These are readings using Table 5-3 as guidance, right?
For places to start, I suggest measuring inputs across C10, C12, C14. A quick check for AC ripple across these caps to confirm there's no outrageous ripple present would also be a good preamble to further tests.
Next I suggest recording TP 31, 33, 37, and all Q8 and Q9 voltages--- all re +S. Perhaps there's simple failure in the "Reference Regulator."
Test results: TP31 = 6.14V TP33 = -6.17V TP37 = 12.26V
Q8 = E -6.17V, B -5.59V, C 8.74V
Q9 = E 16V, B 15.3V, C 6.14V
I took "measuring inputs" to mean hook up to a scope? The probe is connected to one side of the capacitor and the probe ground to the the other side of the capacitor like so?
Q8 = E -6.17V, B -5.59V, C 8.74V
Q9 = E 16V, B 15.3V, C 6.14V
I took "measuring inputs" to mean hook up to a scope? The probe is connected to one side of the capacitor and the probe ground to the the other side of the capacitor like so?
Defacto2 said:
Testing Results:
0 volts on pin 31 to +S -should be 6.2
-------------------------------------------------------
Above is from post 20, but results in post 23 suggest the Reference Regulator looks ok. Would you clarify present state? Same in other channel?
Your scope photo is just what I was suggesting, but I can't tell ripple amplitude--- about one box~ 1V p-p? Looks like good symmetry, and probably fine. (You may want to revisit when supply is again working with full loading.). If these photos are representative of all sections, I think you're good to pursue trouble shooting.
Testing Results:
0 volts on pin 31 to +S -should be 6.2
-------------------------------------------------------
Above is from post 20, but results in post 23 suggest the Reference Regulator looks ok. Would you clarify present state? Same in other channel?
Your scope photo is just what I was suggesting, but I can't tell ripple amplitude--- about one box~ 1V p-p? Looks like good symmetry, and probably fine. (You may want to revisit when supply is again working with full loading.). If these photos are representative of all sections, I think you're good to pursue trouble shooting.
That is what I had recorded at that time. Likely my error in measuring, idk.
The current reading is 6.14V. Using an oscilloscope is new to me too. I'll try for a single P2P in the future. lol
C12:
The current reading is 6.14V. Using an oscilloscope is new to me too. I'll try for a single P2P in the future. lol
C12:
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Do you have a digital multi-meter with a diode test function, and if so, do you know how use it to test diodes and transistors for "open" and "short" conditions?
One of my first troubleshooting steps is to check as many semiconductors as possible for this, with the power off, of course.
One of my first troubleshooting steps is to check as many semiconductors as possible for this, with the power off, of course.
In general, my preferred trouble-shooting is powered diagnosis. Be safe, one-handed probing, other hand well away from the equipment and paths to ground. NO CURRENTS ACROSS THE CHEST.
My imagined approach for this supply:
I'd confirm back-panel terminals are strapped as depicted in the schematic, page 120. Note that much of manual uses +S as measurement reference. Consequently, I'd make a power-off ohmmeter test to make sure there's no continuity between +S and earth ground. With confirmed isolation between +S (by extension, the entire regulator) and ground, I'd be comfortable connecting scope ground (and multimeter reference) to +S. (For added conservatism, connect a 1K resistor between +S and scope ground until confirmed no surprises/not needed.)
I'd focus on section 5-45 as trouble-shooting guidance, especially paragraph 2. Given the output seems to be frozen high, I'd pursue Table 5-5.
BTW, what time zone are you in?
My imagined approach for this supply:
I'd confirm back-panel terminals are strapped as depicted in the schematic, page 120. Note that much of manual uses +S as measurement reference. Consequently, I'd make a power-off ohmmeter test to make sure there's no continuity between +S and earth ground. With confirmed isolation between +S (by extension, the entire regulator) and ground, I'd be comfortable connecting scope ground (and multimeter reference) to +S. (For added conservatism, connect a 1K resistor between +S and scope ground until confirmed no surprises/not needed.)
I'd focus on section 5-45 as trouble-shooting guidance, especially paragraph 2. Given the output seems to be frozen high, I'd pursue Table 5-5.
BTW, what time zone are you in?
Here is a very useful link to a cross reference between HP part numbers and commercial parts: https://www.qsl.net/n9zia/hp/index.html Some HP semi's are special selections or custom IC's but most are COTS parts.
Thanks 1audio for the useful HP parts link! I have more old, broken HP stuff and that link is great.
And thanks to you again techtool. I appreciate the tips. My multimeters do have diode test and I will do some diode and transistor testing.
Hopefully you sleep like a normal person. 🙂
Well, I have to fess up. The strapping pattern is not as pictured in Fig. 3.2. (post 14)
The other supply is the same. No strap between ground and any other terminal.
I am going to put the strap to ground on now.
Well, I have to fess up. The strapping pattern is not as pictured in Fig. 3.2. (post 14)
The other supply is the same. No strap between ground and any other terminal.
I am going to put the strap to ground on now.
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new Table 5-3 values with normal strapping
6.12V normal Vdc 6.2
4.66V normal Vdc 6.2
10.42V normal Vdc 12.4 (this value starts at 12.2V and settles at 10.42 in a few seconds)
28.17V normal Vdc 24
4.56V normal Vdc 4.4
30.6V normal Vdc 28
41.1V normal Vdc 38
6.12V normal Vdc 6.2
4.66V normal Vdc 6.2
10.42V normal Vdc 12.4 (this value starts at 12.2V and settles at 10.42 in a few seconds)
28.17V normal Vdc 24
4.56V normal Vdc 4.4
30.6V normal Vdc 28
41.1V normal Vdc 38
Hi again,
I'll suggest a few readings and a couple experiments to narrow the search.
I can tell the suggested meter measurements in Table 5-3 are arranged to generate positive meter deflection on classic analog voltmeters. As a convenience, you can tie your DVM reference lead to +S and report readings as signed DVM measurements.
Using +S as the reference, I surmise you'll observe more -30V at -S. Would you monitor A8 as you exercise the Voltage control pot? The observed DVM voltage should vary smoothly as you rotate the control. Assuming this is the case, leave the control at mid-rotation and note the A8 voltage for later reference.
Next, would measure a bunch of test points:
TP 11,12,13,16,17,19,22,23,24,26,27,38,41?
I hope these will narrow the search, and lead to fault-confirming experiments. 😉
Thanks!
I'll suggest a few readings and a couple experiments to narrow the search.
I can tell the suggested meter measurements in Table 5-3 are arranged to generate positive meter deflection on classic analog voltmeters. As a convenience, you can tie your DVM reference lead to +S and report readings as signed DVM measurements.
Using +S as the reference, I surmise you'll observe more -30V at -S. Would you monitor A8 as you exercise the Voltage control pot? The observed DVM voltage should vary smoothly as you rotate the control. Assuming this is the case, leave the control at mid-rotation and note the A8 voltage for later reference.
Next, would measure a bunch of test points:
TP 11,12,13,16,17,19,22,23,24,26,27,38,41?
I hope these will narrow the search, and lead to fault-confirming experiments. 😉
Thanks!
Thanks BSST I'll grab he measurements that you list.
I have been trying to figure out why TP27 and -S bounces from 24V to 0V to 24V to 0V to 24V, etc.
(The reading really go more like 23, 0, 25, 0, 22, etc.) Schematic says it is supposed to be 38V. This is with the selector switch at 24V; it acts
different with the switch at 2.4V.
I have been trying to figure out why TP27 and -S bounces from 24V to 0V to 24V to 0V to 24V, etc.
(The reading really go more like 23, 0, 25, 0, 22, etc.) Schematic says it is supposed to be 38V. This is with the selector switch at 24V; it acts
different with the switch at 2.4V.
Would you describe this phenomenon as an oscillation with a consistent period and repeatable dynamics, or is chaotic, random, noisy? The behavior seems slow; any correlated behavior across C6? Does it "feel" causative or only a reaction? Also, I'm under the impression the meter circuit is only monitoring and not involved with the regulator dynamics. But your DVM sees regulator behavior change with meter range?
Apparently this is a dual supply. Is the other channel working properly--- or at least failing in a more static manner? If the latter, I suggest trying to get the more constant section working properly, and then returning to the erratic half. Having a working model may be a good reference for normal behavior.
I doubt this is the culprit, but I am bothered by some of the solder joints in your first post, especially the joint that's at about 4 o'clock re the Phillips-head screw. I've seen similar looking joints that were in fact open or intermittent. I recommend wicking this joint clean and trying to work the component lead a bit farther through the hole. The core of the lead may be steel and not receptive to solder, but the lead's cylindrical surface should be tin-plated and wet to 60/40 solder if you can get enough accessible area.
I surmise this supply has been worked-on in the past. What portion of the circuit got prior attention?
Apparently this is a dual supply. Is the other channel working properly--- or at least failing in a more static manner? If the latter, I suggest trying to get the more constant section working properly, and then returning to the erratic half. Having a working model may be a good reference for normal behavior.
I doubt this is the culprit, but I am bothered by some of the solder joints in your first post, especially the joint that's at about 4 o'clock re the Phillips-head screw. I've seen similar looking joints that were in fact open or intermittent. I recommend wicking this joint clean and trying to work the component lead a bit farther through the hole. The core of the lead may be steel and not receptive to solder, but the lead's cylindrical surface should be tin-plated and wet to 60/40 solder if you can get enough accessible area.
I surmise this supply has been worked-on in the past. What portion of the circuit got prior attention?
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Although I didn't time it, it seemed a consistent time period to me. I only noticed a different behavior of the whole unit when changing to 2.4V. I never did any measurements.
Both sections of the dual supply seemed to have similar behavior. I believe they were linked in operation. Any work done prior to me is unknown, I bought the not working units in an auction. I only have one working unit now since I broke one CR4 rectifier.
Is this the solder joint that you meant?
Both sections of the dual supply seemed to have similar behavior. I believe they were linked in operation. Any work done prior to me is unknown, I bought the not working units in an auction. I only have one working unit now since I broke one CR4 rectifier.
Is this the solder joint that you meant?
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Reading with +S connected to meter positive lead.
Meter common: 11=2.8V 12=3.4V 13=2.66mV 16=3.4V 17=2.8V 19=3.4V
22=0.65V 23=7.3mV 26=1.49V 27=0.74V 38=25.77V 41=4.5V
It seems what I thought was flux on the back of the boards doesn't come off using contact cleaner.
Meter common: 11=2.8V 12=3.4V 13=2.66mV 16=3.4V 17=2.8V 19=3.4V
22=0.65V 23=7.3mV 26=1.49V 27=0.74V 38=25.77V 41=4.5V
It seems what I thought was flux on the back of the boards doesn't come off using contact cleaner.
I need to find and learn tools to mark-up pics. ;(
In the the pic above, the referenced screw head is about 30% down from top, 55% from left. The suspicious joint is slightly down and right of the screw, is flux-covered, and the component lead looks like the center of a moon crater. Sorry for such inept targeting.
Thanks for readings. I'll ruminate for a bit.