Stryker 955hp bias test point?

[357]

My Chinglish aint so good.
Anyone know where the test points are?
I just put 4 new finals in this and need to set the bias.

thanks

 

[357]

I think the measure point is at the power cord.
I measured it at the fuse and measured it at the lowest the VR would go, say 460ma then upped it to 560ma, followed the list and now I dont hear the "crunchy" background noise.
RX is now the required 400ma
bias set.

 

[Ranch55]

I think the measure point is at the power cord.
I measured it at the fuse and measured it at the lowest the VR would go, say 460ma then upped it to 560ma, followed the list and now I dont hear the "crunchy" background noise.
RX is now the required 400ma
bias set.

View attachment 18043

No, that is not the measurement point.

 

[sonoma]

I did not find the service manual for this radio. does it have a mirror board in it?
found some info for it.

http://www.cbtricks.com/radios/stryker/sr_955hpc/graphics/SR-955HP alignment.pdf

 

[rabbiporkchop]

I did not find the service manual for this radio. does it have a mirror board in it?
found some info for it.

http://www.cbtricks.com/radios/stryker/sr_955hpc/graphics/SR-955HP alignment.pdf

That looks like a good place to start and should get you somewhere in the ballpark anyway.

 

[Robb]

Look . . . if you cannot test the bias setting properly; then don't bother to do it at all. You don't want to ruin your radio. I'm sure that it has MOSFETs, so you might consider sending to to the Stryker repair station if your radio is acting like it is out of whack - as I'm sure that it is probably still under factory warranty.

 

[Ranch55]

Yes, the Stryker SR-955 has MOSFETS for the finals. Some have FQP13N10 finals, and I do believe the most recent radios have IRF520 finals.
The Schematic diagram for the radio indicates the measurement points for the bias settings. The Alignment procedure documentation instructs the correct procedure. And the procedure instructs the bias setting in milliamps, but also instructs that all four final MOSFETS to be checked for same voltage.
The data sheets for both of these MOSFETS show the ON characteristics for the GATE voltage to be a minimum of 2.0 volts, and a maximum of 4.0 volts.

 

[357]

Stryker doesn't answer the phone, return messages or emails.
I had to set the bias cause I had to replace the finals, otherwise I wouldn't have bothered.
It has FQP13N10

 

[sonoma]

for those mosfets I set them at 3.5 volts. like rance 55 stated 2 to 4 volts. 3.5 has always worked well for me.

 

[nomadradio]

There is one back-door method.

Start with all the trimpots set to zero gate voltage.

Put a digital current meter in line with the radio's positive power wire.

Set mike gain to zero, select either USB or LSB and key the mike.

You will see a steady current draw. Advance the first trimpot until the reading climbs by 20 mA (0.020 Amp). Repeat this for each one.

You may desire more than 20 mA of idle current per MOSFET, but you should get the idea. Advancing each trimpot so that it raises the current reading by the amount each transistor should draw with no drive power.

73

 

[357]

There is one back-door method.

Start with all the trimpots set to zero gate voltage.

Put a digital current meter in line with the radio's positive power wire.

Set mike gain to zero, select either USB or LSB and key the mike.

You will see a steady current draw. Advance the first trimpot until the reading climbs by 20 mA (0.020 Amp). Repeat this for each one.

You may desire more than 20 mA of idle current per MOSFET, but you should get the idea. Advancing each trimpot so that it raises the current reading by the amount each transistor should draw with no drive power.

73

thats exactly what I did.

I think the measure point is at the power cord.
I measured it at the fuse and measured it at the lowest the VR would go, say 460ma then upped it to 560ma, followed the list and now I dont hear the "crunchy" background noise.
RX is now the required 400ma
bias set.

View attachment 18043