BA BA2 BA4 BAD Dual99v Build Thread

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Fri Sep 06, 2013 10:51 pm

HI Joe from memory I think the voltages were the same as what I've just listed. I don't think 2520 has killed the BA. I have now tested my new 2520 in a known working BA and the the power supply cuts out so it's definitely a dud2520 build on behalf. I have also tested a known 2520 in my new BA circuit and I get good signal level, clean gain, however I still can't work out the bad voltages when the 2520 is removed.

Out; 9V to 10V
-IN: 9v to 10v

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Fri Sep 06, 2013 11:11 pm

ajsteel wrote:HI Joe from memory I think the voltages were the same as what I've just listed. I don't think 2520 has killed the BA. I have now tested my new 2520 in a known working BA and the the power supply cuts out so it's definitely a dud2520 build on behalf. I have also tested a known 2520 in my new BA circuit and I get good signal level, clean gain, however I still can't work out the bad voltages when the 2520 is removed.

Out; 9V to 10V
-IN: 9v to 10v


Once a opamp has been powered in the BA it will charge the 470uF caps at -IN and OUT so the 19v will slowly discharge once the opamp has been removed. This is not a fault.
Joe :-)
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Fri Sep 06, 2013 11:23 pm

OK. So just to confirm. If I get 39V at +V (using a 39V Zener) and 19V at +N with no OPAMP fitted (Powered unit)then the OPAMP circuit is good to go and the -IN and OUT will be charged once the OPAMP is fully powered?

THanks AJ

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Sat Sep 07, 2013 7:33 am

ajsteel wrote:OK. So just to confirm. If I get 39V at +V (using a 39V Zener) and 19V at +N with no OPAMP fitted (Powered unit)then the OPAMP circuit is good to go and the -IN and OUT will be charged once the OPAMP is fully powered?

THanks AJ


Yes correct if you have tested -IN and OUT are not shorted to 0v with a ohmmeter before you plug and power the opamp.
Joe :-)

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Sat Sep 07, 2013 8:16 am

Hi Joe,

I've just test Out and -IN before powering the unit (no OPAMP fitted)with Ohm meter and I'm getting 10V at both points. All other points I get 0V with no power, 0V, 1/2V and +V

I don't seem to see any shorts on the BA PCB. Is something wrong if I'm getting 10V at -N and Out with now opamp and no power?

Thanks
A.J.
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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Sat Sep 07, 2013 3:35 pm

ajsteel wrote:Hi Joe,

I've just test Out and -IN before powering the unit (no OPAMP fitted)with Ohm meter and I'm getting 10V at both points. All other points I get 0V with no power, 0V, 1/2V and +V

I don't seem to see any shorts on the BA PCB. Is something wrong if I'm getting 10V at -N and Out with now opamp and no power?

Thanks
A.J.

You should have your meter on ohms looking for shorts NOT volts. If there is volts stored in the caps obviously then there cannot be a short.
Joe :-)

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Sun Sep 08, 2013 6:56 pm

Hi Joe,

I think I'm getting closer. I've tested the channel with a known working GAR2520 I get good level with no hiss or fuzz. Seems good to me. However I think I'm getting confused with a few things;

What are the voltages should I be getting at; Should I be getting 19V at each +N and -N or only at +N as the B runs on a single rail.

+N
-N
Out

when the BA is on with no Opamp? I get 19V at +N, 18.5V at Out and 38V at +V I guess it's alright.

I tested -N and Out using Ohms and was getting about 220kOhm between each point and 0V after I saw the 47PF cap leg was touching a resistor so I assumed there was no short now. When I measured the same points on channel one which I think operates correctly the resistance was more like 6.6MOhm. Do I still have a problem?

I did smoke the 10R resistor when I plugged in my troublesome GAR2520 so I replaced it. It was burnt and crusty. Have I fixed my mistakes?

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Mon Sep 09, 2013 1:11 am

Hi Joe,

I think I've worked it out. I got 38V at +V and 19V at +N with no opamp but with the BA unit turned on. Then when I slotted in a working GAR 2520 I got 19V at +N, 19V at -N and 19v at OUT. All seemed to work ok. No smoke, no smells and good strong clean signal into Pro Tools with heaps of quiet gain.

A.J.

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Mon Sep 09, 2013 9:32 am

ajsteel wrote:Hi Joe,

I think I've worked it out. I got 38V at +V and 19V at +N with no opamp but with the BA unit turned on. Then when I slotted in a working GAR 2520 I got 19V at +N, 19V at -N and 19v at OUT. All seemed to work ok. No smoke, no smells and good strong clean signal into Pro Tools with heaps of quiet gain.

A.J.


Yes in a negative feedback opamp setup that has a capacitor to 0v on -IN like the BA circuit the opamp OUT and -IN will always follow the +IN voltage. Because the gain is unity at DC.
Joe :-)

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Mon Sep 09, 2013 11:08 pm

Hi Joe,

I had to get some more 220pf capacitors and got 220pf that is 221k, +-10%. Is this going to be a problem? I notice the other 221caps aren't marked with a letter? Also I need to get some more carbon 10R resitors. Is there a certain Watts I should get?

Also do you have a suggestion for connecting all the wires to Ov on the PCB. I find they keep popping out of there socket? I'm little anxious about doing anything that may affect the audio quality. :)

Thanks
A.J.

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Tue Sep 10, 2013 9:53 am

ajsteel wrote:Hi Joe,

I had to get some more 220pf capacitors and got 220pf that is 221k, +-10%. Is this going to be a problem? I notice the other 221caps aren't marked with a letter? Also I need to get some more carbon 10R resitors. Is there a certain Watts I should get?

Any 220pF (221) ceramic will work fine. Standard 10R carbon 1/4 types work perfect.

Also do you have a suggestion for connecting all the wires to Ov on the PCB. I find they keep popping out of there socket? I'm little anxious about doing anything that may affect the audio quality. :)

Use only thin hook up wire there is NO need for thick power cable wire and tightly twist and/or solder all wires together to make one wire before putting it in the screw terminal
Joe :-)

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Tue Sep 10, 2013 12:08 pm

Hi Joe,

If I can only get 10R 1/4W metal film resistors, is that going to be a problem?

Thanks
AJ

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Tue Sep 10, 2013 12:32 pm

ajsteel wrote:Hi Joe,

If I can only get 10R 1/4W metal film resistors, is that going to be a problem?

Thanks
AJ


Metal film work fine. But if there is a fault they go open circuit with no external sign that they are now open circuit.
Joe :-)

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby ajsteel » Fri Sep 20, 2013 12:33 am

Hi Joe,

I don't think I fixed Channel 3 in my BA4 kit. I built a new GAR 2520 to replace the one that was a dud and when I insert into Channel 3 the Power Supply LED Blinks off like there is a short somewhere I guess. I have used a good opamp in Channel 3 and it works but I feel the sound is not as open as the other three channels, I have the Impedance knob full clockwise. I'm getting 38V at +V and 19V at +IN with no opamp and the power on.

Any suggestions? I'm a little stumped. Also if worse comes to worse can you recommend anyone mic pre guru in Melb that may be able to take over for me and get it working.

Thanks
AJ

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Re: BA BA2 BA4 BAD Dual99v Build Thread

Postby Joe Malone » Tue Sep 24, 2013 8:11 am

ajsteel wrote:Hi Joe,

I don't think I fixed Channel 3 in my BA4 kit. I built a new GAR 2520 to replace the one that was a dud and when I insert into Channel 3 the Power Supply LED Blinks off like there is a short somewhere I guess. I have used a good opamp in Channel 3 and it works but I feel the sound is not as open as the other three channels, I have the Impedance knob full clockwise. I'm getting 38V at +V and 19V at +IN with no opamp and the power on.

Any suggestions? I'm a little stumped. Also if worse comes to worse can you recommend anyone mic pre guru in Melb that may be able to take over for me and get it working.

Thanks
AJ


I am not sure what you mean as you say you insert ? channel 3 and the power supply goes into hiccup mode protection due to over current so usually means a short circuit and you usually will not get sound then.

But then you say you have sound? Is the power supply still blinking on and off?

Send me a large in focus macro on well lit photo of the underside of the PCB if you want me to check it for shorts again.
Joe :-)

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