Valve Itch phono

[Salas]

And the boat im working with, and some storage

Reminds espionage for stopping an evil top secret heavy water transportation.

 

[stajo]

Reminds espionage for stopping an evil top secret heavy water transportation.

Actually before we left to the dry-docj we had some manly consumptiom of gin and tonic on the roof top on a neighbour boat. That one had been used by stasi on the channels fot contra espionage on the european rivers. Good damn it was nice equipment in that boat.

Our boat, or my friends boat, contains around 30-40 thousand tubes. One third sorted. All the P-tubes thrown away and now were about to renovate the public areas. Well. Thers some tons of old transformers, chokes, caps, resistors and stuff also.

We unloaded 6 tons of speakers etc last week. Imperial horns, Infinitys....

 

[merlin el mago]

 

[stajo]

Friday i'm leaving for bringing the ship home. Its place are on a tourist walk on an island called Skeppsholmen. 100 more ships layes there. 6-7 hours I guess, on 5-7 naughts. Your welcome to visit us!

 

[merlin el mago]

I'm only 2711 km far from Stockholm.....

 

[merlin el mago]

Salas could I use 5mV of ripple and 308V for B+ to test the Itch? The question is because I don't want to take off one of the two chokes 10H 100'mA that I have installed in my #26 preamp.

 

[Salas]

To have B+ and make repairs its good enough. The Itch will reject enough of that ripple also bcs it has some PSRR.

 

[merlin el mago]

Great, time to work, I keep you informed.

 

[stajo]

delay 2-3 more second to the sim and you get the actual simulated value

 

[merlin el mago]

Thks, not too much difference 4,35mV

 

[stajo]

True. Tho one can wonder why you sim on 23,6 mA?

 

[merlin el mago]

20mA for the Itch and the rest for the 220K bleeder resistor

 

[Salas]

Its 10mA for two channels Itch. You asked very recently.

 

[merlin el mago]

Yes you are right Salas, my mistake 10mA for the Itch and the rest for the 220K bleeder resistor.

I measured B+ 325VDC with the Itch connected, I left this voltage or I have to increase 1K32 resistor between the two PSU caps?

 

[Salas]

Don't leave it, its too much for the upper tubes cathodes to heaters. Go near 300V B+

 

[merlin el mago]

OK now I have 300V B+

 

[merlin el mago]

Use your generator and scope for typical debug procedure then to find the fault.
100mV 1kHz, then attn -40dB, input to SUT each channel after another.
Scope SUT out, 1st stage out, second stage out, see where the signal stops and why.

Starting to catch the issue.

 

[merlin el mago]

Scoped both SUT channels and are OK. I will follow with first stage out check.

 

[stajo]

Yes you are right Salas, my mistake 10mA for the Itch and the rest for the 220K bleeder resistor.

Well that doesnt make sense either but its ok if you have got voltage to 300 in some way. Otherwise ohms law is good.

 

[merlin el mago]

V1 pin 1 scope don't measure sine wave, V1 pin 2 measure sine wave coming from SUT.