DX60B V3 Final Voltages

[ko4nrbs]

Thought I would start a new thread.

I am now focusing on the Final V3 since its screen voltage is much higher than the voltage supplied by V4 6DE7.  Took voltage readings on V3.
Pin 1- 0vdc supposed to be 1.2vdc
Pin 5- -149vdc supposed to be -38
Pin 3- 171vdc now

All taken in AM mode.

I will take a look around this circuit now.  Hope I am not off on another wide circle!!

73,
Bill KO4NR

[WD8BIL]

With the grid (bias) voltage at - 149VDC the tube is in cutoff. That's why pin 1 is at 0! Check R33 for an open or something amiss in the bias supply path to pin 5.

[ko4nrbs]

With the grid (bias) voltage at - 149VDC the tube is in cutoff. That's why pin 1 is at 0! Check R33 for an open or something amiss in the bias supply path to pin 5.

I verified the path from R33 all the way to V3, V2 and V1.   Voltages taken in AM mode.  R33 was open but still not working correctly, Thanks!!
V3 now
Pin 3- 210vdc
Pin 1- 0vdc
Pin 5- -93vdc

Bias dropped some but is still too high.  All the resistors are new.

Bill

[N1BCG]

The control grid voltage cannot be measured at pin 5 if there is R.F. on it. The D.C. voltage without R.F. has to be measured at the C12 end of the 1.1mH choke, however, the Grid Current reading should suffice for checking if things are within spec.

Also:

1) Is there any voltage drop across R28?

2) There's going to be some variation with such a large resistor (22M) setting the voltage on the grid of V4. Just a slight change in R24 will make a big difference in the 6146 screen voltage.

3) The R.F. drive level to V3 will affect the screen voltage. See if it changes on other bands too.

You might be fine as-is.

[ko4nrbs]

The control grid voltage cannot be measured at pin 5 if there is R.F. on it. The D.C. voltage without R.F. has to be measured at the C12 end of the 1.1mH choke, however, the Grid Current reading should suffice for checking if things are within spec.

Is there any voltage drop across R28?

Also:

1) There's going to be some variation with such a large resistor (22M) setting the voltage on the grid of V4. Just a slight change in R24 will make a big difference in the 6146 screen voltage.

2) The R.F. drive level to V3 will affect the screen voltage. See if it changes on other bands.

You might be fine as-is.

R28 is -1.3vdc across it and about -330vdc from each end to ground.  No change in either band.

R24 on V4 was replaced with a 1 meg ohm resistor as recommended to help eliminate hum on the audio.

Bill

[N1BCG]

R24 on V4 was replaced with a 1 meg ohm resistor as recommended to help eliminate hum on the audio.

Good idea, but that could be the cause. Do you still see (about) 25V on pins 2 and 6 on V4? A higher voltage would increase the V4 screen voltage.

Does changing the drive level affect screen voltage. It should but it's worth demonstrating.

[ko4nrbs]

R24 on V4 was replaced with a 1 meg ohm resistor as recommended to help eliminate hum on the audio.

Good idea, but that could be the cause. Do you still see (about) 25V on pins 2 and 6 on V4? A higher voltage would increase the V4 screen voltage.

Does changing the drive level affect screen voltage. It should but it's worth demonstrating.

Pins 2 and 6 on V4 are 25vdc when the mic is plugged in but about 53vdc with the mic disconnected from the rig.  When modulated it will kick up to about 80vdc on peaks.

V3 Pin 3 is 147vdc with the mic disconnected and about 56vdc when the mic is connected but tops out at 65vdc when modulated.

Looks a lot better but on AM max plate current is about 50ma on peaks with low power out.  Adjusting the Audio gain didn't increase it.

Drive Level did affect the voltage a little.

Now to figure out why the power is low.  The rig tuned up fine and has full power out on CW.  May be the D104 mic??

Bill

[DMOD]

I would suggest a close inspection of the rear lugs of the Function Switch.

In the AM mode, Pin 9 of V4 should be 165V, the voltage on the right side of R27/C36 should be 65 to 75 volts no modulation.

The Function Switch determines whether the V4 cathode's voltage goes to the Final screen (AM mode) Pin 3 or if the CW voltage from R28 goes to the screen.

Someone may have rewired it or it was misswired.

Make sure the 60 is loaded properly into a dummy load.

210V dc on the screen Pin 3 is too high for AM or CW.

[ko4nrbs]

I would suggest a close inspection of the rear lugs of the Function Switch.

In the AM mode, Pin 9 of V4 should be 165V, the voltage on the right side of R27/C36 should be 65 to 75 volts no modulation.

The Function Switch determines whether the V4 cathode's voltage goes to the Final screen (AM mode) Pin 3 or if the CW voltage from R28 goes to the screen.

Someone may have rewired it or it was misswired.

Make sure the 60 is loaded properly into a dummy load.

210V dc on the screen Pin 3 is too high for AM or CW.

Rig has PTT Modification

Resting voltage on V4 Pin 9 is 148vdc and 160 when the rig is keyed.
The right side of R27/C36 is 67vdc with the mic plugged in with no modulation but drops to 66vdc when I key the mic with no modulation.  It is 147vdc with the mic unplugged.
V3 resting voltage is 148vdc and 77 when the rig is keyed.

I verified the Function Switch a few times this week and it is ok.

Thank you for the information.

Bill

[DMOD]

"....Looks a lot better but on AM max plate current is about 50ma on peaks with low power out.  Adjusting the Audio gain didn't increase it.

Drive Level did affect the voltage a little.

Now to figure out why the power is low.  The rig tuned up fine and has full power out on CW.  May be the D104 mic??

Bill"

Power is low in what mode, AM or CW? The mic has nothing to do with the RF power output.

Check the Drive Level pot R7. Pin 8 V2 should go from 0V to about 80V

[ko4nrbs]

"....Looks a lot better but on AM max plate current is about 50ma on peaks with low power out.  Adjusting the Audio gain didn't increase it.

Drive Level did affect the voltage a little.

Now to figure out why the power is low.  The rig tuned up fine and has full power out on CW.  May be the D104 mic??

Bill"

Power is low in what mode, AM or CW? The mic has nothing to do with the RF power output.

Check the Drive Level pot R7. Pin 8 V2 should go from 0V to about 80V

Low power in AM mode.

Pin 8 is 0vdc to 260vdc when the Drive Level is adjusted through its range.

My old mike would easily peak the plate current up to over 75ma.  I kept it below that.  The element in the D104 may be weak or??

The rig tunes up normally.

Bill

[DMOD]

Resting voltage on V4 Pin 9 is 148vdc and 160 when the rig is keyed.
The right side of R27/C36 is 67vdc with the mic plugged in with no modulation but drops to 66vdc when I key the mic with no modulation.  It is 147vdc with the mic unplugged.
V3 resting voltage is 148vdc and 77 when the rig is keyed.

I verified the Function Switch a few times this week and it is ok.

Thank you for the information.

Bill

Please note (and many tend to forget this) when the mic is Unplugged it is in "Key" mode. This is why I change the Keyjack to a simple 1/4" Mono Jack.

[ko4nrbs]

Resting voltage on V4 Pin 9 is 148vdc and 160 when the rig is keyed.
The right side of R27/C36 is 67vdc with the mic plugged in with no modulation but drops to 66vdc when I key the mic with no modulation.  It is 147vdc with the mic unplugged.
V3 resting voltage is 148vdc and 77 when the rig is keyed.

I verified the Function Switch a few times this week and it is ok.

Thank you for the information.

Bill

Please note (and many tend to forget this) when the mic is Unplugged it is in "Key" mode. This is why I change the Key jack to a simple 1/4" Mono Jack.

On my list to do now!!

When I said keyed in the thread, I mean I keyed the mic. in the mic. connector and wasn't using the CW key.
Bill

[DMOD]

Power is low in what mode, AM or CW? The mic has nothing to do with the RF power output.

Check the Drive Level pot R7. Pin 8 V2 should go from 0V to about 80V

Low power in AM mode.

Pin 8 is 0vdc to 260vdc when the Drive Level is adjusted through its range.[/quote]

The voltages you measure at Pin 8 are correct. There are 11 to 18 mA flowing through R8 and R7 so about 75V should be dropped across R8; 350V - 75 = 275 at the junction of R8 and R7, so the grid should see 0V to as much as 265V.

As for low power in AM, if your screen voltage on the final is 65V for AM, the power out will be less than 1/2 the power in CW mode when it is 180V.

[ko4nrbs]

Thank you!!
Bill KO4NR

[ko4nrbs]

Resting voltage on V4 Pin 9 is 148vdc and 160 when the rig is keyed.
The right side of R27/C36 is 67vdc with the mic plugged in with no modulation but drops to 66vdc when I key the mic with no modulation.  It is 147vdc with the mic unplugged.
V3 resting voltage is 148vdc and 77 when the rig is keyed.

I verified the Function Switch a few times this week and it is ok.

Thank you for the information.

Bill

Please note (and many tend to forget this) when the mic is Unplugged it is in "Key" mode. This is why I change the Keyjack to a simple 1/4" Mono Jack.

If I would have known that I needed to plug in the microphone in order to get the correct AM voltage readings it would have saved me a lot of time troubleshooting!!
Bill