[BUILD] STA LEVEL PCB OFFICIAL BUILD & HELP THREAD
- Thread starter bernbrue
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Help Support GroupDIY Audio Forum:
Hi,
I finished the wiring, and i powered on. Without any tube, i got 2 of the 3 leds illuminated,but the third one remains unlighted.. Do i need to put the 6al5 to have It illuminated ? Also, i do not have light on the bulb and maybe those 2 things are related ?
Thank you
Hugo
I finished the wiring, and i powered on. Without any tube, i got 2 of the 3 leds illuminated,but the third one remains unlighted.. Do i need to put the 6al5 to have It illuminated ? Also, i do not have light on the bulb and maybe those 2 things are related ?
Thank you
Hugo
bernbrue
Well-known member
Hi Hugo,
the LEDs just indicate a working psu. The third LED is probably the 5V rail. Just measure if you've got voltage there. I would suggest to power it up with everything connected and tubes plugged in. Without the tubes the voltages go up to heaven. So measure under load.
Bernd
the LEDs just indicate a working psu. The third LED is probably the 5V rail. Just measure if you've got voltage there. I would suggest to power it up with everything connected and tubes plugged in. Without the tubes the voltages go up to heaven. So measure under load.
Bernd
Hi,
I realised that i did not have any power on filaments, and after checking all components/connections, i just have a doubt on my LM338 TO-3 version... I respected the polarity of IN and ADJ, but in datasheet, there is written that the V out is "the case" of TO-3...should i add some connection ?. Also, i soldered it straight in the pcb, is it a problem ?
Thank you,
Hugo
I realised that i did not have any power on filaments, and after checking all components/connections, i just have a doubt on my LM338 TO-3 version... I respected the polarity of IN and ADJ, but in datasheet, there is written that the V out is "the case" of TO-3...should i add some connection ?. Also, i soldered it straight in the pcb, is it a problem ?
Thank you,
Hugo
bernbrue
Well-known member
Yes, you should mount it with isolation on chassis, otherwise it will get very hot and turn into thermal shutdown (-> no heater voltage).
Bernd
Bernd
bernbrue
Well-known member
You need a TO-220 voltage regulator.
Bernd
Bernd
Ok, now the PSU seems to work (all leds are illuminated), but :
1 - the meter does not react when i power on the unit..even with trimmer fully CW.. Which part could i check for this ?.
2 - Is there a diagramm to wire an T-Pad as output ? I do not figure how to do..
Thank you
1 - the meter does not react when i power on the unit..even with trimmer fully CW.. Which part could i check for this ?.
2 - Is there a diagramm to wire an T-Pad as output ? I do not figure how to do..
Thank you
bernbrue
Well-known member
What are the specs of the meter? There is a meter trimmer as well. Are the tubes inserted?
Bernd
Bernd
I solved meter problem, but now i have an other issue...Sound passes fine through the preamp, the input poyt react well, but not any compression is applied to the signal.. How to check where i made a mistake ? I use a 6386 that i am not able to test...but before buying a new one i prefer to be sure it does not come from an other spot..
Thank you..
Thank you..
bernbrue
Well-known member
Hi Hugo,
Quote from my third post:
6) A few things to keep in mind when using different input tubes (6386 or 6BA6 combo):
- with the 6BA6 combo the unit sounds almost the same as with the 6386 tube, but the gain structure and threshold is completely different.
- First I tested the 6BA6 combo with a 1:4 input transformer, input pad, all values according to original schematic: works fantastic and sounds very good.
- Then I replaced the combo with a single 6386 tube. I had to crank up the input pot in order to get some slight compression. Not very satisfying.
- So I removed the input pad and lowered the threshold by reducing R32 (24K). I replaced the resistor with a 20K pot plus a 4K7 to ground in order to find the right threshold. Finally ended with around 18K.
I hope that helps. I finally convinced the seller in Paris to ship the MKS30 to me!
Bernd
Quote from my third post:
6) A few things to keep in mind when using different input tubes (6386 or 6BA6 combo):
- with the 6BA6 combo the unit sounds almost the same as with the 6386 tube, but the gain structure and threshold is completely different.
- First I tested the 6BA6 combo with a 1:4 input transformer, input pad, all values according to original schematic: works fantastic and sounds very good.
- Then I replaced the combo with a single 6386 tube. I had to crank up the input pot in order to get some slight compression. Not very satisfying.
- So I removed the input pad and lowered the threshold by reducing R32 (24K). I replaced the resistor with a 20K pot plus a 4K7 to ground in order to find the right threshold. Finally ended with around 18K.
I hope that helps. I finally convinced the seller in Paris to ship the MKS30 to me!
Bernd
Thanks for replying...
Now i have compression, the T-pad is connected and everything seems to work fine EXCEPT:
- When i push the momentary switch, the ground loop disappear, and i have big noise when the swith is "off".. I tried to swap the star ground wire to the other lug of the momentary switch, and i have permanent humm. It should be the opposite, i can not understand why..
- Also, i have a saturation hearable when the track is mainly 1khz.
I will try to remove the input pad, and change R24 with 18k (i did not understood what you meant by 4k7 to ground)..
hugo
Now i have compression, the T-pad is connected and everything seems to work fine EXCEPT:
- When i push the momentary switch, the ground loop disappear, and i have big noise when the swith is "off".. I tried to swap the star ground wire to the other lug of the momentary switch, and i have permanent humm. It should be the opposite, i can not understand why..
- Also, i have a saturation hearable when the track is mainly 1khz.
I will try to remove the input pad, and change R24 with 18k (i did not understood what you meant by 4k7 to ground)..
hugo
bernbrue
Well-known member
You need a "momentarily off" switch, i.e. when pushing the switch, the contact to ground is interrupted. This causes noise , which is taken as a kind of test signal in order to balance the two 6ba6 tubes and the two halves of the double triode output tube.
Bernd
Bernd
bernbrue said:
Yes, i just realized this !
I will try to finish this evening...I already love that unit.Oh i forgt to mention one point : I accidentally powered on the unit with Output Tx disconnected.. I saw smoke arround the 10w resistor, but i prefered to switch off the unit before breaking something, and i did not see fro which component exactly the smoke. I noticed at the same time that i made a big mistake by swapping one EL90 and the 6AL5..I corrected thos 2 points and unit started to work fine..But should i replace tubes, caps, or resistor in this case ?
bernbrue
Well-known member
Hi Hugo,
where did you use 82R instead of 68R. I don't know what you are referring to, power supply, main board?
In case your 5V rail doesn't give you enough power you can connect the relays to the heater supply.
Bernd
where did you use 82R instead of 68R. I don't know what you are referring to, power supply, main board?
In case your 5V rail doesn't give you enough power you can connect the relays to the heater supply.
Bernd
bernbrue said:
Oh sorry, i was replying to one koslik post, which describes a "U pad" with 2x 270R and one 68R, to put before a t-pad...
Everything works fine except the fastest recovery position, which does not recover at all...will take a look at the switchs board
