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

[Ganetta]

Hello
I got problems and i need some help.
Unit seems to work (red led is on) but it does not pass some audio.
When i press the filter knobs on the hfp i get some pops.
The opamp is 0252 is a fully assembled from CAPI, so this one should be good.
Nothing seems to get hot or to be burned.
I checked for bad solder joints...
I tried to meassure and i get not the values mentionied in the TestPoints PDF
TP1 = 1.3 mV AC
TP2 = 2.2 mV AC
TP3 = 1.4 mV AC
TP4 = 1.4 mV AC
TP5 = 1.3 mV AC

The Values should be something like this...
#1, 606mV (after A1 receiver)
#2, 517mV (after HPF PCB)
#3, 515mV (after A3 follower)
#4, 509mV (after A4 follower)
#5, 410mV (after A2 2520)

Has someone an idea what i can do?

Thanks alot

Raffaele

 

[jsteiger]

Hello
I got problems and i need some help.
Unit seems to work (red led is on) but it does not pass some audio.
When i press the filter knobs on the hfp i get some pops.
The opamp is 0252 is a fully assembled from CAPI, so this one should be good.
Nothing seems to get hot or to be burned.
I checked for bad solder joints...
I tried to meassure and i get not the values mentionied in the TestPoints PDF
TP1 = 1.3 mV AC
TP2 = 2.2 mV AC
TP3 = 1.4 mV AC
TP4 = 1.4 mV AC
TP5 = 1.3 mV AC

The Values should be something like this...
#1, 606mV (after A1 receiver)
#2, 517mV (after HPF PCB)
#3, 515mV (after A3 follower)
#4, 509mV (after A4 follower)
#5, 410mV (after A2 2520)

Has someone an idea what i can do?

Thanks alot

Raffaele

If your AC voltage is down after TP1 it will never come back up. That tells us the problem is before TP1 so you have likely made an error on the DTO7 amp.

 

[hasanova]

UPDATE: After de-soldering the mentioned parts, I re-soldered both transistors, with the correct orientation, and re-soldered the DTO7 back in place: now all is fine!

Cheers!

--------------------------------

I've built two 553F EQ's. Just did some test readings with my multimeter and a soundtest. One fired up nicely and is working perfectly. The other not, turns out the orientation of two transistors is the wrong way on the receiver DTO7 pcb: Q7 ( BC550C - matched hFE) & Q4 (2N5088).
I managed to remove the PCB and the two transistors. I don't know if they still work...

Should I ask Jeffrey for a new receiver DTO7 kit, or should I try and resolder everything and see if every works?

 

[abeLovesDIY]

This EQ won't pass audio properly and the power LED won't light. There's no continuity short, and I've swapped in a known-working DOA with no change. Voltage followers look good. I can't see any difference between this unit and a working one. Any hints?

 

[jsteiger]

This EQ won't pass audio properly and the power LED won't light. There's no continuity short, and I've swapped in a known-working DOA with no change. Voltage followers look good. I can't see any difference between this unit and a working one. Any hints?

The LED issue is probably specifically the LED like its in backwards.

Since you have a good working unit I would run a sine wave in the good one and notated the AC voltages at the Test Points then compare to the not so good one. See where things go bad.

 

[andYz00m]

Hey there. Had no issues with the build, kit is lovely.

Fried my tester op amp on first power up. It’s a known working gar2520 and the two big power resistors (R12/13) got smoked after about 30 second of power from my known good rack (Radial workhorse)

Any ideas? Without the DOA slot populated the unit powers fine and are showing proper voltages on the socket pins. Not a lot to mess up in the build.

 

[jsteiger]

Hey there. Had no issues with the build, kit is lovely.

Fried my tester op amp on first power up. It’s a known working gar2520 and the two big power resistors (R12/13) got smoked after about 30 second of power from my known good rack (Radial workhorse)

Any ideas? Without the DOA slot populated the unit powers fine and are showing proper voltages on the socket pins. Not a lot to mess up in the build.

I would check DCR from the opamp's output socket to ground. No power needed and no opamp installed. The resistance should be low but not a direct short.

 

[Potato Cakes]

View attachment 101387
This EQ won't pass audio properly and the power LED won't light. There's no continuity short, and I've swapped in a known-working DOA with no change. Voltage followers look good. I can't see any difference between this unit and a working one. Any hints?

Unfortunately you are going to have take it all apart and start examining all of your solder joints. If your voltages are good as you say then it's highly likely there's a missed or cold solder joint.

Thanks!

Paul

 

[Potato Cakes]

UPDATE: After de-soldering the mentioned parts, I re-soldered both transistors, with the correct orientation, and re-soldered the DTO7 back in place: now all is fine!

Cheers!

--------------------------------

I've built two 553F EQ's. Just did some test readings with my multimeter and a soundtest. One fired up nicely and is working perfectly. The other not, turns out the orientation of two transistors is the wrong way on the receiver DTO7 pcb: Q7 ( BC550C - matched hFE) & Q4 (2N5088).
I managed to remove the PCB and the two transistors. I don't know if they still work...

Should I ask Jeffrey for a new receiver DTO7 kit, or should I try and resolder everything and see if every works?

If nothing smoked on power up and the board isn't damaged you should be fine to solder them back in correctly and reinstall the DTO7.

Thanks!

Paul

 

[andYz00m]

I would check DCR from the opamp's output socket to ground. No power needed and no opamp installed. The resistance should be low but not a direct short.

56R from O to ground test point.

The resistance between C and V+/V- is about 4M Ohm.

Another note, I just realized the output jumper is on 600Ohm not hiz but that didn’t seem like it would cause a problem.

 

[andYz00m]

56R from O to ground test point.

The resistance between C and V+/V- is about 4M Ohm.

Another note, I just realized the output jumper is on 600Ohm not hiz but that didn’t seem like it would cause a problem.

Checked through my assembly and everything is solid. Cant find any incorrect components or bad joints. Continuity is good.

Another thing to note, the resistance readings between ground and V+/V- are inconsistent, seems like depending on what I measure before they change a bit. They are always above the 100K stated in the "preflight check" doc. I cant imagine what would be frying the opamp as its basically just power from the rack through the diode into the resistor and into V+/V-

Not sure what else to check.

I have three more kits to build so maybe I’ll compare once I have one working and see if there was a mistake.

 

[andYz00m]

Update: I reflowed a few joints around the power section even though there was no continuity issues.

Used a known good 0252 DOA (not one of my fancy new potted units), worked fine no smoke sounds great.

Not sure why the gar2520s were not friends with this guy.

Anyway, unit sounds really sweet and test points showing correct voltages.

 

[jsteiger]

Update: I reflowed a few joints around the power section even though there was no continuity issues.

Used a known good 0252 DOA (not one of my fancy new potted units), worked fine no smoke sounds great.

Not sure why the gar2520s were not friends with this guy.

Anyway, unit sounds really sweet and test points showing correct voltages.

Any of our opamps should work just fine in the module. Maybe the amp was not fully seated? Classic Audio Products, Inc.

 

[andYz00m]

Any of our opamps should work just fine in the module. Maybe the amp was not fully seated? Classic Audio Products, Inc.

Possibly, not sure. Either way were good now.

Just was messing around with some drums into this and then into a 165A crushed. Pretty awesome!!

 

[ElijahSound]

Hello everyone!
I've got 2 of the 553Fs that I've assembled over the last month or two, and I believe I need some help or guidance with one of them (the other one worked perfectly and sounds great!).

Here is the situation as a starting point, please let me know if you would like any more information. I believe I am doing this correctly, but don't want to leave anything out of the problem list.

• Input signal is a sine wave @ 400Hz and +4dBu / +1.79dBV (Vrms of 1.22v) - I am driving this using a QA403 by QuantAsylum.
• Measure the Test Points following the Test point document with an Oscilloscope (after not having luck with the DMM, I switched to better "see" what was happening)
  • TP 1: 1.20vrms
  • TP 2: 1.04vrms
  • TP 3: 1.04vrms
  • TP 4: 1.04vrms
  • TP 5: 2.0 Vdc
• Output Load is set to HiZ by jumper.
• Output Load is connected to the QA403 and the input impedance of this device is specified as:
  • Input Z 100KΩ AC-coupled unbalanced (single-ended) or 200KΩ AC-coupled balanced
  • I believe I am using it balanced, which would mean the load impedance of the EQ would be 200kOhm... is that too high?

From my measurements it would seem that there are a few "weird" things:

1. The voltages are all higher than expected (606mV to 410mV)
2. The Test Point 5 (after the 2520) is 2V and from my oscilloscope it is actually DC, not a sine.

Maybe this would indicate that the 2520 is failing in some way. Can anyone think of any follow up tests I could do on the 2520 to diagnose or resurrect it?

Thank you so much for any help.

Best,
Eli

 

[jsteiger]

I would swap 2520 opamps between the units and see if the issue follows the opamp. There should be only a few mV of DC offset after the 2520 opamp so it sounds like that amp is a problem.

 

[ElijahSound]

Hi Jeff,
Thank you for your assistance. The working unit is in service at a studio already (and the producer wouldn't let me take it out of the vocal chain), so I went ahead and ordered 2 SL-2520s from Scott.

Would it make sense to troubleshoot the bad 2520, or would I be better off in just tossing it?

Best,
Eli

 

[ElijahSound]

Swapped to the new 2520 and it is passing audio, although the TP voltages are still higher than expected. Is that an issue I should be concerned with?

 

[jsteiger]

Swapped to the new 2520 and it is passing audio, although the TP voltages are still higher than expected. Is that an issue I should be concerned with?

Higher like .5dB or 10dB?

 

[ElijahSound]

Higher like .5dB or 10dB?

Hi Jeff,
I believe the test point document on your website says that the TP's should measure about 0.6 Vrms with a +4dBu input signal at 400Hz. I consistently measure about 1.0 Vrms, which should be about a 3 dB increase. Does that make sense?
Cheers,
Eli