[Build] CAPI BT50, 500 Series EQ (a la 550), Official Support Thread

[jsteiger]

Hi all!
I just finished this build. It's my first from CAPI. I am however having a few issues. I sent an email to Jeff after I finished the build regarding the issues, but I have come to some better conclusions after tests the next day.

I initially thought the unit was not receiving power because the red LED was not illuminated when the switch was engaged. I thought I had the polarity wrong so I flipped it around just for testing and it still didn't illuminate. My next thought process was the switch had a short or cold joint. I couldn't see any noticeable shorts or cold joints. I didn't feel like desoldering the 90-degree header on the switch PCB to check further, so I just looked through the small gap to examine the joints. I checked the LED outside of the circuit and it illuminated so that rules out a bad LED. I'm not really sure where to check next.

Next issue, probably the biggest is a constant static noise when the unit is plugged in. I noticed that when I touch some of the knobs the static noise is amplified. I feel as if there is a short to ground somewhere. I've checked for shorts, but can't seem to find any. I've been constantly cleaning up joints and removing excess solder, but haven't seemed to hit the right joint yet.

With some small bits of testing I think the unit works, I tried a few boosts/cuts with the mid band and it seemed to work fine, just that annoying static noise. I'm not sure if this will help at all, but I was slightly sloppy on a single joint and got a thin layer of solder on the J3-14 contact and have not been able to remove it. I really hope this is not the cause. I'm going to be doing some testing in the meantime as I have some other ideas of things to test, but I'm hoping someone with a better background in electronics can maybe point my troubleshooting in the right direction.

Thank you!

The LED circuit is very simple. It consists of R1 on the main PCB (from gold finger pin-1 to R1 to J1-1), onto the switch PCB also J1-1, SW1 shorts out the LED when disengaged, when engaged the LED is connected to -16V thru J1-3 on both boards.

As for the noise, what opamps are they and who built them? Have they been tested and verified elsewhere?

 

[rtg603]

The LED circuit is very simple. It consists of R1 on the main PCB (from gold finger pin-1 to R1 to J1-1), onto the switch PCB also J1-1, SW1 shorts out the LED when disengaged, when engaged the LED is connected to -16V thru J1-3 on both boards.

As for the noise, what opamps are they and who built them? Have they been tested and verified elsewhere?

Was just about to update you on some further tests I did all night.

As for the LED circuit, I noticed that R1 had a copper contact pad missing. Don't remember that coming out. Going to try to repair with copper tape or something similar. That issue is figured out.

Fixed the static noise, probably just a short or something. I reflowed a bunch of joints too.

Now I could actually test the unit. IN switch works, HPF switch works, LPF switch works. So pretty much all good for the switch PCB besides the LED.

Low band shelving is working, but peaking is not. I think I remember another copper contact coming out of the low band mini toggle switch, so I'll repair that too. Boosts all appear to be accurate for the low band.

Now the mid and high band is where I'm having some trouble. The boosts/cuts are not accurate. For the mid band when the unit is set to +12 dB, I'm only reading about a +2 dB boost/cut same across all frequencies on that band.

High band is similar but only about +5 or +6 dB when set to +12 dB. Shelving and peaking are both working for the high band.

The unit output is also much quieter when hardware insert is engaged in PT. I had my signal generator at -18 dBFS @ 1 kHz and when the HW Insert was engaged it dropped to -28 dBFS. I've swapped all slots with same issue, no other 500 series units are affected, so it appears to be something I messed up on.

Finally, op amps were built by myself, and no they have not been verified elsewhere which I know I'm not supposed to do, but I don't have any other op amps to test with.

Thanks for all the help thus far, Jeff.

 

[rtg603]

The unit output problem is probably just the output op-amp, going to try and borrow a friend's op-amp to see if that fixes it. Inspected both and don't see any bridges or excess solder. All parts seem to be in the correct place. That aside, any ideas on the boosts/cuts being inaccurate for me? Not entirely sure where the signal flows after the switch.

 

[rtg603]

@jsteiger I'm kind of at a loss for troubleshooting. My roommate just got in some of the prebuilt CAPI 0252 Op-Amps for his VP28 and he let me try those. No change. I haven't touched the PCBs since my last post, just testing everyday.

Overall level of the unit is down -3 dB now, even when bypassed. Really weird. Could just be a PT issue, but I don't know. None of my other hardware inserts decrease in level when engaged. Made me think it was the chassis, but every slot works with other non-DIY modules no issue.

The static noise also came back, no clue why that happened. Boosts and cuts seem to be working fine, was just an idiot and didn't test properly. Really could use your help. I still feel like the thin layer of solder I got on contact J3-14 may be causing the noise issue, possibly even the level drop problem. I just don't know enough about this unit to say for sure.

The noise is also an issue when using the knobs. I found it gets worse when using the knobs.

 

[jsteiger]

@jsteiger I'm kind of at a loss for troubleshooting. My roommate just got in some of the prebuilt CAPI 0252 Op-Amps for his VP28 and he let me try those. No change. I haven't touched the PCBs since my last post, just testing everyday.

Overall level of the unit is down -3 dB now, even when bypassed. Really weird. Could just be a PT issue, but I don't know. None of my other hardware inserts decrease in level when engaged. Made me think it was the chassis, but every slot works with other non-DIY modules no issue.

The static noise also came back, no clue why that happened. Boosts and cuts seem to be working fine, was just an idiot and didn't test properly. Really could use your help. I still feel like the thin layer of solder I got on contact J3-14 may be causing the noise issue, possibly even the level drop problem. I just don't know enough about this unit to say for sure.

The noise is also an issue when using the knobs. I found it gets worse when using the knobs.

The input is unbalanced so you will likely use 6dB if driving from an electronically balance source. That is what the +6dB shunt jumper is for. If you have random noise issues coming and going then I'd look for cold solder joints.

 

[rtg603]

The input is unbalanced so you will likely use 6dB if driving from an electronically balance source. That is what the +6dB shunt jumper is for. If you have random noise issues coming and going then I'd look for cold solder joints.

Probably just going to give up on fixing this. I solve one problem and two more pop up. Fixed the LED circuit, got rid of the noise, but now the output level is all whack and the high band has some sort of ground loop when I touch the knob. Peak/Shelving doesn't work at all for the high band, and peaking doesn't work for the low band. I don't know enough about electronics to be trying to repair this, probably shouldn't have even done this build, I thought it would be fun. Might just try to sell for someone to repair themselves.

 

[ScottD]

Just finished my first BT50. Wondering if there would be an obvious cause for a major jump in output when turning HF past 0? Everything else, aside from the LED seems to function normally. Switch engages/disengages EQ, but LED not working at the moment. Boosting the HF at all causes a big jump, to the point of peaking the interface and overdriving. Basically not usable. Appreciate any insight. Thanks in advance.

 

[jsteiger]

Just finished my first BT50. Wondering if there would be an obvious cause for a major jump in output when turning HF past 0? Everything else, aside from the LED seems to function normally. Switch engages/disengages EQ, but LED not working at the moment. Boosting the HF at all causes a big jump, to the point of peaking the interface and overdriving. Basically not usable. Appreciate any insight. Thanks in advance.

I would look for misplaced resistors specifically behind the HF Grayhill switch.

 

[ScottD]

@jsteiger I doublechecked HR1-HR20 and all are correct values. No solder bridges. Reflowed most of the points. Any thoughts as to where to look next?

 

[jsteiger]

@jsteiger I doublechecked HR1-HR20 and all are correct values. No solder bridges. Reflowed most of the points. Any thoughts as to where to look next?

I would check with good magnification for a small solder bridge. Could be on the HF Grayhill switch. Sounds like something is getting grounded when the switch is activated causing full gain.

 

[Zjcc56]

Hello im having two problems with two units and i just want to know where i should look for errors

i have 4 units two are perfect the second two are close but ill refer to the problem ones as A and B

when i was comparing them i had all Knobs centered and the unit, high cut ,and low cut bypassed
i used rew to do measurements and pulled units out and swapped them around with a 500 series extender so the only variance was the unit under test

A. maybe within tolerance but it is a 1 db louder than than the others
EDIT: Im a knob and forgot a jumper

B. matches my working two units until i get down to 100 HZ where it looks like a very low (below 20hz) high pass filter my interface dosen't go down to 5 hz but thats where it looks like the -3db point would be

ive switched op amps from the working units to eliminate them as avarable and the problems follows the unit and not the op amps

next steps are to reflow solder joints and clean again but i thought id throw this out there to the group mind

 

[rbkonline]

Hi folks

I am having an issue here...
I have recently built a BT50 with two Gar1731 opamps. The final assembly went well and I have cross checked everything before adding the unit in my Capi 511 rack.
Now ,the issue is whenever a signal is passed through the unit, the signal gets super distorted and fuzzy along with a massive drop im volume.
The situation remains the same even if I disengage the eq.

I am using two Gar 1731 which I buit with the bt50.

I have tried using Rouge 5 from louder than liftoff....same result.

I have also used the Gar 1731's i built in other gears. They were working fine there

Can anyone help me to troubleshoot ?


Thanks n regards

 

[jsteiger]

Hi folks

I am having an issue here...
I have recently built a BT50 with two Gar1731 opamps. The final assembly went well and I have cross checked everything before adding the unit in my Capi 511 rack.
Now ,the issue is whenever a signal is passed through the unit, the signal gets super distorted and fuzzy along with a massive drop im volume.
The situation remains the same even if I disengage the eq.

I am using two Gar 1731 which I buit with the bt50.

I have tried using Rouge 5 from louder than liftoff....same result.

I have also used the Gar 1731's i built in other gears. They were working fine there

Can anyone help me to troubleshoot ?


Thanks n regards

Did you get this sorted? Bad solder joint? Misplaced transistor maybe?

 

[rbkonline]

Did you get this sorted? Bad solder joint? Misplaced transistor maybe?

Yes I sorted it myself! One of the op amp sockets wasn't getting the required voltage...its was due to a poorly soldered resistor.

 

[audiophil_studio]

Hey, I've built a pair of BT50 a few years ago - they always sounded great now BOTH of them distort no matter if engaged or not.
Any idea where I should start troubleshooting?
Thanks, br Philipp

 

[jsteiger]

Hey, I've built a pair of BT50 a few years ago - they always sounded great now BOTH of them distort no matter if engaged or not.
Any idea where I should start troubleshooting?
Thanks, br Philipp

I would first rule out the opamps but it does sound like it could be a cold solder joint(s) somewhere on the build. It is strange that both started at the same time. Have you ruled out any outside issue?

 

[audiophil_studio]

Hey Jeff, thanks for the ultra fast response!
I've tried other modules in the same 500 Slots (RND551 EQ and an FC526) which sounded fine.
I use prebuilt red-dot opamps in both BT50s and also tried to exchange it with others - same problem...
I also cleaned the pcb and re-flowed the solder on some points but had no luck with that either.
Is it possible that transformers or other components go bad after this short time (maybe due to heat)? Any other ideas?

 

[craigmorris74]

Just finished building a pair of these. One works well, the other loses signal at TP8. Used the same opamps, cables, and slot for both. Any place in particular to look for issues? Thanks!

 

[craigmorris74]

Just finished building a pair of these. One works well, the other loses signal at TP8. Used the same opamps, cables, and slot for both. Any place in particular to look for issues? Thanks!

Hi, just bumping this to see where I could check for faults. I’ve looked hard, but don’t see any glaring issues.

 

[craigmorris74]

Fixed my problem. I had to repair the HF switch when one of the pole pins got bent. Where I made the repair, there was a connection to ground where there should have been. Easy fix, just not where I was looking.