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Old 8th Apr 2012, 8:04 pm   #37
Neil Purling
Nonode
 
Join Date: Jul 2005
Location: Hull, East Yorkshire, UK.
Posts: 2,083
Default Re: Mullard 3-3 information required

I followed the Sterns manual in the making of the group board etc. I omitted the filtration for the input though.
I was re-using an existing chassis, just punching new holes for the two Noval bases and extra control pot.
I bought a pair of Svetlana (Winged 'C') EF86 with 'cheese-grater' anode structures, dated 07/85.
I am not able to spend money like a sailor on a run ashore.
Partridge power & output transformers & Telefunken valves are waay out of my league.
Fellow Forum members have been a great help with parts.
You know who you are: I don't know if it is okay to name names, but you know who you are.
I had only one EL84. You will have seen my appeal for Soviet EL84 on the Forum. Among thos I was offered was a pair of 6P14P out of a Rigonda dated 1968 & 1969 respectively. They are perfectly OK.
This thread brought about the offer of some Hinchley output transformers.
The Sunday weather wasn't very promising, so I got stuck in.
Sure-enough I made two wiring mistakes. I fixed one & tried again to discover I had created a Banshee. It howled ferociously.
I was ready for that! I think that it was the Sterns manual that mentioned it. You reverse the connections to the output transformer Primary.

In operation you can't see the EF86 heater is working except a dim glow in a blacked-out room. The tone controls are very effective.
Maybe someone can enlighten me as to what harmonic distortion sounds like?
If it makes the amplifier tinny sounding, then that was what afflicted my previous effort. Not so with the Mullard 3-3.

Another 3-3 is born.....
I need a set of matching knobs and proper decals for the controls, but the beggar is working well without them.
Enjoy the pictures.
I have made changes after those images were taken during construction. The white ceramic 3W 330R resistors were removed & a extra piece of earth bus to reach pin #2 of the EF36
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Last edited by Neil Purling; 8th Apr 2012 at 8:08 pm. Reason: Extra Text
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