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My BuffIII legato and four input board was working fine and when I upgraded to the new AVCC module I was losing lock very often. I raised voltage to 5.5vdc and it got worse. When I lowered voltage to below 5.2 all is working perfectly. All LEDs on tridents and AVCC are bright. I do not get it.
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The SPDIF4 board works best right at or slightly below 5V. That's really what is coming into play.
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A resistor and a electrolyt 100 uf ? How big shall the resistor be ? I only have to cut the red marked ribbon cable ?
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so I'm my system I am using a HD placid for the lagato and 1/2 of a LCDS for the buff. So maybe I should use the other half just for the SPDIF4 board at less than 5vdc if I can figure out how to power it
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You would just cut the VD conductors on the ribbon that go to the DAC and then wire 4.5 - 5V to the VD pads. Edited by user Wednesday, December 19, 2012 10:16:12 PM(UTC)
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ok I will give this a try
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Just to be absolutely clear.
pins 19/20 on the ribbon cable between BuffIII and the SPDIF-4 is the VD power.
The 3.3 controller header marked "ADC" on the BuffIII board near the power input
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nn Edited by user Saturday, December 29, 2012 1:56:31 PM(UTC)
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Unfortunately the 3.3V does not work at all. I have the same problem - losing lock every 1-2 seconds depending on how many inputs are connected to the board at the same time. I will try the resistor now. I found a 56 Ohm resistor in my parts bin and applied it. That solves the problem (or at least it appears so). Touching the coax jack sleeve will still sometimes cause a loss of lock but that's not a big issue (and can probably be solved by connecting it to chassis ground or GND on the spdif board). Voltage drop on the resistor is just above 1V. Edited by user Wednesday, December 19, 2012 4:50:17 AM(UTC)
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I had also tried powering the board using 3.3V, but this did not work at all. I got the best results powering the baord using 3.9-4.1V. I raised it a bit to 4.3V because it is powered via the sidecar. The relays will not switch properly at lower voltages. I'll still want to do some more experiments with it as it is still not fully stable. There are one or two unlock events every 10 minutes. I'll give it a try this weekend and post the results. |
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I solved the problem by eliminating ribbon cable use and stack sidecar directly on Buffalo and 4 input board connectors, no more unlocks.
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Originally Posted by: Corpius  I had also tried powering the board using 3.3V, but this did not work at all. I got the best results powering the baord using 3.9-4.1V. I raised it a bit to 4.3V because it is powered via the sidecar. The relays will not switch properly at lower voltages. I'll still want to do some more experiments with it as it is still not fully stable. There are one or two unlock events every 10 minutes. I'll give it a try this weekend and post the results. According to the DS The lowest the comparator can go is 4.75V. But I have managed to run it lower. Still technically 5V into the DAC inputs should be fine... So I have always been stumped why some people have better success with the lower voltage. I have done both the low voltage and normal 5.5V myself - both worked just fine. Edited by user Wednesday, December 19, 2012 10:05:44 PM(UTC)
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Originally Posted by: aos Unfortunately the 3.3V does not work at all. I have the same problem - losing lock every 1-2 seconds depending on how many inputs are connected to the board at the same time. I will try the resistor now.
I found a 56 Ohm resistor in my parts bin and applied it. That solves the problem (or at least it appears so). Touching the coax jack sleeve will still sometimes cause a loss of lock but that's not a big issue (and can probably be solved by connecting it to chassis ground or GND on the spdif board). Voltage drop on the resistor is just above 1V. What do you mean "not work at all"? It stops working? yes looking back through my notes, 3.3V is too low. 4.75V is the datasheet min supply voltage. Likely your issue is about grounding. You may need to connect the cold side of the input transformers to GND. Edited by user Wednesday, December 19, 2012 10:14:45 PM(UTC)
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Originally Posted by: luisbock I solved the problem by eliminating ribbon cable use and stack sidecar directly on Buffalo and 4 input board connectors, no more unlocks. Yes this is the ideal scheme.
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I am not using side car yet so I decided to cut the ribbon cable on pins 19 and 20 and power the 4 input board from the unused side of the LCDPS power supply set at below 5 vdc
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Originally Posted by: Corpius I had also tried powering the board using 3.3V, but this did not work at all. I got the best results powering the baord using 3.9-4.1V. I raised it a bit to 4.3V because it is powered via the sidecar. The relays will not switch properly at lower voltages. I'll still want to do some more experiments with it as it is still not fully stable. There are one or two unlock events every 10 minutes. I'll give it a try this weekend and post the results. You are correct 3.3V won't work - I had forgotten that the comparator min voltage is stated as 4.75V. I was mistaken - I have tried to edit things to prevent further confusion :) I have a better solution in the works in any case. The odd thing is that the comparator output voltage will always be < 3.5V which is well within the input range (5V tolerant inputs) FWIW I don't have any trouble running at 5.5V myself. Cheers! Russ
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Originally Posted by: Russ White Originally Posted by: aos Unfortunately the 3.3V does not work at all. I have the same problem - losing lock every 1-2 seconds depending on how many inputs are connected to the board at the same time. I will try the resistor now.
I found a 56 Ohm resistor in my parts bin and applied it. That solves the problem (or at least it appears so). Touching the coax jack sleeve will still sometimes cause a loss of lock but that's not a big issue (and can probably be solved by connecting it to chassis ground or GND on the spdif board). Voltage drop on the resistor is just above 1V. What do you mean "not work at all"? It stops working? yes looking back through my notes, 3.3V is too low. 4.75V is the datasheet min supply voltage. Likely your issue is about grounding. You may need to connect the cold side of the input transformers to GND. My input board doesn't work well on 5.25V. I power sidecar (not yet in use), then the input board from sidecar. When powered by 3.3V from DAC board (cut ribbon cable and wire to DAC 3.3V), the input module does not work at all. When inserting a 56 Ohm resistor between the two ends of the cut ribbon cable (wires 19/20 on both sides), therefore reducing voltage to input board to about 4.1-4.2V, everything seems to work. Is it possible there isn't enough bypass capacitors on the input board for the mux chip? That would explain why the board works when directly plugged into DAC and not through Sidecar and why it is erratic depending on how many inputs are plugged in. I am pretty sure I had zero problems at full voltage before I added Sidecar in the path. I see only C13 at 100nF. Perhaps replacing it with a 10uF electrolytic in parallel with a smaller 0.1uF (so it can fit on board) would be a simpler fix to try. Edited by user Wednesday, December 19, 2012 10:47:09 PM(UTC)
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Hi aos,
I actually have a theory i am going to test tonight. I will report my results soon. :)
if my theory holds true I will have a very simple fix for you folks who are effected.
BTW, the bypass should be enough - but it does not hurt to try out adding some more. You could easily solder a 47uf low ESR electrolytic across the existing cap.
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