Madell Frequincy counter

[paronaram]

Hello everybody.
I purchased used Madell F1000-C frequency counter, and it was advertised as working.
Counter arrived, and it does work, but it's not calibrated, it's off about 200kHz
I borrowed another frequency counter from friend just to compare ... and actually that's how I find out that it's off

What is involved in calibrating this device?

Thank you.

PS Display cable disconnected by me ...

[xrunner]

Probably the reference is in the metal box with the adjustment screw hole. Let it warm up for an hour or so. Turn the screw until you are as accurate as possible to the best reference you can compare to.

[BrokenYugo]

How certain are we that the borrowed counter is calibrated? 

[coromonadalix]

/as writen on earlier posts

yep  the metal box is the main time base oscillator, you need to compare it against another counter to adjust it,  some counters have a 10Mhz timebase

This one has an 10Mhz timebase indeed ...

If you have access to a scope it could roughly help to readjust it,  at least warm the counter for 1 hour before doing so

[Miti]

Hello everybody.
I purchased used Madell F1000-C frequency counter, and it was advertised as working.
Counter arrived, and it does work, but it's not calibrated, it's off about 200kHz
I borrowed another frequency counter from friend just to compare ... and actually that's how I find out that it's off.

First of all, did you let both counters warm up? What makes you think that your friend’s counter is perfectly calibrated? Does it have a GPSDO or at least an OCXO? If not, you have two watches and you don’t know which one shows the correct time.
Your time base looks like a TCXO, don’t expect too much stability from it.

[TimFox]

An error of 200 kHz at what frequency?  200 kHz error at, for example, 10 MHz is not likely a crystal calibration error (2%), but could be a circuit failure.

[floobydust]

It also goes by ATTEN F1000C. Manual says 20 minute warmup, 13MHz ref osc. I'd make sure VDD is OK assuming 5VDC.

[coromonadalix]

Seems a clone of Atten AT F1000-C 

https://www.eevblog.com/forum/repair/atten-f2700c-digitech-qt-2202-repair-review/

LOLL  got  me  while posting it  loll

[paronaram]

Thank you all for all recommendations.
Counter that I borrowed is LEADER

Will test this all tomorrow with 1kHZ calibration from my scope

Thank you

[Kleinstein]

The 2 nd borrowed counter looks like about same quality grade. This is OK for a crude test, but not really for a calibration. For frequency there are good reference frequencies available as RF signal in many places.

The difference of 200 kHz is huge ( still depends on the frequency, but even at 200 MHz, which would be close to the maximum of the slower of the 2 counters thus would be 1000 ppm and thus more than what a quartz crystal could sensible drift or be detuned. This looks more like a problem (e.g. quality of the test signal) or defect with the input stage (causing double triggering) or maybe just a very poor setting for one of the instruments (e.g. select external reference if not present).
With such a large error it would at least be possible to see which reading / counter is off. Even the mains frequency is better with some patience or using info on the actual measured frequency from the web.

[paronaram]

So I did more testing, and it looks like it's working, I mean it looks like calibrated , maybe type of signal? ...
On the picture you can see it's connected to a scope calibration 1kHZ output.

Before I was connecting to a Heathkit RF Generator SG-8
Maybe signal is not stable from RF generator?

http://pdf.textfiles.com/manuals/SCANNERS-F-R/Heathkit-SG-8.pdf

 

[TimFox]

On page 15 of the Heath manual, it states that frequency accuracy of 2 - 3 % is “expected”.  Again, at what frequency did you see 200 kHz error?

[xrunner]

So I did more testing, and it looks like it's working, I mean it looks like calibrated , maybe type of signal? ...
On the picture you can see it's connected to a scope calibration 1kHZ output.

Before I was connecting to a Heathkit RF Generator SG-8
Maybe signal is not stable from RF generator?

http://pdf.textfiles.com/manuals/SCANNERS-F-R/Heathkit-SG-8.pdf

That Heathkit RF signal gen starts at 160 kHz. Is the low pass filter button depressed on the counter (looks like it might be - also the attenuator)? It may be attenuating the signal you were trying to count but you didn't specify what freq. the Heathkit generator was set to. A 1 kHz square wave will pass OK if the low pass filter button is depressed but a much higher freq. will not.

[paronaram]

OK, did more testing this AM.
It's all working, I can't replicate this issue... RF 455kHZ was showing 600kHz+ (I don't remember exact number) the day I was trying to do a RF alignment on tube radio. I was at my friends house, and the only difference from what I was doing that day and now, is BNC cables.
I used his cables on the same equipment that have here... and counter was off ... today and yesterdays test was not showing any issues at all with my BNC cables.
I set the Heathkit to 455kHz and both counters output 455 on the display 

It's just weird

[TimFox]

Yes, 200 kHz error on 455 kHz is not a calibration problem.  My guess is that the bad cables had an open circuit, so that the signal getting through was capacitively coupled and exaggerated noisy stuff on the 455 kHz sine wave.  One would expect less than 20 kHz error with that generator at 455 kHz, even if it was not recently calibrated.

[paronaram]

Thank you everybody for your help and support!