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Post by kcatthedog on Jan 23, 2018 4:36:45 GMT -6
Super pleased with my delta journey so far: props to JimW, Wiz, TonyC, DanD and Joe for helping me out with mods, advice and friendly support. This is getting seriously RGO international with the Board and module mods coming from CA, other parts for the hpf mods coming from the land down under, op amps coming from the mid west and tons of advice and support from TonyC and wiz: thanks all. So the problem is sometimes the board powers up but is either noisy or doesn't pass signal. I have the Power One psu from Jim so it must be rock solid. It has no power switch. I have noticed that the wires into the connector on the back of the board seem a little bendy and or loose and when the board doesn't pass signal if I manually disconnect the power and then reconnect it, then it re-powers up fine. So do people think I should open up the connector ( unplugged  and check its solder joints and or trim the leads and re-solder with fresh wire. Or do the pins on these connectors wear over time and I should replace the connector (male and female parts). thx ! Attachment Deleted |
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Post by svart on Jan 23, 2018 6:33:34 GMT -6
Could be a lot of things, but my money would be on oscillation outside the hearing range. It usually happens at start up when rails don't sequence and settle at the same times.
Do you have meters in the board? Do they peg out?
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Post by kcatthedog on Jan 23, 2018 6:37:00 GMT -6
Thx.
There are peak indicators on each channel and led meters on the groups and master outs.
The leds do show signal on power up: what’s normal?
Would you like video of power up of leds ?
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Post by kcatthedog on Jan 23, 2018 7:18:57 GMT -6
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Post by svart on Jan 23, 2018 8:42:54 GMT -6
Not sure it's the power supply itself. It's going to be a function of the collective circuitry. Overly fast opamps are notoriously finicky, even with good layouts and proper decoupling. Unfortunately this is one of the usual outcomes of sending modules for "upgrades", but I digress.
The fact that the LEDs are partially lit tells me that it's likely detecting either DC offset or oscillation. It's going to be hard to troubleshoot this without an oscilloscope, because the oscillation is likely much above the audio band, into the MHz region with opamps that are (not?) compensated for high bandwidths on non-impedance controlled PCBs.
You could take a DMM and set it to DC and probe portions of the audio path during the failure mode and see if there's an opamp railed out somewhere. Alternately, you could put your finger on each opamp and see if one or more is really hot.. Oscillation or railed opamps are going to get pretty toasty.
Also, probe the V+ and V- rails at various points in the circuit and see if one is being pulled further away from nominal voltage at some points.
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Post by kcatthedog on Jan 23, 2018 8:54:21 GMT -6
Understood, but I have the op amps, which normally are not problematic (lme 49720). Oddly, I have one noisy module, one of three original, ( the rest are modded), it is currently immediately to the left of the groups, should I remove it and see what happens, perhaps it is throwing the power up off ? I'll send a video of the leds on start up, should they be full scale due to the normal power surge in rush ? Remember this problem is inconsistent. If there is an inherent problem shouldn't it be consistent ? Do you mean railed or failed op amps ? Railed, as in, they are not getting the correct level of electricity and or its is oscillating. Thx: always more to learn  |
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Post by svart on Jan 23, 2018 9:37:52 GMT -6
Understood, but I have the op amps, which normally are not problematic (lme 49720). Oddly, I have one noisy module, one of three original, ( the rest are modded), it is currently immediately to the left of the groups, should I remove it and see what happens, perhaps it is throwing the power up off ? I'll send a video of the leds on start up, should they be full scale due to the normal power surge in rush ? Remember this problem is inconsistent. If there is an inherent problem shouldn't it be consistent ? Do you mean railed or failed op amps ? Railed, as in, they are not getting the correct level of electricity and or its is oscillating. Thx: always more to learn Ok, the LME aren't terribly high bandwidth compared to some opamps, but high enough to oscillate easily in an standard audio application.. However, in some circumstances like in EQ, where phase margin is very close, they can oscillate a LOT more easily if not compensated for the bandwidth and phase margin. A little higher theory than I think you care about though! The meters will move, simply because all the amps and meter drivers are all pulling currents and the power rails are coming up. Essentially there is a short period of complete chaos in the power system.. Railed is a generic term, which means that the transistors in the opamp have pulled themselves completely to one power rail or the other. This can be a very short time, or it can be continuous depending on what is happening. I know that Jim loves to take DC blocking caps out of the channels he mods, but they are there to keep the opamps from seeing any DC offset of a magnitude that would force them to try to "amplify" DC, which means that their outputs will source a much higher DC voltage.. If the power rails don't come up in a reasonably similar timeframe, then the opamp will spend a period of time pulled to one rail, aka "railed" and then pass DC to the next opamp, etc. Taking a quick peak at the LME part datasheet, it doesn't seem to be "rail-to-rail" capable, so it stops being able to source current a volt or more from the power rail. It also makes no mention of being latch-up immune either. It also goes into great detail about proper layout and decoupling, which is usually a sign that the manufacturer thinks the part is on the edge of stability during average usage too. These are all good clues that the parts might be oscillating in your application. |
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Post by kcatthedog on Jan 23, 2018 9:56:50 GMT -6
hmm,, but oscillation would not be my board's friend ?
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Post by kcatthedog on Jan 23, 2018 10:25:02 GMT -6
ps what do oscilloscope's cost ?
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Post by svart on Jan 23, 2018 13:40:26 GMT -6
ps what do oscilloscope's cost ? Cheap or expensive? Cheap but decent digital, around 200-300$. Expensive? 50K-100K$. |
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Post by kcatthedog on Jan 23, 2018 16:45:55 GMT -6
Cheap sounds my speed! |
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Post by kcatthedog on Jan 24, 2018 16:41:13 GMT -6
Wiz rides to the rescue
Peter knows that I am planing like him to not use my 4 groups; just the 16 mono modules for their eq. He , like svart , had talked to me about the in surge and rail problem as the board powers up.
I fixed a few small problems last night and everything was powering up ,including 15 channels. I am getting some op amps for the 16 th channel maybe tomorrow in the mail, but then the surge problem happened again.
Point being, wiz had suggested I just disconnect the 4 groups ,so they draw no power at all. With them off line, so far, I have powered up 5 times with 15 modules on online with no problems at all !
Yea Wiz !!
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Post by keymod on Jan 25, 2018 5:16:03 GMT -6
I would think it would be prudent to at least clean & tighten all connections on both ends of the power supply cable, perhaps using something like Caig DeOxit. Svart, would using a Variac to slowly bring up power be helpful? I would imagine that would limit in-rush current and help things stabilize more peacefully.
Disconnecting the groups seems more like a band-aide, no? ( pun intended ) I bet somewhere down the road you might want to utilize them.
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Post by svart on Jan 25, 2018 7:11:44 GMT -6
I would think it would be prudent to at least clean & tighten all connections on both ends of the power supply cable, perhaps using something like Caig DeOxit. Svart, would using a Variac to slowly bring up power be helpful? I would imagine that would limit in-rush current and help things stabilize more peacefully. Disconnecting the groups seems more like a band-aide, no? ( pun intended ) I bet somewhere down the road you might want to utilize them. A variac could help, if the problem is inrush currents. I asked about monitoring voltages at various points in the board via a DMM, but I'm guessing since there was no reply to that, it's not going to happen. That would have told us if the issue is the power supply hitting overcurrent protection due to the inrush currents being drawn, or if it's something in the channels like opamps getting latched. However, these types of issues are absolutely rife in the modding arena. The board power supply and it's traces/wires were designed for a specific opamp and decoupling, and their associated current draw during inrush and operation. Higher speed opamps use more current during operation, while increased decoupling increases inrush currents considerably. Both stress the physical layout, and the physical layout is the most ignored part of modding. If the wires/traces are too narrow/thin, then you're going to resistively and inductively restrict current flow during power up and get all kinds of issues. There is such a thing as going for *too much* decoupling in these cases. I'd suggest backing off the decoupling some. There is no appreciable reason to go for more local bulk decoupling than 10uF+100nF per power pin at the opamps, 220uF+100nF per rail within a few inches of opamp groups, and maybe 470uF+100nF per rail on the channel inputs. |
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Post by kcatthedog on Jan 25, 2018 8:27:06 GMT -6
"I asked about monitoring voltages at various points in the board via a DMM, but I'm guessing since there was no reply to that, it's not going to happen."
Hi Svart,
I am happy to continue to diagnose as I appreciate your help. Initially, I just wanted to get the modules operational , but I agree I would like to ensure that the groups can be powered up too.
I do have a DMM, if you looked at the schematic can you direct where you would like me to take readings ? Remember too that I have 4 sets of modules, 3 original, 2 modded by Jim a number of years ago, 4 done by Jim last summer and 8 modded by Tony.
I have seen on line that I can also use my DMM to read how much power the module are drawing. I presume the power consumption follows the list of types of modules above with the original drawing the least power and Tony's drawing the most: only because a number of the parts/caps he used are much bigger than those used by Jim. ?
If you could advise where to add different value de couplers back into the circuit I would be happy to do that as well.
Thx.
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Post by svart on Jan 25, 2018 8:45:49 GMT -6
"I asked about monitoring voltages at various points in the board via a DMM, but I'm guessing since there was no reply to that, it's not going to happen." Hi Svart, I am happy to continue to diagnose as I appreciate your help. Initially, I just wanted to get the modules operational , but I agree I would like to ensure that the groups can be powered up too. I do have a DMM, if you looked at the schematic can you direct where you would like me to take readings ? Remember too that I have 4 sets of modules, 3 original, 2 modded by Jim a number of years ago, 4 done by Jim last summer and 8 modded by Tony. I have seen on line that I can also use my DMM to read how much power the module are drawing. I presume the power consumption follows the list of types of modules above with the original drawing the least power and Tony's drawing the most: only because a number of the parts/caps he used are much bigger than those used by Jim. ? If you could advise where to add different value de couplers back into the circuit I would be happy to do that as well. Thx. Sorry, that sounded harsh and that's not how I meant it. I simply meant that it seemed like you got it working in another way and didn't need to really dig into the circuits anymore. However, I looked at the link you sent and I don't see any schematics. There were just block diagrams in the files, which aren't enough to go by. I did go searching and found a set of schematics, but they didn't actually show the decoupling on the audio path pages at all. In typical fashion, I think the decoupling is probably shown on a single page that wasn't included in the PDF that I found, so I don't know what's currently on the board, nor how it was modified. Maybe some pictures of the unmodded and modded boards to see what was changed might help. |
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Post by kcatthedog on Jan 25, 2018 8:52:05 GMT -6
No probs. I understood what you meant. I'll post pics later than. |
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Post by kcatthedog on Jan 25, 2018 13:15:40 GMT -6
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Post by svart on Jan 25, 2018 13:52:31 GMT -6
That stuff is strictly for cleaning grease and grime off of connections. It doesn't de-oxidize the metal like DeOxit does. |
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Post by kcatthedog on Jan 25, 2018 15:36:46 GMT -6
Thx, so deoxit is best ? So, my errant 6 op amps showed up today: thx to TonyC and DanD, dropped them in module 16 and all 16 are powering up fine and passing signal. I will want to continue to diagnosis the power up issue and solution but job 1 was getting the 16 channels running and they all have the hpf filter mod too thx to Wiz and Joe ! So, I finally feel like I have my board operational as I really wanted to use the 4 band eq while mixing.  |
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and check its solder joints and or trim the leads and re-solder with fresh wire. Or do the pins on these connectors wear over time and I should replace the connector (male and female parts).
