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

Thanks Scott.

After re-doing Q-bias successfully many times, null adjustment perfectly, the 3rd calibration eludes me. Also no compression on 4 or 8 Ratios. Meter stops moving in those ratios.

Did reflow solder joints in Ratio PCB and Meter PCB. May consider just reflowing all joints everywhere  just in case, but that's a PIA.

If anyone knows any thoughts on what this might mean I'm open. Meanwhile I'm trying to read this whole thread plus many others to get to an answer.

Thanks everyone,

Mike

0dbfs said:

Got through the null-adjust-cal and moved to tracking adjust when my 0-set-adj and tracking-adj trimmers both affected the GR meter exactly the same. Also, had to go back and adjust for 1/2 db overbias/q-bias to get the desired ip/op settings for 10db compression (output level) and 0 with GR bypassed. Those steps are with 20:1 selected and switching between gr active/bypassed tweaking I/O until you consistently read -10/0 on the meter.

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Hey Jonathon care to elaborate on this? I can't get the 3rd calibration step to work - maxes out at 7-8db range. I tried what I thought you did, starting with +1.5 db on the Q-bias first step, but this did nothing to affect the 3rd calibration range.

Thanks for any thoughts.

Mike

Phrazemaster said:

Also no compression on 4 or 8 Ratios. Meter stops moving in those ratios.

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So there's no compression on 4 & 8 ratios or is it just the meter not showing compression???.......

The qbias sets all the compression right? The meter calibration is just for the meter to show the compression that should already be working??

Weird...

scott2000 said:

So there's no compression on 4 & 8 ratios or is it just the meter not showing compression???.......

The qbias sets all the compression right? The meter calibration is just for the meter to show the compression that should already be working??

Weird...

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Hi Scott, I'm not sure if it's actually compressing, but it doesn't sound like it in 4/8. Weird thing was, originally 8 was working. When I damaged the trace and repaired it, both 4 and 8 stopped working. But Beeping it out with my DMM shows the trace repair is OK. I may run a couple of wires to the other components anyway. I'm starting to wonder if I should swap out the FETs and BJTs. I hate to do that - expensive and time consuming!

I did reflow all solder in the GR Meter and GR control amp sections, just to make sure. But no joy I also rechecked wiring and it all appears correctly. Obviously I've made some mistake or something is faulty.

The 20 and 12 ratios seem to work very well! So partial victory.

I'm reading the whole thread through in hopes of finding some ideas. Any other help is greatly appreciated.

Thanks,

Mike

Spent almost the day working on the beast. After reading more in the thread, someone else had a similar problem to mine, and it turned out for that guy that his ratio board was faulty.

I beeped out my ratio board and discovered to my chagrin that several traces just didnt' make continuity. I've never run into this before. I snaked some trace wires over the broken traces and compression started for 4 and 8! But, it's a bit dodgy; it will spontaneously stop compressing. Sounds like cold solder joints only thing is I reflowed all joints. I just think the board is wacky so I'll be replacing that.

Still have the issue with only a 7db drop on 3rd calibration step.

She passes audio and sounds good, but it's hard to judge with the intermittent thing going on. At higher output levels distortion is terrible but perhaps that is normal as it is probably just too hot. Input control has to be fairly high on this unit. Using a real O-12. Not sure if that's why.

Any ideas what would prevent the unit from calibrating at 10db drop? I don't mind replacing the 5088s or even the FETs. I just want her working.

Thanks everyone,

Mike

Seems to be one of the most common problems, not getting the -10db drop.
I have Rev A and Rev D, both I am able to get -10db drop but not in the conventional way so to my mind they both don’t work how they should.
Only thing is I don’t have enough time at the moment to check them out!!
It’s so frustrating I know!

Spencerleehorton said:

Seems to be one of the most common problems, not getting the -10db drop.
I have Rev A and Rev D, both I am able to get -10db drop but not in the conventional way so to my mind they both don’t work how they should.
Only thing is I don’t have enough time at the moment to check them out!!
It’s so frustrating I know!

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Thanks Spencer.

Anyone has an answer to this?

Phrazemaster said:

Thanks Spencer.

Anyone has an answer to this?

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Do you know if the O-12 is working properly or if it matches the exact pinout of the Ed Anderson version that is used in the Hairball kits? Have you ruled out the FETs? I've build 5 of the Rev A's and they all calibrated with no issues. And if you are have the new chassis style kit there are less things to go wrong as the build has been simplified quiet a bit. So either the transformer is bad, the FETs are bad, or you are not feeding it enough signal. There is also the issue of bad solder joints or misplaced component.

Thanks!

Paul

Potato Cakes said:

Do you know if the O-12 is working properly or if it matches the exact pinout of the Ed Anderson version that is used in the Hairball kits? So either the transformer is bad
Paul

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If the o-12 is bad, it looks like soundguy recommends trying other ones anyhow. Interesting.

https://groupdiy.com/index.php?topic=10611.0

Thanks fir pointers.

O-12 has different pinouts as noted on original data sheet. It uses pins 1,5 and 6,8.

I might think it was bad except many others have reported this 7db drop problem on this forum, only problem is I didn’t find any solutions yet. I’m sure all of them didn’t have bad transformers.

I checked the components 3-4 times each before stuffing. Verified wiring as well.

I would never have thought part of the problems was due to a “bad” ratio PCB but right here in this thread Mike from Hairball discovered that was the issue for Steve-h on this forum. I checked continuity in my own ratio PCB and found to my shock some of the connected traces were in fact not connected. I ran wires from the components and this got the 4 and 8 ratios working, although it’s a little intermittent. I have successfully put together many many kits like 7th Circle Audio and SoundSkulptor, and several DIY microphones, so I know how to solder.

Kit is the old one.

Maybe the FETs are bad. I checked all voltages against the mnats schematic and all came out fine but one, Q3 had 4.26V instead of 6.6v at the drain. I might consider replacing  the 5088s as well.

I’ve reached out to Mike at Hairball for his thoughts and will let you guys know how this progresses. I will replace the ratio board and possibly FETs as well as a starting place.

I have another O12 I could try in the meantime.

Thanks Paul and Scott for suggestions.

Mike

You do keep bringing up those fets....

I think CJ mentioned somewhere that just picking them up wrong can mess transistors up....Could've been something else so don't hold me to that though I'm pretty sure.....

And soundguy just mentioned that he thought there were other options that might actually sound better than the 12....I always hold his input in a special place.....

Keep at it....You'll get it for sure! You already know this though.....

scott2000 said:

You do keep bringing up those fets....

I think CJ mentioned somewhere that just picking them up wrong can mess transistors up....Could've been something else so don't hold me to that though I'm pretty sure.....

And soundguy just mentioned that he thought there were other options that might actually sound better than the 12....I always hold his input in a special place.....

Keep at it....You'll get it for sure! You already know this though.....

Click to expand...

Thanks buddy. Egging me on DOES HELP lol! I will keep the saga updated here as I traverse through the issues, and hopefully this will help someone else too.

Thanks!

Mike

too bad there are so many dead links....I've come across a few things I wanted to peek at and no dice....

There seems to be some kind of thing going on with different board versions too....Can't put my finger on it yet but will let you know what I'm talking about when I figure it out...lol

Thanks Scott. I'll keep at it. I'm going to keep reading the board today. I'm reluctant to swap out all the 5088s just yet, but I will if that might help. Thanks.

Saw this on GS thread....kinda different method???

https://www.gearslutz.com/board/geekslutz-forum/956121-1176-calibration-clarification.html

Also on another thread there, some guy from Studio electronics pm'd a guy to help with the same issue so, I guess contacting them is always another option...


funny quote on one of the threads there

" the meter calibration alone on the mnats board is a bit of a mind bender .........."

Funny! Thanks Scott!

So I replaced every 5088 and the J309s today. Only transistors I didn’t change were the 5457s because I didn’t have more.

No change. At all. Well except now audio cuts out for a few seconds randomly. You would think I was a complete noobe.

I am seriously considering remaking a new board. I already have to replace the ratio board anyway. I had a similar bizarre experience when I built an M49 and ended up rebuilding both the mic and the PSU twice until all gremlins were vanquished.

Strange.

Thing is, I check, and recheck, every part and every step as I go.

I will post back status.

Thanks kindly.

Mike

ugh,,,,

Anyhow, I do see there must be some differences in the revisions.....

this quote from this version 1.12 thread mentions this...

https://groupdiy.com/index.php?topic=63600.20

is yours newer or older? I'm not familiar with the numbering.....  seems it would be newer????

post 881 touches on a similar issue....

I’ve got PCB 1.2.5

I’ll try to do some more troubleshooting but I know for sure I need a new ratio board.

Thanks Scott. I’ll post back status when I have something more to share.

OK more troubleshooting. My "4" ratio button is intermittent. That's why I've been getting intermittent results in 4, and probably also affected 8 too. Ordering another ratio board and switch set. DAmn! This could be my fault; maybe when using flux remover some of it got into the switch. But the others are all fine, and it did this from the beginning.

In any case people - lesson learned - don't assume ANYTHING in your builds! Even basic traces on a PCB can be faulty, and switches can also not work correctly, or possibly be affected in the soldering/cleaning process. This has been a good experience. And, it's not over yet lol! Will report more status when I have the new parts and can rebuild. Rebuild. Rebuild.

Mike

In other news - I'm starting to feel like a one-man thread here lol - I discovered after fixing another dodgy trace on the ratio board, I was at last able to do the full 3 steps of calibration! With a 10db drop. Output on the compressor is considerably hotter now!!!

Remaining issue - ratio board buttons are intermittent, and so are the meter board buttons. I may have oversprayed flux remover, or maybe I just got a bum set of switches. I'll take the blame, but I'm going to replace those asap.

I'll report back when I get the new ratio board/switches and get them installed. I'm anxious to test the beast out and see what she's capable of!

Best,

Mike

EDIT: again reflowed all solder joints on transistors, which I had replaced. The usual problems with a lifted pad here/there. I was dterminted to find the fault.

Well...she works! I believe correctly!!! For first time. I am still going to replace the ratio board and intermittent switch.

Just goes to show you guys - if you are not getting the specified results, with 10db drop on 3rd calibration, THERE IS a problem!!! In my case I believe it was a combination of bad traces on the ratio board as well as I think replacing the transistors helped.

Will do another report soon after more testing, and replacing the ratio switches/board etc.

Thanks Mike at Hairball, Mnats, Scott, and everyone on this board for making this project possible!!

And by the way - it sounds SO NATURAL and organically smooth! I can't believe compression is even happening it's so subtle but smooth! Simply a great box!!! (I used all carbon comp resistors, including Allen Bradley's and Pihers, throughout audio section.) There is no "brightness" that I can hear due to the 5088's I used, but I haven't compared this directly with an original that uses 3707's or 3708s.