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sgenevay  
#1 Posted : Wednesday, January 28, 2015 1:04:10 PM(UTC)
sgenevay

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Hi .. Just to be sure...
I'm trying to feed the whole system with a 18v DC power because i need 18v to feed my headphones amp which are in the same case.
What is makes me a bit worried is that the relay driver board is getting very hot at highest volume settings. I can still put my fingers on it but i don't ket them for a long time. As if the regulator was warming more at higher level.
Is this normal ?
the main problem is that after a while ... the relays become crazy when i'm touching the potentiometer. if i move just a bit they don't stop to make on/off noise....
And this is linked to the temperature cause if i wait a bit on lowest position to let it getting cold a bit, then everything is back to normal and the relays act normally....
Any Hint ?
Thanks a lot.
Sylvain
sgenevay  
#2 Posted : Wednesday, January 28, 2015 3:25:33 PM(UTC)
sgenevay

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After several tests, it appears that it start warming and getting hot even by staying on first step... and stop warming at mute position ...
If someone has any idea...
Best.
Sylvain
Brian Donegan  
#3 Posted : Wednesday, January 28, 2015 4:34:14 PM(UTC)
Brian Donegan

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At full volume, you have most of the relays engages, so the voltage regulator is supplying the most current, thus the added heat. At mute, only one relay is engaged.

Can you measure the output voltage of the regulator when hot and displaying the issue? Does it sag?

It may be a lack of available current. The relays use ~23mA each, so each relay board is using around 160mA near full volume.
sgenevay  
#4 Posted : Wednesday, January 28, 2015 4:55:15 PM(UTC)
sgenevay

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Hi Brian . Thanks for your answer.
Well ...when it's on mute position i have 4.90v at the regulator output.
and when it start to get hot it start to fall slowly and it sag and turns around 2.50v and 3.10v (the higher volume is, the faster it gets hot but even at first step i get the same problem... just a while after).

Concerning the current, i'm using a modified JLM Audio AC/DC which is supposed to give me like 1.5A. By the way, the AC/DC regulator gets very hot too in the same time.
I have hesitating to plug the transformer directly in the JT for a test as i have between 25-26vAC at the output. Would it damage the Relay Driver board ? as it supposed to be limited to 24v....
Thank you
Sylvain.
Brian Donegan  
#5 Posted : Wednesday, January 28, 2015 5:48:59 PM(UTC)
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The max input voltage for the LM7805 is 35VDC. Supplying 25VAC to the JT will result in roughly (25 * 1.4 = 35) 35VDC, so that is too close to the line.

Does the output voltage of the JLM regulator sag as well?
sgenevay  
#6 Posted : Wednesday, January 28, 2015 5:57:49 PM(UTC)
sgenevay

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mmmm not really ... as i'm starting at 18.00 .... and maybe it was a bit under then i'm finishing at 17.99 .... and when relay board is driving nuts, i'm still at 17.99 at the output of the AC/DC board while relay driver board reg is starting to sag. but the JLM reg is getting hot a lot also.
Hope it's going to work properly :-/
Sylvain
sgenevay  
#7 Posted : Wednesday, January 28, 2015 6:26:49 PM(UTC)
sgenevay

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ok Add-on.

looking at my old stuff i found a toroidal transformer with 2 coils, 12v/1,25A per coil
in fact it gives a little bit more 13v. so i tried to feed the board directly from the transformer.
i have better result. as the JT regulator stopped to sag.
But the board is still getting very hot and i’m afraid about the cap which is stuck to the regulator due to board design. then the cap is warming also. isn’t it bad for the cap ?
Plus i’m just testing it so i’m running 1 board only. 2 will be plugged at the end. and i’m afraid it could warm more…. cause i already can’t touch the pcb with only one relay board.
btw the heat sink feet where supposed to be soldered at the pcb right ?
Sylvain
Brian Donegan  
#8 Posted : Wednesday, January 28, 2015 6:32:21 PM(UTC)
Brian Donegan

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It sounds like you got the wrong capacitor in your kit. It should fit between the bridge and heatsink with a little room to spare. I can send you a replacement.

Feeding 12VAC direct to the JT should be fine. The heatsink temp by itself should not be an issue. Sagging voltage is.

Soldering the heatsink pins to the circuit board is okay, but not required.
sgenevay  
#9 Posted : Wednesday, January 28, 2015 6:44:09 PM(UTC)
sgenevay

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So ok... if you tell me the whole board can get hot (surly cause i soldered the heatsink to the board to the heat transmit ion is easier) without create problem i will try to find a way to use this transformer instead. as for the moment... out of the pcb getting very hot, the relays are acting well without getting crazy now, and the voltage on the regulator is stable. (it's getting hot the same from first step to last step... it just take longer time at first step...
Concerning the cap, it's pushing the bridge in one side, and pushing the regulator in the other side... So if u have any smaller that would be with pleasure !!! :)
Thx again for your help anyway. i will keep an eye on regulator voltage for a while to be sure :)

Best regards.
Sylvain
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