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The totalizer runs and all digits are displayed. No counting light at all in frequency mode, the counting light in period flashes but no count is displayed. Checked 5V and -12.5V both good.

Chase the input signal path. Sounds like your input isn't making it all the
way to the counting circuit.

Dave Casey
On Wed, Mar 28, 2018, 8:55 PM lop pol via Groups.Io <the_infinite_penguin=
[email protected]> wrote:

The totalizer runs and all digits are displayed. No counting light at all
in frequency mode, the counting light in period flashes but no count is
displayed. Checked 5V and -12.5V both good.

If the totalizer runs OK you should have input pulses getting through to the counter chain.

Have you checked S160 which selects internal / external clocks? If external is selected that could explain both the frequency and period oddities.

If S160 is OK then follow the time gating signal from U160 -> U180A -> U217A etc through to U220C where the gate pulse is combined with the signal pulses.

Likely failures are 74xx logic ICs and segments of the cam switch S200.

Regards,

Roger

I'm thinking there should be an oscillator here? /g/TekScopes/photo/37195/9?p=Name,,,20,1,0,0

It's all in the manual - U160 is a 1MHz crystal oscillator and programmable divider.

Roger

Looks like a crystal socket to the right of the variable capacitor. Maybe a 1 MHz reference crystal?

Yep. I hooked up a probe to the 1mhz TP and nothing but DC. I think I figured out one thing anyway.

There won't be any signal until you install the crystal.

There are different options for the oscillator xtal IIRC, 'ovenised' (opt 1?) or not and either 5 or 10MHz - so one empty socket may be ok if there is a crystal somewhere else I guess!

Good hunting!

Adrian

What does the manual say should be in that location? What frequency oscillator does this plugin use? It is going to be either 10MHz or 5MHz.

The two pins I can see may be for the oscillator. The oscillator needs a total of 4 pins: Vcc, ground, output, and a 4th pin which is unused but it supports that corner of the module.

To save space they sometimes mount the oscillator on the back side of the PC Board as long as you can still get to the frequency adjustment hole in the top of the oscillator.

Dennis Tillman W7PF

Manual calls Y160 a 1Mhz quartz crystal. I ordered this