mysticmerlin

Well it is indeed the mid band PCB that is faulty. When swapped the unit works fine. However I am unable to find where the fault is.  I relflowed the joints twice. Any ideas where to look for now?

Thanks
Bruce


jsteiger

Well it is indeed the mid band PCB that is faulty. When swapped the unit works fine. However I am unable to find where the fault is.  I relflowed the joints twice. Any ideas where to look for now?

Thanks
Bruce
It is a short to ground somewhere. Its hard to tell in the pic but I see a handful of solder joints with excess solder that could be shorting to the ground plane. Look for the little blobs on the side of the solder pads that touch the ground plane. Looks like one on a switch wiper and a few on resisters near the back of the board.
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mysticmerlin

As usual you are right.  there is a short between the ground and the 3 rd resistor from the bottom. Fixed. Thanks a lot for your help. These units sound great and I've been longing for this particular eq for a long while.

jsteiger

As usual you are right.  there is a short between the ground and the 3 rd resistor from the bottom. Fixed. Thanks a lot for your help. These units sound great and I've been longing for this particular eq for a long while.
Glad you found it!!
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mysticmerlin

And this project brings me to the end of my DIY eq adventure. The idea was to have 16 eqs for my little 16 channel desk. I've also  built 14 compressors just need to finish 2 pyes. the patch bay is noramlled Converter->EQ -> Comp -> Line In plus a mult from the comp outs to the converter ins so I can track the 16 channels at the same time as the Mix out. Still working on the fairchild 670 for the Buss out but it's 90% done.
I just wanted to give a warm thank you to all the Group DIY community for making the whole thing possible. You're an amazing bunch.
Cheers

Jeff! I just finished my sixth or eighth BT50 now and i went to test it. Everything works except the high band stays flat when switched to shelving mode. peaking works just fine.  :( :-[ :'(

Can you give me a lil help please

jsteiger

Jeff! I just finished my sixth or eighth BT50 now and i went to test it. Everything works except the high band stays flat when switched to shelving mode. peaking works just fine.  :( :-[ :'(

Can you give me a lil help please
OK, to begin with, the mini toggle SW4 either connects the signal to the peak or shelving network. When in shelving mode, the wiper (rear middle pin) of SW4 is connected to the top rear SW4 pin. From there it goes to the nearest front wiper pin of Grayhill SW2. You can see in the attached screen shot. That said, you should have continuity from the mini toggle wiper to the respective Grayhill pin (inside the green box) depending on the freq setting. If not, check the toggle itself or related solder joints. If you have continuity from the toggle wiper to all respective output pins of the GH front lower deck, we will take it to the next step.
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...the mini toggle SW4 either connects the signal to the peak or shelving network. When in shelving mode, the wiper (rear middle pin) of SW4 is connected to the top rear SW4 pin. From there it goes to the nearest front wiper pin of Grayhill SW2. You can see in the attached screen shot. That said, you should have continuity from the mini toggle wiper to the respective Grayhill pin (inside the green box) depending on the freq setting. If not, check the toggle itself or related solder joints. If you have continuity from the toggle wiper to all respective output pins of the GH front lower deck, we will take it to the next step.

Thanks for the quick reply, Jeff!  Your customer service has been second to none.

I measured continutity between the wiper of SW4 to all 5 output pins and we have connection to each frequency selection.  What would the next step be?



jsteiger

From
I measured continutity between the wiper of SW4 to all 5 output pins and we have connection to each frequency selection.  What would the next step be?
From those contacts of the Grayhill, each tap goes to its respective cap array. The 5 sets of caps (one or more for each freq point) all end up connecting together and go to the wiper of the E deck which is the 5th deck from the front. In the attached screenshot you will see all of those pads and tracks in highlight mode. This is the shelving Q deck and sets the bandwidth per step of boost/cut. This E deck wiper goes thru one or more R's to ground depending on the amount of boost or cut selected. I would make sure you have continuity from one of the highlighted cap pads thru the respective pin on the E deck of the switch. No contact is made when in 0. That said, you should have resistance to ground from the E wiper when in any boost/cut other than 0. HR4 is the last R in the string so the E deck connects the E wiper to HR4 which goes to ground when set to +/-12.
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... I would make sure you have continuity from one of the highlighted cap pads thru the respective pin on the E deck of the switch. No contact is made when in 0. That said, you should have resistance to ground from the E wiper when in any boost/cut other than 0. HR4 is the last R in the string so the E deck connects the E wiper to HR4 which goes to ground when set to +/-12.

Alright, Jeff.  I made sure and all of the highlighted cap pads have continuity through each respective pin on the E deck.  I also measured and found that E wiper has resistance to ground in each position except for 0.  To be expected as per your quote.  Please let me know where else the trouble might lie, sir!


jsteiger

Alright, Jeff.  I made sure and all of the highlighted cap pads have continuity through each respective pin on the E deck.  I also measured and found that E wiper has resistance to ground in each position except for 0.  To be expected as per your quote.  Please let me know where else the trouble might lie, sir!
Well man, that is pretty much it for the high freq shelving part of the circuit. Its essentially nothing more than a series cap and a series resistor hanging off of the mini toggle. Its just a very complicated way to get the right frequency and right bandwidth.

If the above all checks out, it seems very strange to me that peaking works OK and shelving does not.
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Whatever it was that happened it's working now!  I'm guessing I had a less than perfect joint somewhere in that chain and maybe the probes re-engaged contact.  I reflowed the solder joints that I had to probe during this troubleshooting session juuust in case!  Whatever the case it's working and she's ready to aggravate some audio :D Thanks so much for the attention, Jeff.  You're the best and I will continue to pimp out your gear as much as I can 8)

Hugs n kisses,
Billy

jsteiger

Thanks so much for the attention, Jeff.  You're the best and I will continue to pimp out your gear as much as I can 8)

Hugs n kisses,
Billy
Glad you got it sorted Billy!  \m/
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Hi Jeff!
I was hoping for a little help here... I have 2 BT50s here and one is working great. The other one is almost there - the only problem is that 200hz on the low band seems to do absolutely nothing in shelving mode. However, it is fine in peak mode! Where should I troubleshoot?
Thanks!
-Dryw

jsteiger

Hi Jeff!
I was hoping for a little help here... I have 2 BT50s here and one is working great. The other one is almost there - the only problem is that 200hz on the low band seems to do absolutely nothing in shelving mode. However, it is fine in peak mode! Where should I troubleshoot?
Thanks!
-Dryw
Hey Dryw, 200Hz shelving is only 1 cap and the 3rd pin up on the front deck of the LF Grayhill. See the highlighted track and pads in the attached screenshot. I would reflow those 2 pads.
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Hey Dryw, 200Hz shelving is only 1 cap and the 3rd pin up on the front deck of the LF Grayhill. See the highlighted track and pads in the attached screenshot. I would reflow those 2 pads.

Thanks so much, Jeff.
I reflowed the pads in question to no avail. As I continue to test with a simple DAW analyzer, I'm noticing that the 200hz shelf (while not affecting 200) IS affecting something around 50hz or lower, but only in shelf mode. Peak works great.
This is making me think a cap mix-up may have occurred... Is this a possibility for the behavior I am describing? If so, can you advise me on which caps to desolder and check? I'd check 'em all, but I don't want to risk damage to the components or PCB with that much desoldering.

jsteiger

Thanks so much, Jeff.
I reflowed the pads in question to no avail. As I continue to test with a simple DAW analyzer, I'm noticing that the 200hz shelf (while not affecting 200) IS affecting something around 50hz or lower, but only in shelf mode. Peak works great.
This is making me think a cap mix-up may have occurred... Is this a possibility for the behavior I am describing? If so, can you advise me on which caps to desolder and check? I'd check 'em all, but I don't want to risk damage to the components or PCB with that much desoldering.
Well, I would start by removing LC5 and seeing what value it is. It should be .022µF.
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Well, I would start by removing LC5 and seeing what value it is. It should be .022µF.

I just pulled LC5 and it reads µ22k63... Is this the right one, or off by a zero?

jsteiger

I just pulled LC5 and it reads µ22k63... Is this the right one, or off by a zero?
That is super strange. I just sifted thru the parts bin and all say 22nJ100 just like pic 2.B.14 shows here http://capi-gear.com/catalog/Build_BT50_Rev_B.php#Sec2B

Odd thing is I don't even have a µ22k63 cap here. The closest thing is µ33J63. Can you post a pic?
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That is super strange. I just sifted thru the parts bin and all say 22nJ100 just like pic 2.B.14 shows here http://capi-gear.com/catalog/Build_BT50_Rev_B.php#Sec2B

Odd thing is I don't even have a µ22k63 cap here. The closest thing is µ33J63. Can you post a pic?
Just DM'd you photos.