Teaberry Stalker XV full power but no bias at idle.

[RichardHartman]

Hello again!

I have been able to bring this Teaberry back to life with your guy's help. I have a situation now that doesn't seem to make sense. To me anyway!

I should mention a couple of things.. Xtra channel and clarifier lock have been performed on this unit. It is up and running with full TX power and good receive. I am still waiting for my caps to arrive so I can recap it.

I was working thru the TX alignment procedure and I am supposed to set the bias current TP8 35mA and then TP7 45mA. I have no current on either one of the test points and adjusting doesn't change anything. I am confused on how the unit will still TX full power with no bias? I was talking to another gentleman and he mentioned there was a diode for the bias. Are you aware what he might be talking about and maybe someone could explain how it still TX without any bias current and if this is possible then why is there bias current?

73

Richard Hartman

 

[Dmans]

no bias at idle

You are testing the bias in SSB, mike keyed and mike gain turned off-correct?

Your amp meter should complete the circuit between the test points and the wire hooked to them.

73
David

 

[RichardHartman]

no bias at idle

You are testing the bias in SSB, mike keyed and mike gain turned off-correct?

Your amp meter should complete the circuit between the test points and the wire hooked to them.

73
David

Hi David,
When I read the Sams it doesn't actually say TX like in the other procedures before this one so I was not. I was thinking idle current meant while power was on but not TX. I was not keying the mic. Its works now. Thank you...this was an easy one! Live and learn.

73

 

[Dmans]

 

[Handy Andy]

Hmmm...You guys already sorted this out but I think this will need to sit in here somewheres to help out the next one...

To correctly set the BIAS - you'll need to find the correct trim VOLTAGE the BASE of that Transistor needs, to JUST TURN ON - at that "XX mA" setting...you use the VR pots to set this threshold.

But you look at, and use, the Collector to Emitter junction as an amperage measurement to set this Draw figure.

So that means...

Review this - Study carefully...

If you still have posts intact...try this method...

Follow below to help you thru this...​

• FOR BEST RESULTS...
• Use a Dummy Load...
• PERFORM BIAS adjust with BOTH COLLECTOR wires pulled from their board locations - NO POWER except thru respective METER connector - so No Driver and No Final power to main board during this adjustment. Keeps things from getting too messy and tangled - less likely to fail too.
• For rear wire (Solidly soldered jumpers, (e.g. - RWOB refurb) Ammeter uses WIRE as POSITIVE, and BOARD as NEGATIVE - power flows thru WIRE into METER then to board for DIODE bias to be properly set USING mA reading of TURN ON AMPERE draw on the COLLECTOR to EMITTER junction. In Milliamps! (Fused leads work best here)
  • TP7 and TP8 posts intact -
  • Disconnect both terminals - if they can be removed - if not you can unsolder and install new terminals and fixture - else if destroyed and you wish to use this as your tap point then remember...
  • Ammeters Positive wire to one of either TP 7 or 8 posts locations, (Origin)
  • Wire FROM the pot it enters back to the board by, either - it's color code to correspond to Driver or Final - and or by proximity to work VR8 for DRIVER, VR9 for FINAL.(Destination)
  • Ammeters NEGATIVE Lead goes to corresponding Wire by Color and location by VR for respective Driver or Final adjustment.
• VR8 for DRIVER
• VR9 for FINAL
• Adjust respective BIAS mA reading in SSB TX mode while watching Ammeter current draw.

Then, once completed remove and restore all wiring to proper connections - verify that while on the Dummy load, you have S/RF meter and reset RF meter and Power levels as necessary for proper and accurate meter indication.