Need help finding audio transformer for PDB DI Box

[Marshtech]

Rare as it is, the transformer in a customer's ART Passive Direct Box failed. The primary side is 1.6K, secondary is 220 Ohms. I inject a signal in the primary side and absolutely nothing (on scope) from the secondary, tested out of circuit.
When searching, I find 1:1 as well as ratios that don't suit this device.
The part number is TFB040EMS1. SYE 1123. It's a conventional 'square' tranny, not a round mu metal enclosure. Any ideas where to find one or a functional substitute? Physical size is about 1" x 1.25". thanks.

[bbsailor]

Rare as it is, the transformer in a customer's ART Passive Direct Box failed. The primary side is 1.6K, secondary is 220 Ohms. I inject a signal in the primary side and absolutely nothing (on scope) from the secondary, tested out of circuit.
When searching, I find 1:1 as well as ratios that don't suit this device.
The part number is TFB040EMS1. SYE 1123. It's a conventional 'square' tranny, not a round mu metal enclosure. Any ideas where to find one or a functional substitute? Physical size is about 1" x 1.25". thanks.

Read this link to better understand the required transformer characteristics for your specific application.
https://www.behindthemixer.com/passi...hould-be-used/

Typically the 50K ohm input is too low for a passive guitar pickup using 250K to 500K volume pots. Active pickups that require a battery to operate, inside the guitar, will work better with a 50K input impedance.

Post more details about how this direct box is planned to be used. Include the length of wires being used on the input and output connections.

Joseph J. Rogowski

[Jon Snell]

Idealy you want a 7.5 - 1 ratio.
This is not far off; https://uk.rs-online.com/web/p/audio...ormers/6676066

If you have DC resistance on both primary and secondary, surely the transformer is OK.

[Enzo]

Sounds lke you were measuring resistance, which is not impedance.

You want to know where to find a transformer like that? In another direct box. I see transformers i catalogs or from suppliers, and really, it seems they cost more than entire direct boxes in many cases. Just get a used one and strip the part, or buy a cheap new one even and raid it.

[J M Fahey]

1k6 is WAY too low for a passive box, agree with others you must be measuring DC resistance.

But if you have measurable resistance both at primary and secondary, transformer is fine.

Please draw your setup: transformer - how you feed it signal - how you read signal out.

A hand drawn sketch is fine, if you can also add a picture, even better.

[Marshtech]

True, I'm reporting DC resistance, out of circuit so no parallel components to interfere. When testing the transformer out of circuit, I'm using a tone generator app from my cell phone wired directly to the 2 primary winding leads. The freq is 440 Hz. I check, using the oscilloscope, that the level (can't recall how many mV of signal) isn't loaded down when connected to the primary. That's ok. I move the scope to the 2 secondary leads and get absolutely no signal there. The schematic is conveniently silkscreened on the case of the DI box, pictured here.
Earlier, I injected the signal through the input jack(s) and verified the attenuator was working (need to use the 0 db setting for full signal strength). The scope showed full signal at the transformer primary and nothing on the secondary. I examined all solder connections and re-soldered them for good measure. No change.

[Helmholtz]

I move the scope to the 2 secondary leads and get absolutely no signal there.

Did you connect the probe ground to one end of the secondary?
You won't a signal if the secondary is floating.

The secondary signal should be about 9 times lower than at the primary.

[g1]

You can try it backwards as well. Use a small signal level.

[Marshtech]

g1 - yes. I was planning on doing that next (reverse feed). Also going to re-check that there's a ground connection. I never wanted to believe that the transformer would fail. We'll get this eventually.

[Marshtech]

I tested the tranny again, feeding the signal into the secondary. Lots of signal on the primary (ten to one ratio). I put it all back together and tested. All is well. I believe the signal I fed into the primary was of such small amplitude that there was virtually no detecting it at the secondary when cut down by a factor of ten.
The only thing that could have fixed this was the re-soldering I did earlier.
Thanks folks.