[BUILD] STA LEVEL PCB OFFICIAL BUILD & HELP THREAD

[fallout]

I poorly photoshopped one for myself and it's working out fine on my Drip build. If anyone has a better one you should probably use theres but in the meantime.

Thank you! It doesn't look bad at all.

 

[SKJGProject]

will try to work on this in 2020....anyone wants to share his mouser cart/project?

anyone?

 

[fallout]

anyone?

I have a Mouser project for the main PSU and Bias PCBs I can share but that said, I'm using some parts that you may or may not not want to use such as Molex headers/housings instead of the screw terminals, etc. I also skipped all of the .25W resistors as I had them on hand.

I can also share my Mouser cart for the Main PCB but it's incomplete as I had some of the stuff on hand and again, I might be using parts that you're not too keen on using for your build.

 

[Dr_J]

Hi,

i blew the dust of my half finished unit after laying around nearly 5 years... :
(but that's another story...)

I just finished wiring and powered it on the first time, no smoke   - tubes are glowing 

I measured the test points. Some values seem to be a bit high. Should i go for R3?

But what makes me really nervous is that some values are jumping around! (No audio input)
Any quick ideas on that?

ROCK-ON!

 

[Dr_J]

Hey,

found some time to go on.

Put some audio through, sounds not to bad for the first start... 

Then I calibrated (momentary switch) the unit. Worked fine.
The Meter isn't hooked up yet.

Then I measured again and the good news was that now all values are stabile
But some are still high out of range. Something to worry about?

The noise level is still not satisfying:
-75db@50Hz (Output fully ccw, SLOW MODE)
-57db@50Hz (Output fully ccw, DOUBLE MODE)
-57db@50Hz (Output fully ccw, TRIPLE MODE)

The DOUBLE MODE shows a repeating pop/hum sound. (No audio in)
It's starts at input around 9 o'clock, frequency increases when input turning cw,
>3 o'clock it disappears. Similar behavior on TRIPLE MODE.

The output is way to high. I'll have to go for a pad!
1000Hz@Sinus INPUT (SLOW MODE)
1.07VAC IN => 9.7VAC OUT 
0.09VAC IN => 2.1VAC OUT 

I guess the pad will work on the noise floor although.

My power TX gets hand warm, normal?

ROCK-ON!

 

[Bowie]

Then I measured again and the good news was that now all values are stabile
But some are still high out of range. Something to worry about?

The noise level is still not satisfying:
-75db@50Hz (Output fully ccw, SLOW MODE)
-57db@50Hz (Output fully ccw, DOUBLE MODE)
-57db@50Hz (Output fully ccw, TRIPLE MODE)

The DOUBLE MODE shows a repeating pop/hum sound. (No audio in)
It's starts at input around 9 o'clock, frequency increases when input turning cw,
>3 o'clock it disappears. Similar behavior on TRIPLE MODE.

I don't know if this will relate to the designations on your build, but check your R37/C11/switch, etc and make sure they're doing what is indicated on the original schematic. I had this exact thing in a build where there was a cold joint in that section.   

My power TX gets hand warm, normal?

Power transformers do that.

 

[Dr_J]

Hey,

thanks alot Bowie!!

In the mean time I found one mistake; stupid man: i'm i forgot the solder bridges on the MODE/RECOVER PCB...  :-[

At SINGLE MODE the noise floor is now -90db@50Hz!!
It's working fine, i'll think. 

BUT on DOUBLE and TRIPLE MODE then I got a loud motor-boat/distortion >10 o'clock!! 

Thanks to Bowie, I re-soldered some joints from BOTH sides of the pcb!!
Now it's quite. 
Noise Level on all Modes now around -95db@50Hz  ;D
(Not sure if it now works correctly, changing the modes seams to make no big difference...)

So far so good!

Next, i'll have to put the H-pad into it...

ROCK-ON!

 

[Bowie]

Thanks to Bowie, I re-soldered some joints from BOTH sides of the pcb!!
Now it's quite. 
Noise Level on all Modes now around -95db@50Hz  ;D
(Not sure if it now works correctly, changing the modes seams to make no big difference...)

Great to hear!
Regarding the difference it makes, run some material with a prominent beat/kick and you should be able to hear it working.

 

[Dr_J]

Hey Bowie,

thanks for the tip.

In the meantime I tried some Snare Track, with that I was able to hear (a bit of) difference between
the modes and the recover settings.
I also watched the youtube video bernd posted. I think mine is behaving similar.

So far so good. I'll go on.
Next output H-Pad, hooking up the meter and posting some pix 


ROCK-ON!

 

[Dr_J]

Hey,

did some quick audio testing and printed some audio (snare track and drum room track).
There's nearly no visible difference between the waveforms when switching around 
Here's something not working right. I'll have to check the control board PCB again.

ROCK-ON! 

 

[Dr_J]

Hey,

it's time to move forward...

Last night I put a -25dB H-Pad in... and ... bang... the unit is alive! 
I think there was/is no problem on the control board PCB, the input level was just too low.
Now I can clearly hear a difference between the different settings.

The noise-floor has dropped to -110db!!

Down side of the H-Pad is that the output knob works only half to control the output level (voltage) now.
The other half is "blocked" by the H-Pad.

ROCK-ON!

 

[Dr_J]

... and here're some waveform (snare hits) screenshots from prints I did when testing the control board.
The smaller peaks are bleed from the kick.

To me it all looks quite ok.
... and the sound is great!


ROCK-ON!

 

[Dr_J]

... it's me again... 

I did some more testing, including a -15dB H-Pad, which seems to fit a bit better.

Is it normal that the output pot mainly reacts only on the first 60 degrees?
>> Ok, my mistake. I found out that I installed a LOG Pot...

>>> Now I put a LIN 50k Pot in and it gets even worst... 
        Here's something wrong...


ROCK-ON!

 

[IanB]

Hey guys.
I decided to stick in the original simple tube/choke PSU (but using a 6x4 rectifier, & original OB2 regulator).
Voltages are good but man it thumps on attack at higher compression & fast release settings in anything but Single mode!! It’s not great at all!
Why did I do it? Cos it was there to be done/tried I guess. I also had to really dampen Steve’s power tranny to hell to get B+ in the ballpark which I was never stoked about. I just had a LOT of stuff in there that seemed ridiculous cf the original circuit.
I’ve swapped out the 6386 (GE & Sylvania) but no difference. Balancing the output tubes a good place to start??
Any advice appreciated!
Cheers!

 

[Dr_J]

Hi IanB,

I'm not good in remote diagnosis... but maybe some simple hints would help you to keep going...
Did you remove all the mods for 6386!?
As on mine I would check (double) the two control boards!?

Bernd has described some good trouble shooting tips in this thread, have a look.
(I found out later that my "LOG Output Poti problem" has been described already)


ROCK-ON!

 

[IanB]

Hi IanB,

I'm not good in remote diagnosis... but maybe some simple hints would help you to keep going...
Did you remove all the mods for 6386!?
As on mine I would check (double) the two control boards!?

Bernd has described some good trouble shooting tips in this thread, have a look.
(I found out later that my "LOG Output Poti problem" has been described already)


ROCK-ON!

Hey Dr!
No I left the main board as is - I just removed the power supply boards and replaced with the original power section to give me 300vdc B+ and 105vdc for the bias supply. I’ve got 6.3vac for heaters. I’m not using the relay bypass - I can just bypass it on the patch bay.
I’m going to take the 6X4 rectifier out and put in the original 5y3 and see if it’s happier.
It’s weird cos my voltages are great but I’m getting such terrible thumping.
The original power section is so beautifully simple - I’m regretting trying it now though! Haha!

 

[Dr_J]

I'm still struggling with my output pot...  :-\

Now I'm a bit confused... the BOM calls for a 50k LIN Pot, the MOUSER Part-No. points to a 50k LOG.
The original schematic (i have) shows a 1k...
Looking at my output curve, it looks like a 7k pot will nicely fit...

What have you guys used?

ROCK-ON!

 

[IanB]

I'm still struggling with my output pot...  :-\

Now I'm a bit confused... the BOM calls for a 50k LIN Pot, the MOUSER Part-No. points to a 50k LOG.
The original schematic (i have) shows a 1k...
Looking at my output curve, it looks like a 7k pot will nicely fit...

What have you guys used?

ROCK-ON!

I used the CAPI/hairball output attenuator. Works, or should I say “worked” great....until I pulled it all apart.

 

[IanB]

Update: original rectifier tube is in (vs the 6X4 which was pooing it’s pants) & it WORKS!!!....and sounds great!!!
Only weird/annoying thing is the regulator tube intermittently/randomly cuts out every few minutes. Not acceptable so I’m still not quite home & hosed!

 

[Dr_J]

Update from my build:

I've ordered some pots and carried out some testing...
Here're some results.

You guessed it; like the schematic points out... the 1k LIN won 

Maybe I would try a -10dB H-Pad later ... later ...


ROCK-ON!