The Other Not Ultralinear PCL86 Monos

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Mike H
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#16 Re: The Other Not Ultralinear PCL86 Monos

Post by Mike H »

Cressy Snr wrote: Sat Sep 29, 2018 2:20 pm It's looking good Mike. You'll get yours done before me. :)
Ta muchly
I've just finished a mammoth exterior painting and repair job that included me and our Ant fitting a new chimney pot and cowl to the front stack.
Bluddy hell. :shock:

(I don't "do" ladders.)

Further to the previous, also and as well as, I was convinced I should have 3 (THREE) Cosmos pots, could I find 'em ... Image

I knew I'd used one for the EL84 p-p amp (built 2016), so there should be a small plastic box of the remaining pair (is what they come in).

To borrow a quote from Foul Ole Ron from the Discworld books, "Buggrit buggrit buggrem millennium hand and shrimp"

So I buys another pair off E-of-the-Bay, yes you guessed it, yesterday I finds the previous pair still in their plastic box, in another storage box that I hadn't looked in previously. Image

So now got three Cosmos pots and what must over a dozen gold plated ceramic B9A's

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"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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Mike H
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#17 Re: The Other Not Ultralinear PCL86 Monos

Post by Mike H »

Mike H wrote: Sat Sep 29, 2018 12:26 pm Sorting out components today.
This took a surprisingly long time (or maybe not), I have HEAPS of components, but never the right ones.

Anyway think I've got all the resistors and caps I need now.

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"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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Mike H
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#18 Re: The Other Not Ultralinear PCL86 Monos

Post by Mike H »

My modified Mullard diagram:
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My Mullard 3W amplifier.jpg
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"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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Mike H
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#19 Re: The Other Not Ultralinear PCL86 Monos

Post by Mike H »

Today's progress . . .
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PCL86_2171-b.jpg
 
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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Mike H
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#20 Re: The Other Not Ultralinear PCL86 Monos

Post by Mike H »

Secret weapon revealed . . .
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PCL86_2175-b.jpg
 
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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Mike H
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#21 Re: The Other Not Ultralinear PCL86 Monos

Post by Mike H »

OK the PSU Voltmeter works . . .

. . . a triumph of planning and forethought (aka, back of fag packet design).
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PCL86_2177.jpg
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Ignore the decimal point it's actually 250V.
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PCL86_2176-b.jpg
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OK not actually a fag packet, but close - note multiple crossings out: :D
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PCL86_2178.jpg
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"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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#22 Re: The Other Not Ultralinear PCL86 Monos

Post by Mike H »

PS: I should explain the above enables the digital Voltmeter module to work from up to 300V supply (nomally 30V max.); solution: use a high Voltage MOSFET as a source follower Voltage regulator / limiter.

The SMPS has a 5-turn pot to vary the output which is too easy to do so some sort of permanently ensconsed Voltage indicator is highly desirable. Resolution: 1 - 2 Volts. Quite accurate too, straight off.

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"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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#23 Re: The Other Not Ultralinear PCL86 Monos

Post by IslandPink »

Neat !
Nice to see you beavering away there Mike.
Just about to go out and do a bit of beavering myself before the light fades.
"Once you find out ... the Circumstances ; then you can go out"
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ed
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#24 Re: The Other Not Ultralinear PCL86 Monos

Post by ed »

whenever I hear that somebody has been beavering I get suspicious.
It comes of reading Kurt Vonnegut when I was an impressionable teenager.....

you boys go steady now, we're not getting any younger.
There's nowhere you can be that isn't where you're meant to be
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Dave the bass
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#25 Re: The Other Not Ultralinear PCL86 Monos

Post by Dave the bass »

Mike H wrote: Thu Oct 04, 2018 7:38 pm Secret weapon revealed . . .
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PCL86_2175-b.jpg
Heheheheheh,I like that.
"The fat bourgeois and his doppelganger"
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Mike H
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#26 Re: The Other Not Ultralinear PCL86 Monos

Post by Mike H »

Image "I have a cunning plan, my Lord."

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"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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#27 Re: The Other Not Ultralinear PCL86 Monos

Post by Mike H »

PCL86_2180.jpg
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"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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#28 Re: The Other Not Ultralinear PCL86 Monos

Post by IslandPink »

ed wrote: Sat Oct 06, 2018 7:59 pm whenever I hear that somebody has been beavering I get suspicious.
In my case, 'beavering' was quite apt, as I was chewing away at pieces of wood.
"Once you find out ... the Circumstances ; then you can go out"
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#29 Re: The Other Not Ultralinear PCL86 Monos

Post by Mike H »


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PCL86_2181.jpg
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PCL86_2182.jpg
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There are a few problems:

1. One valve is WAAA-AY down on gain. I think the triode may be screwed. DC Voltages don't match at all. I've got some Mazda NOS ones on order, supposed to be new unused.

2. There is a LO-OTTA noise. Mostly RF, so I'm now looking at supply line filters. Annoyingly I've misplaced my small bag of ferrite bobbin chokes, had them out couple of days ago but last night spent 2 hours trying to find them again, eff knows where I've put them. Hate that cr4p - my pet moan is how much time I spend looking for stuff. Anyway found some common mode (I think?) ones so will play with those.

4. Forgot to earth the case which may also account for the noise.

5. The dropper resistor idea for the valve heaters didn't work out too well. It was smokin' and melting the solder joints. So I went and got one of my netbook supplies which I was reserving for heating duties, and rigged that up, works but again noisy output.



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"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
Cressy Snr
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#30 Re: The Other Not Ultralinear PCL86 Monos

Post by Cressy Snr »

I've got 100K carbon-comp grid stoppers on my g1s. That silenced the buggers completely.
I think these valves sound great, but the bastards, as I found out, will oscillate in the box if you're not careful.
Cutting back the operating bandwidth seems to be the sledgehammer solution that works with these things.

I got the big grid stopper idea off Bruce Rozenblit, who uses 100K on the g1s of his EL509 OTL "Son of Beast"
In his "Tubes And Circuits" book, he talks about it in more depth when detailing the S.O.B build. But basically it's "smash the bandwidth down" or the S.O.B will "simply sound terrible"

Anyway....tea break over, back on the Mini Beast job.
Sgt. Baker started talkin’ with a Bullhorn in his hand.
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