Old Iron

[John EH]

Anybody have any use for the old iron in the SEX 2.0 kit?  I did the upgrade and can't really see me doing anything with them.  Be happy to send them to someone for trade of a tube or paid shipping or if'n you are somebody I know from way back when I'll just send them to you.

John

 

[vetmed]

IIRC there is a way of using them to turn a Quickie into a headphone amp. If you like to experiment then might be a good excuse to get a Quickie :

Robert Lees

 

[Paul Joppa]

You can replace the 620 ohm resistor in the power supplies with the old plate chokes.

 

[John EH]

I've got a taker. Thanks guys.

John

 

[mcandmar]

You can replace the 620 ohm resistor in the power supplies with the old plate chokes.

Any chance you could document that, specs of suitable chokes etc.  I wonder about that whenever i see chokes on ebay going cheap, and i'm sure there are plenty of 2.0 owners who have upgraded that are using them as paper weights.

 

[Williston]

You can replace the 620 ohm resistor in the power supplies with the old plate chokes.

Hi

 

[Paul Birkeland]

I'm rebuilding my SEX amp 2.0 with the 2.1 upgrade iron and I'm interested in re-using the old plate chokes. Can anyone provide a little guidance on how to wire this?

Remove one 680 Ohm resistor from the power supply (it will be flanked by some big black caps).  Wire the choke in its place (with the stock jumper in place).

Repeat for the other side.

 

[mcandmar]

Soo, any chance you can share the specs of the 2.0 chokes, henries, ma, and resistance?

From my research i see the Triad C7X is a common mod for Crack owners, which i can get locally for

 

[Paul Birkeland]

The 2.0 plate choke was ~30H at somewhere between 30 and 40mA.  (PJ knows the exact numbers, but these should be pretty close)

The C7X is overkill for power supply duty in the SEX amp, as you'll never pull anywhere close to 90mA through it.  (The Crack + Speedball is just a hair under 90mA)

 

[mcandmar]

Thanks Paul,

I've also had these C3X chokes on my watch list for a while, 10H, 500 ohms, 50mA maximum, and physically compact so easier to squeeze into the chassis. Look suitable?  or too small to be bothered with?

http://www.ebay.com/itm/Triad-C3X-10H-50mA-smoothing-choke-/380691013292?pt=UK_Sound_Vision_Valves_Vacuum_Tubes&hash=item58a2f3deac

I'm trying to model the power supply in PSUDesignerII but cant figure out how to split it into two sections for the parallel supply to each tube. Any idea?

 

[Paul Birkeland]

The C3X is a more reasonable choice, and 500 Ohms of resistance is close enough that I wouldn't sweat the difference.

When you're referring to modeling the power supply and splitting the supply to each tube, I would infer that you have a SEX 2.1?

You can draw one channel and put a current tap in at the first set of caps that's 35mA to simulate the draw for the other channel.

 

[mcandmar]

Found a beefier option, a Hammond 194E, listed for a Vox AC30 guitar amp. 30H, 100ma, and 517.2ohms. http://www.hammondmfg.com/pdf/EDB194E.pdf  Which of those two would you go for?

I'm still trying to get PSUDII setup correctly, its one fussy SOB, will only let me add a current tap after a C or RC filter which i dont want. I need it to be directly after the voltage doubler. I also need to measure the transformer secondary to add in the ohm rating, or do you happen to know its value off the top of your head?

Thanks again,

Mark

 

[Paul Birkeland]

Found a beefier option, a Hammond 194E, listed for a Vox AC30 guitar amp. 30H, 100ma, and 517.2ohms. http://www.hammondmfg.com/pdf/EDB194E.pdf  Which of those two would you go for?

I would go for the physically smaller one (which will be the C3X).  The inductive reactance at 120Hz for either choke will provide better filtering than the 680 Ohm resistor.

PSUD is fussy, but you have a known set of operating parameters from which to start, and you can work backwards to determine the transformer specifics.

Also, if we assume that each half of the amp draws about 35mA, and you are decreasing the power supply resistance by 180 Ohms, this will raise your power supply voltage about 6V (which is immaterial).  Modeling becomes pretty unnecessary at this point.

 

[jrebman]

PB -- can you tell me where the jumper goes on the Pc-1 and where the external connections are made (which tabs on the choke) -- I have a pair of these gathering dust and want to try this at some point.

Thanks,

Jim

 

[johnsonad]

It's well worth it Jim. I'm very happy with mine. You can do what I did and super glue the chokes to the bottom of the iron under the chassis. This works very well.

 

[Paul Joppa]

PB -- can you tell me where the jumper goes on the Pc-1 and where the external connections are made (which tabs on the choke) -- I have a pair of these gathering dust and want to try this at some point.

Thanks,

Jim

It's on page 23 of the SEX 2.0 manual. Jumper choke terminal 1 to terminal 8 (they are diagonally opposite), and use terminals 4 and 5 as the choke wires (they are the other diagonal).

 

[jrebman]

Hi Paul,

Thanks much -- can I assume that that pin 1 is the upper left corner as you face the choke sitting on its mounting tabs? Would the dot matter and which pin would it be?

Thanks,

Jim