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Trying to find the secondary load resistor on the GA80071. I injected sign wave 1khz into primary leads, and put variable resistor between the secondary leadds and measured with an oscilloscope while turning the resistor ohms...

510ohms is where the waveform looks like the cleanest. Does this mean I need a 510 ohm resistor permanently soldered into the circuit across the secondary leads in place of the variable resistor?
 
Trying to find the secondary load resistor on the GA80071. I injected sign wave 1khz into primary leads, and put variable resistor between the secondary leadds and measured with an oscilloscope while turning the resistor ohms...

510ohms is where the waveform looks like the cleanest. Does this mean I need a 510 ohm resistor permanently soldered into the circuit across the secondary leads in place of the variable resistor?
No. This would load the secondary and drop the level enormously.
The secondary should be loaded with a Zobel (RC in series across the secondary). The capacitor will make sure that the low and mid frequencies are not unduly loaded, and only the HF around the resonant peak are loaded.
Check this thread Damping transformer ringing (Zobel network question)
 
This is kind of off-base and probably already well-known, but the guys at Audio Transformers By Cinemag Inc. make some phenomenal parts, including transformers using "rare" metals.

They have quite the lineup already, but they also do custom stuff. I can't remember who I spoke with when I called to order a CM-2461NiCo mic output transformer for a tube mic build that I'm currently sourcing parts for. He was great to talk to, patient with me, and very knowledgeable.

They had to make mine as there weren't any on the shelf, so it took a few weeks to arrive, but it's beautiful! I will be going back for other parts when needed. From my perspective, they do a great job, so maybe not a Japanese part that you're looking for but made in America still stands strong for some companies, and Cine is one of them.

I recommend giving them a call and talking through your needs. Maybe you'll find what you're looking for right here in the US. Sorry if this is out of line or not allowed (sharing links). I don't work for them, I only ordered one part, but I was extremely impressed. Hope you find what you're looking for. Good luck!
 
This is kind of off-base and probably already well-known, but the guys at Audio Transformers By Cinemag Inc. make some phenomenal parts, including transformers using "rare" metals.

They have quite the lineup already, but they also do custom stuff. I can't remember who I spoke with when I called to order a CM-2461NiCo mic output transformer for a tube mic build that I'm currently sourcing parts for. He was great to talk to, patient with me, and very knowledgeable.

They had to make mine as there weren't any on the shelf, so it took a few weeks to arrive, but it's beautiful! I will be going back for other parts when needed. From my perspective, they do a great job, so maybe not a Japanese part that you're looking for but made in America still stands strong for some companies, and Cine is one of them.

I recommend giving them a call and talking through your needs. Maybe you'll find what you're looking for right here in the US. Sorry if this is out of line or not allowed (sharing links). I don't work for them, I only ordered one part, but I was extremely impressed. Hope you find what you're looking for. Good luck!
I LOOOOOVE Cinemag. But this project isn't something terribly important. It's just a spare board that was from a dead unit I had lying around, that I would poach parts off of and learn on, especially how multi-layered pcb's work and how the traces can short out between the layers and how to fix it. So I thought id use some spare parts I have accumulated over there years and create a working unit. All the while trying to optimize performance and make some experimental changes to each section (mic preamp, compressor, eq, master out). So with $0 dollars spent, I managed to trace the short in between the layers, repair all the ripped off pads and traces, make some changes, get it operational, AND learn alot from you guys here on this forum. So thank you everyone!
 
Anyone has experience with Tamura TK-1.?

Datasheet gives 50-10k as range. Roughly what I need for a project.

But am wondering what a real curve of a transformer like that would look like. Above 10k I don't care much. But something below 50 would be good.

Any idea or advice?
 
Just uploaded a pdf with a few catalogue pages on Sansui transformers to the tech section.

Some of their ST series (mini transformers) might be interesting for experimenting. Size of a sugar cube some of them though, somewhat like TM xfrms, I guess.
 
What would I need to know -- some basic formula maybe or experience with comparable transformers -- to be able to deduct those 'suggested' numbers by myself?
The LF response of a xfmr is in first approximation, that of a 1st-order high-pass filter.
When you know the -3dB point, you can deduct the rest of the response.
HP2.jpg

HP1.jpg
 
That is a schematic to the normal method of making signal transformers called interleave winding. Even a speaker output. So, for instance, you might have a 4 ohm center tapped at 2 ohm (which is two two ohm windings tied in series as a coil set) Then a set of 4 ohm that is tied in series started at the 4 ohm connection to make 8 ohm tap, then a set of 8 ohm coils tied on top of that at the terminal for a 16 ohm.
This is not the way things work.
A 2ohm winding in series with another 2ohm winding result in an 8ohm winding.
Putting an 8 ohm winding in series with another 8ohm results in 32 ohms.
 
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