8 Channel, 3U NEVE 1073 completed

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Noise from the power supply bleeding through? The Meanwell has an output with 240 mVPP ripple + noise

Try adding a LC filter to the 24v supply output, before attaching to the 1290 board.
 
Noise from the power supply bleeding through? The Meanwell has an output with 240 mVPP ripple + noise

Try adding a LC filter to the 24v supply output, before attaching to the 1290 board.
Thanks for the quick reply. Perhaps the Meanwell wasn't the best choice after all...!
Do you think I would ultimately be better off by forgetting the SMPS and using, for example, Volker's POS48 psu circuit?
 
All switcher modules require additional filtering. The 'noise' on their outputs is sufficiently low to not 'radiate' so much that it exceeds EMC regulations (not interfering with other gear by radiation) but as a user YOU have to ensure whatever you power with it continues to be 'radiation' free and of course actually work for your particular project. Class A designs may be more sensitive to supply 'noise' but there are several different ways the noise can get in.
 
Hi everyone. I'm nearing completion on a little 1 unit preamp and this thread has been a lifesaver, but I'm unsure about the voltage. I have a JLM power plant. From what I can gather, you should set the voltage closest to what your country uses (115 for US 230 for UK for example), however I live in Japan where the voltage is 100. Should I go 115v on the power plant? Also very possible I am misunderstanding some assumptions here.
 
Hi everyone. I'm nearing completion on a little 1 unit preamp and this thread has been a lifesaver, but I'm unsure about the voltage. I have a JLM power plant. From what I can gather, you should set the voltage closest to what your country uses (115 for US 230 for UK for example), however I live in Japan where the voltage is 100. Should I go 115v on the power plant? Also very possible I am misunderstanding some assumptions here.

What is the “JLM Power Plant”?

Post a link here of that unit
 
Hi everyone. I'm nearing completion on a little 1 unit preamp and this thread has been a lifesaver, but I'm unsure about the voltage. I have a JLM power plant. From what I can gather, you should set the voltage closest to what your country uses (115 for US 230 for UK for example), however I live in Japan where the voltage is 100. Should I go 115v on the power plant? Also very possible I am misunderstanding some assumptions here.

I ran a Roland Juno 106s on the 100V Japan tap on US 120V just fine. Not the same but in your case I'd think it's even less risk.
100V might work to turn everything on and I don't think will hurt anything but maybe there's a more proper answer out there? Maybe it doesn't work.
I'd use the USA 115V(120V?) on the power plant and see what happens. Risk of smoke i think is low but do at your own risk.

JLM Power *Plant
 
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I checked the Link and the schematic, so for Japan where mains voltage is 100V you have to set the voltage switch to 115V.
That doesn't present any problem, what happens with a lower input voltage is that the voltage at the transformer secondary will be a little bit lower, so for example for a 12V secondary, you might have 11V or 10V instead of the 12V. Then it goes into a full wave rectifier and the DC voltage will be 1,414 times higher than that and it feeds the input of the voltage regulators.
Voltage regulators in this schematic have a good margin in the voltage they can accept at the input

for example (approximate values):

So with 2x12VAC at the tx secondaries, when connected in series you have 24VAC, after rectification that will be 33,94VDC that will feed the regulator input to regulate to 24VDC

if you have 10VAC instead of 12VAC (with Japanese 100V mains), then in series you have 20VAC,
after rectification that's 28,28VDC which is fine for the regulator to be able to output 24VDC.
Actually it's even better as it will run cooler as it doesn't have to dissipate as much heat.

Rule of thumb, in Japan when using foreign equipment use the 115V or 110V input.

In the case of the JLM power plant, use the switch at 115V, measure the ouput rails, if it outputs 24VDC and 48VDC (for phantom power) all is well.

You will not damage a transformer or PSU by feeding a lower input voltage (100V into a 115V unit), only the opposite, for example feeding 230V into a 115V transformer.
 
I ran a Roland Juno 106s on the 100V Japan tap on US 120V just fine. Not the same but in your case I'd think it's even less risk.

I fixed a Juno 106 keyboard, the PSU transformer had a 117V tap. Check it you unit has that because it would be better for you.

Screen Shot 2023-03-05 at 22.01.05.png


What will happen by using US 110V/115V/120V mains is that the voltages at the power transformer secondaries will be higher, that could fry some type of regulator circuits, but if it's working well then it's fine, you are just running the PSU a bit hotter and more heat will need to be dissipated.
Don't know if that extra heat will make the Electrolytic caps ot the regulators fail in the long run or not, maybe not, it depends on the unit and the component placements and the actual amount of extra heat
produced.

100V might work to turn everything on and I don't think will hurt anything but maybe there's a more proper answer out there? Maybe it doesn't work.

It's fine in the JLM Power plant case, I explained above

I'd use the USA 115V(120V?) on the power plant and see what happens. Risk of smoke i think is low but do at your own risk.

No risk of smoke at all, it's fine.
The only risk could be the voltages in the Tx secondary being to low to feed a proper voltage into the regulators, but that would not damage anything you just wouldn't have the correct voltages at the output rails or no voltages at all
 
My 3U 8ch unit has been working quite wonderfully for almost 10 years now. (well, besides the issues i had last year which were easy fixes) About a week ago, one of the channels just seemed to up and die on me. (ol' #6). I'm having a time trying to track down the issue. I replaced all transistors on the card (the little BC's and the big guy in the back). The symptoms got "better" if i dare use that word. Prior to me swapping them out, the unit would pass signal if i MAXED the gain and fed the unit a pretty loud signal. Since replacing the transistors, I dont have to max the gain out for signal to pass through, but it wont pass signal at lower level inputs (like from a mic...) It's almost acting like a gate. To me it kinda sounds like somewhere someone is being starved for voltage and only when a strong enough signal passes, the gate is opening up. Since its an 8ch unit in a 3u case... getting in there to that single card isn't easy. If anyone has some thoughts as to what I can possibly look at, that will save me from having to get that card in and out a bunch of times. I'm going to see if i can find an old power supply to be able to test the card by itself outside the unit tomorrow.

So far ive done the following:
  • Replaced all transistors on the board
  • Re-flowed solder to the entire board
  • checked the trim pot and connection.
  • checked and re-flowed solder to the output transformer components
  • checked the input transformer (working as intended... im able to get a DMM in there to see the signal coming into and out of the transformer) I do have the hi/low tap on the input transformer, and that is working as expected as well.
  • at the lowest gain setting, a signal of -9.7dbfs out of the daw will barely pass through, anything lower its mute.
  • a -20dbfs line signal from the daw will pass when the gain is set to 35db.
EDIT: I was able to trace signal from input to the base of TR5, i cant get the probe down far enough to see if i get past there, but, the signal is definitely getting squashed after TR4 and before it hits the second stage.
 
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I'd test the gain switch. The switch includes the NV section at high gain and bypasses it at low gain. Check if the working positions is because the NV board either is faulty or the switch has a bad connection.
 
I'd test the gain switch. The switch includes the NV section at high gain and bypasses it at low gain. Check if the working positions is because the NV board either is faulty or the switch has a bad connection.
thanks for the reply. Im definitely losing the signal after TR5 in the NV looking part of the AV section. Im trying to see if i can get the card out of the chassis enough to power it and get a meter in there. If i put the gain to 55 and above the signal is proper going into the next stage, so all good there.

Any chance this could be a capacitor? Signal is good all the way to C11 (the cap right before TR5) and the base of TR5.
 
Was able to get the card out and powered. My mains is a little light at 23.5V but thats an easy fix. I found that at the R11, 33k, one side was B+ the other side was almost nothing. (3mv) I started taking out the components one by one, resistors were good, the 22uf cap there was reading 25uf, and the 680p cap would not measure on my DMM. It wasn't shorted, just no reading. I DO get a reading on the replacement cap of the same make/size/voltage, so im going to replace that bad boy and see what happens. The 47K resistor read fine and im getting a reading on the 100p cap as well... Wish me luck.
 
If you used a Polystyrene Cap then they're realy sensitive to heat, sometimes just taking a second more while soldering damages the cap.
I always have to use my Low Wattage soldering iron for Polystyrene caps and try to solder it very quickly, they can't be abused
wondering if the transistor went over there and heated up a resistor next to it and damaged it...
Do you think the sound will change significantly if i went to WIMA caps instead?
 
Do you think the sound will change significantly if i went to WIMA caps instead?

No way a sound of a complete unit and circuit like this will change because of just a different dielectric in a small capacitor.

In my builds I used Polystyrene and Tantalum where Neve used it originally just because I could, and was having fun also trying to have all the components as close as possible to the original, but one cap will not change the sound at all. Its all fine
 
No way a sound of a complete unit and circuit like this will change because of just a different dielectric in a small capacitor.

In my builds I used Polystyrene and Tantalum where Neve used it originally just because I could, and was having fun also trying to have all the components as close as possible to the original, but one cap will not change the sound at all. Its all fine
Hello, Would you sugges using polypropelene then for a bit less fragility? Thanks
 
Hello, Would you sugges using polypropelene then for a bit less fragility? Thanks

Well, Polystyrene are not fragile after they are in the circuit, it's just that you have to be careful while soldering, just solder it quick with the least heat possible temperature on the iron or a low wattage iron, it's just that. If you are aware of this all is good and easy.

So I would use Polystyrene anyway in the places where Neve used it, but if you use a Film cap or ceramic cap you will be well also
 
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