SB4001 Support / Build Thread

[gandhalf3]

ok, i will change it.

What could be the problem, of the left channel of the Unit 2 ?

I removed the 4 VCA  of the Audio secion on each channel and jumped pins 1 and 8 on U2. On each channel.

Same problem on the left channel...

 

[gandhalf3]

Some help ?

 

[gandhalf3]

please ruckus

 

[ruckus328]

Nicolas, sorry I have not had internet for nearly a week, Verizon had an outtage, caused me alot of grief and delays.  Maybe thier sleezy way to try and get me to switch from DSL to Fios.

Anways...

Ok, not much that could be wrong.  If you haven't inserted VCA's back yet, just put one into the left channel (you can insert all 4 in the right channel since this channel is working).  If you have inserted all 4 back in the left channel, then just leave all 4 in, not worth the hassle to remove them again.

Set gain knob to somewhere around +10.  Measure DC voltage at R13R (the side closest to VR2R).  You should have somewhere around 500mVDC (exact voltage is not important).  Note whatever voltage you have here, you should have the same voltage at R13L.

If you DO have this same voltage at R13L, then other side of R13L isn't soldered correctly or something is wrong with the NE5534 (U8L).  Either bad solder joint, wrong part installed, or part is blown and should be replaced.

If you DON'T have this same voltage at R13L, it is your ribbon cable.  Either connector is not soldered properly or ribbon cable is bad.  Check continuity of J1 Pin 4 to J2 Pin 4.  Swap ribbon cables from another unit if possible to verify. 

I will check support thread this evening.

 

[gandhalf3]

I have n't the Leaf this week so i could not measure the voltage.

Continuity of J1 and J2 is good.

But i swapped ribbon from other unit : Doesnt solve the problem.

Iv' changed  both NE5534. : doesnt solve the probleme.


Could it come from C4 ? just an idea because, i'v put it in the bad way, and changed it to the right way, before first power up, but it seem to be clean.

 

[ruckus328]

I have n't the Leaf this week so i could not measure the voltage.

Not sure what you mean by leaf but I need you to check the voltage here, need to establish if signal is getting to this point, otherwise it's not possible for me to narrow down the issue.

Some other things to check as well:

Also check DC voltage on the other side of R13L/R (the side closest to C6L/R), With Gain at 10 you should read somewhere around 60mV here.

Check DC voltage at U8L/R Pin 6, you should read this same 60mV.

Next,

Feed unit a signal, measure AC voltage at TP1L & TP1R, you should have same amount of AC voltage at both of these test points (this is in audio path before the VCA's). 

Also check AC voltage at TP2L & TP2R (this is audio path after the VCA's).  Should be around the same voltage you read at TP1L/R.

Do all of this and I should be able to tell you where the problem is.

Could it come from C4 ?

No, I don't think so.

 

[sonic02]

Ruckus,
Have a small problem, when i engage the 'comp in' the right channel goes dead, no sound at all. When it is bypassed the right channel comes back. There is also a random clicking sound in the left channel when engaged. Maybe Relays? should I replace them, what type?
stu.

 

[gandhalf3]

Ruckus,
Have a small problem, when i engage the 'comp in' the right channel goes dead, no sound at all. When it is bypassed the right channel comes back. There is also a random clicking sound in the left channel when engaged. Maybe Relays? should I replace them, what type?
stu.

Try to put the make up gain at max, and see if the signal is still there when the compressor is "comp in" on your right channel.
maybe you have the same problem as me. (-80dB on your right channel when comp is in ).

So you shoudl try to test all the steps that ruckus told me.

 

[gandhalf3]

Home work done. Iv replaced all the VCA one the right channel, and put just one VCA on the Left.


the gain was set somwhere around +10.

Right channel R13R / VR2R side : -778mVDC
Left channel R13L / VR2L side : -776mVDC

Right channel R13R / C6 R side : -37mVDC
Right channel R13L / C6 L side : -35mVDC

U8 Pin 7 (i got the good voltage on PIN 7 not PIN 6)(Pin 6 was more around -1500 :

U8R : -37mVDC
U8L : -35mVDC


(The voltage were positive when the gain was at -6db, and around zero at zero. and negative when at +XdB. I'v got something around -2000mVDC at R13R / VR2R side when gain at +18)


AC voltage :


TP1R : 720 mVAC
TP1L : 720 mVAC

TP2R : 1000mVAC (with makeup gain at somwhere +10dB and threshold at +20)
TP2L : 350mVAC the problem should be there or this is caused by the fact that i'v put just one VCA on this channel ?

 

[ruckus328]

or this is caused by the fact that i'v put just one VCA on this channel ?

Voltage will be approx 1/4 expected voltage if only 1 VCA installed.  Taking into consideration you haven't calibrated for unity gain, 350mV seems about right, so no, everything up to this point looks good.

So, your control voltage to the VCA's is good.

Your audio chain up until the output of U6L is good.

Which means your problem is either bad part/faulty solder joint at:

C8L
U7L (THAT1646)
C9L
C10L
L1L (jumper)
L2L (jumper)
K2L

Prime suspect would be your output driver chip (U7L). 

Measure voltage at U7L Pin 4, if 350mV at TP2L you should read same AC voltage here at Pin 4.  If so this rules out C8L.

Measure voltage across pins 8 & 1 on U7L, you should read 700mV if 350mV at TP2L, I suspect you will read very little/nothing here though.  If no voltage here, this confirms that U7L is the problem.

 

[ruckus328]

Ruckus,
Have a small problem, when i engage the 'comp in' the right channel goes dead, no sound at all. When it is bypassed the right channel comes back. There is also a random clicking sound in the left channel when engaged. Maybe Relays? should I replace them, what type?
stu.

Debug process is same instructions I've given to Gandhalf.  Needle in a haystack until you've taken some measurements, it could be anything.

 

[gandhalf3]

pin 4 : 350mvac
PIN 1 : around 0
PIN 8 around 0


With another thatchip :
that changé :

Pin 4 : 350mvac
Pin 1 : 315
Pin 8 : 0,1

i didn't measured btween 1 and 8;

but the sound came Back !!! thanks ruckus, i will buy another chip tomorrrow.

Thanks alot, you are my heroe

 

[john12ax7]

So I'm finally getting around to building this.

What was the typical build time for people? I've probably been at it 4 hours so far and still not done with the resistors, oh so many resistors.

 

[SKJGProject]

17 hours

 

[sonic02]

Ruckus,
Have a small problem, when i engage the 'comp in' the right channel goes dead, no sound at all. When it is bypassed the right channel comes back. There is also a random clicking sound in the left channel when engaged. Maybe Relays? should I replace them, what type?
stu.

Debug process is same instructions I've given to Gandhalf.  Needle in a haystack until you've taken some measurements, it could be anything.

Found the problem, i missed one of the pins on the right channel relay. A simple fix, and didn't even have to take it apart. Sounds fantastic too, very versitile, great job ruckus  8)

 

[john12ax7]

Are the THAT VCA chips supposed to sit flush in the socket? They seem rather hard to get in compared to the DIP ICs. How much force should you use?

 

[john12ax7]

Ok got it all powered up and seems to be working.

1) One issue is at 1.5 ratio the meter does not zero, it starts at about 3 and works accordingly, all the ratios zero.

2) A second issue is I can't get a full 18 db gain even after adjustment. Seems to max at around 15-16 db.

3) How do you solder the TRS connector with the pot already on board?

4) Any special tool to mount the faceplate? The two middle ones are tucked away pretty good, where they is hard to get to.

5) I forget to cut pin 4 of the sidechain VCAs,  :'( how critical is this?

 

[john12ax7]

Ok I went through and fixed all the problems, except one.

The meter still doesn't zero at 1.5 ratio. Is this typical?

 

[mulletchuck]

My meter zeroes at that ratio setting.  Perhaps your meter is messed up?

 

[john12ax7]

My meter zeroes at that ratio setting.  Perhaps your meter is messed up?

All the other ratios work fine, wouldn't that suggest it is more the supporting circuitry?