Re: Nearly non-existent output power, no mod

Clark Martin

Sorry, but you description below is akin to bad driving directions… (turn right at the green house, etc).  

It would be far easier and more accurate to specify where the signal was measured (and how).  
KT2-14 2.6V
using an RF probe and DC voltmeter

check on both sides of the filter (input and output) and on each of the contact pins of the relay in question.

Note: all the resistors connected to the driver and pre-drivers are “bias” resistors.  The 10 ohm would, presumably, be the emitter bias resistor.

You replaced the final transistors, did you readjust the bias pots (RV2, RV3)?

Clark Martin

On Sep 16, 2019, at 5:49 PM, Ted via Groups.Io <k3rta@...> wrote:

On Thu, Sep 12, 2019 at 07:42 PM, Clark Martin wrote:
Use an RF probe or oscilloscope to trace the signal through the relays / filters.
OK, here we are: 

On 80m and 60m, only the filter between the T/R relay and KT3 shows strong RF.  Power out on 80m is 2 watts CW, 1/2w SSB. 60m shows 1 watt/1/2 watt.

On 40m and 30m,  only the filter at KT3 shows strong RF. Power out on 40m is about 3/4w CW and 1/2w SSB; 30m shows 1w CW.

On 20m and 17m, only the filter at KT2 shows strong RF with power out the best: 2.5w CW but only 1/4w SSB on 20. 17m shows about 1/3 & 1/4 if that....

15m and 10m show strong RF on the filter near KT1, with output on both bands less than 1/4w either mode (or should I just say, at barely detectable limits).

The meter used is the analog dial on a MFJ 949D as my 5W slug is missing from the Bird wattmeter  :(

The two predrivers and 4 drivers are all steel-can 2N2222's with 10-ohm bias resistors.  All six run fairly hot - with heat sinks added - though the 4 more so than the pair. The finals (even reputable ones) certainly get hot enough, too. if i put my fingers on the predrivers or drivers, the RF power (such as it is) decreases somewhat. Q90 is also a 2N2222 can with I believe a 15-ohm bias chip on it.  None of this changed prior to the output failure. 

Obviously, energy is being produced but to what end?  It certainly isn't going into the dummy load or out the aerial/antenna/wirethingy.

More guidance would sure be fantastic.  Thank you, all, for your input.

Join to automatically receive all group messages.