Requesting troubleshooting help: Hypex Hybrid DLCP set up

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Set up: SMPS400_(1) J5:3,5,7 to DLCP:J16:3,5,7


DLCP:J16:2 (amp_standby) to SMPS_400_(1):J5:2, SMPS_400_(2):J5:2
DLCP:J16:1 is ignored. (at least for now)
DLCP not connected to SMPS180. OEMs (connected to SMPS180) are put on by amp enable via DLCP:J1:17, not via J16:2)

Grounds of SMPS_400 (1), SMPS_400 (2) and DLCP are interconnected.
Chassis connected to IEC earth.

Result: System switches on and plays, but volume does not work at all. (In the previous set ups, it would work correctly initially and then stop working a few minutes later)
 
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Did that. (ie Updated Control Firmware).

No success. Volume control works sometimes, doesn't work at other times.

To be sure, the attached schematic is the exact connection.


One comment: At one time, months back, I had mistakenly connected a pull up resistor also to OEM:dc_error pin, in addition to the dc_error connection to SMPS:J3:4. I now realise that if I am using an SMPS of Hypex, I don't have to put a pull up resistor to OEM_dc_error pin. So that is not there anymore.
 

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I agree - that's what I tried Frank. (That's how this thread started)

DLCP and SMPS alone works fine.
All SMPSs work fine on their own.

DLCP and OEMs usually misbehave.

The fact that ground of SMPS180+OEM is different potential from ground of DLCP (ie DLCP SMPS) led me to the hypothesis that that may be causing the instability. Possibly DLCP getting confused about something. (See post 15). Your idea of bypassing DLCP SMPS did not occur to me. That should help solve this ground potential difference problem.

The fact that it works fine on start up, but starts misbehaving after say 3 to 4 minutes is also suggestive: some capacitance issue?

I also strange behaviour like - working fine on XLR inputs, but not on SPDIF.

Hypex mentioned that sometimes firmware upgrade via HFD does NOT work for some boards, and one should try with a programmer. Will try that next and see.

I can see AC voltage (89V) on heatsink of OEM - was wondering if this is expected?
 
Updates:

Got rid of DLCP SMPS. Used power from SMPS to power DLCP.
Only bare minimum - amp on, dc error.

Results:
1. Problem occurs with 1 UCD or 1 OEM as well.

That leaves us with no option but to point fingers at DLCP or control board.

This is a 2015 DLCP board. Would switching to old firmware (1.2) work? Pls share thoughts if you have tried doing so.
 
Hi Prasanth,

are your DLCP + amp electrically tied to the same earthed chassis?

DLCP J16/5 and UCD180 5/6/7/8 should connect both units to the same GND potential of SMPS400

Yes they are. Yes, GNDs are as per your suggestion.


Has nothing to do with firmware, you have some ground loop problems because it is triggered when you use the unbalanced spdif input.

I just didn't know to how to get rid of that. I was not doing anything extra ordinary. The components were connected to chassis with spacers as recommended. IEC earth connected to chassis at 1 point.

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Update: I think we have been able to fix the issue!
First off: Thank you Frank, ds23man and others for trying to help.

1. These components were inside chassis. I had moved them to a test bench, which is just a piece of wood, and I was trying out simple set ups - like 1 UCD, DLCP, SMPS alone etc. Reasoning was that the spacers are only meant for EMF performance (don't really know what means). As mentioned earlier, the problems were not fixed.

2. Yesterday, I tried to mimic a chassis on the test bench.
  • I first tried connecting a peice of wire from each metal spacer to IEC earth. Egs - DLCP to IEC earth; SMPS spacer to IEC earth and so on. No good.
  • I then tried to connect the wires in a sequence. For egs, SMPS to DLCP spacer. DLCP spacer to IEC earth. And viola! it works. I was able to trigger stand-by off/on (via remote button) 20+ times without issues.

Emboldened, I then proceeded to connect them all. So, the sequence was: SMPS (HG) spacer --> SMPS (OEM) spacer --> heat sink of UCD 180 OEM --> metal spacer of DLCP --> IEC earth pin. (I don't think the order matters, just that it has to be a sequence)

It's working perfectly. So, ds23man's observations about loops were spot on.

But I really don't understand what the heck is going on. Observe that when we connect all of them to a chassis, in effect it is like connecting all the spacers in a M:N matrix - meaning all of their chassis connection end points are connected to each other. Why the #### should that create some instability in DLCP? Is it the case that some voltage/current is flowing back to DLCP via its metal spacer? Or is it some sort of EMF that is causing instability? Could someone explain please?
 
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