Mosfet conversion for Cobra 29lx

[Harley3315]

Anyone got any info on how to make a mosfet final work in this old cobra 29 xlr?

 

[Harley3315]

 

[9C1Driver]

If the radio is working now I would leave it be. If the final is bad I would replace it with the same final it has now. I would only do the mosfet thing if you can no longer get the stock final or they are super expensive.

 

[Harley3315]

If the radio is working now I would leave it be. If the final is bad I would replace it with the same final it has now. I would only do the mosfet thing if you can no longer get the stock final or they are super expensive.

That is indeed the issue no final available and it is non working.

 

[AudioShockwav]

HG makes 2312's and 1969 transistors.

HG-2SC2312

HG-2SC2312

www.icamanufacturing.com

73
Jeff

 

[Dmans]

I bought a dozen or so HG 1969's but have yet to use them. I really wanted to test them and see how the hold up but kind of forgot I had them!

73
David

 

[Harley3315]

I bought a dozen or so HG 1969's but have yet to use them. I really wanted to test them and see how the hold up but kind of forgot I had them!

73
David

They ain't worth a shit for 29's like ltd with the tip120 type mod you'll pop them pretty quick. thus why I would rather do a fet on this than those.
Might be fine for ssb radios but not this application In my opinion.

 

[Uncle Ronnie 336]

i normally get 25ish from an HG final. I modded/recapped a 21xlr which is now happily being used in a semi running the eastern seaboard, dimmer knob repurposed into the DK control, and it pushes 27w pep. limiter is intact but modded to have a bigger threshold. I'm curious what he used for a FET in that 29xlr to get 60 from it.

 

[Harley3315]

i normally get 25ish from an HG final. I modded/recapped a 21xlr which is now happily being used in a semi running the eastern seaboard, dimmer knob repurposed into the DK control, and it pushes 27w pep. limiter is intact but modded to have a bigger threshold. I'm curious what he used for a FET in that 29xlr to get 60 from it.

He's being super tight lipped about the new one he's using just saying that it will take more current.

 

[nomadradio]

it will take more current.

Sure enough. You want more RF power out, you need more current from the power supply going in.

And more audio power to modulate it the DC current feeding the final/driver. Might want to stock up on modulation transformers. Fortunately the audio-power chip is easy to source. Now if they could just come up with a socket for it they'd have something.

73

 

[Harley3315]

Sure enough. You want more RF power out, you need more current from the power supply going in.

And more audio power to modulate it the DC current feeding the final/driver. Might want to stock up on modulation transformers. Fortunately the audio-power chip is easy to source. Now if they could just come up with a socket for it they'd have something.

73

Well the audio chip on these xlr are pretty damn hard to find these days seems like that Swiss radio guy did a video on YouTube once to switch to the Toshiba but it didn't stick around long wish I would have downloaded it at the time.

 

[nomadradio]

What we need is a foolproof setup to substitute the TDA2003 used in newer radios to replace the uPC1156. Soon enough the Toshiba 7222 will be just as rare.

73

 

[Harley3315]

What we need is a foolproof setup to substitute the TDA2003 used in newer radios to replace the uPC1156. Soon enough the Toshiba 7222 will be just as rare.

73

Does this help? Maybe you can work up instructions and share with us here.

 

[nomadradio]

What I need is a mechanical setup that bolts in place of the old one to bleed heat into the heat sink properly. That, and the 2003 chip needs a bypass cap placed perfectly to keep it from oscillating. The ideal would be a small module that fits where the old chip was previously mounted, or near it.

But that's what I'm thinking, a plug-and-play.

73

 

[Harley3315]

What I need is a mechanical setup that bolts in place of the old one to bleed heat into the heat sink properly. That, and the 2003 chip needs a bypass cap placed perfectly to keep it from oscillating. The ideal would be a small module that fits where the old chip was previously mounted, or near it.

But that's what I'm thinking, a plug-and-play.

73

Problem is the newer radio aren't even a real heatsink anymore no aluminum just sheet metal.