[Elecraft] Alignment of VCO - Problem

[David C Dawson]

Thanks,
Here's the measurements.
Note: the transistors are quite close to the board, so I had to figure
out which adjacent pad to tap; I think I have measured correctly.


The DC Voltages at Q18 are:

Point	Measured	Chart
-----	--------	-----
Gate:	0.00		-1.0
Source:	3.19		2 to 3
Drain:	8.02		6.3

!

Q16:

Point		Measured	Chart
-----		--------	-----
Emitter:	0			0.0
Base:		0			0.6
Collector:	7.98		2.2

!!



T5 is correct according to the diagram on page 55; leads 1 and 3 come
from the top of the core and leads 2 and 4 come from the bottom, and I
think that being so, the green winding cannot be reversed.

On Tue, Nov 14, 2006 at 03:56:31PM -0500, Don Wilhelm wrote:
> David,
> 
> The PLL Reference is apparently OK and your problem is in the VCO itself.
> The lack of RF voltage says the circuit is not oscillating - but we cannot
> declare Q18 dead just yet.
> 
> OK, next step is to check the DC voltages at Q18 - compare with the DC
> Voltage chart in Appendix E.
> 
> Double check T5 against the diagram in the manual page 55 (leads 1 and 3
> should come from the top of the core and the green winding must be in the
> same direction as the red winding) - if one of the windings is reversed, the
> oscillator will not oscillate.
> 
> Check the voltage at the drain of Q17 and compare with the DC voltage
> chart - measure the gate and source while you are at it, and just for a bit
> of additional information, check the DC voltages at Q16.
> 
> Tell us what you find.
> 
> 73,
> Don W3FPR
David Dawson