Holger

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #140 on: January 01, 2021, 03:45:15 PM »


I'm currently building a second unit. As you can see, I've did a couple of mods.
I used an external PSU to get rid of the usual power transformer AC hum.
I rewired the tubes for 12.6V heaters, I use an SMPS here.
I'm actually measuring -80 dBu noise floor flat.I omitted the output attenuator section and replaced it with a simple 1k pot (Ian's Neve trick).

In this build I use a Lundahl 1540 which works fine. OP TX is a Sowter 1232. The meter is an old Weston 301 stamped May 1964 on the back.
Note: in an earlier post I wrote that the meter circuit needs to be modified. I was wrong. The meter circuit works well
for the Sifam meter in my first build as well as for the Weston meter when the meter is strapped with a resistor.
I used a 22R which works perfect for both meters.


petermontg

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #141 on: January 14, 2021, 07:30:32 AM »
Holger, where did you get the cans? Were they from Sowter when you got the trafos.

I am down to -80 flat also. I am going to shield up the toroidal and try get another -5db or so out of it. Mine is still in the chassis. I can some psu noise in there on the scope.

Best
Peter

Holger


Rob Flinn

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #143 on: January 17, 2021, 05:11:31 AM »

Sowter, story told here:


https://groupdiy.com/index.php?topic=75702.msg964557#msg964557

Apparently they have taken on more staff according to their website.
regards Rob

electrisizer

Re: [BUILD] NU VARIMU 436 build & help thread
« Reply #144 on: January 17, 2021, 08:23:35 AM »
Note: in an earlier post I wrote that the meter circuit needs to be modified. I was wrong. The meter circuit works well
for the Sifam meter in my first build as well as for the Weston meter when the meter is strapped with a resistor.
I used a 22R which works perfect for both meters.

hello holger can you explain a bit more. what do you mean with a strapped resistor?
have you used a 500R trimmer for the meters as suggested?


 

Related Topics

  Subject / Started by Replies Last post
322 Replies
84240 Views
Last post December 31, 2020, 02:12:28 PM
by ElSmurf
5 Replies
3666 Views
Last post January 04, 2010, 01:56:11 AM
by syn
213 Replies
37487 Views
Last post November 17, 2020, 05:11:30 AM
by Thunbo
2 Replies
737 Views
Last post November 03, 2019, 08:36:42 PM
by andyfromdenver