811a SET amp.

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pre65
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#1 811a SET amp.

Post by pre65 »

Going on from the 10W SET amp thread in the "valves" section, this is the project. :wink:

First thing is to strip the old KT66 & PT15 (mk3) monoblock chassis of superfluous parts, I'm on the first one at the monent.

Next is to modify the octal adaptor (in a septar size hole) to take the UX-4 base. I already have a 4mm socket to take the flying anode lead.

It's a bit parky round the ears today, so the wooly hat has emerged from summer storage. Can't bear to put the heating on just yet. :lol:
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pre65
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#2

Post by pre65 »

Here is a view of what it will look like. The 811a are not in my possession yet so a 300b is standing in.

The two 4mm sockets (red and black) on the side are for the 811a external filament supply. I will be using my 4A Tentlab modules, and I've just ordered two 100va 12v transformers to power them. 12v is too high really but 9v was just a gnats smidge too low, so I will resistor down to approx 10v.

The first cap has been increased from 2uf to 22uf as I need a few more volts HT. I would like 500v but may have to settle with less, perhaps 450-470v according to Duncan.

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#3

Post by Dave the bass »

Shoddy!

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#4

Post by pre65 »

Dave the bass wrote:Shoddy!

DTB
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#5

Post by Mike H »

Ah the chassis with the wood end-cheeks
 
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#6

Post by pre65 »

Mike H wrote:Ah the chassis with the wood end-cheeks
Sure is

So far its been

829b PSE
826 SET
KT66 SET
PT15 SET

and one other I think, but can't remember.

Hopefull this will be the bestest. :wink:
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#7

Post by Mike H »

Natch! :D
 
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#8

Post by pre65 »

I was short of a few vital bits so I ordered them from HFC yesterday.

True to form the came in today's post.

Main items were the Clarity cap coupling caps. Only the 12v filament transformers and a couple of power resistors to come now.

Some bits have been soldered in already, but I'm having a day off today. :wink:
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#9

Post by pre65 »

Could not stop myself plugging the soldering iron in.

Everything that was here is now in place, just one cathode resistor and 12v transformer to do when they arrive. :)
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#10

Post by Mike H »

Must clean me glasses....
pre65 wrote:I was shot in the vital bits
Image
 
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#11

Post by pre65 »

Painfull. :lol:

The filament modules are now fixed to their bases, they are up high cos the air is cooler at altitudes. :wink:

Just a few wires to connect them up to the main amps and it's all done.


Can't get the 811a valves till next week now so there's no panic.

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#12

Post by Mike H »

pre65 wrote:The filament modules are now fixed to their bases, they are up high cos the air is cooler at altitudes. :wink:
:lol:

Is that MDF or "proper wood" ?
 
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#13

Post by pre65 »

Just hordinery MDF from the scrap pile. 8)

The weight of the 100va transformer gives it stability. The transformers came from a low voltage lighting specialist.
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#14

Post by jack »

pre65 wrote:The filament modules are now fixed to their bases, they are up high cos the air is cooler at altitudes. :wink:
Which "filament modules" are you using?

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#15

Post by pre65 »

nickds1 wrote:
pre65 wrote:The filament modules are now fixed to their bases, they are up high cos the air is cooler at altitudes. :wink:
Which "filament modules" are you using?

Ta
Hi Nick, they are the Tentlab 5 amp ones which I originally purchased for my 845 project, but have been used on 300b for quite a while.
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