[BUILD] 1176 Rev F/G - new board, new transformer!

[Echo North]

The polarity is right which is why I'm confused :S ahh I didn't know to leave out R5. The one next to the input? Just get rid of it completely?

Ya it's a load resistor not needed for transformers input.

Did you test your power rails (-9 VDC and +30 VDC)?

 

[Finlaywatt]

Okay took it out. I did but not sure if i tested in the right place? Is it on the power stage where it says +30V and -10V. Where do I measure that from?

 

[Echo North]

Okay took it out. I did but not sure if i tested in the right place? Is it on the power stage where it says +30V and -10V. Where do I measure that from?

Of course.  Measure those points from the CT of your power transformer secondary connection.

 

[Finlaywatt]

So is that just CT on the main PCB? Sorry for the stupid questions. If so its reading 22V at the 30V pad and 0V at the 10V pad.

 

[Echo North]

So is that just CT on the main PCB? Sorry for the stupid questions. If so its reading 22V at the 30V pad and 0V at the 10V pad.

Did you test the power supply before stuffing the rest of the board?

You've got a major issue somewhere you'll need to find.  Start in the PS.

 

[Finlaywatt]

Nope, I did small stuff to big stuff because that's just how I'd been taught to do it. :/ totally wish I hadn't now. Power is wired IEC hot to front lug on the top row of the Off switch. IEC neutral to the one beneath. Power transformer: brown wired to middle lug of top row of the off switch. Blue to the one beneath it. Black, orange, red and yellow wired to a connector block. Yellow in the 1st connector bit, red + orange in the middle, black at the other side. The lilac/purple and grey are joined together. From the connector block there is a red wire coming out each side and a black in the middle for the CT. Wired the same at input. Does that sound right for the power transformer etc for 240V?

Whatever is happening seems to be causing r26 to dome out slightly over time.

 

[Echo North]

Nope, I did small stuff to big stuff because that's just how I'd been taught to do it. :/ totally wish I hadn't now. Power is wired IEC hot to front lug on the top row of the Off switch. IEC neutral to the one beneath. Power transformer: brown wired to middle lug of top row of the off switch. Blue to the one beneath it. Black, orange, red and yellow wired to a connector block. Yellow in the 1st connector bit, red + orange in the middle, black at the other side. The lilac/purple and grey are joined together. From the connector block there is a red wire coming out each side and a black in the middle for the CT. Wired the same at input. Does that sound right for the power transformer etc for 240V?

Whatever is happening seems to be causing r26 to dome out slightly over time.

You need to be careful.  Something could explode on you.  I have no idea, but you have something wrong happening.  IF your transformer image (on your actual transformer) matches the one below, orange and red should be going to your CT.

You may want to consider finding a tech to help you at this point.  Maybe look for shorts/bridges, check your wiring, check your component values.  Start in the power section.  You may have a dead/shorted capacitor.  It could be a million things.

Mike

 

[Finlaywatt]

Yeah, matches that schematic. Had one of the best techs going looking at it today, but because it was all powered on and passing signal I never figured problems with the power section. We were having a hell of a time finding the problem :/ I'll go over the circuit and take it in to him again.

 

[Echo North]

Yeah, matches that schematic. Had one of the best techs going looking at it today, but because it was all powered on and passing signal I never figured problems with the power section. We were having a hell of a time finding the problem :/ I'll go over the circuit and take it in to him again.

Sounds like a plan.  The only thing you should be concerned about right now is getting your +30/-10 VDC rails correct +/-5%.  Once you do that I think you'll be on the right track forward.  Good luck!

 

[Finlaywatt]

Cheers, my +30 is sitting at about 27-28V. I just can't get the -10V to budge. I'm guessing flux residue can cause shorts?

 

[Echo North]

Cheers, my +30 is sitting at about 27-28V. I just can't get the -10V to budge. I'm guessing flux residue can cause shorts?

I doubt it.

I's start with C24 and 26, R85 and 86, CR6 through 10.  Check orientation...value...health...

If your C26 is swelling, get it out of there and put a new one in.  It may be dead and shorting or backwards which would cause your issue.

 

[Finlaywatt]

Okay, R86 reads correct. R85 takes forever to count up and only gets to like 980. How do I measure CR6 through CR10? Okay, it's the 2nd c26 to swell from the same batch of 5 so I'm gonna get another batch. Does specifics matter or am I just looking for a 2200uF 50V electrolytic?

 

[Echo North]

Okay, R86 reads correct. R85 takes forever to count up and only gets to like 980. How do I measure CR6 through CR10? Okay, it's the 2nd c26 to swell from the same batch of 5 so I'm gonna get another batch. Does specifics matter or am I just looking for a 2200uF 50V electrolytic?

To measure R's correctly they need to be out of circuit (de-solder and lift one leg). 

For the caps and diodes, refer to the overlay (http://mnats.net/files/1176_REVFG_SCREEN_LAYER.pdf) to make sure they are oriented correctly.

Mike

 

[Finlaywatt]

Okay, thanks a lot! Will try all this and see how I get on.

 

[frazzman]

Still troubleshooting my unit that is passing audio but not compressing. Just realised I accidental used log pots where lin was required. Coold this stop the unit from compressing ? Checked all cabling between mainboard and meter and ratio boards, appears fine. Any specific areas to focus on if getting no compression ?? Thanks in advance

 

[Echo North]

Still troubleshooting my unit that is passing audio but not compressing. Just realised I accidental used log pots where lin was required. Coold this stop the unit from compressing ? Checked all cabling between mainboard and meter and ratio boards, appears fine. Any specific areas to focus on if getting no compression ?? Thanks in advance

This is usually easy to sort out.  Read the 2-3 pages of this Steve_H exchange. 
http://www.groupdiy.com/index.php?topic=29981.msg614820#msg614820

You'll want to check:

1. Your Q1 gate bias
2. Your AC at pad 22 at various ratio's
3. Your DC at pad 21 at various ratio's

Odds are one of those is off.

 

[frazzman]

Still troubleshooting my unit that is passing audio but not compressing. Just realised I accidental used log pots where lin was required. Coold this stop the unit from compressing ? Checked all cabling between mainboard and meter and ratio boards, appears fine. Any specific areas to focus on if getting no compression ?? Thanks in advance

This is usually easy to sort out.  Read the 2-3 pages of this Steve_H exchange. 
http://www.groupdiy.com/index.php?topic=29981.msg614820#msg614820

You'll want to check:

1. Your Q1 gate bias
2. Your AC at pad 22 at various ratio's
3. Your DC at pad 21 at various ratio's

Odds are one of those is off.

Hi Echo - thanks a lot for your help.

I think you're onto something. Pad 21 AC & DC voltage increases as the ratio goes from lowest to highest so I think we are ok here.
However - on pad 22 - I don't get any reading at all.
The link between pad 22 from mainboard to meter PCB is solid so I know that its not that. Should pad 22 react simularly to pad 21 in that the voltage increases when the ratio does?

In regards to pad 22, am I missing something, are there any obvious components that come to mind if I'm not getting any reading here? I've got over all the solder points to weed out the possibility of any dry joints but its all good and all clean.

Q-Bias adjustment moves the meter left and right respectively when in GR mode. Turning the ratio toggle makes the meter shift a little also.

Appreciate your patience, i'll built so many pultecs and other comps but this is my first FET comp so my head is swimming a little!

 

[Echo North]

Please open up the schematic on the first page of this thread.  Locate pad 22, it's near the middle-bottom.  You'll see a "22" near C17, that is pad 22 and everything to the right of it is your main PCB.  If you follow the trace up you'll see it leads to the GR odd switch (back of the attack pot) then to 1/2 of your ratio switch and eventually to your output pot.

So in a nutshell, the audio output (AC) of the first amp stage is tapped off the output pot and sent through a simple resistor ladder (the ratio switch) where the AC is decreased depending on the ratio selected (it goes through more resistors as the ratio gets higher) and then fed to pad 22 which is at the start of the GR amp. 

So you have no AC at pad 22 with GR on?  But you are passing signal which means you have AC at your output.  So you're losing it along that path.  Let's look at the schematic and trace your audio from the output pot to the GR amp and see where is stops. Make sure GR is on. 

1. There is a wire that goes from the output pot to pad 15 on your ratio PCB.  Your AC at output pot and pad 15 should be the same. Check?  If not the wire is messed up.
2. Pad 4 on the schematic is where your audio exists the ratio PCB.  This pad is listed as GRN on your ratio board.  Check your AC here.  It'll be smaller depending on the ratio selected but it should still be strong.  Check?  If not there is a problem on the ratio PCB.  This is my guess for your issue.
3.  With GR on the GRN pad should be connected to your wire connected to pad 22 via your switch.  Check for audio at GRN on your attack switch and pad 22.  Check?  No signal here means your switch is wrong.

Mike

 

[frazzman]

Please open up the schematic on the first page of this thread.  Locate pad 22, it's near the middle-bottom.  You'll see a "22" near C17, that is pad 22 and everything to the right of it is your main PCB.  If you follow the trace up you'll see it leads to the GR odd switch (back of the attack pot) then to 1/2 of your ratio switch and eventually to your output pot.

So in a nutshell, the audio output (AC) of the first amp stage is tapped off the output pot and sent through a simple resistor ladder (the ratio switch) where the AC is decreased depending on the ratio selected (it goes through more resistors as the ratio gets higher) and then fed to pad 22 which is at the start of the GR amp. 

So you have no AC at pad 22 with GR on?  But you are passing signal which means you have AC at your output.  So you're losing it along that path.  Let's look at the schematic and trace your audio from the output pot to the GR amp and see where is stops. Make sure GR is on. 

1. There is a wire that goes from the output pot to pad 15 on your ratio PCB.  Your AC at output pot and pad 15 should be the same. Check?  If not the wire is messed up.
2. Pad 4 on the schematic is where your audio exists the ratio PCB.  This pad is listed as GRN on your ratio board.  Check your AC here.  It'll be smaller depending on the ratio selected but it should still be strong.  Check?  If not there is a problem on the ratio PCB.  This is my guess for your issue.
3.  With GR on the GRN pad should be connected to your wire connected to pad 22 via your switch.  Check for audio at GRN on your attack switch and pad 22.  Check?  No signal here means your switch is wrong.

Mike

Mike - thank you very very much for taking the time to reply and to assist! I'm a long time Hairball customer and its great to get support like this even when you're not obligated to

Anyhow - did some more work on this with schematic in hand.

In regards to your point (1) - AC is ok on output pot and then compared to pad 15 on MB. At both points the AC fluctuates depending on the loudness of the audio. I had a snare sample running through and when a roll came up the AC reading rose when measuring at pad 15 on mainboard and on the output pot itself.

In regards to pad GRN... I'm sorry but I can't find this for the life of me. I've got a pad 4 on ratio PCB and pad 4 on meter PCB - these two are linked by a wire. Is that the pad you're referring to when you say GRN?

I certainly concede with your finding that theres no AC at pad 22 so I know the general area its being lost in but just trying to narrow it down.

Thanks again

 

[frazzman]

Oh the penny just dropped .... in case I didn't mention earlier I'm building a rotary version not push button so I'm using the old school gyraf style ratio and meter pcbs.