[BUILD] CAPI LC53A~500 Series~Love Child EQ Kit~Official Support Thread
- Thread starter jsteiger
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Help Support GroupDIY Audio Forum:
kante1603
Well-known member
Hello and welcome,
congrats to your builds.
I really like the way how you got everything prepared in the first pic!
That's the way to go people!
Also a cool idea with a nose pliers and a rubber band creating a vise-excellent and very creative I must say.
Enjoy your lovechildren,
Udo.
congrats to your builds.
I really like the way how you got everything prepared in the first pic!
That's the way to go people!
Also a cool idea with a nose pliers and a rubber band creating a vise-excellent and very creative I must say.
Enjoy your lovechildren,
Udo.
Thanks a lot Udo.
I started handcrafting circuits late 80´s when I was 13. Last year I recovered this passion forever, with a pair of CAPI VP28. As a multimedia artist, being able to build your own tools, has many, many advantages. Besides the money, more important ones. The "lab" was improvised for this studio located at the Andes, S.A. beautiful place. Those nights where just perfect.
Long live DIY!!!.
Next: Passive network on silver wire / teflon. I hope to find a local artisan / supplier.
I started handcrafting circuits late 80´s when I was 13. Last year I recovered this passion forever, with a pair of CAPI VP28. As a multimedia artist, being able to build your own tools, has many, many advantages. Besides the money, more important ones. The "lab" was improvised for this studio located at the Andes, S.A. beautiful place. Those nights where just perfect.
Long live DIY!!!.
Next: Passive network on silver wire / teflon. I hope to find a local artisan / supplier.
Hello all I just finished my first LC53A eq. After building a VP28 and it working right I was hoping to get the same result with this build. I am close I would say 85% works. Hopefully someone can help me track down the issues so I can fix it.
1. When boosting the high shelf at 10k it seems to just boost the overall audio...all other bands in the HF section seem to work. 10k DOES seem to work correctly if I switch to peak instead of shelf. I read through the forum build and the closest I could find was capacitor 23 was an issue for some other HF issues but they were not exactly like mine. Thoughts
2. The LPF and HPF don't seem to be working.
I'm assuming that with the first problem the audio is just passing through somewhere without hitting the circuit that boosts and cuts 10K. However, I figured this would make more sense if it happened on both peak and shelf. So again I'm guessing that the problem has to be somewhere after the shelf switch that doesn't effect other frequencies so maybe this would be a specific cap or resistor.
I'm attaching a dropbox link to some images of my build.
Thanks!
https://www.dropbox.com/sh/49j9sp3g70cnptc/AABGRTakGSDlg2sT5qw73tcAa?dl=0
1. When boosting the high shelf at 10k it seems to just boost the overall audio...all other bands in the HF section seem to work. 10k DOES seem to work correctly if I switch to peak instead of shelf. I read through the forum build and the closest I could find was capacitor 23 was an issue for some other HF issues but they were not exactly like mine. Thoughts
2. The LPF and HPF don't seem to be working.
I'm assuming that with the first problem the audio is just passing through somewhere without hitting the circuit that boosts and cuts 10K. However, I figured this would make more sense if it happened on both peak and shelf. So again I'm guessing that the problem has to be somewhere after the shelf switch that doesn't effect other frequencies so maybe this would be a specific cap or resistor.
I'm attaching a dropbox link to some images of my build.
Thanks!
https://www.dropbox.com/sh/49j9sp3g70cnptc/AABGRTakGSDlg2sT5qw73tcAa?dl=0
The 10kHz shelf is C28 and C29 in parallel, then R14 in series to ground. I would remove C28 and measure it for DCR. It should be open with no measurable resistance. IIRC, that was the problem cap in the other 7kHz situations. I have been checking all of these before we kit them up but maybe this was a straggler from before.
Are you running a sweep to verify that the HP and LP filters are not working? That is the best way to test. Testing by ear can be misleading. The LP is @ 15kHz and the HP is at 50Hz. They are separated by voltage followers so have no interaction with each other. The fact that neither is working seems odd to me.
Are you running a sweep to verify that the HP and LP filters are not working? That is the best way to test. Testing by ear can be misleading. The LP is @ 15kHz and the HP is at 50Hz. They are separated by voltage followers so have no interaction with each other. The fact that neither is working seems odd to me.
I pulled both C28 and C29 out and check both for any resistance and there wasn't.
What is IIRC cap for 10K...as I'm not sure what that is and how do I test it?
Just wanted to remind you that I don't have a common pin on one of the voltage followers...you didn't seem to think it would be a big deal to get up an running without but just wanted to throw that out there. I will have that fixed when my shipment comes in.
I will run a few test tones (low and hight) through the unit and into my DAWs spectral display which should tell me if anything is happening.
Any other items I should check or test before putting it back together and running some more tests?
Thanks!
What is IIRC cap for 10K...as I'm not sure what that is and how do I test it?
Just wanted to remind you that I don't have a common pin on one of the voltage followers...you didn't seem to think it would be a big deal to get up an running without but just wanted to throw that out there. I will have that fixed when my shipment comes in.
I will run a few test tones (low and hight) through the unit and into my DAWs spectral display which should tell me if anything is happening.
Any other items I should check or test before putting it back together and running some more tests?
Thanks!
Ok so I put it all back together and now no eq function works...
It passes audio fine but no eq function.
I tried directly into the chassis and also with the JLM extension jig.
If pushed a bit from side to side on the JLM extension rig it would work very quickly but it was too short to tell. I just left one of the mid bands boosted and twisted around the card connection and I could get it to jump in level like it was boosting but it was very short lived.
So any thoughts...I didn't think it was going to get worse but...it did.
It passes audio fine but no eq function.
I tried directly into the chassis and also with the JLM extension jig.
If pushed a bit from side to side on the JLM extension rig it would work very quickly but it was too short to tell. I just left one of the mid bands boosted and twisted around the card connection and I could get it to jump in level like it was boosting but it was very short lived.
So any thoughts...I didn't think it was going to get worse but...it did.
kante1603
Well-known member
Hello,bdunard said:
I have a feeling now that the issue is just loosing the ground connection on the filters side.About two years ago I asked Jeff how the bypass switch works or better if it is a true bypass or not.Here's the reply:
http://groupdiy.com/index.php?topic=48426.msg615008#msg615008
Leads me to think that your bypass switch might be broken or at least the ground connection gets lost in this area.
Just an idea......
Good luck,
Udo.
That makes sense why things aren't working now...possibly the bypass switch but not sure that explains the earlier problem with the 10K shelf.
Who knows maybe I have fixed the problem on the 10K shelf, but created another problem before I could test it. One thing I should mention is that when I was taking it apart I forgot to take the faceplate off so I did slightly bend a jumper between boards...totally my fault but maybe that made the jumper solder joint loose.
I don't think I have any solder joints that are touching the chassis but I can see one of the screws that holds the two boards together is close but it looks like that shouldn't matter anyway.
So outside of replacing the "in/out" switch...do you have any recommendations for chasing this down?
Thanks for your reply Kante1603.
Who knows maybe I have fixed the problem on the 10K shelf, but created another problem before I could test it. One thing I should mention is that when I was taking it apart I forgot to take the faceplate off so I did slightly bend a jumper between boards...totally my fault but maybe that made the jumper solder joint loose.
I don't think I have any solder joints that are touching the chassis but I can see one of the screws that holds the two boards together is close but it looks like that shouldn't matter anyway.
So outside of replacing the "in/out" switch...do you have any recommendations for chasing this down?
Thanks for your reply Kante1603.
I touched up a few solder joints and took my straight edge to make sure no solder pads or legs are higher than the casing threshold.
If I use my JLM extension cable and apply pressure to one side of the connection on the LC53A the eq does come on and it seems to be working. I don't know if it causes something to make contact or it is causing something to not ground out. I checked the solder pad heights to hopefully help rule out the 2nd one.
Does anyone know what this may point to as far as the problem?
Any other tests I could do?
Thanks!
If I use my JLM extension cable and apply pressure to one side of the connection on the LC53A the eq does come on and it seems to be working. I don't know if it causes something to make contact or it is causing something to not ground out. I checked the solder pad heights to hopefully help rule out the 2nd one.
Does anyone know what this may point to as far as the problem?
Any other tests I could do?
Thanks!
kante1603
Well-known member
Does it behave the same way directly seated in the rack?
Could it be it's just a broken extension cable,e.g. ribbon cable not seated well in the idc headers,cold solder joint etc.?
I'd sort that out first and measure the contacts for continuity from both sides.
Best done with aligator clips instead of probe tips and moving the cable/wires while measuring.
Best,
Udo.
Could it be it's just a broken extension cable,e.g. ribbon cable not seated well in the idc headers,cold solder joint etc.?
I'd sort that out first and measure the contacts for continuity from both sides.
Best done with aligator clips instead of probe tips and moving the cable/wires while measuring.
Best,
Udo.
I did put it in the rack. It passes audio fine but I can't push or contort it to get the eq'd sound to intermittently come on like I can with the cable.
I also now notice when I push the in/out button there is a bit of a "thump" sound.
Could you explain your continuity test a bit more? I do know that particular slot on the rack works because I double checked it with another module.
I'm assuming that if the engage switch just lifts the ground to bypass the eq circuit then the problem must be something related to that. I'm just not sure what I did to have this thing basically working then take it apart, reassemble and it doesn't work?
I also now notice when I push the in/out button there is a bit of a "thump" sound.
Could you explain your continuity test a bit more? I do know that particular slot on the rack works because I double checked it with another module.
I'm assuming that if the engage switch just lifts the ground to bypass the eq circuit then the problem must be something related to that. I'm just not sure what I did to have this thing basically working then take it apart, reassemble and it doesn't work?
Are you 100% sure the long headers are in their sockets properly? Sounds like the issues lies there. You can beep them out with your DMM to make sure you have continuity from board to board.
Jeff,
Good news and bad news.
One of the long header sockets was indeed out and putting it in does make the eq almost function.
I can tell that both LPF and HPF are both working too.
However, there is a new problem...
At every frequency band I try to boost more than a couple of notches to the clockwise it starts to oscillate and distort and jumps greatly in level...I can't tell how much because it clips everything and sends the dogs a runnin'
If I were going to guess with my limited knowledge...I would say it is much like the circuit is feeding back into itself much like a microphone and a speaker.
Any thoughts as to why this might be occurring?
EDIT: I should also note that no audio has to be passed through the eq for these loud distorted oscillations to happen.
Good news and bad news.
One of the long header sockets was indeed out and putting it in does make the eq almost function.
I can tell that both LPF and HPF are both working too.
However, there is a new problem...
At every frequency band I try to boost more than a couple of notches to the clockwise it starts to oscillate and distort and jumps greatly in level...I can't tell how much because it clips everything and sends the dogs a runnin'
If I were going to guess with my limited knowledge...I would say it is much like the circuit is feeding back into itself much like a microphone and a speaker.
Any thoughts as to why this might be occurring?
EDIT: I should also note that no audio has to be passed through the eq for these loud distorted oscillations to happen.
This sounds like an opamp or discrete follower problem. Early in the thread there are test points. I would check all of those and see where the issues start.
Jeff is this the test that I should perform to figure out my issue? Just wanted to check and make sure since I don't have a properly functioning unit to compare it with.
Also, I don't think it's the opamps because I used my red dots from my functioning VP28 and it has the same issue.
It doesn't seem like anything has changed since it first worked (minus the 10K and LPF,HPF issue)
Since the HPF and LPF now work do you think it could be somehow related to that part of the circuit now effecting all of the boost points on the peaking bands?
Also, I don't think it's the opamps because I used my red dots from my functioning VP28 and it has the same issue.
It doesn't seem like anything has changed since it first worked (minus the 10K and LPF,HPF issue)
Since the HPF and LPF now work do you think it could be somehow related to that part of the circuit now effecting all of the boost points on the peaking bands?
jsteiger said:
It could also be one of the DTO5's.
