BAN Build Thread

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theaterguy
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Joined: Sat Apr 07, 2012 11:42 pm

Correct voltages?

Post by theaterguy »

Hello, I am almost done with my new BANs with gar2520. The 10k trim is set to 15V. Is this ok?
The 2604 is fitted but the 2520 is not and the phantom led is very dim. I'm getting correct 48V on the input but between the phantom legs it is about 20V. Ok?

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Re: Correct voltages?

Post by Joe Malone »

theaterguy wrote:Hello, I am almost done with my new BANs with gar2520. The 10k trim is set to 15V. Is this ok?
Just leave the 10k trim pot at the rear of the BAN PCB in it centre position it comes set to new. No adjustment is needed with a 2520. To re-centre pot turn until hear clicking and turn back 12.5 turns.
The 2604 is fitted but the 2520 is not and the phantom led is very dim. I'm getting correct 48V on the input but between the phantom legs it is about 20V. Ok?
Led should not be dim so not sure what is wrong there as it is only a 6k8 resistor in series with the 48v rail. Have you soldered the LED to the correct place which is the top two legs of the 48v switch with the long LED leg closest to the edge of the PCB? See go between build thread for more led detail.

The phantom power will drop if a condensor mic is plugged into the mic input and the voltagw will depnd on the current it draws.

If nothing is plugged into the mic input then the phantom power should read 48v on pin 2 and pin 3 of the input XLR.
Joe :-)
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theaterguy
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Joined: Sat Apr 07, 2012 11:42 pm

Re: Correct voltages?

Post by theaterguy »

Joe Malone wrote:
theaterguy wrote:Hello, I am almost done with my new BANs with gar2520. The 10k trim is set to 15V. Is this ok?
Just leave the 10k trim pot at the rear of the BAN PCB in it centre position it comes set to new. No adjustment is needed with a 2520. To re-centre pot turn until hear clicking and turn back 12.5 turns.
CW or CCW? Can you give voltage values? If there is clicking it must be very faint. Now there is +30,7V at +pin (2520 supply) and 0V at -pin


Led should not be dim so not sure what is wrong there as it is only a 6k8 resistor in series with the 48v rail. Have you soldered the LED to the correct place which is the top two legs of the 48v switch with the long LED leg closest to the edge of the PCB? See go between build thread for more led detail.

The phantom power will drop if a condensor mic is plugged into the mic input and the voltagw will depnd on the current it draws.

If nothing is plugged into the mic input then the phantom power should read 48v on pin 2 and pin 3 of the input XLR.
Thanks, it was the LED backwards

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Re: Correct voltages?

Post by Joe Malone »

CW or CCW? Can you give voltage values? If there is clicking it must be very faint. Now there is +30,7V at +pin (2520 supply) and 0V at -pin


OK set trim pot as described on PCB then so TP3 so has roughly half voltage between TP1 and TP3 and TP3 and 0v. So for 2520 TP3 should be roughly 16v from 0v or TP1.
Joe :-)
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theaterguy
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Re: BAN Build Thread

Post by theaterguy »

Thank you.

Now I have two boards, one singing beatifully but with the another I cant get correct voltages. Either I have broken the 10k trimmer or the #681 is faulty.
The voltages are now: 0v - TP1 = 30,8V, 0v - TP3 = 1V, TP3 -TP1 = 29,6V no matter how I turn the trimmer.
What you say?

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Re: BAN Build Thread

Post by Joe Malone »

theaterguy wrote:Thank you.

Now I have two boards, one singing beatifully but with the another I cant get correct voltages. Either I have broken the 10k trimmer or the #681 is faulty.
The voltages are now: 0v - TP1 = 30,8V, 0v - TP3 = 1V, TP3 -TP1 = 29,6V no matter how I turn the trimmer.
What you say?
BD681 is working fine as the voltage is 30.8v. Check you have no solder shorts under the PCB shorting the 1/2v rail to 0v.

You can check the trim pot with the BAN turned off by adjusting it and measuring the resistance between the output pot pins to see if it changes between 0ohm and 10k.

You can set the trim pot with the BAN turned on and no output opamp so you get about 16v to 0v on one end of the pot. The other end will stay at 30.8v.
Joe :-)
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theaterguy
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Re: BAN Build Thread

Post by theaterguy »

Joe, now I am clueless.
The new trimpot did not help, and the old one was faulty. But still I did not get the 16V.
Now I removed all the #-parts and put it into normal 48V mode.
There should be between 24 to 48 volts on those 470µF caps on the + side, right? Near that #10k resistor I have very close to 0V.
The middle row seems normal.
On the other side near the 10 ohm resistor the second gives 48,7V and the first 0,3V.
There must be a short that draws voltage at some point but I cant locate it.
Any ideas how to proceed?

Edit. ok I put back the #10k and it gave correct voltages on those near 10ohm resistor.
I also compared the schematics and the pcb and found some diffencies. The third leg from 10k trimmer should go parallel with 0.1µF(?), 10k and 470µF to ground but it goes staight to ground?

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Re: BAN Build Thread

Post by Joe Malone »

theaterguy wrote:Joe, now I am clueless.
The new trimpot did not help, and the old one was faulty. But still I did not get the 16V.
Now I removed all the #-parts and put it into normal 48V mode.
There should be between 24 to 48 volts on those 470µF caps on the + side, right? Near that #10k resistor I have very close to 0V.
The middle row seems normal.
On the other side near the 10 ohm resistor the second gives 48,7V and the first 0,3V.
There must be a short that draws voltage at some point but I cant locate it.
Any ideas how to proceed?

Edit. ok I put back the #10k and it gave correct voltages on those near 10ohm resistor.
I also compared the schematics and the pcb and found some diffencies. The third leg from 10k trimmer should go parallel with 0.1µF(?), 10k and 470µF to ground but it goes staight to ground?
Please answer short and simply the 3 questions I asked in the last post and any new posts as without that it is impossible to help you.

You are removing things that I said were working which is just going to make things more complicated to fault find.

If you get 48v at one end of the 10R and 0.3v at the other end the 10R is open circuit or a lot of smoke is pouring out of it and it soon will be open circuit.

Remove the 2520 opamp and let me know what voltages you get at the 6 sockets for the 2520 measured to 0v?

Also a large clear well lit in focus photo of the top and bottom of the PCB sent to my email so I can look for any solder shorts would help solve this quicker.
Joe :-)
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Re: BAN Build Thread

Post by Joe Malone »

Image
Image

The 5 solder pads circled 3 to the left are at 1/2 rail voltages and others 2 on the right are 0v. So blob soldering like this shorting the 3 centre pads will short the half rail to 0v casing the problems you were having.

Also we do not recommend doing any mods on new builds. Just use the correct size power supply for the correct number of BANs.
Joe :-)
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theaterguy
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Re: BAN Build Thread

Post by theaterguy »

Ok, done and works now beatifully.
Thank you Joe.

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Re: BAN Build Thread

Post by Joe Malone »

theaterguy wrote:Ok, done and works now beatifully.
Thank you Joe.
Cool good to hear :D
Joe :-)
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prhunt
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Fuse rating recommendation

Post by prhunt »

Joe,

What would be recommended fuse rating for 4 channels of BAN, using 2 x LME49860 per channel, powered with a JLM +48V smps.

I will use the on-board Darlington regulator with a 39V Zener.

Specs for the LME49860:

quiescent current at +/- 18V 10.2ma, at +/- 22V 10.5ma, maximum 13ma.
output current (Rload=600R) +/-31ma at +/-20V.
Instantaneous short circuit current +53ma and -42ma

Oh, the input transistor pair is a MAT12 (if that is significant)

Thanks! PaulH

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Re: BAN Build Thread

Post by prhunt »

Bump 8)

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Re: Fuse rating recommendation

Post by Joe Malone »

prhunt wrote:Joe,

What would be recommended fuse rating for 4 channels of BAN, using 2 x LME49860 per channel, powered with a JLM +48V smps.

I will use the on-board Darlington regulator with a 39V Zener.

Specs for the LME49860:

quiescent current at +/- 18V 10.2ma, at +/- 22V 10.5ma, maximum 13ma.
output current (Rload=600R) +/-31ma at +/-20V.
Instantaneous short circuit current +53ma and -42ma

Oh, the input transistor pair is a MAT12 (if that is significant)

Thanks! PaulH
Easiest way to check is measure the volts across the 10R resistor at the back corner of the BAN or BA or BAD PCB. A = V/10. So if meter read 500mV current will be 50mA x the number of channels if driving 10k loads. So 200mA.

But having the smallest fuse that will not blow with all channels just clipping into a 600ohm is a good idea and will usually be 2 to 3 times the above value.

These 10R are the actual fuse for each BAN BA BAD PCB. The standard 500mA slow blow we usually have after the 48v 520mA SMPS is just for any wiring short circuits and power supply faults.
Joe :-)
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prhunt
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Re: BAN Build Thread

Post by prhunt »

Thanks for fuse info, Joe.

I have finally built my 4 BANs and have power tested and performed alignment.

As mentioned previously, I am using the BD681 and a 39V zener, which gives about 38.6V at the base of the BD681 and about a volt less at the emitter. I'm setting 1/2V at TP3 at about 18.8V.

I found that the voltages took a while to settle during the alignment procedure, particularly the gain pot trim. Is this expected?

In any case, I am going to double-check everything - I'll let the boards idle and warm up for 10-15 minutes and test voltages again before installing in the case.

Thanks again.

Paul

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