[BUILD] 1176 Rev A - Back to the beginning...

[Potato Cakes]

I had similar voltages to what you are seeing on Q13, and it turned out to be a bad 2k trimmer on R75 (Null adjustment).

 

[JulienB]

Hi,
CR1 are correctly oriented and look okay.
I tested the junction=0,619v .

I remplace with a new 2Kohm trimmer pot R75, same voltage.

Julien

 

[hymentoptera]

Julien, can you post more pics, like the entire PCB? And some of the wiring. Can't hurt, I mean, if you got  a minute. Sometimes (not always) we see something that way.

 

[Potato Cakes]

When I get a chance, I'll post some voltages at points leading up to the ones already listed. If you are indeed getting +30V and -10V at the PSU test points, then I can only I can guess there must be a simple error that can be easily overlooked (cold solder joint, mixed up resistor placement, solder bridge, etc). That as been the case the majority of the time with most problems posted on this thread. Especially when I have an issue. There has been only one time when I've actually had a bad component, and that was the 2k trimmer I told you about.

I'll open one of mine up later this week and give you some other voltages at some other different places on the PCB and hopefully that might reveal the culprit.

Thanks,

Paul

 

[JulienB]

Hi,
here is a picture of PCB. It starts to move, the SignalLineAmp section gave me better results. All voltage are returned in the correct range. By cons nothing has changed for the portion in the GrMeterDriver GrControlAmp aussi. I trials which could be located in common in each section. I'll see if I have enough components to try to replace 2N3707, or test the outside of the circuit. Thanks for your help.

Julien

 

[JulienB]

New voltage

 

[keevhren]

I wouldn't worry too much about level at this point. The real issue is that with GR ON you have AC signal at pad 15 and none at pad 22. That's a problem.

Good news is that there isn't much in between.  Open the schematic:
http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

Turn GR ON (must be on) and go into 4:1 ratio. Locate pad 15 at the top middle of the schem. The AC leaves the output pot by wire to pad 15 on the ratio PCB.  Then is travels though  R78->R19->R20-R21 on the ratio PCB and out a wire at pad GRN where it then connects via the switch to pad 22.

Trace that AC through that and see where is dies.

Mike

Hi Mike,

Been mad busy the last two weeks so just got around to giving this a look.  I traced the signal through the 4 resistors on the Ratio PCB and have narrowed it down to the final output foot on R21.  I've pulled the resistor out and it's the correct value, but with every time I solder it back in, I get .000vac on the output foot. 

In lieu of that, I went in and measured the vac at all the pads and have the following:

R78 in - .126vac
R78 out - .096vac
R19 in - .096vac
R19 out - .059vac
R20 in - .059vac
R20 out - .029 vac
R21 in - 0.29vac
R 21 out - 0.000vac

So it appears that the rest of them are working correct as I think the signal should be getting lower in VAC as you go through them down the list. 

I also measured these same spots on my working unit and at the very end of the line (at R21 out) I have .099vac so know there should obviously be signal there. 

I'm at the point where I might just start from the top of the signal flow and measure every point and compare it to my working unit to see where things might be acting up. 

 

[junkface]

Trying to trouble shoot this friend's build, and I've cleaned up most everything that was glaringly janky looking. Checked the voltages to the schematic and there's not anything unusually out of range. Not getting compression tho, thought I'd see what you think. 
pad 22 is showing the larger to smaller trend
20:1 • .19vac
12:1• .11vac
8:1•.071vac
4:1• .036vac
pad 21 however is not
20:1 • -9.7 vdc
12:1• -9.7 vdc
8:1• -9.7 vdc
4:1• -9.7 vdc

If you're not getting correct compression check:

With in/out knobs mid way apply a 1khz 0dB signal and adjust the output to 0dB on the output
- that you see ac at pad 22 that starts larger and get's smaller as you move from ratio 20 to 4.
- that you have a negative DC voltage at pad 21 that starts larger and get's smaller as you move from ratio 20 to 4.

Post the values at each pad at each compression setting.

Mike

 

[Echo North]

Trying to trouble shoot this friend's build, and I've cleaned up most everything that was glaringly janky looking. Checked the voltages to the schematic and there's not anything unusually out of range. Not getting compression tho, thought I'd see what you think. 
pad 22 is showing the larger to smaller trend
20:1 • .19vac
12:1• .11vac
8:1•.071vac
4:1• .036vac
pad 21 however is not
20:1 • -9.7 vdc
12:1• -9.7 vdc
8:1• -9.7 vdc
4:1• -9.7 vdc

If you're not getting correct compression check:

With in/out knobs mid way apply a 1khz 0dB signal and adjust the output to 0dB on the output
- that you see ac at pad 22 that starts larger and get's smaller as you move from ratio 20 to 4.
- that you have a negative DC voltage at pad 21 that starts larger and get's smaller as you move from ratio 20 to 4.

Post the values at each pad at each compression setting.

Mike

Pad 21 is getting a negative DC voltage from the -10VDC rail. It's voltages are lowered or "tapped off" using a simple series resistor ladder on the ratio switch (S4B below). 

R64 is connected below to the -10VDC rail and pad 21 is over by C21.  If ratio switch 20:1 is selected/closed (far right of S4B) the neg voltage only passes through R64 and R63 so the voltage is higher than in say ratio 4:1 (far left) where the voltage is reduced now by R64, R63, R62, and R61. To get the reduction we need voltage, resistance, and current. If the voltage is not reducing through these resistors, you have no current flowing in that section of the circuit. You need a DC path to ground. C21 is the AC path but C21 blocks DC. So the DC path is after R58 where the wire ties back to the release pot (pad 18) and then to ground. Something is off there, or you have a bad joint, pad at R61.

Mike

 

[junkface]

nailed it mike. once i got that reflowed R61 and got DC going in there everything was hunky dory. thx as always for the quick and thorough assistance.

 

[Echo North]

nailed it mike. once i got that reflowed R61 and got DC going in there everything was hunky dory. thx as always for the quick and thorough assistance.

I wish they were all that easy! 

 

[bxershrts]

Hello Everyone,

I have been looking though the GroupDIY pages and have not found anything definitive. I am sure I am not the first to ask.

I have built a few of the 1176's from Mike. Recently I was purchased an 'auction lot' of parts, -- a company that went out of business. Inside was a box of 100's of 2n5458's and other transistors. I thought I could try to use these in either of the REV A or D I have built or in any future builds. The spec sheets show them being quite similar. Has anyone used these 2n5458's over the 2n5457's ? What were your results.

Thanks

 

[dbonin]

Hello Everyone,

I have been looking though the GroupDIY pages and have not found anything definitive. I am sure I am not the first to ask.

I have built a few of the 1176's from Mike. Recently I was purchased an 'auction lot' of parts, -- a company that went out of business. Inside was a box of 100's of 2n5458's and other transistors. I thought I could try to use these in either of the REV A or D I have built or in any future builds. The spec sheets show them being quite similar. Has anyone used these 2n5458's over the 2n5457's ? What were your results.

Thanks

Too close to call.  They are pretty much equivalent for this use case.
http://www.onsemi.com/pub_link/Collateral/2N5457-D.PDF

 

[felix1988]

Hi Everyone, hi Mike,
I just finished a 1176 Rev A with mnats pcbs v 1.25. I'm having trouble doing the calibration because I can't get constant output level. It constantly fluctuates within a Range of 20 mV and over time it even rises. (in a matter of minutes…)
I just rechecked all the cabling and didn't find any mistake.
I just wanted to know if the problem rings any bells that might help me narrow down my search?

Thanks!

 

[Echo North]

Hi Everyone, hi Mike,
I just finished a 1176 Rev A with mnats pcbs v 1.25. I'm having trouble doing the calibration because I can't get constant output level. It constantly fluctuates within a Range of 20 mV and over time it even rises. (in a matter of minutes…)
I just rechecked all the cabling and didn't find any mistake.
I just wanted to know if the problem rings any bells that might help me narrow down my search?

Thanks!

Not really.  I'd check every wire/terminal block solder connection. Maybe something is loose?

 

[django32]

Hiya, first post, i'm having a nightmare with my build! I'm not getting any signal to the input of the board. I'm driving it up on the scope and there is signal on the output of the input transformer when it's unloaded but once it's plugged into the board its gone. I feel like I'm doing something stupid here, I've checked for shorts etc and checked the components around the input of the board but it's got me stumped. anyone got any ideas?

 

[Echo North]

Hiya, first post, i'm having a nightmare with my build! I'm not getting any signal to the input of the board. I'm driving it up on the scope and there is signal on the output of the input transformer when it's unloaded but once it's plugged into the board its gone. I feel like I'm doing something stupid here, I've checked for shorts etc and checked the components around the input of the board but it's got me stumped. anyone got any ideas?

Using you DMM what is the resistance in ohms between the two "input" pads on the main PCB? Without the transformer attached?

 

[django32]

It's 270 ohm drops down to about half that with the transformer in line, just tried lifting one end of the 27k to sleep if it was something further down the line loading it. The input control seems to have little to no effect aswell.

 

[Echo North]

It's 270 ohm drops down to about half that with the transformer in line, just tried lifting one end of the 27k to sleep if it was something further down the line loading it. The input control seems to have little to no effect aswell.

That all seems normal.

Try pulling out your Q1 FET.

 

[django32]

okay found a hairline crack on the transformer pcb, new problem though, signal dies after the 27k, pulled the 2n5457 it comes back and put a new one in and it's gone again. All the other components around the 2n5457 test good.

all voltages in the rest of the compressor are in line with the schematic with the voltages on