SB4000 Support Thread

[Bowie]

I cannot for the life of me get the 12 volt rail to be less than 14-15 volts, I have changed regulataors double checked my transformer wiring about a hundred times and rechecked all the resistor/caps...everythign is as it should be...

Even under load it remains at like 14.57 volts...

I know this is not a huge deal but I do worry about the life of the regulator since it is getting hot...

I did use the 50mA transformer so there's that...

Any thoughts or comments?

Edit; I looked at the BOM and your PT should be fine. Personally, I'd adjust the psu board to get it closer to 12v.

 

[iomegaman]

There is no way to adjust the 12 volt rail, the only adjustment is for the =/+ 15 volt...

And I'm using the VPT36-1390 listed in the BOM...

 

[Bowie]

There is no way to adjust the 12 volt rail, the only adjustment is for the =/+ 15 volt...

And I'm using the VPT36-1390 listed in the BOM...

Sorry, I should have been more specific, I meant to alter it via the PSU board by changing resistor values or adding resistors to the 12v rail.  I've been doing this to some of my gear recently to fine-tune the power values.

I built two of these and the 12V was dead-on but if you're sure everything is the correct value and it's still a bit high under load, you may wanted to alter the circuit in the power section.

 

[iomegaman]

Changed out R182, R183 for 12 Ohm and everything tamed down to acceptable voltages...thanks for the help.

 

[Barton]

As usual, I've returned with what it likely a dumb question.  I powered up the power supply board and got the correct voltages, but when I connected the main board and powered up, the voltages on all the rails were very low.  i suspect that it may be a problem in the VCA section, which has me a little confused.  I have the quad VCA (2181B), so I used the component values listed in the table on the schematic.  I've interpreted the schematic to mean that I do not populate anything on the main board in the VCA section, with the exception of JMP1/JMP4, and that the VCA components are all populated  on the separate quad board.  Is my interpretation correct?

 

[critterkllr]

I know this question has to have been asked a lot, but I just can't find it anywhere. Are any modifications needed if using the Quad VCA in a GSSL?

 

[gabygab]

Hello,

I'd like to thank everyone who's contributed to this thread, it's been so much help!

I'm a DIY noob. I've reached a bit of a snag when it comes to powering the unit along with the power switch.  I am using the transformer from the BOM and am living in Canada (120V). I currently have  my primaries, Blue and Violet, hooked up to the COM of the switch. A hookup wire going from the switch back to the L of the IEC. Brown and Grey are going to Neutral on the IEC.

I'm sorry if this has been addressed before but I can't seem to find the solution.

Kind regards,

Gabriel

 

[Bowie]

Hello,

I'd like to thank everyone who's contributed to this thread, it's been so much help!

I'm a DIY noob. I've reached a bit of a snag when it comes to powering the unit along with the power switch.  I am using the transformer from the BOM and am living in Canada (120V). I currently have  my primaries, Blue and Violet, hooked up to the COM of the switch. A hookup wire going from the switch back to the L of the IEC. Brown and Grey are going to Neutral on the IEC.

I'm sorry if this has been addressed before but I can't seem to find the solution.

Kind regards,

Gabriel

Pardon if I missed it but I didn't see what, specifically, the question was.

 

[gabygab]

Hello,

I'd like to thank everyone who's contributed to this thread, it's been so much help!

I'm a DIY noob. I've reached a bit of a snag when it comes to powering the unit along with the power switch.  I am using the transformer from the BOM and am living in Canada (120V). I currently have  my primaries, Blue and Violet, hooked up to the COM of the switch. A hookup wire going from the switch back to the L of the IEC. Brown and Grey are going to Neutral on the IEC.

I'm sorry if this has been addressed before but I can't seem to find the solution.

Kind regards,

Gabriel

Pardon if I missed it but I didn't see what, specifically, the question was.

Oops sorry if I wasn't clear. I was just not sure if this was the correct way to hookup the transformer.

Thanks!

 

[Lordward]

Hi,

I've recently started my SB4000 build and it all went quite well until the first power rail test.  I'm getting the values:
-15.13 (-15)
-19 (-12)
12.11 (+12)
2.92 (+15)

I'm wired up for 230 V (Europe) and nothing has started smoking so far.    What could be the reasons I'm getting these (obviously wrong) values?

Cheers,
DW

 

[Harpo]

-19 (-12)

double check orientation of diode D29

2.92 (+15)

double check parts value of R179 for 120 ohm, as well as parts value of VR19 for either multiturn-trimmer dialed in for or fixed value resistor for about 1K33.

Other two rail voltages are within parts tolerances.
Measurement of the 5th. iso. +12VDC rail is missing.

 

[Bowie]

Hello,

I'd like to thank everyone who's contributed to this thread, it's been so much help!

I'm a DIY noob. I've reached a bit of a snag when it comes to powering the unit along with the power switch.  I am using the transformer from the BOM and am living in Canada (120V). I currently have  my primaries, Blue and Violet, hooked up to the COM of the switch. A hookup wire going from the switch back to the L of the IEC. Brown and Grey are going to Neutral on the IEC.

I'm sorry if this has been addressed before but I can't seem to find the solution.

Kind regards,

Gabriel

Pardon if I missed it but I didn't see what, specifically, the question was.

Oops sorry if I wasn't clear. I was just not sure if this was the correct way to hookup the transformer.

Thanks!

Looking at my build pics, that sounds correct.  However, be sure to reference the schematic/layout on your xformer because manufacturers sometimes change the color coding and you can end up w/ disastrous results if you just go by the colors every time.

 

[gabygab]

Thank you very much  for taking the time to answer me Bowie!

Fired it up earlier today. I checked the rails and they were fine. I then hooked up the power supply to the main board and got some smoke coming from R183 due to my TL047 chips being inserted backwards. I'll write this down for future builders using the search function that the  TL047 chips #1 position is indicated by the U shape and not the dot.  I'm going to replace the chips and the resistor and giver her another go on monday. Cheers!

 

[Lordward]

-19 (-12)

double check orientation of diode D29

2.92 (+15)

double check parts value of R179 for 120 ohm, as well as parts value of VR19 for either multiturn-trimmer dialed in for or fixed value resistor for about 1K33.

Other two rail voltages are within parts tolerances.
Measurement of the 5th. iso. +12VDC rail is missing.

Hi Harpo, thanks for your help   GDIY was down the past couple days here and I couldn't answer.
Anyway, this morning I measured again and it reads:
+15 = 15.03
+12 = 12.12

-12 = -19.30
-15 = -15.13

iso. +12 = =12.03

So it's *only* the -12 rail.  I've checked and double checked all components but can't find the issue.  Values are all correct and I measured them to be sure.  Diodes are placed correctly and I have 1K33 resistors instead of trim pots.  It's just not my day I guess...

Any other possibilities?

 

[Harpo]

-12 = -19.30
... Any other possibilities?

Missing load? Some vregs behave a little unpredictable without min.load connected. A temporary 1k2 (for 10mA) down to maybe 470 ohm (for 25mA) load between -12V and 0V reference voltage without overheating this temp.resistor will prove this -12VDC rail working correctly (or not).
Good luck.

 

[Lordward]

-12 = -19.30
... Any other possibilities?

Missing load? Some vregs behave a little unpredictable without min.load connected. A temporary 1k2 (for 10mA) down to maybe 470 ohm (for 25mA) load between -12V and 0V reference voltage without overheating this temp.resistor will prove this -12VDC rail working correctly (or not).
Good luck.

That was it.  I put in the 1.2k and it then measured-11.89.  Seems ok, doesn't it? Does this mean that it is safe to continue?

Thanks!

 

[Harpo]

-12 = -19.30
... Any other possibilities?

Missing load? Some vregs behave a little unpredictable without min.load connected. A temporary 1k2 (for 10mA) down to maybe 470 ohm (for 25mA) load between -12V and 0V reference voltage without overheating this temp.resistor will prove this -12VDC rail working correctly (or not).
Good luck.

I put in the 1.2k and it then measured-11.89.  Seems ok, doesn't it?

Yupp.

 

[Lordward]

Yupp.

Great stuff. So, I wired it all up and did the calibrations.  For some reason my Bar LED is not working.  No blink, nothing.  So I was not able to calibrate this.  Everything else went well and the unit sounds very promising so far

had the bar graph in upside-down.  Now it lights up.  Checked it on a mix and it's  always in the red in both input and output on a mix that has 5 db headroom.  Normal?

I'll have to wiggles some things around to see if I can get the bar meter working. 
One last question:  There are so many trim pots and I find it strange that in the calibration I did not have to touch all of them, specifically the 2 on the VCA boards...what am I missing?

DW

 

[Lordward]

I find it interesting that I cannot find, with the GDIY search or Google, any information about what the 50k trim pots on the VCA boards are for.  I did find a few people asking the same question- unanswered.  I've tried turning them just to hear the difference but I hear nothing. 

Any insight would be greatly appreciated!

 

[Harpo]

I find it interesting that I cannot find, with the GDIY search or Google, any information about what the 50k trim pots on the VCA boards are for.  I did find a few people asking the same question- unanswered.  I've tried turning them just to hear the difference but I hear nothing. 

Any insight would be greatly appreciated!

Wild guessing, all of your questions have been answered numerous times in this thread. (For your last request, maybe read my replies from FI. pg.62, there are more....)