[BUILD] CAPI 553F~500 Series~LC Equalizer~Official Support Thread

[Flukes]

So the incorrect pre-flight measurements I'm getting from my 553F have nothing to do with the reduced output?

 

[jsteiger]

If you mean the DCR from the opamp voltage pins to ground, then no. We are mainly looking for a direct short or close to it in that measurement. Reduced output can be from a bad opamp build, problem on discrete follower(s), resistor(s) placed incorrectly or bad solder joint(s) somewhere throughout the build.

 

[NoahShain]

I've noticed there's a spot on the main pcb for hi-z/low-z jumpers but none are included in my kit or in the assembly aid.

Ignore?

 

[jsteiger]

I've noticed there's a spot on the main pcb for hi-z/low-z jumpers but none are included in my kit or in the assembly aid.

Ignore?

Yes ignore. Same goes for the 2 related R's. I have them listed in the BOM as such.

 

[NoahShain]

So I have my special cable built.
Probes Are in the right spots.  Moving rv1 trimmer creates no change at all.
Tell me it's something simple...
Signal generator to special cable to input...
+probe at the + terminal of C2 to pin 2 of the xlr
- probe at R11 is connected to pin 1 of the xlr
Pin 3 is floating
Xlr to patch bay DAW input.

Is this right?

 

[NoahShain]

I just checked and re-checked everything. All 4 of the 553fs I built are not responding to the cmrr cal. Turning the rv1 trimmer does nothing.
I rebuilt my monitoring cable so that pin 1 is ground, pin 2 is + and pin 3 is - 
On the probe end of the cable I have red (+) on pin 2 and - and ground both on black (-) probe.

Am I making some newbie blunder?

Total newb here and stumped.

 

[jsteiger]

Hi Noah, sorry you are having trouble. If you are using my Extension Jig, you do not need a "special cable". The Extension Jig takes care of that. All you need to do is engage the pushbutton switch during CMRR adjustment. The instructions printed on the silkscreen of the Extension Jig PCB should get you there. If you are using the jig AND a special cable, that could be your trouble?

 

[NoahShain]

Hi Noah, sorry you are having trouble. If you are using my Extension Jig, you do not need a "special cable". The Extension Jig takes care of that. All you need to do is engage the pushbutton switch during CMRR adjustment. The instructions printed on the silkscreen of the Extension Jig PCB should get you there. If you are using the jig AND a special cable, that could be your trouble?

Thanks for the reply Jeff. I bought an extension jig but I botched the build! I broke the ribbon cable connectors trying to clamp down on the ribbon cable. I was gonna order a new one last night but the store was closed so I just made everything.
It's entirely possible I have made other mistakes...
*facepalm*

 

[NoahShain]

Thanks for the help Jeff. So assuming my test cable is correctly built, is my test procedure correct?
Does it sound as if my test cable must be incorrectly made?
Ugh

 

[jsteiger]

You should be able to measure with your DMM at the output end of the special cable to make sure it is functioning properly. I mention this in the doc about building the cable. You should be able to adjust the output of your sig generator to give you appx 1V AC at both pins 2 and 3 of the output XLR.

 

[NoahShain]

You should be able to measure with your DMM at the output end of the special cable to make sure it is functioning properly. I mention this in the doc about building the cable. You should be able to adjust the output of your sig generator to give you appx 1V AC at both pins 2 and 3 of the output XLR.

Yep! The cable is measuring correctly. Got 1v at the output.
Rv1 still doesn't affect the signal.
I built the xlr with alligator clips so I could clip in as described in the doc and feed directly to my daw. Am I supposed to be taking the output from the 500 series chassis instead? The normal output xlr jack?

 

[andycallison]

a friend has just handed me one of these bad boys, i've had nothing to do with the build.. i plug her in and she works and eq sounds great, but there is a huge loss in volume when in line.. where do i start trying to fault find this bad boy.. cheers

 

[andycallison]

I've read what jeff is saying to Flukes and this is giving me little idea of where to start.. to be honest my knowledge is very limited.. it all sounds like gobelygook! any help very much welcome.. cheers

 

[andycallison]

so i have tested all the resisters that are on the pcb.. there seem to be a few issues

R2 should be 130k and its 11.75K
R3 should be 13k and it's 11.75K
R10 should be 14.3K and it's 4.1K
R14 should be 10K and it's 4.83K
R15 should be 10K and it's 4.11L
R20 should be 2M2 and it's 5.92K
R26 should be 220K and it's 199R

i also did the test points...

1.  5.7Mv
2.  5.6Mv
3.  53.5Mv
4.  2.6Mv
5.  56Mv
6.  .6Mv
7.  .2Mv

so none of those seem to match either!! any advice would be greatly appreciated

cheers

Andy

 

[jsteiger]

so i have tested all the resisters that are on the pcb.. there seem to be a few issues

R2 should be 130k and its 11.75K
R3 should be 13k and it's 11.75K
R10 should be 14.3K and it's 4.1K
R14 should be 10K and it's 4.83K
R15 should be 10K and it's 4.11L
R20 should be 2M2 and it's 5.92K
R26 should be 220K and it's 199R

i also did the test points...

1.  5.7Mv
2.  5.6Mv
3.  53.5Mv
4.  2.6Mv
5.  56Mv
6.  .6Mv
7.  .2Mv

so none of those seem to match either!! any advice would be greatly appreciated

cheers

Andy

Andy, resistors cannot be accurately measured when they are soldered in circuit. The results will vary. If you are really questioning their values, either use the color codes or one end must be desoldered and lifted from the PCB before measuring.

Did you eliminate opamps? From what you posted, your signal is not getting past the receiver stage so no need to test further. Who built the opamps? Have they been tested in something other than this build? Also, make sure your DMM is set for ACV when measuring audio.

 

[andycallison]

defo not the opamps.. they are red dot's bought built.. they work great in my vp28.. whats the reciever stage? that will help me know where i'm looking for faults.. cheers

 

[jsteiger]

The receiver stage is comprised of the A1 opamp and most of the components surrounding it all the way over to C2. If this stage is not operating in a -6dB capacity, (since it won't be the red dot) it will either be misplaced components or shoddy solder joints. The biggest nemesis of DIY projects by folks just starting out are bad solder joints. I would start with checking component placement and a good reflow of the solder joints. I just saw a project where a guy just starting out trimmed the leads so close to the PCB that he shaved the bottom of the pads and a few traces clean off the board. Just when I thought I had seen it all.....

 

[NoahShain]

Just finished my first LC53 build.
:-\
Not passing signal at all...just a buzz. Like a nice loud 60 cycle hum.
Any tips where to start diagnosis? My instinct says the little op amps or followers...they're tough!

Thanks all

 

[kante1603]

Just finished my first LC53 build.
:-\
Not passing signal at all...just a buzz. Like a nice loud 60 cycle hum.
Any tips where to start diagnosis? My instinct says the little op amps or followers...they're tough!

Thanks all

Wrong thread.....

 

[NoahShain]

Jeff
Curious if it's possible to change the frequency points of a 553?
I love the sound of them and I'd like to customize a couple for specific jobs.
Would it be a matter of R values or something relatively simple or more complex than that?
Thanks