1290 Build Thread

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Joe Malone
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Re: 1290 Build Thread

Post by Joe Malone »

LosinPwdr wrote:
Thu Feb 10, 2022 1:16 am
Joe Malone wrote:
Fri Jan 28, 2022 11:03 am
LosinPwdr wrote:
Thu Jan 27, 2022 11:38 pm


No. No pops at all. Only the symptoms I mentioned previously. It seems like it must be something pretty small because the faulty channel is only slightly quieter and the noise is not super audible either.

Are there any parts on the mini pcb that would cause noise and gain loss ? Maybe a capacitor or one of the opamps ? I read someone previously had an issue on the DI (my DI's are fine although they are also affected when the faulty mini pcb is connected) due to an opamp- Maybe that's where I should be looking ??
Check the audio level at the output pots between outside pins with pot pulled out full CW and a AC meter and a 500Hz or 1khz tone. If the voltages are different then it is the preamp section. If they are the same it is the output amp and / or transformer.
Hi. Ok, so just to be sure we are on the same page. I measured the outer pins of the rows that contain three pins on the output pot with the pot turned all the way clockwise and a 500hz test tone running through the di. The main gain is turned all the way down ( dunno if this is relevant). So the outer pins on each row measured the sam with a multimeter set to AC voltage. They measured 0.013v.
The voltage should be the same on each pot for the same gain settings. If they match then the gain difference is to do with output module and/or output transformer. The 1k5 in series with 100uF adds 4dB of boost and the resistor can be made smaller or larger to trim level but if both 1290 have them they should match.
Joe :-)
JLM Audio
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LosinPwdr
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Re: 1290 Build Thread

Post by LosinPwdr »

Joe Malone wrote:
Thu Feb 10, 2022 8:31 am
LosinPwdr wrote:
Thu Feb 10, 2022 1:16 am
Joe Malone wrote:
Fri Jan 28, 2022 11:03 am


Check the audio level at the output pots between outside pins with pot pulled out full CW and a AC meter and a 500Hz or 1khz tone. If the voltages are different then it is the preamp section. If they are the same it is the output amp and / or transformer.
Hi. Ok, so just to be sure we are on the same page. I measured the outer pins of the rows that contain three pins on the output pot with the pot turned all the way clockwise and a 500hz test tone running through the di. The main gain is turned all the way down ( dunno if this is relevant). So the outer pins on each row measured the sam with a multimeter set to AC voltage. They measured 0.013v.
The voltage should be the same on each pot for the same gain settings. If they match then the gain difference is to do with output module and/or output transformer. The 1k5 in series with 100uF adds 4dB of boost and the resistor can be made smaller or larger to trim level but if both 1290 have them they should match.
Oh...understood. I thought you were referring to the voltage difference between the two rows of the same pot. The voltages are different between the "good" pot and the "bad" pot. But I suspected the problem might be in the preamp section (mini pcb) as the issue follows the mini pcb when they are swapped around.

If I the issue is in the preamp section, how would I go about locating the exact location of the problem ? As you said , if the resistors are the same , they should match. Changing out the resistors to adjust the trim would also not address the noise issue , correct ?

LosinPwdr
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Re: 1290 Build Thread

Post by LosinPwdr »

….just an additional thought….

I had a similar issue with a gssl diy build and it turned to be a grounding issue. Would a grounding problem possibly cause the symptoms I have described?

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Re: 1290 Build Thread

Post by Joe Malone »

LosinPwdr wrote:
Mon Feb 14, 2022 12:38 am
….just an additional thought….

I had a similar issue with a gssl diy build and it turned to be a grounding issue. Would a grounding problem possibly cause the symptoms I have described?
The 1290 should have 0v on the whole case and make sure you have 0ohms to all 0v terminals. Make sure terminal blocks are all tight on the wires and no wires can be pulled out.

If you are good at unsoldering you could remove the 2 preamps on the faulty micro pcb and swap them over as at low gain only the centre preamp module is used which seems to be the one that has the problem if your volts testing was correct and was AC volts. But then at the very low volts of 0.013ac that is way down in the noise so had to be sure that test means anything. You really want something close to a volt. And be sure to be on AC on the meter.

If swapping the preamp modules over only refit the centre one and check noise and level are fixed at 5 lowest gainsettings. If so you need a new BAX83NV module
Joe :-)
JLM Audio
Capturing Audio without Injury

LosinPwdr
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Re: 1290 Build Thread

Post by LosinPwdr »

......I have a new problem with my 1290.

The output transformer seems to be making a clicking noise.....and the leds are flashing on and off in time tiht the output transformer clicks.

I think it is probably a power thing as I have tried swapping everything round and the click follows the main gain switch board.

Do I maybe need to ground something ?

Or maybe the dc input needs to be isolated or something ??

Thanks!

Mat.t

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Re: 1290 Build Thread

Post by Joe Malone »

LosinPwdr wrote:
Sat Jan 28, 2023 1:29 pm
......I have a new problem with my 1290.

The output transformer seems to be making a clicking noise.....and the leds are flashing on and off in time tiht the output transformer clicks.

I think it is probably a power thing as I have tried swapping everything round and the click follows the main gain switch board.

Do I maybe need to ground something ?

Or maybe the dc input needs to be isolated or something ??

Thanks!

Mat.t
Something is shorting and overloading the SMPS power supply so it is in hiccup protect mode. If using s TREX or any power supply etc check you have 24v going to the 1290 module.
Joe :-)
JLM Audio
Capturing Audio without Injury

LosinPwdr
Posts: 9
Joined: Wed Jan 19, 2022 12:58 am

Re: 1290 Build Thread

Post by LosinPwdr »

Joe Malone wrote:
Sat Jan 28, 2023 1:52 pm
LosinPwdr wrote:
Sat Jan 28, 2023 1:29 pm
......I have a new problem with my 1290.

The output transformer seems to be making a clicking noise.....and the leds are flashing on and off in time tiht the output transformer clicks.

I think it is probably a power thing as I have tried swapping everything round and the click follows the main gain switch board.

Do I maybe need to ground something ?

Or maybe the dc input needs to be isolated or something ??

Thanks!

Mat.t
Something is shorting and overloading the SMPS power supply so it is in hiccup protect mode. If using s TREX or any power supply etc check you have 24v going to the 1290 module.
I'm using the power supply that came with the kit ... It wouldn't be an issue with the kettle lead would it ? Change of fuse ? I've checked continuity with a multumeter and everything seems fine. I'm stumped (which is not hard).

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Re: 1290 Build Thread

Post by Joe Malone »

LosinPwdr wrote:
Sat Jan 28, 2023 10:55 pm
Joe Malone wrote:
Sat Jan 28, 2023 1:52 pm
LosinPwdr wrote:
Sat Jan 28, 2023 1:29 pm
......I have a new problem with my 1290.

The output transformer seems to be making a clicking noise.....and the leds are flashing on and off in time tiht the output transformer clicks.

I think it is probably a power thing as I have tried swapping everything round and the click follows the main gain switch board.

Do I maybe need to ground something ?

Or maybe the dc input needs to be isolated or something ??

Thanks!

Mat.t
Something is shorting and overloading the SMPS power supply so it is in hiccup protect mode. If using s TREX or any power supply etc check you have 24v going to the 1290 module.
I'm using the power supply that came with the kit ... It wouldn't be an issue with the kettle lead would it ? Change of fuse ? I've checked continuity with a multumeter and everything seems fine. I'm stumped (which is not hard).
No you are looking in the wrong place. With the power supply unplugged from the 1290 rack do you get 48v at the dc connector ??? and does the the light on the power supply stay on ???
Joe :-)
JLM Audio
Capturing Audio without Injury

LosinPwdr
Posts: 9
Joined: Wed Jan 19, 2022 12:58 am

Re: 1290 Build Thread

Post by LosinPwdr »

Joe Malone wrote:
Sun Jan 29, 2023 8:06 pm
LosinPwdr wrote:
Sat Jan 28, 2023 10:55 pm
Joe Malone wrote:
Sat Jan 28, 2023 1:52 pm


Something is shorting and overloading the SMPS power supply so it is in hiccup protect mode. If using s TREX or any power supply etc check you have 24v going to the 1290 module.
I'm using the power supply that came with the kit ... It wouldn't be an issue with the kettle lead would it ? Change of fuse ? I've checked continuity with a multumeter and everything seems fine. I'm stumped (which is not hard).
No you are looking in the wrong place. With the power supply unplugged from the 1290 rack do you get 48v at the dc connector ??? and does the the light on the power supply stay on ???
Ye . I checked the dc for 48v and it was fine....47.8v .....

I swapped out the TIP122s and that fixed it. I had a couple spare.Shot in the dark.

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