SB4000 Support Thread

[Harpo]

All the links online are all dead.

Link at reply #1285 from pg.65 seems to be working ?

 

[Blackdawg]

Can someone please upload the SB4000 schematic.

All the links online are all dead.

I need to know resistor / jmp values for the dbx202c gold can VCAs.

I posted it literally 9 posts before yours..

 

[Chrome Heart]

Im using the Hairball meter, and for some reason just turning the threshold knob makes it jump. It'll pin, then settle back down. Ive check the feed pins from the pcb and it looks there is DC voltage going to the meter when I turn the knob. It'll go up 3 volts and settle back down. Any ideas?

 

[Chrome Heart]

Im guessing I must be the last guy to build one of these, this thread seems pretty dead.

 

[Chrome Heart]

:bump:

 

[oscarat50]

I built one a few months ago. It's a beast, love it

 

[Chrome Heart]

Hello... lo... lo... lo...lo

 

[Chrome Heart]

I'll try again. At R111 I get a voltage spike of around -3 Volts, it starts to bleed down to 0 and then spikes again. It happens roughly every 3 seconds, like a clock. Any suggestions where to look?
Also, only seems to happen when the control board is plugged in. All the connections are good, and I dont see any problems with component orientation.

 

[Chrome Heart]

Well, it looks like the jumper at R169 is the culprit. I put in the 47K resistor and it seems to have eliminated the problem, however Im not getting as much throw on the threshold as before. Any ideas?

 

[Chrome Heart]

After I first built the unit I tested and calibrated using a Behringer style round meter. I didnt start experiencing the weird stuff untill I swapped in the Hairball meter.

 

[JMan]

I’m still building this project. I got in on this late, so I’m just finishing up stuffing my boards.  I also have some pretty basic questions. 

First off, and I think there may have been some earlier discussion of this, but I can’t seem to find it now: has anyone got a good way of mounting the transformer without having that awful bolt head on the underside of the case? 

Second, with regards to the trim pots, are there pre-trim values for all of them? I think I located all of the values listed on the schematic, but that doesn’t cover every trim pot on the board.  Are the others purely for adjustment after the fact and don’t need to be pre-trimmed?  (I think I did a bad job of wording this question, but I imagine you will understand what I’m asking).

 

[Chrome Heart]

If you bought the kit. the trimmers in the VUDriver circuit have been replaced with resistors. Except for VR15, which is the Bargraph adjustment.  Replaced trimmers are VR11, VR12, VR13 and VR14.

 

[oscarat50]

I’m still building this project. I got in on this late, so I’m just finishing up stuffing my boards.  I also have some pretty basic questions. 

First off, and I think there may have been some earlier discussion of this, but I can’t seem to find it now: has anyone got a good way of mounting the transformer without having that awful bolt head on the underside of the case? 

Second, with regards to the trim pots, are there pre-trim values for all of them? I think I located all of the values listed on the schematic, but that doesn’t cover every trim pot on the board.  Are the others purely for adjustment after the fact and don’t need to be pre-trimmed?  (I think I did a bad job of wording this question, but I imagine you will understand what I’m asking).

I soldered the bolt inside the case, no problems at all. Just try not to over do it when soldering or you will make a hole in the case.

 

[oscarat50]

If you bought the kit. the trimmers in the VUDriver circuit have been replaced with resistors. Except for VR15, which is the Bargraph adjustment.  Replaced trimmers are VR11, VR12, VR13 and VR14.

I can't calibrate my VU meter properly. It's getting the signal too loud and I can't turn it down using Vr15. I bought the kit with the resistors instead of the trimmers. Any ideas on how i can fix this? Thanks

 

[Chrome Heart]

I can't calibrate my VU meter properly. It's getting the signal too loud and I can't turn it down using Vr15. I bought the kit with the resistors instead of the trimmers. Any ideas on how i can fix this? Thanks

which meter? Reduction or bargraph?

 

[oscarat50]

The bargraph

 

[Chrome Heart]

The bargraph

Make sure the bargraph isn’t installed upside down.

 

[oscarat50]

It works as it should but the input signal to the meter is too loud. It's installed properly. The only thing I need is to reduce the input signal to the meter, maybe the calibration pot needs a higher resistance?

 

[Chrome Heart]

It works as it should but the input signal to the meter is too loud. It's installed properly. The only thing I need is to reduce the input signal to the meter, maybe the calibration pot needs a higher resistance?

It shouldn't,  unless the wrong value is currently installed. Are you sure the test signal is 1.228vac?

 

[JMan]

If you bought the kit. the trimmers in the VUDriver circuit have been replaced with resistors. Except for VR15, which is the Bargraph adjustment.  Replaced trimmers are VR11, VR12, VR13 and VR14.

Yes, I see that the parts kit provides fixed resistors in the bargraph driver circuit with an option to use trim pots for fine adjustment.  I’m putting in trim pots there just cause I have them.  Will set them to the values of the fixed resistors and hopefully won’t need to touch them again.

Still, any info on actual pre trim values elsewhere on the board?  Here’s what I was able to grab from the schematic:

VR7 - 6k4
VR8 - 6k4

VR15 - 10k
VR16 - 6k (is this right? It’s a 50k pot, why such a high value pot with such a low pre trim value?)
VR17 - 2k

That still leaves a bunch of trim pots, and I am not sure if they need to be set to any particular values before putting them on the board.  Any help?