Re: Did I build it wrong?
- Please note in the third paragraph, I left out the NOT... It should
read: "Keep in mind the signals up to T1's primary are NOT
referenced to the main ground... sorry for any confusion.
--- In firstname.lastname@example.org, "Terry Fox" <wb4jfi@...> wrote:
> This is my first post, please ignore the potential duplicate...
> I'm not really an expert, but I had to do some troubleshooting
before mine was working as well as the version 5 I also have. My C2
resistance is about 1.15k with the meter either direction. Looking
at the circuit, I see the R14/R15 voltage divider right across the
+5V. The combined resiustance is 2k, so you should be seeing below
2k (given the ICs and transistors also across the supply). I would
verify the values of those two resistors, and the mid-point betweem
them should be 1k or less. My unit shows 785 ohms at the center-tap
( connection 4) of T1.
> Have you verified the oscillator and dividers are working? If it's
a 40 meter version, look at pin 1 of JP1. You should see a wierd not-
quite square wave at the 28.2MHz freq. Each of the first three flip-
flops will divide that by two. On U3, pin 5 you should see 7.057MHz
(again, assuming 40 meters & JP1 jumpered 1-2). If you have a scope,
put one proble on U3, pin 5 and the other on U3, pin 9. Each of
these IC pins have a convenient eyelet very near them. You should be
able to see the I/Q clocks as clean square waves with the 90-degree
delay (pin 9 will go high or low halfway through the pin 5 pulse. If
they are good, your oscillator and dividers are creating the proper
clocks. DC volts should be about 2.45V on each of these two pins.
> The next spot to look is the transformer and input filter. This is
where my problem was, probably a cold joint on one transformer
connection. If you have a signal generator, feed a signal into the
input, and look at the transformer primary. You should see the same
signal, but 180-degree shifted (mirror image). If I feed 50mv of RF
into the ant (return=ant ret), I see 50mv of rf on T1, pin 1. Keep
in mind the signals up to T1's primary are referenced to the main
ground, use ant return for the scope and signal generator when
> Also, make sure you are using the correct pads for both L1 and L2,
which are near the edge of the board. Do not use the tie-down
eyelets near the center of each inductor. Plus, make sure Jumper JP2
> T1 pins 3, 4, and 5 should all have about 2.45VDC on them. Pins 3
and 5 should have a combined 50mv at 7MHz with a lower-freqency. Pin
3 should be in phase with the signal at the input, pin 5 should be
> U5, pin 2 will be a conglomeration of pulses, at 50mv (or the same
level as the rf input). The right and left outputs should be an
audio (IF) signal that varies according to the input frequncy and
level. For example, with 50mvp-p @ 7.062MHz input from a signal
generator, (and LO of 7.055MHz) I see a roughly 6.3kHz of audio on
the output, at about 1.8Vp-p. THe right (ring, red) channel leads
the left by about 90 degrees.
> That's more than you may need, but I am going out of town Monday,
and won't be able to play for a while. Hope that helps.
> ----- Original Message -----
> From: tazbecx
> To: email@example.com
> Sent: Saturday, September 16, 2006 7:33 PM
> Subject: [softrock40] Did I build it wrong?
> I have completed building a Softrock v6.1, well almost.
> I did all the checks using rocky 1.5, but was not getting any
> then when doing further testing, found that my resistance was
> the exspected 1.2k on c2.
> Tried all the resistors and transistor seem ok on tester. looked
> everywhere for dry joints of solder, but now at a complete loss
> where to look next :(
> All help gratefully received.