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8116A Code 42

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Mick B:
 :clap: I did it! my HP 5005A is alive. That was not fun, but in the end the 3 coax cables were successfully replace with RG316 and a sheath from an old O2 sensor out of one of my Saabs.
After putting it together there were error messages E18 & E15 this turned out to be the ribbon cables connecting the 3 boards together, after reseating them a few times no errors. As far as I've tested is the quick test as far as the test leads go there supposed to measure approximately 100K all 3 are 98.7 ohms winner winner chicken dinner!
Now I can get back to testing the HP 8116A's before I was so rudely interrupted by a faulty coax cable.       

Mick B:
Hello, I posted this conversation of HP5005A unit in a new thread. Apparently, there is more work to do. 

 https://www.eevblog.com/forum/testgear/hp-5005a-a6-pod/msg5593715/#msg5593715] [url]https://www.eevblog.com/forum/testgear/hp-5005a-a6-pod/msg5593715/#msg5593715[/url]

Mick B:




--- Quote --- Quote from: MarkL on:  August 02, 2024, 04:14:00 pm
You could measure the quiescent Vbe and the voltage across collector resistor R526 to calculate if you're near or above 350mW.  Unfortunately, if R526 is close to 12.1V, then the parallel VR502 will interfere with the measurement, in which case you could more annoyingly measure across all the emitter resistors R519, R521, R523, R529, and R531 to compute the total collector current.
--- End quote ---

Hi Mark, I have the voltage readings across the emitter resistors.
Setup: Amplitude 999mV. Offset 0V. Frequency 1K. No Waveform. Mode Normal. 0utput on, Bk. lead on the emitter side.
R519 = 031.5mV
R521 = 0.144V
R523 = 031.5mV
R529 = 030.5mV
R531 = 022.0V

NOTE: Readings are the same at 16.0V
I do not know what the formula for this measurement is.
I know this about Q205, but this might be relevant. Attached are pictures of the trigger signal with Overshoot and Preshoot. The readings are jumping around from an OS of 53%~60% and PS of 7%~20%

I also acquired an HP 8007B Pulse Generator for calibrating the HP 5005A, to check the ICs on the HP 8116A 

MarkL:
So, what we have is five resistors connected to the emitter of Q502.  By computing the current through each and adding them, you can get the current through the emitter.  Then, by measuring the voltage drop from collector to emitter (I said Vbe, sorry I meant Vce), you can calculate the power dissipation in Q502.

Like this:
                   ohms
                   ----
  R519 = 031.5mV / 59    =   0.533mA
  R521 = 0.144V  / 1k    =   0.144mA
  R523 = 031.5mV / 1k    =   0.250mA
  R529 = 030.5mV / 866   =   0.035mA
  R531 = 022.0V  / 1.78k =  12.3mA
                            --------
                            13.262mA

  Power Dissipation = Vce * 13.262mA

This assumes you've measured the resistors all in the same direction (e.g., + probe to the emitter or visa-versa), and you've reported the polarity of the reading.

As for the overshoot/undershoot on the trigger out, do you have another 50 ohm pulse output from another piece of equipment that you can look at to verify this is not a measurement setup problem?  Is this a piece of coax with a terminator on it going to the scope?  Does the overshoot change with the length of coax?

Mick B:

--- Quote from: MarkL on August 07, 2024, 03:53:26 pm ---So, what we have is five resistors connected to the emitter of Q502.  By computing the current through each and adding them, you can get the current through the emitter.  Then, by measuring the voltage drop from collector to emitter (I said Vbe, sorry I meant Vce), you can calculate the power dissipation in Q502.

Like this:
                   ohms
                   ----
  R519 = 031.5mV / 59    =   0.533mA
  R521 = 0.144V  / 1k    =   0.144mA
  R523 = 031.5mV / 1k    =   0.250mA
  R529 = 030.5mV / 866   =   0.035mA
  R531 = 022.0V  / 1.78k =  12.3mA
                            --------
                            13.262mA

  Power Dissipation = Vce * 13.262mA

This assumes you've measured the resistors all in the same direction (e.g., + probe to the emitter or visa-versa), and you've reported the polarity of the reading.

As for the overshoot/undershoot on the trigger out, do you have another 50 ohm pulse output from another piece of equipment that you can look at to verify this is not a measurement setup problem?  Is this a piece of coax with a terminator on it going to the scope?  Does the overshoot change with the length of coax?

--- End quote ---


Hello Mark, Fantastic it's way under spec. Using the numbers in the quote above.
VCE is 10.627V
Power Dissipation = 10.672V * 13.262mA = 140.935mW
yes? Also when taking voltage readings is it OK for instance, to wright 10.5V and -10.5V is it assumed if there is no minus sign its positive? I ask this because all of meters do this.

As for the overshoot, have a multitude of Tektronix 50 Ohm 2W passthrough adaptors looking at them on my spectrum analyzer they are very flat out to 3.2GHz somewhere between -1 & -2.5 dB down. Using these with different size and length coax makes little difference. I also have another function Gen that has a 50 Ohm output and has very little overshoot and preshoot both 2.6%.

But I just realized Q503 & Q504 also in a TO92 package with heat sinks I will see what these are and check them also. After looking at the schematic this seems a little more complicated, looks like the same resistors and their counter parts but what about R532?
Thanks Mick
 

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