Should unplugged active EQ/Comp pass same signal when powered off?

[poppaflavor]

Hi All, myself I can't stand unfinished stories, so to close out the scenario here goes... Today I had a couple of exchanges with the company Tech team and management today. The responded right at the start of their workday and then again after hours on a Friday. So as responsive as I'd hoped for.

I'm posting below the smoking gun pic. This will mean more to you than to I, but it still let's me know things went off the rails for this device (at least for the +Rail). All 3 LED should be lit when the power is on. But the +15V LED and the PWR UP LED do not light up when device is powered up. The company replied at the end that it looks like the device is thrown into hard bypass, which I think supports @Harvey Birdman proposition about the structure of the relay and like what @gyraf described to be opposite his preferred wiring of "on" for a bypass.

Does this also explains the burning plastic smell?



I've messaged the couple of folks in this thread who asked to know what the brand and model was and provided it to them. If you'd like to know the brand and model please message me and I'll provide that info as well as identifying pictures.

However, I don't want to name the brand and model here generally because I posted here for technical insight into a bizarre (to me) problem, not to flame the company even if somewhere a failure happened. If I wanted to flame-on, I'd have posted at the Purple Site. I'm not even sure the problem didn't happen at the online supplier's waylay station. With no evidence I can't indict.

 

[Evertide]

With brand and model we sometimes can find a schematic , it tells us more about how the unit works...

We can measure the voltages and find a defect component , in this case maybe a burnt resistor that makes the 15 Volt diaper.

 

[poppaflavor]

With brand and model we sometimes can find a schematic , it tells us more about how the unit works...

We can measure the voltages and find a defect component , in this case maybe a burnt resistor that makes the 15 Volt diaper.

Totally, yes. I still haven't resolved the replacement with the manufacturer so I've messaged you just now with the information directly and can update the thread when it's replaced.

 

[gyraf]

It looks like you lost your positive supply line, and as the bypass relays are apparently powered from there, you're now stuck in bypass.

I'm not entirely sure what your question is?

/Jakob E.

 

[Rob Flinn]

On the other hand, a bypass-when-unpowered relay would require power to be "in" - and as it's electromagnetic'ly activated, I prefer to keep this from not happening near my audio transformers.

So I wire bypass relays so they bypass when powered (and any magnetic interference thus dosen't matter), not the other way around

/Jakob E.

The Klark teknik dn27 graphics used to do this the other way round. I think because if they were used for live sound & the dn27 psu failed then the box would still be passing audio, although probably with masses of feedback that the graphic had tuned out ...

 

[gyraf]

Yup, for live sound, broadcast, it makes sense the other way sround

 

[poppaflavor]

It looks like you lost your positive supply line, and as the bypass relays are apparently powered from there, you're now stuck in bypass.

I'm not entirely sure what your question is?

/Jakob E.

You and the other folks here like @Harvey Birdman answered the question, thank you. The question was whether it was possible or normal for a device to pass signal when it was not powered. I didn't know about the different ways to power a relay, so your answers helped me understand what was going on.

The Klark teknik dn27 graphics used to do this the other way round. I think because if they were used for live sound & the dn27 psu failed then the box would still be passing audio, although probably with masses of feedback that the graphic had tuned out ...

Wow. I'm glad you mentioned this. I actually have two of those en route right now. They should be here in a few days. I'll check that out when they get here. If I understand you correctly, then when I get the DN27As here they should also pass audio with the power off.

 

[Evertide]

Sometimes if I smell something burning , I cut the power.

On the hand , when powered the failing component can burn and show him self...

An infrared-camera can show it to.

When reading a manual , I also mean the schematics , sometimes a block-diagram will be shown unpowered , the signal-lines will bypass the active parts of the unit and leave the unit the same...

Follow the instructions from the manufacturer , as it is a new unit , they should / could help you better , because they made the unit...

 

[poppaflavor]

Sometimes if I smell something burning , I cut the power.

On the hand , when powered the failing component can burn and show him self...

An infrared-camera can show it to.

When reading a manual , I also mean the schematics , sometimes a block-diagram will be shown unpowered , the signal-lines will bypass the active parts of the unit and leave the unit the same...

Follow the instructions from the manufacturer , as it is a new unit , they should / could help you better , because they made the unit...

Yup, I cut power, but sometimes new devices do emit a "new car smell" kind of odor as they get initially used (in my experience) and I had a hard time determining by nose if this was waaay outside the bounds of normality or was just a burn in process. I've had other devices that were clear cut decisions to cut power. I just received a old device used for broadcasting and upon plugging it in it immediately gave me some 'magic smoke'. Apparently, it still has ample reserves of magic smoke in it's components because it now appears to be working. For the device in question here, my nose deemed it as borderline. So I forged ahead to take one for the team.

GREAT idea on the infrared cam. I've used an infrared cooking temp probe and phone video pointing to different areas so far. It helped me diagnose some heat problems. I haven't tried a infrared cam for audio engineering, but have to admit that in another life as a scientist I've been on projects that used infrared cam monitoring to watch the rate of poop cooling on pavement.

Most importantly, THANKS for clarifying about schematics/block diagram vs the manual. I thought you meant instructions or contact info in the manual. I didn't know that the block diagram would sometimes be shown unpowered. I understand that won't always be the case, but this helps me look at them going forward.

In this case you are exactly right, and with the knowledge I've got in hand now from this thread I'm better armed to figure out similar situations and decipher diagrams.

Here is the device's block diagram, and as I read it, and with my certainty that it is indeed passing signal unpowered I think your assessment of this schematic is right; it's shown unpowered. Sorry for the low-res image, this is all they had in the manual and online.



BTW- The manufacturer was helpful, but since they are on an opposite workday time zone and we are running into the weekend I wanted to lean into the gurus here to get some insight. I've since been communicating with the manufacturer and they acknowledged it is broken and will be replaced. But, through this thread I learned WAY moar and became empowered in a way that simply would not have happened through the communication with the manufacturer (who, understandably is giving disclaimers about their strict QA/QC and is concerned about the embarrassment to their reputation).

 

[JohnRoberts]

UL approved products could briefly release "magic smoke" (vernacular for devices or components failing) but will open internal or external fuses/breakers before putting humans or building at risk.

JR

 

[Rob Flinn]

You and the other folks here like @Harvey Birdman answered the question, thank you. The question was whether it was possible or normal for a device to pass signal when it was not powered. I didn't know about the different ways to power a relay, so your answers helped me understand what was going on.



Wow. I'm glad you mentioned this. I actually have two of those en route right now. They should be here in a few days. I'll check that out when they get here. If I understand you correctly, then when I get the DN27As here they should also pass audio with the power off.

There are various versions. I have had about 6 or 8 of these over the years. Some have the relay bypass mod some don't, some have transformer i/o, some don't. So it depends on the individual units. The ones I was using live I always modded to have the relay bypass. The current pair I have for my studio do not have relay bypass. The DN27/a is the best sounding graphic, they have an inductor for every band, not sure if that makes them sound better, but they just sound lush.

 

[Evertide]

So the modern equipment is still using Indian communication ; magic smoke...

You are helping the manufacturer , the unit is possible not fit to be shipped...

 

[poppaflavor]

There are various versions. I have had about 6 or 8 of these over the years. Some have the relay bypass mod some don't, some have transformer i/o, some don't. So it depends on the individual units. The ones I was using live I always modded to have the relay bypass. The current pair I have for my studio do not have relay bypass. The DN27/a is the best sounding graphic, they have an inductor for every band, not sure if that makes them sound better, but they just sound lush.

Cool, thanks for the context and info. I'll be keen to check out the two DN27As when they get here to see what type they are. I've been reading about relays all day It helps me understand some other gear I have, like my new Signal Art Electronics SAE47 mic that has a reed relay for switching the mic pattern from cardioid to omni. It's that silver mu metal goodie at the top on the board.



I do have the DN22 already and yes it is so gorgeously delicious!! I absolutely adore it. The DN22 I have has transfos on both inputs and outputs (pic below). The DN27As I am acquiring look to only have transfos (toroidal Belclere)on the outputs.

As much as as I love my DN22, the prospect of having moar bands per channel was really appealing (DN22 = 11 inductors/bands per channel, DN27 welp obviously has 27). Perhaps this is naive of me, but I imagined that having more finely resolved bands, where each band is an inductor, would provide more finely resolved saturation across the frequency spectrum. But that is still to be explored.

So the modern equipment is still using Indian communication ; magic smoke...

You are helping the manufacturer , the unit is possible not fit to be shipped...

I think you may have misread my post. I described that an old vintage FM broadcast device from the 1980s that I also received at the same time produced magic smoke. The new EQ I posted about here did not throw out any smoke. It just smelled like hot plastic. Maybe that's splitting hairs though.

With your second statement, it almost seems like you are criticizing me for not being harsher and calling out the manufacturer publicly. Hopefully I have misunderstood your point?

Because, of course I am 'helping' the manufacturer to identify the issue and helping them figure out where the problem arose. I am absolutely not 'helping' them by hiding any (un)intentional faults they might have done. I messaged you privately yesterday and listed the brand and model to you. I did this as well for several other folks. I'm not 'helping' them by hiding anything.

I am sure the manufacturer does several QA/QC checks before it leaves them, it would be very hard to miss this particular issue. Also, the distributor as well as online retailers will sometimes open boxes and check the device before delivering it. Perhaps the issue arose while it was waylaid en route? I like to give the benefit of the doubt rather than sling stones and arrows at first.

So, long story short, I have no direct evidence it was the manufacturers fault. So I do not feel it is appropriate to drag their name through the mud without sure knowledge they are at fault. I will certainly update this thread as I learn more about what might have gone awry, but suffice to say that I am not beholden to the manufacturer or hiding anything on their behalf. I do respect their work though; I own a couple of their gears already (purchased used) and they work great and seem to be solid builds.

 

[Evertide]

I have worked in the 80's on a unit with no connection inside , simply no function...

To day every unit will have bean checked , before leaving a factory.

You did not make the mistake to set the unit on 120 and give 240 , the unit would have bean dead and not have LED's on on the front.

On the road from the uk to the us many things can have happened , it can happen to an other unit in the future , with your unit the manufacturer can find these and make sure it will not happen again. In this way you are helping..

Working on a same kind of unit with tubes they gave us the calibrating info , so we could service the unit and is still a very good part of the studio...

I have collected info and parts for a Fairchild 670 , in 1959 they produced 3 different schematics , with small differences , and from photo's on the net I am sure of an other part that have bean changed.

The new 670 from Telefunken has a part of the 660 , so it is not a clean reproduction.

I hope to have 1 audio path recreated at the end of the year.

Hope your new unit will have a long live in your studio.