bernbrue

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #40 on: January 22, 2019, 02:30:00 AM »
Unfortunately, we can’t give any recommendations concerning specific brands. It’s up to your personal taste and of cause to your budget, which tube brand you want to use.  Same applies to the choice of transformers. Any decent 1:1 input transformer with center tap will work fine. The output transformer from Sowter is certainly  first choice in terms of quality and availability.  I used  transformers from AVD Audio. He is a member of this forum and makes decent transformers. Search in the white market.

I suggest you to build the NU Varimu 436 with easily available parts. Later you can tweak the unit and test various tube and also transformer brands according to your personal taste.
Cheers
Bernd


Unit-8

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #41 on: March 13, 2019, 02:11:50 PM »
Hi Bernd,

I found an error on Motherboard  + Control board  components list where R10A-B and R11A-B the value is 10k while on schematic is 18k.
Also R10, R11, R13 has the same Mouser ref code.
Could you please double check on MB + CB list, PSU list and schematics?

Thank you!

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #42 on: March 13, 2019, 07:29:33 PM »
whats the estimate price for all parts, PSU, PCB and case in total?

weiss

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #43 on: March 20, 2019, 06:37:07 PM »
Same question here..
Also are there pcb's in stock?

zayance

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #44 on: April 05, 2019, 05:13:53 AM »
Same question here..
Also are there pcb's in stock?

PCB's are in stock no prob, in terms of pricing, Bernd can maybe give an idea? The answer always depends on what you'll choose and use etc... as you all know.


Best,


T.

zayance

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #45 on: April 05, 2019, 08:17:24 AM »
Hi Bernd,

I found an error on Motherboard  + Control board  components list where R10A-B and R11A-B the value is 10k while on schematic is 18k.
Also R10, R11, R13 has the same Mouser ref code.
Could you please double check on MB + CB list, PSU list and schematics?

Thank you!

Hi There,


Sorry for the long reply time, me and Bernd are pretty busy with life, so having a hard time doing our part on these lately.
Anyway,

R10A & B is 18K
R10-11-13 is just me doing copy paste on refs when doing the BOM, thanks for pointing that out, BOM updated.

Don't hesitate to come back here if you find something wrong on BOM, always nice to have a second view by members.


Thanks a lot.


Best,


T.

Kid Squid

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #46 on: April 05, 2019, 08:21:35 AM »
Gorgeous !

Deffo thinking of doing a case for this Beauty.

It is not the same as 4+12, nor is it the same as 4+8, but 4+12 IS the same as 4+8+12....

http://www.facebook.com/LazyLizardLabs

Unit-8

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #47 on: April 09, 2019, 11:18:15 AM »
Hi guys,

On control board BOM I found R120 A & B and R9 A & B have their values reversed compared to silkscreen on the boards and also on the schematics.
There is also the HTRLED value on the BOM is 24.9k and on board and diagram is 47k.
No others errors found so far.
I have finished to populate the PCBs and I would like to know about measuring points and voltages readings.

Cheers

bernbrue

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #48 on: April 09, 2019, 11:36:00 AM »
Man, you are fast! Thanks for spotting these errors. I’ll do detailed measurements when I’m back home from holiday in about two weeks.
Cheers
Bernd

zayance

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #49 on: April 21, 2019, 11:22:31 AM »
Hi guys,

On control board BOM I found R120 A & B and R9 A & B have their values reversed compared to silkscreen on the boards and also on the schematics.
There is also the HTRLED value on the BOM is 24.9k and on board and diagram is 47k.
No others errors found so far.
I have finished to populate the PCBs and I would like to know about measuring points and voltages readings.

Cheers


Thanks for that.
Use 24.9K value for LED Resistor, since we need a 250VDC supply, and a 10mA at LED, then you spotted
a minor errata on value for the Schematic PSU & PCB.
47K won't do here....

Best,


T.
« Last Edit: April 21, 2019, 02:13:36 PM by zayance »


Unit-8

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #50 on: May 30, 2019, 10:19:42 AM »
Hi Bernd,

Here are some snippets of the NU436. I'm just waiting for Sowter's trafos I should have next week.
It would be nice now to have all the informations on voltages, calibration and any tip for doing these jobs the right way.
We're just waiting for you, man :)

Best
« Last Edit: May 30, 2019, 10:27:39 AM by Unit-8 »

Unit-8

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #51 on: May 30, 2019, 10:22:30 AM »
NU436 inside

bernbrue

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #52 on: May 30, 2019, 11:59:19 AM »
Looks great. I’ve listed my measurements in the third post. Please take them as rough reference. Meter and output transformer need to be connected.
Cheers
Bernd

Unit-8

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #53 on: May 31, 2019, 08:41:37 AM »
Hi Bernd,

Thanks so much for the info about measuring  points and voltages readings.
However, my trafo has slight different specs:
1 sec: 220v - 0.2A
2 sec: 9v - 2.5A
3 sec: 12v - 1A
It follows that I will certainly get different readings from the measurements.
So I have to rely on the specifications of the tubes and find a middle ground between minimum and maximum or for this circuit there are precise values (voltages) to observe?
Then I wanted to know something about the eventual modding to do on the release knob that I think changes its timing.

Cheers

bernbrue

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #54 on: May 31, 2019, 08:49:00 AM »
Hi,
your power tx will work fine. The release mod will divide the release time by two. Theoretically it could be done with the attack time as well. I think this has been done before. Just strip a resistor in parallel to the attack pot (same value) and make it switchable.
Best
Bernd

Unit-8

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #55 on: June 18, 2019, 12:38:29 PM »
Hi Bernd,

I’m ready to go, at last. Output trafos installed.
It would be nice if you wrote a sort of mini-tutorial in PDF with all the steps to do to calibrate the NU436, I mean all the tips and/or tricks to do the job as it should be done.

E.G: do the valves have to be on their sockets during the voltage calibration?

Best

petermontg

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #56 on: June 18, 2019, 03:51:42 PM »
Hi,

Will you post some sound samples once you get your build finished.

Best
Peter

bernbrue

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #57 on: June 18, 2019, 04:10:37 PM »
E.G: do the valves have to be on their sockets during the voltage calibration?

Yes, measure the voltages with tubes.
Bernd

Unit-8

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #58 on: June 19, 2019, 08:40:17 AM »
Hi,

Will you post some sound samples once you get your build finished.

Best
Peter

Hi Peter,

I will post some samples for sure :)

Best

Andrea

bernbrue

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #59 on: June 19, 2019, 09:50:53 AM »
Some basic strategies before powering up the unit the first time.

1) check for shorts. Disconnect the power tx from the pcb and measure for shorts at the AC input terminals. You should have at least some kind of resistance between the power tx terminals on the pcb. When there is a short, something is wrong, don’t power it up and check once again

2) connect the power tx rail by rail. Start with the relay rail and connect the 12VAC (24VAC) first. Very important!!, Isolate the other two secondaries from the power tx. Test the relays.

3) next connect the heater rail and verify that all tubes glow.
4) connect the high voltage secondary and measure B+ at the test point.

5) power up the unit only just for a moment and switch it off immediately.  Check for any unusual noise or smell.
6) leave it on for a few minutes and wait for the meter to rise. Start checking the knobs and switches. Check if it passes audio.

Bernd


 

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