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

[Echo North]

Thanks Mike! (and sorry for the slow reply, I don't have a ton of time to put into troubleshooting).

As per the Troubleshooting Guide, I measured TP18 and got bad voltages, so I replaced CR2 and CR3. Unfortunately that did not fix things.

Right now, at TP18 I measure -2.874vdc and -0.002vdc, at the extremes of Qbias trimmer R59.

That's good for an older Rev A PCB.  That's perfect.

So what is your issue again?  Can't set qbias?

 

[diylan]

Okay, getting closer then!

The issue is, I'll try to set the appropriate qbias, but once R59 is trimmed so that the measured output drops about 1db, the output level also starts drifting around. It's steady when R59 is set for max output gain though.

 

[Echo North]

Okay, getting closer then!

The issue is, I'll try to set the appropriate qbias, but once R59 is trimmed so that the measured output drops about 1db, the output level also starts drifting around. It's steady when R59 is set for max output gain though.

Check the soldering around your release and attack pot. Re-flow all those lugs.

Mike

 

[diylan]

I reflowed the solder on the lugs of both the attack and release pots, but no change. Once I trim the qbias pot to the point where output reduction is measurable it starts drifting. I got it to 2.44vac, but then watched it drift around from about 2.2 to 2.7 over a minute or two.

 

[weiss]

If someone is interested in a Rev A kit (stuffed, with transformers), i need to get rid of one 

 

[Sinkia]

If someone is interested in a Rev A kit (stuffed, with transformers), i need to get rid of one 

I might be interested ! Can you send me a pm with details ?  8)

 

[Echo North]

I reflowed the solder on the lugs of both the attack and release pots, but no change. Once I trim the qbias pot to the point where output reduction is measurable it starts drifting. I got it to 2.44vac, but then watched it drift around from about 2.2 to 2.7 over a minute or two.

Hmmmm. That maybe too much flux too.  Have you cleaned your joints? Especially on that release network and around Q1/Q11?

Mike

 

[diylan]

Unfortunately my output continues to drift and I'm still at a loss

I made a point of thoroughly cleaning the main and release network PCBs to get rid of any excess flux (there was a little, but it wasn't bad). I also made sure that the connections to the lugs of the release pot were solid and not overflowing with excess solder/flux.

 

[Echo North]

Unfortunately my output continues to drift and I'm still at a loss

I made a point of thoroughly cleaning the main and release network PCBs to get rid of any excess flux (there was a little, but it wasn't bad). I also made sure that the connections to the lugs of the release pot were solid and not overflowing with excess solder/flux.

If you remove CR2 and CR3 does it still drift?

Mike

 

[diylan]

That stopped the drift!

So something in the GR Control Amp then. Think it's a bad transistor?

 

[Echo North]

That stopped the drift!

So something in the GR Control Amp then. Think it's a bad transistor?

I would start with putting in new CR2 and CR3s.  If it drifts again then it's probably a bad semi or cap in the GR AMP.

 

[diylan]

I did replace CR2 and 3  at an earlier point in all this troubleshooting, but I'll test the diodes before putting them back in the circuit. Hopefully I can figure it out from here. I'll post whatever winds up doing the trick to help future problem solvers.

Thanks for sticking with me on this Mike!

 

[weiss]

Hey guys,

I'm having trouble finding information on how to wire this older version of the h-pad pcb (wasn't able to find anything by searching).
I can't see any +/- marks on the output (J2). do i have to use jumpers?
what would be meant with the "potentiometers between pads 1 and 5"?
thanks for clarifing!

Ansgar

 

[TillM]

I’ve the same „problem“, but as far as I understand you just have to jumper the h-pad,
The white lines who are linked the h pad on the pcb.

 

[TillM]

I've one question about the EA-5002.
I've an old one with a silver wire soldered to the chassis.
I'm a bit confused how to wire it.
Just solder it to the XLR grounds was my first think of.
Hope anyone can help me.

 

[Echo North]

I've one question about the EA-5002.
I've an old one with a silver wire soldered to the chassis.
I'm a bit confused how to wire it.
Just solder it to the XLR grounds was my first think of.
Hope anyone can help me.

You want to ground it to the enclosure. However, if you are screwing the 5002 to the enclosure, and the frame is making contact with the metal of the enclosure (remove any powder) you can just clip off the wire.

Mike

 

[TillM]

You want to ground it to the enclosure. However, if you are screwing the 5002 to the enclosure, and the frame is making contact with the metal of the enclosure (remove any powder) you can just clip off the wire.

Mike

Thanks for that Mike !

 

[TillM]

well, I buy the revision A from a member who already soldered it.
After build it the meter doesn't work, when a signal came in.
Now I checked how it sound without calibration, to see if the signal goes trough the 1176.
This is how it sounds
https://www.dropbox.com/s/b5yyxzb5wd6jp92/%201176%20noise.wav?dl=0

As you hear, it sounds like something is not grounded, but I'm sure, that I nothing forgot (remove the powder coat and so on).
I checked the voltage schematic and at TP10 and TP11 I only get 2,5v.
I changed already the transistors.
I'm a bit confused what could be the problem.
Also checked the resistance at the input transformer. It shows not 500ohm and 200ohm.
Maybe you guys had an idea, where I can start with the troubleshot.

 

[TillM]

hey guys,
still at troubleshooting.
Test with my DMM the continuity. Well, besides that some voltages are not right, i noticed, that at my input transformer I don't get continuity.
I hear a beep beetween pin 1 and 4, which is good and between 5 and 8.
Can anybody tell me the resistance between Pin 1 and 4 and between 5 and 8 ?
So when i test the continuity at the input transformer pcb i don't hear the beep between the two + poles.
I have the idea that maybe my input transformer is faulty (old Altran) and thats the reason, that I don't can calibrate my unit.

 

[Echo North]

hey guys,
still at troubleshooting.
Test with my DMM the continuity. Well, besides that some voltages are not right, i noticed, that at my input transformer I don't get continuity.
I hear a beep beetween pin 1 and 4, which is good and between 5 and 8.
Can anybody tell me the resistance between Pin 1 and 4 and between 5 and 8 ?
So when i test the continuity at the input transformer pcb i don't hear the beep between the two + poles.
I have the idea that maybe my input transformer is faulty (old Altran) and thats the reason, that I don't can calibrate my unit.

AC Impedance and DC resistance are two different thanks. Dc resistance will tell you if there is a break in the coil.

The DC resistances are about:

1-4: 50Ω
5-8: 12Ω

Mike