66HP's. Sadly I liked them better than the Shuguangs and Tung Sols -- they ghosted less -- but the Shugs and TS tubes sound fine as well.

The Tung Sols KT66's have been in my Super PA since it was built in August '06, but since I'm not a regular gigger at the moment I can't be sure how many hours I've got on it, but I played it pretty exclusively for a few months after it was done, every afternoon when I got home early enough to do so.

frenchie · Post by **frenchie** » Sat Nov 03, 2007 11:56 am

damn ...flame ....after looking a your web site i saw you put ...530v ..on the plates of your shuang kt66 !!!!!!!!!!!!!!! how many chinese quartets do you blow before you find one which fits theses voltages when you build an amplifier !!!!! you must sell your amps for the price of a boeing !!!

Flames1950 · Post by **Flames1950** » Sat Nov 03, 2007 12:04 pm

That's what George's original 1202-43 power transformer runs put out, I had little to do with that decision. I do run them a little cold on bias (about 27mA when the math says I could do up to about 31mA) to keep them from dissipating too much heat, but it is still hard on them. Such is the price of being close to authentic.
I'm not sure if his newer runs of that transformer still put out that much -- his flagship '66 clone is only running about 490VDC on the tubes I believe, but I'm not sure is it's the same power tranny that's available in the store or not.

neikeel · Post by **neikeel** » Sat Nov 03, 2007 12:38 pm

I'm running one of George's PTs (not sure which version or incarnation, but I believe one of the first batches) with GEC KT66s and from memory my voltages were pretty similar to those on the schematic I posted, I will have to check my notes...........

frenchie · Post by **frenchie** » Sun Nov 04, 2007 1:56 pm

well with gec it is obvious ...but if i can't find a quartet of those collectible ones i will have to find another grid for chinese ones....someone knows where to find nos grey coated gec ???????????

St August · Post by **St August** » Sun Nov 04, 2007 3:18 pm

PM Tube Tramp .Im sure he can help you out

frenchie · Post by **frenchie** » Mon Nov 05, 2007 7:51 am

cool ! thanks

Marshall Growl · Post by **Marshall Growl** » Tue Nov 06, 2007 11:38 am

my super 100JH "marshall" has over 500, like 530v.

frenchie · Post by **frenchie** » Tue Nov 06, 2007 3:41 pm

and you run valve art kt 66 with it ???

wdelaney72 · Post by **wdelaney72** » Tue Nov 06, 2007 10:58 pm

If you are talking new production tubes, with that voltage the Shuguang 11th Gen will take it. Contact TubeTramp... he'll set you up.

frenchie · Post by **frenchie** » Thu Nov 08, 2007 8:13 am

i tried to find him but i didn't succeded in .....where is he ? on this forum?