(Topic ID: 231068)

Help me find this audio transformer


By semicolin

11 months ago



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  • 14 posts
  • 6 Pinsiders participating
  • Latest reply 10 months ago by semicolin
  • No one calls this topic a favorite

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#1 11 months ago

So I want to clone the sound board for Interflip Dragon. I'm sick of folks going without their Baooooooo, and a small batch of them wouldn't be hard to get together and have around. Most everything can be done with modern components, but the audio coil is eluding me. It's easy enough to find centre-tapped audio coils, but I'm trying to find a) the coil/impedance values and b) a reasonably priced source for the component.

So... can you help me?

(Also, would anyone be interested in a board if I did a run?)

dragon1 (resized).jpgdragon2 (resized).jpg
#2 11 months ago

You need an impedance bridge to measure the transformer. I have one, but I'm not in your area. You need to find an audio or ham radio hobby fan in your area. They will have one.

I'm assuming there are no other markings or numbers on the transformer?

#3 11 months ago
Quoted from Skidave:

You need an impedance bridge to measure the transformer. I have one, but I'm not in your area. You need to find an audio or ham radio hobby fan in your area. They will have one.
I'm assuming there are no other markings or numbers on the transformer?

I'm VA3CSG... and I don't have one. Heh.

Nah, I know I can measure this out, but I figured I'd ask the folks here in case someone already has replaced the part or is familiar with Interflip's parts notation... or has better documentation than I do.

I'll stick my head deeper into the cabinet later as there may be additional markings on the side of the component.

2 weeks later
#4 10 months ago
Quoted from semicolin:

So I want to clone the sound board for Interflip Dragon. I'm sick of folks going without their Baooooooo, and a small batch of them wouldn't be hard to get together and have around. Most everything can be done with modern components, but the audio coil is eluding me. It's easy enough to find centre-tapped audio coils, but I'm trying to find a) the coil/impedance values and b) a reasonably priced source for the component.
So... can you help me?
(Also, would anyone be interested in a board if I did a run?)[quoted image][quoted image]

Funny you that should mention making a repro board.

I'm in the process as well. I'm currently populating some repro boards for a Bally Midnight Marauders for another pinside member. As soon as I'm done I'm sending him the boards and my dragon sound board. The guy will then design me a new board.

Hope one of us makes a good repro soon. I'm tired of fixing these originals!

#5 10 months ago

You'll get more relevant answers in the SS forum.

#6 10 months ago
Quoted from Moto_bone:

Funny you that should mention making a repro board.
I'm in the process as well. I'm currently populating some repro boards for a Bally Midnight Marauders for another pinside member. As soon as I'm done I'm sending him the boards and my dragon sound board. The guy will then design me a new board.
Hope one of us makes a good repro soon. I'm tired of fixing these originals!

Keep me posted: if you've got an actual engineer working on it they're going to do a better job than I will. I was planning on just doing a direct copy with tweaks made for obsolete components. I don't really want to get into the repro business; I've just seen enough posts and knew that it's within my skill level and I have one I can copy.

#7 10 months ago

Try looking up fellow Pinsider 'Too-many-pins'. He has a pin business with a lot old stock. He posted about selling it recently, but he might still be taking orders. I just PM'd yesterday about some old Williams plastic rollovers and he did reply.

OK, now if you REALLY want to wind one, I can chime in (some). I use inductors in my designs, but not so much transformers - so clearly not a magnetic expert. But I've wound many an inductor over the years on cores that are used at high power, so I have some of the 'oh crap' trophies when I screw up. And they are at RF, not lower freqs.

Here's what you need to do:

1) Remove the transformer.
2) The schematic shows a single winding on one side, tapped windings on the other side. Measure the inductance of each winding. Leave the other leads unconnected as you measure. I just got a cheapie analyzer on eBay for $20 that measures inductance (and other things). No clue about accuracy of the inductor measurements. (But wow, it correctly identified 3 transistors and determined they were OK and even indicated beta). I plan on taking it into work and comparing.
3) Now here's the problem area: You would need to determine the permeability of the core. One way to do that is to count the windings and work it backwards. Pretty much defeats the purpose since now you would be tearing apart your only transformer. You could maybe 'wing it' and guess, but another issue is the core could saturate if not selected correctly. Might be ferrite tho since the transformer is at low freq. And you'd have to find a core too, might not be easy unless you don't mind changing the footprint..

So, option 1 (contact Too-many-pins) is a better choice, at least initially. Only pointed out the steps that if you absolutely had to wind one, it can be done.

BTW, KB9TAF here (if the FCC renewed my license!).

Good luck!
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#8 10 months ago

I think, though, that we might be overthinking it. I might just build my circuit, get a few inexpensive audio transformers, and just try them. This doesn't strike me as the kind of thing with tight tolerances; just a need for isolation.

#9 10 months ago
Quoted from semicolin:

I think, though, that we might be overthinking it. I might just build my circuit, get a few inexpensive audio transformers, and just try them. This doesn't strike me as the kind of thing with tight tolerances; just a need for isolation.

No doubt about that with my post. I'd at least try to measure the inductance. Or find some used.

#10 10 months ago

If you figure out the correct input and output impedance, try Allied Electronics, Digi-Key, Mouser or Newark. They sell PCB mount audio transformers.

#11 10 months ago
Quoted from hazmat7719:

If you figure out the correct input and output impedance, try Allied Electronics, Digi-Key, Mouser or Newark. They sell PCB mount audio transformers.

Saving this link for later: https://www.alliedelec.com/stancor-ttpc-6/70213326/

#12 10 months ago
Quoted from hazmat7719:

If you figure out the correct input and output impedance, try Allied Electronics, Digi-Key, Mouser or Newark. They sell PCB mount audio transformers.

The output vs. input impedance is based on the transformer turns ratio. But but the reactance is an important part of the equation too. The reactance can do a very good of getting you close on the turns ratio. An easy way to determine the turns ratio if you can measure.

The transformer Semicolin posted might be fine. I'd probably take a little bit of a closer look to get in the ballpark. Not sure what the original designer was shooting for w/the turns ratio. But I bet they designed it around an 'off the shelf' part rather than spec'ing a custom transformer.

#13 10 months ago

Semi,

Is the pin footprint the same?

#14 10 months ago
Quoted from mbwalker:

Semi,
Is the pin footprint the same?

Identical, and it's the only one physically identical currently available within a price range that makes sense. It's also a 600:600CT, which would have been an available and common component back when this board was designed... so it has a non-zero chance of working out.

There's a big price jump on other impedance xfos that fit this package profile, often approaching $20/each, probably because they're less common. If a direct reproduction board is going to cost hundreds of dollars because of obsolete components, then the board needs to be re-engineered with a new circuit design.

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