@5:50 I would pull those caps and check for them leaking, I’ve seen plenty of those big caps leak and still be perfectly functional, don’t want to end up repairing eaten away traces.
From a wattage stand point absolutely but because I am depending on the resistor at the moment to keep the diode in check I needed the temp co of the resister to be on the higher side to stabilize some of the drift tried it with a "normal" resister and the trace was bobbing up and down on the scope screen with off set. The better quality resistor stabilized this issue.
You sure know that the temperature compensated zeners have internally i series one or more diodes. That/they eliminate the appearance of the “forward” voltage, i.e. the 0.6 V knee. The temperature compensation results from the series connection of positive and negative drifts.
The speced diode is 5.2 if I remember correctly. This one was testing at 4.8 there was not enough voltage at this node which was throwing the DC offset self cal out of range of adjustment. Bringing the voltage closer to 5.2 nominal allowed the self cal to adjust. This diode was the DC offset reference.
@@ZenwizardStudios I believe InssiAjaton is referring to 8V unit you put on the curve tracer at about 14:30, explaining why you don't get a Vf. It would only work at higher zener voltages since the temperature coefficient goes negative at lower ones below 6V. Cool trick!
I recommend checking the hulking electrolytic caps anyway. Reason: I recently repaired a HP8901A modulation analyzer and lo and behold, its big cap had spilled electrolyte on the PCB. Eating away some of the green PCB solder resist. HP being HP, the gold plated PCB tracks shrugged off the electrolyte but good it was not obviously. I ended up finding myself a used, but not leaking, cap at a ham fest. Prices are like you mentioned: "off the scale".
@5:50 I would pull those caps and check for them leaking, I’ve seen plenty of those big caps leak and still be perfectly functional, don’t want to end up repairing eaten away traces.
Nice to see any old HP unit back in use, great work. The 0.1% resistor was way overkill I think ! but hey it works...cheers!
From a wattage stand point absolutely but because I am depending on the resistor at the moment to keep the diode in check I needed the temp co of the resister to be on the higher side to stabilize some of the drift tried it with a "normal" resister and the trace was bobbing up and down on the scope screen with off set. The better quality resistor stabilized this issue.
@@ZenwizardStudios :)
You sure know that the temperature compensated zeners have internally i series one or more diodes. That/they eliminate the appearance of the “forward” voltage, i.e. the 0.6 V knee. The temperature compensation results from the series connection of positive and negative drifts.
The speced diode is 5.2 if I remember correctly. This one was testing at 4.8 there was not enough voltage at this node which was throwing the DC offset self cal out of range of adjustment. Bringing the voltage closer to 5.2 nominal allowed the self cal to adjust. This diode was the DC offset reference.
@@ZenwizardStudios I believe InssiAjaton is referring to 8V unit you put on the curve tracer at about 14:30, explaining why you don't get a Vf. It would only work at higher zener voltages since the temperature coefficient goes negative at lower ones below 6V. Cool trick!
I recommend checking the hulking electrolytic caps anyway. Reason: I recently repaired a HP8901A modulation analyzer and lo and behold, its big cap had spilled electrolyte on the PCB. Eating away some of the green PCB solder resist. HP being HP, the gold plated PCB tracks shrugged off the electrolyte but good it was not obviously. I ended up finding myself a used, but not leaking, cap at a ham fest. Prices are like you mentioned: "off the scale".
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