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No attenuation after major mess

delta1

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Re: No attenuation after major mess

Postby OliverD » January 31st, 2019, 4:22 pm

amb wrote:It’s possible that previous stages have resistor shunts to ground, depending on what your volume was set to before disconnecting power. These relays are latching type, meaning that they retain their positions even after power is turned off.

I have checked different volume settings with this board and it always measures to 12,75kOhms.

amb wrote:Is there excessive current draw on that channel? And are you saying that the transform heats up only when the faulty δ1 board is connected? That’s strange because the δ1 is powered by 5V from the LCDuino-1, not the σ22s.


Yes it only heats up when that particular board and both left and right balanced signal sources are connected. It seems as if somehow a lot of current is drawn through the amplifier stage when the faulty board and signals are connected. Although it is weird that this never damaged any of the boards. They work just fine when directly connected to the output of the y3 bypassing the delta1/delta2 boards.
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Re: No attenuation after major mess

Postby amb » January 31st, 2019, 10:38 pm

Very odd.
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Re: No attenuation after major mess

Postby OliverD » February 2nd, 2019, 11:12 am

Ok back to square one:
I switched all the resistors over and hooked everything up. It instantly fried the same relais on the cold side delta 1 board again. The board is now stuck on 16Ohms as well....
Oh, and the transformer emitted the same buzzing noise as well. even though
This means I now have killed a second delta1 board with something that works perfectly when LCDuino and the delta boards are left unused.

I am out of ideas (and parts) to repair this mess. Additionally I have no idea where to start looking. I guess I am done with the I/O selection and attenuation and will simply use this b22 directly from the y3 attenuated with its built in option.
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Re: No attenuation after major mess

Postby amb » February 2nd, 2019, 1:43 pm

How could this happen? Was that board working before? Did you stack the boards using the stack-through pin headers and receptacles or did you wire the boards up individually? Any chance of reverse voltage?
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Re: No attenuation after major mess

Postby OliverD » February 2nd, 2019, 3:31 pm

I have absolutely no idea how it happened. I have stacked all 4 boards using pins and headers. And the Board was working before, I pulled it out of a working but unused M3 build I have.

How would I go about measuring what might have gone wrong? Reverse voltage is not really possible when stacking the boards, right?

It’s the bottom board though and the one with connection to the LCDuino. But I checked that wiring twice and it is correct.
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Re: No attenuation after major mess

Postby amb » February 3rd, 2019, 12:35 am

If you stacked the boards with the pin headers and receptacles, then all boards will get the same voltage polarity.

Since the problem board is the bottom of the stack, is it possible that a circuit trace or solder pad is shorting to something, such as the chassis? Try removing the mounting screws and elevate the stack temporarily to see if it makes any difference.
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Re: No attenuation after major mess

Postby OliverD » February 3rd, 2019, 5:22 am

After doing that the buzz in the transformer is still audible but a lot less. However Instead of measuring for shorts I now measured the entire thing for voltages where there should be none and I guess there should be no voltage between signal ground and chassis ground right? Well I get about 9V of DC there, which is probably what roasted the delta boards when their signal ground wasn‘t properly isolated (wrong standoffs and screws) from chassis ground.

The question is though, where does this voltage come from?

My build uses 2 s22 for 4 b22 boards and an s25 for the LCDuino and a stack of a total of 4 delta1/delta2 (2 each) boards. The transformers, s22s, s25 and SSR are in a different chassis.
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Re: No attenuation after major mess

Postby amb » February 3rd, 2019, 6:08 am

How did you wire the chassis grounds? It should be like “option 2” as illustrated in the Wiring & ground section of the β22 website. The only additional thing in your build is that the digital ground on the δ1/δ2 stack should be connected to the amp chassis via metal standoffs.
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Re: No attenuation after major mess

Postby OliverD » February 4th, 2019, 12:09 pm

I wired it like in Option 1 on that page (since I have both transformer and s22 in the same case), but I will check this again tomorrow. Maybe I have a short I didn't measure/find last time.

I noticed that I should have maybe been more precise. When I said there is voltage between signal ground and chassis ground, what I was trying to say was:
There is voltage between chassis ground and the ground plane of the delta1 attenuation section when I connect the stack to all cables but keep it isolated from the chassis. I guess you inferred that already, but I should still be more precise.

I will examine all interconnections and all ground connections very thoroughly tomorrow and then report back. There must be something I missed the last time I checked those, although 9V DC makes no sense to me since none of the power supplies uses that voltage.
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Re: No attenuation after major mess

Postby amb » February 4th, 2019, 5:27 pm

There are two ground planes on each δ1/δ2 board, analog side and digital side. Which one were you measuring against the chassis?
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