BA BA2 BA4 BAD Dual99v Build Thread

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ajsteel
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by ajsteel »

Joe Malone wrote:
ajsteel wrote:Hi Joe,
IMG_1415.jpg
You have C & E under the BD681 pins solder together so it is bypassing the BD681. You only solder these pins together if NO BD681 is fitted. This may or may not have destroyed the 39v zener.

Remove the solder short and see if you get 36 to 38v at +V or not?

Also check you get 39v volts across the zener or not?
Hi Joe, I removed the solder short at BD681 and I'm getting 7.8mV at +V across the Zener I'm getting 7.4mV

ajsteel
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by ajsteel »

Joe Malone wrote:
ajsteel wrote:Hi Joe,
IMG_1415.jpg
You have C & E under the BD681 pins solder together so it is bypassing the BD681. You only solder these pins together if NO BD681 is fitted. This may or may not have destroyed the 39v zener.

Remove the solder short and see if you get 36 to 38v at +V or not?

Also check you get 39v volts across the zener or not?
Hi Joe,

I have removed the short and replace the Zener and I get 2.9mV at +V on the opamp
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

ajsteel wrote:
Joe Malone wrote:
ajsteel wrote:Hi Joe,
IMG_1415.jpg
You have C & E under the BD681 pins solder together so it is bypassing the BD681. You only solder these pins together if NO BD681 is fitted. This may or may not have destroyed the 39v zener.

Remove the solder short and see if you get 36 to 38v at +V or not?

Also check you get 39v volts across the zener or not?
Hi Joe, I removed the solder short at BD681 and I'm getting 7.8mV at +V across the Zener I'm getting 7.4mV
Remove the zener and see if you get close to +46v at +V. If so zener has gone short circuit and needs to be replaced.
Joe :-)
JLM Audio
Capturing Audio without Injury

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Joe Malone
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

ajsteel wrote:
Joe Malone wrote:
ajsteel wrote:Hi Joe,
IMG_1415.jpg
You have C & E under the BD681 pins solder together so it is bypassing the BD681. You only solder these pins together if NO BD681 is fitted. This may or may not have destroyed the 39v zener.

Remove the solder short and see if you get 36 to 38v at +V or not?

Also check you get 39v volts across the zener or not?
Hi Joe,

I have removed the short and replace the Zener and I get 2.9mV at +V on the opamp
OK sounds like the short killed both the zener and BD681. Replace both and you should have 36 to 38v at +V.
Joe :-)
JLM Audio
Capturing Audio without Injury

ajsteel
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by ajsteel »

You have C & E under the BD681 pins solder together so it is bypassing the BD681. You only solder these pins together if NO BD681 is fitted. This may or may not have destroyed the 39v zener.

Remove the solder short and see if you get 36 to 38v at +V or not?

Also check you get 39v volts across the zener or not?[/quote]



Hi Joe,

I have re[laced the Zener and BD681 and now get 0.6mv at +N (unpowered unit, no opamp) and 38V powered. Also getting 19V at +N powered (no opamp).. seems like it's all good.

Shall I low ratio the primary by connecting the two centre pins on the primary (EA2622) and connect the two centre pins on the secondary (EA2622) to 0V on the BA?

OK sounds like the short killed both the zener and BD681. Replace both and you should have 36 to 38v at +V.

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

ajsteel wrote:
I have re[laced the Zener and BD681 and now get 0.6mv at +N (unpowered unit, no opamp) and 38V powered. Also getting 19V at +N powered (no opamp).. seems like it's all good.

Shall I low ratio the primary by connecting the two centre pins on the primary (EA2622) and connect the two centre pins on the secondary (EA2622) to 0V on the BA?
Cool. Good to hear you have the correct two voltages :-)

Yes low ratio is the correct setting for 600ohm mics
Joe :-)
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by ajsteel »

Hi Joe,

Regarding the Low Ratio option and 600ohm mics, if using Dynamics and LDC's is really necessary? For instance the SM57 has an impedance 150ohm and I do have an Impedance pot on my pres? Am I missing out on anything by not using the low ratio on the Primary of the EA2622?

Thanks for all your great help. This has been a great learning curve in really understanding my gear and how and why it gives me the sound it gives me.

A.J.

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

ajsteel wrote:Hi Joe,

Regarding the Low Ratio option and 600ohm mics, if using Dynamics and LDC's is really necessary? For instance the SM57 has an impedance 150ohm and I do have an Impedance pot on my pres? Am I missing out on anything by not using the low ratio on the Primary of the EA2622?

Thanks for all your great help. This has been a great learning curve in really understanding my gear and how and why it gives me the sound it gives me.

A.J.
600ohm input is for 150ohm and 200ohm mics
150ohm input is for old 50ohm mics

But yes because you have variable impedance setup the centre detent on the Z pot is 600ohm on low ratio and 150ohm on high ratio.
You have a lot of impedance range so can experiment with high ratio if you want too.
Joe :-)
JLM Audio
Capturing Audio without Injury

ajsteel
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by ajsteel »

I went with the low ratio. It seemed a little fatter. I've also added a 10k resistor before the 100k Impedance pot and only soldered the to back three legs and suggested earlier in this build thread. The pre seems more open and extended when the pot is all the way to the right. Two more pre's to build and I'll be away with four. :)

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by ajsteel »

Hi Joe,

My 3rd channel I just finished doesn't seem to get any power. The phantom power LED will not light up either when I switch it on. I've compared it to the other two working channels and can't seem to find a difference. What have I missed? I'm going from +V on Channel 2 to +V on Channel 3.

I also destroyed a BD681 and got replacement but after I inserted it I saw that it was a BD681n. Is that a problem?

I thought I had these nailed now. :)


Thanks.

A.J.
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Last edited by ajsteel on Thu Sep 05, 2013 9:31 am, edited 3 times in total.

ajsteel
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by ajsteel »

This is the bottom side of my 3rd channel with no power.
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by ajsteel »

Hi Joe,

I've fixed my problem with Channel 3. All good.. I didn'y have 0v from channel 2 connected to channel 3. Once connected I had power, LED cam on and correct Voltages at +N. :D

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

ajsteel wrote:Hi Joe,

I've fixed my problem with Channel 3. All good.. I didn'y have 0v from channel 2 connected to channel 3. Once connected I had power, LED cam on and correct Voltages at +N. :D
Cool good to hear you got it going so easy :-)
Joe :-)
JLM Audio
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ajsteel
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by ajsteel »

Hi Joe,

I thought I had it going but I was wrong. :( My voltages aren't correct through the opamp amp circuit. What I get is;

+N 19V
-N 9V
Out 9V
1/2V 19V
+V 39V

When I first plugged in the 2520 I got a little smoke and a smell. Have I blown something up? Photos below; Also when I plug the 2520 in the power supply goes into protection mode. The LED flashes.

A.J.
ba2_3 bottom.jpg
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Joe Malone
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

ajsteel wrote:Hi Joe,

I thought I had it going but I was wrong. :( My voltages aren't correct through the opamp amp circuit. What I get is;

+N 19V
-N 9V
Out 9V
1/2V 19V
+V 39V

When I first plugged in the 2520 I got a little smoke and a smell. Have I blown something up? Photos below; Also when I plug the 2520 in the power supply goes into protection mode. The LED flashes.

A.J.
ba2_3 bottom.jpg
What voltages did you get when you did the votlage tests before the opamp was plugged in for -IN and OUT?

As long as there is no short on -IN or OUT to 0v there is no way the BA kit can damage the opamp so it should only be a opamp fault.

Is it a GAR2520 you built? And has it been tested in a good BA PCB before? I would be testing each new BA PCB with a known good opamp.
Joe :-)
JLM Audio
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