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Stryker SR-440HP is alive, again...

Hawkeye351

Well-Known Member
Jun 27, 2021
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Hi all,

Just got the first Stryker ever on my desk. It's the 440hp version. This thang was a mess, po old radio...

1st, someone tried to install a speech processor module and used the wrong wires. They used the orange and yellow wires leading to the external frequency counter port, hahaha.... That's the reason they never got the module to work.

2nd, they sniped the electrical ground from the echo board.

3rd, they removed tr32, tr53 and clipped r249.

4th, they volted the final back on the regulator with a resistor/diode combo.

5th, they ruined the mic socket board.

6th, they pinched a few wires between the echo board and chassis.

After fixing all that mess, I found the output to be only 35w max on a peak reading meter. I thought these radios were made to do more than that. It has all 3 mosfets installed, but I think they weakened the passthrough regulator (which they had the volt mod on) and it got extremely hot within seconds of keying up.

Gonna replace the 2sb684 passthrough with a tip36c, replace the 1819 AF regulator with a 2sa1012-y.

I have noticed the gate voltage for the driver is around 2.75v, the first final mosfet gate is 2.40v and the last final mosfet gate is 4.19v. But I only see 1 bias adjustment. What gives?

Anyone have the alignment info on these radios.

Thank you in advance...
 

One thing that kills those MOSFET's are...

Excessive Gate Voltages - as in - it's always on.

The thing is rated to Turn on - at 4V

You are already there.

So, when you wonder about that 35W figure, you're LOSING Peak Watts because it can't develop any from the turn on threshold. It is already above the signal turn on level and there is no further room for amplification.

You're also sponging off the signal it can use to even start the bottom of the curve in power delivery - when you have time - look at it on a scope - it's pretty nasty.

So why are you pulsing 20 amps into a 12V circuit - that only produces 35W - when you are dissipating nearly 200 watts just trying to make 35W?

Not very efficient.

Even Class AB does better.

Time to back off the Warp Drive Mr. Scott, you're going to fly her apart...

Use LESS, much less - like follow the mA draw scenarios we talk about - means you might have to get creative with the way you measure - but techniques are there - and the ways to measure them - there out here in the posts...


 
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The driver gate is 2.75v
The 1st final gate is 2.40v
The 2nd final gate is 4.19v

There's only 1 adjustment (thinking it's a bias adjustment) beside the driver on the final board.

Should I adjust that to bring up the gate on the driver, which may increase the gate on the 2nd final above 4.19v, or should I leave it be?

Or, should I just adjust it for current draw and overlook the gate voltages?
 
Last edited:
Clipping the echo board ground wire is called "the high clarity mod" lol. good work, you will get it all ironed out.
Hi clarity mod? You mean like those hifi mic circuit mods? What's it's purpose? Does it improve the radios performance while maintaining stability and keeping things cool? Or is it just a pretty sight on a watt meter, lol?
 
Hi clarity mod? You mean like those hifi mic circuit mods? What's it's purpose? Does it improve the radios performance while maintaining stability and keeping things cool? Or is it just a pretty sight on a watt meter, lol?
Not an expert here, by any means, but I'm pretty sure it just kills the echo bringing "clarity" to the transmit audio.
 
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Should I adjust that to bring up the gate on the driver, which may increase the gate on the 2nd final above 4.19v, or should I leave it be?

Or, should I just adjust it for current draw and overlook the gate voltages?

Adjust for current draw. (Always, please! It's the turn on threshold - 50mA)

But if the Finals are paired together, might be best to pull the Final that has the 4 volts on it. At least, unsolder the legs of it from the board disconnect it..

Then see what it does.

More than likely it will run somewhat cooler.

IF it gives you 35W from the SINGLE final - then you've found the problem - the 2nd MOSFET of the pair - that section needs work.
 
Update:

Got the passthrough regulator replaced.
Got the AF regulator replaced.
Got the main DC filter cap replaced.
Got the passthrough reg cap replaced.
Got the 8v reg cap replaced.

Plugged it up,
Turned it on,
Let it warm for 15 minutes,
Tested it,

Gate voltage on finals equaled out to 3.35v on the 1st final and 3.65v on the 2nd final. Driver gate voltage was around 2.17v.

Now I'm seeing around 40w peak swing forward, with it swinging backwards in average a good bit.

Tried adjusting the only bias adjustment on the PA board (board with mosfet finals) beside the driver. Can't get the driver gate no higher than 3.45v, but then the final gates shift down to around 2.8v to 3.04v. Setting the gate voltage on this thang is a pain in the butt.

I need to know what the driver gate voltage should be set at, where ever the final gates end up is where I'll leave it. As long as the driver is getting the right gate voltage then that's fine with me.

Still no mods installed, no clip, snip, hack, etc....its back to stock.

Passthrough runs very cool now. Doesn't get scorching hot now.
 
When adjusting for current on this radio, do I remove the jumper pin under the driver and touch the red probe of my ma meter to one pin and the black probe to the other pin?

What ma should I set it too?

I'm thinking if I set the ma draw on the driver (since that's where the vr is at), then the finals will fall in into place (since there are no vrs for final bias, just a jumper pin under them too).

Does the above procedure sound right? And what ma should I set it at?

Thanks in advance...
 
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