Bass DI zod / Reddi ?

[Spencerleehorton]

 

[Spencerleehorton]

Turret boards done

 

[Spencerleehorton]

Valve socket in

 

[CJ]

9.3 uA = 715 Henrys.

Move decimal for micro prefix.

Seems high. Nickel core? No.

Stacking error? 1 x 1 lace pattern?

Maybe meter error. Set meter to milli amps. Get on the winding with the most turns which is the primary in this XFMR.

Measure again.

How many primary turns you have?

I usually get 1 ma or below at 20 v and 20 Hz which is about 400 Henrys.

 

[Spencerleehorton]

Pretty sure it silicon steel and I have 4500 turns on Pri and 1250 (2x625 turns) on sec.
I hope I’m connecting it right as I did connect another way and it went down to 4.5uA

 

[Spencerleehorton]

V = 5.2v / 4.3uA = 1.209302325581395

1.209 / 6.28 = 0.192564064583025

0.192 / 24.420 = 0.007885506330181

788 Henries!

 

[Spencerleehorton]

To get in the ballpark for 360 henries it needs to be something like this:

5v / 9uA = 0.55

0.55 / 6.28 = 0.08

0.08 / 24.420 = 0.00362

362 henries

I get the equation and what I should be aiming for just need to get the ammeter and voltage better.

 

[CJ]

a 5 mil gap will bring the Henrys down,

 

[Spencerleehorton]

Weirdly I lowered the voltage to 4.2 and I get 9.2uA which ends up being 297 H.

I have put in a gap of about 5mil by the way, this did seem to lower it a bit.

 

[Spencerleehorton]

Just waiting for mains txf and a few other bits then I can start planning how I’m going to fit inside case

 

[CJ]

Your ammeter might be funny, I know I cooked mine out of tolerance by connecting it to 400 vdc, fried the fuse, replaced the fuse and it acts weird but what do I want for 15 bucks.

You can put a 10 ohm resistor in series with the primary and measure millivolts AC across that.

Example let's say you measure 10 millivolts

0.01 vac / 10 ohms = 1 ma.

 

[Spencerleehorton]

I’ll try again in the morning , think I know my problem, ammeter and generator needs to be in series with the txf, the scope needs to be in parallel, i have been putting it all in series!!

 

[Spencerleehorton]

well its just not working for me? ive connected it up how ive said, tube generator to Ammeter in series into transformer out of transformer and connected back to the generator, then put the scope in parallel on the transformers windings and i get weird readings from both the scope and the ammeter?
it just doesnt seem to want to play ball? i have tested on other multimeters and i get nothing on them?

 

[ruffrecords]

You definitely do not need to connect anything to the transformer output. All you need do is measure the current though the primary and the voltage across it. Leave the secondary unconnected.

Cheers

ian

 

[Spencerleehorton]

Yeah, I’m only connecting the primary (4500 turns) 680ohms winding.
I get 10.2v from the generator at 24hz when I attach the scope, that’s max output and it won’t go down to 20hz.
When the multimeter connected in series I only get 4.5uA ac, no other setting registers anything? It’s a good multimeter, I have several others which are cheap and don’t register anything?
Works out at 160H.
Giving up with this as it just don’t work!

 

[ruffrecords]

Very strange. An alternative method, if you know very roughly what inductance to expect it to place a capacitor across the winding and sweep the oscilator to find the resonant frequency. Knowing this and the value of the capacitor you can work out the inductance.

Alternatively, if you plan to wind a lot of transformers, invest in a decent inductance meter. But I am sure you have thought of that.

Cheers

Ian

 

[CJ]

Put your signal generator in series with your ammeter and a 1 k resistor. Apply 10 vac at 100 cycles per second. Measure your ac current.

 

[Spencerleehorton]

 

[CJ]

open your old meter up and check for a blown fuse,

 

[Spencerleehorton]

yeah as always CJ you got it, on one of my MM the fuse had blown!!
my other Fluke MM seems to have all fuses intact!
now i have sorted my LA2A hum problem im back onto this tube DI and not off to a great start.
The mains transformer arrived today, i took out of the package which had some sort of nasa bubble wrap inside it and the transformer was mashed!!
one of the 170v winding had come off and one of the legs crushed!! they are sending me a replacement so lets see if the next one survives!!