[Test-Equipment] Question Regarding Fluke 8050A

[Barry]

I needed to invert the strobe and I didn't have any 7404s at the time so I used a 7400 and tied one input high.

Thanks,
Barry - N4BUQ

----- Original Message -----
> From: "David" <davidwhess at gmail.com>
> To: "Discussion of Electronic Test Equipment" <test-equipment at mailman.qth.net>
> Sent: Thursday, June 4, 2015 9:24:51 PM
> Subject: Re: [Test-Equipment] Question Regarding Fluke 8050A
> 
> On Thu, 04 Jun 2015 22:08:51 -0400, you wrote:
> 
> >   On 06/04/2015 09:33 PM, Barry - N4BUQ:
> >
> >> Yes, that would be my preference as well.
> >
> >> As an update, I connected all five displays on a breadboard, powered it
> >> with an external supply, and watched the current demand.  The maximum I
> >> could get out of all those was about 310 mA.  I tested them with the four
> >> primary digits connected together and stepped it through 0000, 1111,
> >> 2222, etc. (the first digit the +/-/1 and it doesn't pull much current).
> >> Oddly, 4444 drew the most power.
> >
> >> It turns out I had an SN7400N that I was using as an inverter and I was
> >> testing with that out of the circuit.  When I plugged that in, though,
> >> the current demand shot to over an amp!  I think something may be wrong
> >> with that chip and was the primary reason I was seeing such a high power
> >> demand.
> >
> >> I have secured some SN7404N inverters and am going to see what one of
> >> those does to the circuit.  Hopefully that was the main problem and it
> >> all just might still work as-is (with a 7404).  If not, I may still see
> >> if the problem is the regulator being pushed to its limit and using a
> >> separate regulator might still be an option.
> >
> >   You should be using 74LS04 or 74CH04 devices.  (or a transistor and
> >resistors)
> 
> I agree although I think you mean HC or more likely HCT devices
> instead of CH.
> 
> It seems to me that the 7400 inverter was unrelated to the LED display
> circuits.
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