NORD LEAD 2 (not 2X) power supply question

[isakeliyahu]

EDIT: i just found out i was mistaking cause of lack of concentration, the regulator is LM2940 not LM3940 which is fine, sorry to bother anyone.

cheers.

Hi Guys.

new user here
i got nord lead 2 as a gift from a frien, i have some issues with it.
when turning it on it wont boot up, so i open the NL and sniff around, after soldering few areas that looks suspicious it turn on but not at first time, i need to turn it on wait a bit, turn it off, and turn it on again, after a sec the NL is turn on and working.
so it seems to me like a an electrolytic cap problem to me.
ive tested the power supply board and this is what ive found..
i think i found a flaw in the power supply section, the main power brick is outputting 4x 6V outputs 5.5A for each output,
each output goes to a diodes and regulators that gives +12V, -12V, +3.3V and -5V.
the regulator of the +3.3V is LM3940 which according to the datasheet, the max V in is between 4.5V to 5.5V, when measuring with multi i read 7.4V at the input and 4.95V at the output.
from the power brick, it goes directly to 4,700uF for filtering and from there to the LM3940 regulator.
i'm thinking to my self, why they used the 6V output power brick while the real output is 7.4V and the max V in of LM3940 is 5.5 when it should be 3.3V?
if they needed to use 5V instead of 3.3V why not to use 7805 instead?
isnt this a flaw?
what do you think?

cheers,
Isak.

[MiguelAnswer]

Hey, man.

I must thank you for that info about NL2's power supply section: I have some boot issues, too, and definitely looks like an electrical/PSU problem to me (with my NL2).

I've been looking for solutions or hints to solve this power supply section issue, and seems like everyone who owns a Nord Lead (1, 2, 2X, 3, 4 and their rack relatives) deals with this problem, eventually. Some Reddit users say it could be simply a bad choice from Nord using such bad, insufficient PSU's in the first place. So far, I've found nothing about a once-and-for-all solution or a detailed explanation (just like you did after your own research) about the why's and how's when your Nord is not booting as it should.

So, I have some questions for you:

1) Did you changed the power supply powerbrick inside the board?
2) If you did changed de PS powerbrick, where did you get the right model to supply sufficiently the outputs?
3) Did you desolder/resolder something else from the power section to solve the problem?

I'm also looking for solutions for this thing, 'cause if I wanna use my Nord Lead 2, I have to turn it on and wait for... +8-11 HOURS! (No kidding at all) so the boot can be done properly. After all that waste of time/electricity, everything works A-OK and the sound is clean and nice as usual. It seems like the headphones output throws some low noises and saturation-like sounds (so bad there's not such a thing as a headphone level knob to finetune that, because that output is loud af), maybe it's just some dust inside that jack.

Anyway, would be great to find out how did you work on the power section with your Nord so I can give a try on mine.
Hopefully, we can finally work this out.


Thanks, bro!

[maj869]

Trying to bump this thread...have you had any luck, Miguel? I've got what seems to be a bricked out Rack 2. A friend whose good with electrical stuff thinks the transformer is bad and that a new power supply is necessary. Problem is that I can't find any for sale.

Moreover, does anyone know whether you can swap out the power supply from a different model (maybe the 2x)? Thanks!

[23skidoo]

If the transformer is bad why not just replace it and repair the PSU?

Also, transformers *rarely* are the failed part in a PSU. If you're not seeing the intermediate rails powering the regulation stage, capacitors are typically the first to go, and over long term, diodes too. Check the fuse, of course, because you might just have a blown fuse. If the transformer is in fact the failed part, it probably means other parts failed first, but as a first inclination, I suspect that may not be a complete diagnosis. Cascading failures do occur in a PSU, so it may be more than one thing in total. A careful diagnosis and repair procedure must be followed by someone competent to work with power electronics, but it's a fairly straightforward PSU so I don't expect it should pose any issues to someone moderately skilled.

[Edited for clarity and expansion.]

[Twinfreaks]

Following

[jvq__]

Posting because I also have a broken Nord Rack 2 power supply. In my case it is clear that the transformer is busted; there is a short on the secondaries.

Replacing the transformer is difficult because it is a hard to find part. I wonder if it was custom made.

My Nord Rack 2 has a Hahn UI 39 transformer. What is unusual about it is that it has 4 secondaries (rated at 7.5V each). The intended actual voltage is lower because my PSU was made for Japanese mains power (100V) and the tranformer is rated for 2x115V. For 115V and 230V countries the PSU appears to use a 4x6V transformer. Anyway the unusual part isn't the voltage, it's the number of secondaries.

Two of the secondaries are wired in series to create 12V AC for the +/- 12V regulators. The other two are wired in parallel to double the current available for the 5V regulator.

My Nord Rack 2 is a Japanese model. I did a voltage conversion by changing the jumpers on the PSU board so I could use it at 230V. That then means I have been running it with the unregulated voltages 15% too high, which may have stressed the big filter caps. I also neglected to change the mains fuse which may have contributed to the fried transformer.

Maybe I'm using the wrong search terms and 4x6V replacement transformers can be found. But I haven't had any luck.

[pterm]

Please post some high resolution pictures of the power supply.

The transformer configuration sounds typical of Nord Power supply units.
If you measure short circuits with the transformer in-circuit, you might be measuring a shorted downstream component rather than the transformer. That is, it's possible that a smaller component failed rather than the transformer itself.

The only Nord power supply schematic I found online uses a 4x6V Dantrafo transformer. Their transformers with 2 x 115V in, 4 x 6V out start on page 11, but there's several pages of different models of them.
Dantrafo Catalog page 11

[jvq__]

Sorry, I did not enable notifications and I did not see your post. Nice to see Dantrafo has these quad secondary transformers in their catalogue. I can't tell if you can order them off the shelf anywhere though. I had a hard time and gave up on finding a quad secondary transformer.

In the case of my Nord Rack 2, it turned out the power amplifiers transistors of the right headphone channel were broken causing a short circuit. Probably the result of putting a mono plug in the headphone jack (which shorts the right channel to ground). I replaced the transistors which fixed the headphone amp and I ended up making a replacement power supply using DC-DC converters.

[CaiNord]

Howdy fellow Nord Nerds!

I have recently acquired an old Nord Rack 2 and want to replace the whole power supply or just transformer as it is humming loudly (acoustic hum, not through outputs).

I have contacted Hahn, I suspect they made the transformer in mine. Hahn have said it is custom item and they wont sell direct, but to contact the product manufacturer (Nord) and ask them to order it. If this is true, it is a shame Nord wont order a batch and sell them to us all with our noisy broken synths.

Jvq - I’d love to know more about how your replacement psu please, if you can share details?

Text on my transformer are:

OK230v
V 6646. 22VA
ta 70/B
prim 2x115V

50-60Hz. 2-4/7-9

sekl 6V 5,5VA* 11-12
sekll 6V 5,5VA*14-15
sekIll 6V 5,5VA 16-17
SekIV 6V. 5,5VA 19-20

[CaiNord]

Good news!

So from what I understand the transformer used my Nord Rack 2 is still used in current Nord products. The UK distributer is going make a special order for the transformer component from Sweden, they’ve estimated 6-8 weeks delivery time and cost of £18 + tax + delivery.

I’m hoping this will be useful information for others looking to replace noisy ageing transformers. I suspect the big capacitors will also need replacing, and I’ve heard even the transistors on the power supply board can vibrate and make a noise.

The transformer in my NR2 has 2x 115v Primaries and 4x 6v Secondaries, it is an encapsulated PCB mounted and suspect it is a custom transformer made by Hahn.

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