there are two separate circuits in a relay. One is coil which needs an input voltage and second is the output circuit (which will provide necessary action in event of certain conditions based on background circuit... alll the little to-92 trannies, resistors, caps, etc on the speaker protect.).
so the relay coil voltage (5V, 12V, 24V that u see on relay) is actually the rectified secondary dc that needs to be fed to the relay coil for it to operate. the protect boards have diodes , so if u use 5 v rated coil relay, u need 12V AC secondary. the relays are in series....
the capacity of relay to cutoff a given speaker o/p voltage and current , when there is DC(the relay internal construction circuit ) is altogether different matter.
i think non of the mechanical relays that are specified here( rated at x - amps and x-voltage), would be able to support reasonably high power amp like HB.
relay is can switch 10A at 28VDC but what will happen at 62VDC? what is the current switch capability at 62 VDC? see the relay data sheet graph and you will be disappointed at its capability.
some will argue differently, but listen to advice given by AndrewT.
Correct me if I'm wrong but;
Ref: Soft start: Isn't the purpose of the zener reference/ rectifier "bridge" circuit to hold the coil V at 24V? I would think that this "trigger" voltage would then switch the mains OK (with the relay I've suggested using)?
I'm not too confident about the Speaker Protection Board relays. I'm not sure what the "trigger" voltage is.
Sorry if some of my terms aren't correct. The Aircraft that I primarily work on (ATR-42), has been nicknamed "The All Those Relays-42) accordingly. The MTCE Manuals and drawings were written in Italian, and Translated by a Frenchman to English... Needless to say, some of the terms I use are probably not standard.
Also, in Aviation we designate symbols differently than I've seen here so far, and use a different value system as well (Ex: 4R0 resistor meant nothing to me when I first saw it, lol. I thought It was a typo for 4.0 Ohm)
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haha... i would love to have such a superhuman relay... so also all people (knowledgeable) on diya... 10AMPS at 125VDC ... wow that would be great....
unfortunately for diy, at 50v, its maximum switching capacity into dc is limited....have a look at datasheet...
I'm not trying to be difficult, I promise 
. There is just so much good information that sometimes I miss the answer among the information. I think I miss understood the advice given.
Are you suggesting to use the Speaker Delay portion of the circuit, but not the DC protect?
. There is just so much good information that sometimes I miss the answer among the information. I think I miss understood the advice given.Are you suggesting to use the Speaker Delay portion of the circuit, but not the DC protect?
A 250Vac & 30Vdc relay switching ON/OFF a low current AC signal with maximum voltage upto 30Vac is no problem. This works for delayed speaker connection at start up and instant off if mains power fails.
When/if the amplifier goes faulty and sends supply rail voltage to the speaker, then the DC voltage and the DC current that needs to be broken is way above the DC rating of the relay.
The relay works well as a delay speaker connect/disconnect.
It may fail, when asked to protect the speaker from an amplifier fault.
When/if the amplifier goes faulty and sends supply rail voltage to the speaker, then the DC voltage and the DC current that needs to be broken is way above the DC rating of the relay.
The relay works well as a delay speaker connect/disconnect.
It may fail, when asked to protect the speaker from an amplifier fault.
Okay, so I don't need to worry about the initial 8A draw from the XFMR?
So basically, the suggested relay would work for the connect/disconnect, but if the amp failed in a way that put DC to the relay, it could potentially fail as if the relay wasn't there (weld shut).
So for the soft start I need at least:
1 X 125VAC 10A "Power" switch(or relay controlled by a switch)
1 X 125VAc 8A relay
you have swapped to a different relay. I thought you were still talking about the speaker delay and protect relay !
If you are lucky then the first time it is asked to protect the speaker, it opens with a lot of sparking/arcing and becomes damaged. You repair the amplifier and replace the relay.
If you are very unlucky the relay welds closed, the PSU discharges into the speaker VC and the close rated mains fuse blows quickly. Your speaker might just survive.
This is where a daft idea comes in.
Use a conventional relay for normal delayed speaker and instant off. And in series with that mechanical relay you have a solid state relay (SSR) that is triggered on excess current, either shorting the output or failure of the output device/s.
I have not seen this, so maybe it is unworkable.
Yes.
Soft start bypass relay is the lowest duty.
Mains ON/OFF is a medium duty, rated for the normal maximum load that the transformer presents.
Speaker protection is the highest duty (DC rated).
I am. Sorry for the confusion. I am trying to understand how the circuit works, and at the same time try and order parts for my build. I will be flying to an isolated post in a few days, and an running out of time quickly. I do appreciate all your help. I guess alot of the problem is that I don't know what voltages the components are seeing, so its harder to understand what I am trying to accomplish. I have been "searching" through threads here for a week straight, and can't find what I'm looking for. Once again, I appreciate your help.
Worst case: I will not submit my order, and try to sort it out again next month when I come home.
Would you recommend omitting the Speaker connect/ DC Protect PCB from my build?
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Obviously, via our previous discussion this won't work... but theoretically speaking, if the DC rating of the relays could handle my Rails Voltage, is this the correct configuration?https://flic.kr/p/CsWqVU
I guess it may have made more sense to go with a smaller secondary V since I had the XFMR custom wound now that I think of it.
I guess it may have made more sense to go with a smaller secondary V since I had the XFMR custom wound now that I think of it.
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post 175 diag: That's right.
But the transformer must include the AC to DC PSU.
I would include the speaker delay and instant off.
That does a good job of keeping odd noises from the speakers.
You may never need the DC protect. This is more likely to be needed if you abuse the amplifier.
After thorough testing and working with a dummy load and/or a sacrficial speaker (cheap), the solid state amplifier rarely go wrong. It's what we do to them that breaks them. The cooler it runs, the less likely to become unreliable. The higher the speaker impedance the less likely to become unreliable. Never swapping leads while still switched on is a golden rule.
But the transformer must include the AC to DC PSU.
I would include the speaker delay and instant off.
That does a good job of keeping odd noises from the speakers.
You may never need the DC protect. This is more likely to be needed if you abuse the amplifier.
After thorough testing and working with a dummy load and/or a sacrficial speaker (cheap), the solid state amplifier rarely go wrong. It's what we do to them that breaks them. The cooler it runs, the less likely to become unreliable. The higher the speaker impedance the less likely to become unreliable. Never swapping leads while still switched on is a golden rule.
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Whoops, that's embarrasing! LOL, I had a spot layed out for it and everything.
I'll edit it later incase someone else is reading this in the future and gets confused.
Thanks again for all the advice. I'll be sure to apply it to my process!
Not directly related;
I have a process for troubleshooting DC-GCU(DC Generator Control Unit)/ Generator problems on the Aircraft I work on. I always "ring out" the wires to ground with the GCU disconnected on the suspected bad side, and then the known good system(other wing/engine). I then Compare the readings and look for the pins that read different from the good side. You can apply this informatinon to the wiring diagram to see which component failed. This process only takes 30 mins or less, but its amazing how many people just change the box over and over, costing $15-20,000 in damage each time!
Hi!
I am building this board and I want to ask if I have to connect the transformer directly into the input, or I Will have to rectify it to DC in order to connect?
I Just got a quote from a transformer maker and he is willing to Wind me a 24V secondary rated 0.25A for free on the mains toroidal rated 2x45V 1000VA. Another question I came across might be off topic in this thread: Will the additional 24V winding "affect" the overall Sound of my amplifier using those windings?
Thanks for the help
Sebastian
I am building this board and I want to ask if I have to connect the transformer directly into the input, or I Will have to rectify it to DC in order to connect?
I Just got a quote from a transformer maker and he is willing to Wind me a 24V secondary rated 0.25A for free on the mains toroidal rated 2x45V 1000VA. Another question I came across might be off topic in this thread: Will the additional 24V winding "affect" the overall Sound of my amplifier using those windings?
Thanks for the help
Sebastian
I think the build guide mentions that there are diodes on PCB that will rectify the AC supply. it also mentions that You can supply either AC or DC.
If the circuit is designed for AC better to use it, as DC supply might change the delay characteristics and need to be careful of polarity.
regarding second question, since this is a low power circuit and with 1000VA transformer, it should not affect at all.
reg
Prasi
How is the reference supposed to work fo the dc protection.
I feed my speaker protection board from a secondary 12v - 12v AC from the transformer.
I need to get a reference ground from the PSU running from the main secondary of the transformer. How do I achieve that without putting 12v ac into the main powersupply.
transformer has both both 40v and 12v windings.
I feed my speaker protection board from a secondary 12v - 12v AC from the transformer.
I need to get a reference ground from the PSU running from the main secondary of the transformer. How do I achieve that without putting 12v ac into the main powersupply.
transformer has both both 40v and 12v windings.