Frequency counter won't count.

[neo]

I bought a HP 5340A and when i first got it counted and accurately. Then i put it on the shelf, not one thing changed and all it will show are zeros, and when i change ranges either MHz or GHz and the decimal point also changes. Could someone please help me before i rip my hair out?

[Ampera]

Bolt an HP calculator to it. It will start counting perfectly

The calculator, not the machine.

[neo]

Bolt an HP calculator to it. It will start counting perfectly

The calculator, not the machine.

Good laugh but ultimately not a solution to the existing problem of the expensive paper weight that used to count frequency then stopped.

[Ampera]

You say it's expensive? Attempt percussive maintenance, that always helps matters.

Sorry for joking around, I wouldn't know what the issue would be.

[neo]

You say it's expensive? Attempt percussive maintenance, that always helps matters.

Sorry for joking around, I wouldn't know what the issue would be.

The jokes are fine, they make me laugh and consequently help keep me from doing "advanced percussive maintenance" to the thing

[Vgkid]

Here's the manual:
https://elektrotanya.com/hp_5340a.pdf/download.html
 Since it previously worked, make sure everything is seated. Grab a dmm, and check the power rails. If it is like other HP counters that use a socketed relay for power, a bad connection will cause some strange results.

[TheSteve]

Which input are you using, what is the input selector set to and what voltage/frequency signal are you feeding into it?

[neo]

Which input are you using, what is the input selector set to and what voltage/frequency signal are you feeding into it?

50 ohm bnc i tried front and back. Voltage should be very low level, a hair above min level on my GFG-8020H. Frequency between 10 Hz and 55 MHz. It is through a scope probe but the same probe worked before i moved it.

[TheSteve]

Is it a 10:1 probe? Anyway, you'll need to use the front BNC input for lower frequency use. Keep the range switch fully left.

[neo]

10x/1x probe and yes i did have it on 1x and i tried every range.

[neo]

No matter what i do it locks at 00.000000 MHZ on 1 hz range, it used to go into a KHz range and measure

[Gyro]

I'd check that its crystal oscillator is still working, especially if it's an ovened one. It might have suffered a thermal cycling related failure.

[neo]

I'd check that its crystal oscillator is still working, especially if it's an ovened one. It might have suffered a thermal cycling related failure.

When i tested it it read 7-8 MHz and climbing on my working frequency counter,  i writ it off to the scope probe but could that be it?

[rdl]

Be sure to try with a different connector. Even 2 conductors of straight wire will be okay for testing. I bought a new oscilloscope once that came with 1 probe open, so never trust anything.

[neo]

Be sure to try with a different connector. Even 2 conductors of straight wire will be okay for testing. I bought a new oscilloscope once that came with 1 probe open, so never trust anything.

I know both probes work as i have tested both. With either probe the frequency jumps between 7.5 and 8.5 MHz before semi stabilizing at 8 MHz and some change. I'm going to assume that is bad? It also only outputs when the unit is turned on.

[Vgkid]

That doesn't sound good at all. 7-8MHZ, even measured with a scope. Is very very far from the correct frequency.

[alm]

It could be that the capacitance of the scope probe messes up the oscillation. Especially if set to 1x. Set it to 10x and try to find a buffered node to measure the frequency at (for example an external 10 MHz output).

[neo]

It could be that the capacitance of the scope probe messes up the oscillation. Especially if set to 1x. Set it to 10x and try to find a buffered node to measure the frequency at (for example an external 10 MHz output).

Actually that is what i last tried, the 10 MHz out with 10x on the probe.

[alm]

I must have missed that when reading your posts. If the 10 MHz output is outputting ~8 MHz, then there is definitely something wrong around the oscillator. The obvious place to start is measuring power supply voltages and ripple. The service manual should be helpful for this.

[neo]

-15V      could not find board.
+15V    OK
-5V RF  OK
-5V DG OK
+5V RF OK
+5V DG FAIL 4.67 MAXIMUM
+11 TB OK
While probing that last one it started counting again, i left it in self check and was watching for anomalies, so this give you any clues? I'm thinking maybe a loose card? It also started doing the 10 MHz out it should have been doing.

[neo]

 
I put the cover on and it broke again. By broke i mean not displaying and/or counting properly.

[neo]

Also when it does work properly all i get is 3 digits.

[Vgkid]

Check to make sure everything is seated, then recheck your power supply. Do you have the 175v rail?

[neo]

Check to make sure everything is seated, then recheck your power supply. Do you have the 175v rail?

I took out and put all power cards back in and as for the 175V rail it has to work as the display is fully functional. Every digit lights except when counting where it will only display 3 digits.

[VK5RC]

Does it have a freq standard input switch?  I had an old HP counter that the switch was intermittent, the internal reference goes through it as well.