SSLV1.1 builds & fairy tales

[Salas]

Hope not super current burned MOSFET or resistor. 0.1 Ohm too small to start with 9530 as I mentioned before. Start with 1.5R.

 

[merlin el mago]

Resoldered all near parts and now is going ok, with 0.22R as CCS resistor I measure 1.8A, it's ok for 1,2A or it's too much?

 

[merlin el mago]

IRF9530 seller has two kinds:

14A 200mohms
12A 300mohms

Wich one?

 

[merlin el mago]

With 1.5R CCS 835mA

 

[merlin el mago]

IRF9530 seller has two kinds:

14A 200mohms
12A 300mohms

Wich one?

I ordered 12A 300mohms because is cheaper.

 

[merlin el mago]

With CCS resistor 0.47R I measured 1.474A

I ordered togheter the mosfet 0.33R 7W vítreous enameled.

 

[Salas]

Resoldered all near parts and now is going ok, with 0.22R as CCS resistor I measure 1.8A, it's ok for 1,2A or it's too much?

For heaters 200mA spare is OK. So for 1.2A load try for around 1.4A. Mainly judge from how reliably you can sink the CCS MOSFET at such current level. The shunt MOSFET isn't getting much punishment at 6.3V and 200mA spare.

 

[Salas]

With CCS resistor 0.47R I measured 1.474A

I ordered togheter the mosfet 0.33R 7W vítreous enameled.

1.474A isn't already enough? Unless you think of other tubes too with stronger heaters or there is much tolerance in heater draw between various same type tubes. And you want to avoid possible accidental current limiting. In any circumstances judge spare vs utility vs heat dissipated and ability to sink.

 

[merlin el mago]

Regs. are for Itch. If I remember well 1.2A each reg. incl. the spare current for the reg.

Also ordered 0.68R 7W vítreous enameled.

 

[Salas]

You use special ECC81 instead of its Russian standard input tube type and a normally proposed 6SN7 in the Itch? Simply add their heater spec for each heater supply. Then add spare.

 

[merlin el mago]

Siemens E283CC If 0.33A & Sylvania 7N7 heater nominal 0.64A = total 0.97A + 0.2A Reg = 1.2A

 

[merlin el mago]

Attached pic measuring CCS with the new 0.68R resistor giving 1.3A

 

[Salas]

Success

 

[merlin el mago]

Arrived also the mosfets, time to finish the other reg. Many thanks Salas.

A very big trick is to use a 12nF FT-1 teflon cap bypassing de 4.7uF Auricap, WOWWWWW

 

[merlin el mago]

Salas the new reg. CCS 0.68R 1.215A but can't reach 6.3V because don't have enough current with my dummy load 5R.

3 green LEDs & R106,206,306 270R

Same power tx & psu like the other reg.

I believe that with the real load (Itch filaments) go well because power is 1A +0.2 own reg. and now CCS is 1.215A or have I to increase the CCS reducing the CCS resistor or adding a 4th green LED?

 

[Salas]

6.3V/5Ω=1.26A so all you analyzed is normal

 

[merlin el mago]

Have I to increase the CCS reducing the CCS resistor or adding a 4th green LED?

What's the reason for the difference of CCS using the same components?

 

[Salas]

You still have some voltage headroom before adding another LED because at 0.824V now.

The reason is tolerance. LED VF & MOSFET VGS differ from sample to sample. You may build two same regs but their Rset resistor need be different enough for achieving same CCS current. Tolerances manifest more in strong current settings.

If you match LEDS and mainly MOSFETS with the transistor tester between two regs they will react very much the same for CCS setting.

 

[merlin el mago]

So your advice is that I will try as is?

I'm sorry if my language sounds rude Salas, English isn't my native language.

 

[Salas]

As is, it will just work for your 1A heaters. But better have a little more CCS headroom to match the other reg. If not equipped with a smaller 0.62R resistor right now but you have spare IRF9530s measure VGS of all you got with the DCA Tester. You must remove and compare the one already installed too. Replace with the lower VGS unit you will find. The difference to lower VGS is going to add on your now 0.824V. For in circuit bias it gets bigger. If you will add an LED the new Rset valet to use for 1.3A target is going to become much higher than 0.68R.