Rixsta

Re: SCT700 Mods ?
« Reply #60 on: April 20, 2018, 06:29:41 PM »


Re: SCT700 Mods ?
« Reply #61 on: April 20, 2018, 06:39:19 PM »
I measured it actually for the first time today, as that is the mic that gets my psu hotter. But in that thread someone actually calculated it for me and was right.

Rixsta

Re: SCT700 Mods ?
« Reply #62 on: April 20, 2018, 06:46:25 PM »
Oh cool that's really good of them :) definitely helpful people around here, although I'm still in a state of confusion lol

Ive taken out R2 and put a 100k variable in there when I turn him the anode voltage goes up ..hmmm urrrmmm hmmm


« Last Edit: April 20, 2018, 07:17:43 PM by Rixsta »

Rixsta

Re: SCT700 Mods ?
« Reply #63 on: April 20, 2018, 07:17:19 PM »




Here you can see my Thiersch blue line capsule which Im very glad to have here and I have modified the microphone so that I can swap valves at will without having to unsolder them by using this.




Resistor from the front of PCB had to be moved to the back to fit the large capacitor on front!

Re: SCT700 Mods ?
« Reply #64 on: April 22, 2018, 11:55:02 AM »
Great. I like how you found a way to fit tube socket. That capsule is beautiful!

Rixsta

Re: SCT700 Mods ?
« Reply #65 on: April 25, 2018, 06:36:41 AM »
Hey thanks
So I got a little confused
I took out R2 and put a 100k variable in there instead and when I turn him down to say 50k the anode voltage goes up to like 90v  yet I need to get the anode voltage down :) to half the PSU voltage I think ?  Is it that if the voltage increases the bias level goes down ?
I tried to actual put my 100k variable in series with the original 100k to make 200k and I still could not get the voltage to go down to 60v.

Ok so Im a bit lost here so if anyone can help would be appreciated :)

Cheers!

Rixsta

Re: SCT700 Mods ?
« Reply #66 on: May 17, 2018, 10:57:03 AM »
anyone got any ideas on my Bias issues above ? am I missing something ?  or being dumb ?

RuudNL

Re: SCT700 Mods ?
« Reply #67 on: May 18, 2018, 06:21:13 AM »
If you can't get the plate voltage down (=plate current up), this could have two reasons:

- The value of the cathode resistor is too high (grid voltage too negative)
- The tube has a very low emission
There is a solution for every problem!

http://www.vansteenisaudio.nl

Rixsta

Re: SCT700 Mods ?
« Reply #68 on: June 06, 2018, 03:04:24 PM »
hello!
Is the cathode resistor R8 ?  interesting in the schematic it mentions 200k as well as the 270k I have.
Also is it possible to increase value of C1 ?

RuudNL

Re: SCT700 Mods ?
« Reply #69 on: June 07, 2018, 04:05:13 AM »
R7 (2K7)
You could increase the value of C1, but don't expect any audible changes.
There is a solution for every problem!

http://www.vansteenisaudio.nl


Rixsta

Re: SCT700 Mods ?
« Reply #70 on: June 12, 2018, 11:10:15 AM »
Ok thankyou, I had another capacitor laying around which I can use instead of C1 (needed a smaller cap to fit in space)

Other than tweaking this R7 which other way should I be getting Plate voltage down and current up.

Re: SCT700 Mods ?
« Reply #71 on: June 12, 2018, 11:49:37 AM »
Ok thankyou, I had another capacitor laying around which I can use instead of C1 (needed a smaller cap to fit in space)

Other than tweaking this R7 which other way should I be getting Plate voltage down and current up.

You can't do both. Plate voltage down = plate current down

If you want higher plate voltage (higher current), use a smaller plate resistor. If you want lower plate voltage (lower current), use a bigger plate resistor.

Re: SCT700 Mods ?
« Reply #72 on: June 12, 2018, 02:57:32 PM »
If you want to remove that silly logo and letters you can use acetone. They come right off.