Kenwood TS50 Bias

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Tim
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Kenwood TS50 Bias

Post by Tim »

Can anyone please tell me where they are and which components I need to adjust to set up the bias on a Kenwood TS50? Thanks in anticipation.
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ch25
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Re: Kenwood TS50 Bias

Post by ch25 »

I don't want to sound grumpy, but you checked service manual, and it's not described there?
Chris
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Tim
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Re: Kenwood TS50 Bias

Post by Tim »

All the service manual tells you is that the adjustments are made on VR1 and VR2 but it dos not tell you the test points as to where you place the meter probe to obtain the correct voltages. This is to enable me to obtain the correct output power of the radio.
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ch25
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Re: Kenwood TS50 Bias

Post by ch25 »

Since there is no silver board you measure current consumption on TX from power supply, but I would put current meter in series with L8 for driver and L6 for final.
Or as described on final schematic set 0.67V on L8 and 0.65V on L6
Chris
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Re: Kenwood TS50 Bias

Post by Tim »

Basically it's the idle current, how to test for it and at which points.
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Re: Kenwood TS50 Bias

Post by wa10 »

Theres no bias test points & setting idle current on bipolar finals by base voltage is gambling that the transistors hfe will be very close to spec which is lottery unlikely,

The service manual describes a method that works good enough without having to break into the collector supply to measure idle current like a cb,
Heres how i do it,

FIRST warm the radio up to working temperature before setting idle current so the bias thermal tracking has time to settle down,

To measure Total current place the current meter in series with the power lead to the psu,

usb mode, *NO AUDIO*

TX & observe the current reading - turn vr1 & vr2 fully down / minimum current on meter ,

your reading with both bias pots turned off is "Total current", ( lets say its 500ma as an example )

adjust vr1 drive amp bias so that you have 250ma more than your Total current, 500ma + 250ma = 750ma

now adjust vr2 final amp bias to increase your 750ma to 1000ma,

giving you 500ma Total current + 250ma of drive amp current + 250ma final amp current.

job done.
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Re: Kenwood TS50 Bias

Post by Tim »

Thanks all who helped out with this but I have one more slight issue with this TS50. It is very slightly high on TX and RX on all frequencies, it's not much, just .1 out, example, 14.575.0, to TX and RX on that frequency the readout on the display needs to read 14.574.9 Can anyone tell me where the frequency adjustment is, what pot etc., or weather it may be a cap that needs replacing. Thanks.
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