OK it's been time for a another question here's the 5V3A

[Thenice]

hello everyone
in my internet travels l came across a super 5U4GB called the 5V3A please note there's
a earlier version called 5V3 or 5AU4 these versions demand 3.8amps each there output
is slightly (l believe mostly sure)above 5U4GB though the voltagedrop is like a 5U4G then they came with the 5V3A it has 400millamps dc to the 5U4GB 275 to 300 and again the voltage drop is l ve read to understand is like a 5U4G other things seem similar
as l am the one who comes with obvious questions to those who really know
so here goes could it be used the 5AU4/5V3 in the kit6550 ?

next one the 5V3A 3 amps 42to 45 voltage drop output 400milliamps DC
apparently it came very late in the day before the transistor took over oh the tragedy before
the seller who wrote the thing l believe apparently it was a super tungstenish coating thoriated
could it be used in the kit6550? would l need to uprate the choke?use a kt150?

final question l had a ruggedised slyvania 5U4GB made for fender in 1971 triple mica extra
support rods the works but it made the kit6550 sound horrible after 10 hours l put the pair
in storage never again
yet there are those who put 2 JJ5U4GB in what gives am l missing out on something?
hence the question lhave the original psu parts it sounds great

many thanks to anyone who answers the 3 questions It doesn't get many posts but alot of
visitors vist as a resource which it is
l feel abit stupid on all this but valve amps are sometimes dangerous as l found when a 5U4G from brimar
the good old days before elvis cause my amp to make a thudding noise loud too it was
thank god that john caswell wasthere to repair it and all please be careful so thats why l
ask those obvious questions
at the moment reading a book called introduction to valves from 1953 wireless world
if you're lucky you might find it on ebay for a tenner if you know gcse math at C minus you
get more out of it than l have but l still on the triode bit but already have learnt abit

there's a subtle hint you guys could do a new version with recipes for those with a steady
hand with a soldering iron have fun if you do

[John Caswell]

Why do you want to change the standard 5U4 valve? I am a at a bit of a loss as to what you are trying to achieve!

First I would be very wary of using the 5V3 at all, as its 3.8 amp heater current x2 would be 7.6A and would probably overload the power transformer. Not a good idea.

Cannot see any reason not to use the 5V3A should fit in fine.
6550 HT requirements are about 350-400mA - not sure what the consumption using KT150 would be, but I would guess very similar as it is an "upgraded" KT88.
You would not have to change the choke.

John

[bob orbell]

I tried to read the first post, but got lost, having to stop and take breath for fear of passing out , punctuation would have helped and make the post more readable , I hope John got the questions sorted though. Bob

[Thenice]

hello everyone
lve been a bit misunderstood l don't want to change my 5U4G or anything else
I was trying to ask questions l shouldn't made so many points at once
apologies bob
l was thinking what could happen with the 5V3 at 3.8amps
likewise with the 5V3
I made another comment about using a 5U4GB which didn't work out
hence why l was asking questions
l also made a comment about a rectifier that went wrong l learnt a lesson there
it should had been one question at a time
and why
either way it's to ask something that you not sure of to those who have the knowledge
and experience to answer as l said many visit the forum as a resource l was trying to with
my post to add to this
hope that clears things up
frank

[bob orbell]

Frank, John has answered your question, the 6550 power transformer it rated at 6 amps for the two 5U4 heaters, two 5V3 valves will consume 7.6 amps, so you would overload the transformer by 1.6 amps. it may well work for some time, but will get very hot and possibly burn out. That will be the end of the transformer and a rewind will cost more than the amplifier would be worth. Bob

[Thenice]

hello Bob
thanks for answering the question
l could think this but l wouldn't know for sure
Once again thanks
frank