[bernbrue]

PCB available now !!!!!

https://groupdiy.com/index.php?topic=53011.msg676707#msg676707
ERRATA:
1) pcb version 1.0 had a minor error in powering the relays, which has been corrected on all boards.  The silkscreen numbering for two resistors was the other way round. This has been corrected as well.

2) The heater wiring of the 12AT7 tube as indicated in the schematic and on the pcb is wrong.  I’ll describe an easy fix later.
 
You don’t need to do anything at all. These minor errors have been corrected already.




Update 15.12.2018: prototype works fine.. PCBs will be released!! Limited first run!!

https://youtu.be/iFMu9LjsDOM

————————————————————————————————————————-

Boards arrived!! Time to order some Parts


Mainboard and control pcb

https://docs.google.com/spreadsheets/d/12rNmf9cf7eQ6FiIfqCI5pxBC-OZ4AlS7xxHpd1B_OcY/edit?usp=sharing

PSU

https://docs.google.com/spreadsheets/d/1hXxtk70U6ZL8MWpZI4rOfSMPqCykkMMgWcT4OKrs5u4/edit?usp=sharing

[bernbrue]

NU Varimu Full schematic

[bernbrue]

universal frontpanel design.  Don´t change the drilling holes, adapt meter cutout to your choice of amperemeter (1mA)

[bernbrue]

Here are some voltages from my prototype. My power transformer has the following specs:
Sec 1: 250 VAC, 0,1 A
Sec 2: 24 VAC, 0,5 A
Sec 3:    9 VAC, 2,5 A

B+ is 269 VDC
F+ is 6,3 VDC

Test points:
B= 248V
C= 250V
D= 212V
E= 213V
F= 3,81V
G= 1,15V
H= 1,15V
I= 250V
J= 250V

Measurement were done with DMM minus to star ground, 1mA meter (fsd) and output tx connected (mandatory). Use VR104  for D/ E and VR103 for G/H to get almost identical values. Measure and recalibrate a few times, since almost all values will change when trimming the pots and meter.

Final calibration will be done with a test tone. A detailed description will follow.
Bernd

[dbonin]

Oh yes!

[weiss]

exciting 

[59flame]

this should be good!

[echoplex]

is this a DIY vari-mu to sold in kits soon?
 

[bernbrue]

No kits, just the pcb, bom and frontpanel design. So yes, it’s diy.

[echoplex]

Okay, now you caught my attention! 

Can you give us a little more insight already?
Is this reminiscent of anything (clone, replica) or your complete own design?
And lastly: WHEN will this be available? I want it 

[bernbrue]

You could start reading about the Altec 436 and the mods.
First batch of pcbs has been ordered. Should arrive in about two weeks.
Bernd

[KrIVIUM2323]

Oh!
Looks like 10 years have passed since the first time something like that apeared around here.
I hope it won t end up like last time!
Thanks Bernbrue.
This will be interesting to see how it differ from the one i reverse engineered.

[RO4350]

Count me in ! 

[Unit-8]

Hi Bernd,

I’m up for it! Nice project

[bernbrue]

Boards arrived. They are so blue!

[mysticmerlin]

Looking great. Where can we order these pcb's?

[bernbrue]

Give me some time to build and test it. I’ll keep you up to date.
Bernd

[TwentyTrees]

In my excitement about this project, I've been tinkering with Inkscape and have mocked up a meter insert which more or less reproduces the original Altec design. Fonts aren't perfect, though I'd say it's pretty close. I've sized it to match the Honeywell meters I've got set aside for the project - as far as I can tell, these are the same style & model used on the 436. 

Attached as an SVG - hopefully it will be useful to somebody (you'll need to trim and resize to fit what you're working with).

[TwentyTrees]

And a PNG preview of the insert against the reference photo I used, so you can see what I'm talking about!

[simrfid]

Just beautiful .... no words ... If still possible, you can count me in    !!

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