Mullard Amplifier Project

[Refugee]

I also have become confused by the early date for the EM34. It is NOS and is in a white box as would be more likely for 1969 and is as you say very new looking for 1959.
I am hanging onto it as a spare for one or two vintage instruments I have.

[Terry]

" It is NOS and is in a white box as would be more likely for 1969 " unless the old box had become battered and torn - I wouldn't expect a 1969 valve to be in a white box either unless, of course, it was an equipment manufacturer's surplus (bulk buyers don't get their valves in boxes!)

However, I doubt anyone was bulk buying EM34s in 1959, even, so I'll stick with the torn and battered idea ...

[Refugee]

The white box does have the number printed on it and it came in a box of valves fount in a skip in 1980.
The location of the skip indicated that they could have been bought in bulk.

[Refugee]

I have just had a delivery of parts and sod's law has struck.
0.47uf Vshay capacitors are on back order so we are still awaiting spares

[ppppenguin]

Ref, I've got 0.47uF 630V "yellow perils" in stock. I can send you a few and then you can send me some when they come back into stock. How many do you need?

[Refugee]

We are off the awaiting spares list now and work can start in earnest again.

[simp2005]

Excellent news! Did they come from the same place that orignally had them out of stock?

[Refugee]

Yes they did.
If you order more than there stock they tend to be able to get more pretty quickly and ship them on. They must have contact with a big wholesale broker that we don't know about.

I have made a start on the main challenge of getting into all those stacked components and it has made a huge improvement to the voltages and distortion levels.
It is pretty cramped in there and one of the worst of the leaky capacitors is indeed the one at the bottom of the stack.
   
   
It was so cramped that one of the pots had to come out to get that challenging bottom capacitor out so it was not an easy job at all.
Those metal can capacitors reach a certain voltage and then take currant if you go any higher like a shunt regulator.
They had to come out.
The wax one has a clear sleeve over it and is across one of the tone control pots so it will not matter.
The G1 to earth one in the phase splitter was causing loads of distortion.
The other channel will have to wait till tomorrow.

[simp2005]

Wow thats definately a tight area to work in!looks like you would have a bit of s truggle getting the soldering iron in there? Looking good !

[Refugee]

Yes I had to work out how they were originally fitted and reverse the procedure just to get the leads out far enough to cut them at the ends of the old component and then bend the ends into hooks and solder them to hooks I made on the ends of the new part.
There was one or two that were easier to get to but with leads that were longer than on the new components but sleeves were the quick answer to that.