Yes, that's it. What's the pot's ref des, out of curiosity?
Much to my surprise, it looks like current limit might be on the verge of asserting control. Would you do an ohmmeter check to confirm R16A, R16B are viable? It should show a sensible resistance between A3 and A5. Again with +S as reference, would you measure A1,A5(=A3=A4),TP 14,15,16?
Much to my surprise, it looks like current limit might be on the verge of asserting control. Would you do an ohmmeter check to confirm R16A, R16B are viable? It should show a sensible resistance between A3 and A5. Again with +S as reference, would you measure A1,A5(=A3=A4),TP 14,15,16?
I think you mean between A1 & A5 == a range of 14.3 ohm to 1.5MOhm
A1=1.3mV A5=0.53V TP14=0.51V TP15=10.2mV TP16=3.45V
sorry but I don't follow?
lol It looks decent now -- all the stuff was piled in heap on the rack when I got it.
R63 is an example of a Reference Designator (Slang: Ref Des). They together schematic circuit elements, parts list, PCB design files, etc.
Ok, suspicious data in this area:
1. Schematic indicates nominal TP 16 is 1.5V, but observed 3.45V may be sufficient to assert current limiting, though hard to reconcile this with elevated output voltage.
2. You indicate 14.3 ohm to 1.5MOhm. I'm not sure what to make of that. For greater clarity, I suggest removing the link at A3 so that resistance through R16 can be measured independently of other circuitry. Resistance should range up to 1.8K+20 ohms with control rotation. Restore link after measuring.
3. You measure about about 0.51V at TP14. Can you manipulate the current limit control to lower TP14 and consequently TP16 voltages? How low can you take TP16? At lowest voltage attainable, would you measure A5, TP14,16, and 23?
Ok, suspicious data in this area:
1. Schematic indicates nominal TP 16 is 1.5V, but observed 3.45V may be sufficient to assert current limiting, though hard to reconcile this with elevated output voltage.
2. You indicate 14.3 ohm to 1.5MOhm. I'm not sure what to make of that. For greater clarity, I suggest removing the link at A3 so that resistance through R16 can be measured independently of other circuitry. Resistance should range up to 1.8K+20 ohms with control rotation. Restore link after measuring.
3. You measure about about 0.51V at TP14. Can you manipulate the current limit control to lower TP14 and consequently TP16 voltages? How low can you take TP16? At lowest voltage attainable, would you measure A5, TP14,16, and 23?
I should have thought of doing that when I saw that 1.5 MOhm was way over the R16 value.
New readings are 14.2 ohm to 1.87 kOhm
Did that ---- A5= 4.47V TP14= 5.2mV TP16= 3.48V TP23= 5.3mV
Something's odd at A5. Minimal drop seen at TP23 shows minor voltage across current sensing resistors R54 and R55, as expected since no load applied to the supply. I should have also asked for measurement at A1, but it should be only a few mV different than TP23.
Would you report the variation seen at A5 as the R16 Current Control is exercised through its entire range? I would expect to see minimum A5 voltage when the control is set for max current. At max current-limit setting (minimum R16 resistance), what are A1,A5,TP14,TP16 voltages?
Thanks.
Would you report the variation seen at A5 as the R16 Current Control is exercised through its entire range? I would expect to see minimum A5 voltage when the control is set for max current. At max current-limit setting (minimum R16 resistance), what are A1,A5,TP14,TP16 voltages?
Thanks.
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I ran a series of 3 sets of measurements: Min, Midway and Max on the current control.
A1 Max 10.8mV Mid 2.7mV Min 1.5mV
A5 Max 0.59V Mid 0.52V Min 0.59V
TP14 Max 0.59V Mid 0.53V Min 0.59V
TP16 Max 0.45V Mid 2.76V Min 3.50V
A1 Max 10.8mV Mid 2.7mV Min 1.5mV
A5 Max 0.59V Mid 0.52V Min 0.59V
TP14 Max 0.59V Mid 0.53V Min 0.59V
TP16 Max 0.45V Mid 2.76V Min 3.50V
OK, a mystery to be solved: If the current control has only 14.2 ohms resistance (presumed max CW rotation) per resistance measurement in post 51, how can the voltages at A1 and A5 differ by almost 0.6V? Can you sort out this dilemma with your DVM?
PS. Are the A3,A4,A5 links in place?
PS. Are the A3,A4,A5 links in place?
The links are in place.
I disconnected the A3 link and restested.
A1=0.1mv A5=0.632V TP14=0.632V TP16=3.5V
The current control range confirmed.
I disconnected the A3 link and restested.
A1=0.1mv A5=0.632V TP14=0.632V TP16=3.5V
The current control range confirmed.
I can't think of what else to test regarding the A1 - A5 voltage discrepancy.
I did try also disconnecting the voltage control range. With both disconnected the voltage meter was still pegged.
I did try also disconnecting the voltage control range. With both disconnected the voltage meter was still pegged.
In case this helps:
The unit often shows 24V (or less depending on the voltage adjustment) when it is started with probes on S+ and S- but then
pegs the meter and goes to 41V or so after a short period.
The unit often shows 24V (or less depending on the voltage adjustment) when it is started with probes on S+ and S- but then
pegs the meter and goes to 41V or so after a short period.
Confusing symptoms, certainly.
OK. A couple more diagnostic tests, since I've steered us into the current limiting. Disconnecting all the A3,A4,A5 links is an interesting experiment, so let's do that. With these links absent, measure resistance of R18//R19-select pair, just so we know.
Leave links open and power on. The supply limit should not be in current-limit mode with these links floating, but I won't be surprised if the output voltage remains pegged.
Would you confirm -6.2V at A4? A3 should be same voltage as A1 and both should be nearly equal to TP23. What are voltages at TP14,16? And the output voltage? Assuming it doesn't respond to the Voltage Control pot, would report -S,TP 17,18,19,20,22,23,24,26,27,38,41?
Thanks again.
OK. A couple more diagnostic tests, since I've steered us into the current limiting. Disconnecting all the A3,A4,A5 links is an interesting experiment, so let's do that. With these links absent, measure resistance of R18//R19-select pair, just so we know.
Leave links open and power on. The supply limit should not be in current-limit mode with these links floating, but I won't be surprised if the output voltage remains pegged.
Would you confirm -6.2V at A4? A3 should be same voltage as A1 and both should be nearly equal to TP23. What are voltages at TP14,16? And the output voltage? Assuming it doesn't respond to the Voltage Control pot, would report -S,TP 17,18,19,20,22,23,24,26,27,38,41?
Thanks again.
Thank you BSST!
You've spent a lot of time and energy on a problem that isn't yours and I appreciate it..
Here's something that I came across:
I can't get to the component side. Measurements from underneath show R15 at 240Kohm. Spec is 5.28Kohm.
The other is R16 I think. Measures 330Ohm. Spec is 5.2 Ohm. Is it possible my measurements are right?
You've spent a lot of time and energy on a problem that isn't yours and I appreciate it..
Here's something that I came across:
I can't get to the component side. Measurements from underneath show R15 at 240Kohm. Spec is 5.28Kohm.
The other is R16 I think. Measures 330Ohm. Spec is 5.2 Ohm. Is it possible my measurements are right?
"I've steered us into the current limiting. Disconnecting all the A3,A4,A5 links is an interesting experiment, so let's do that. With these links absent,
measure resistance of R18//R19-select pair R18= 9.68 KOhm
R19= 9.68KOhm
confirm -6.2V at A4? A4= 6.11V
A3= 3.4mV
should be same voltage as A1= 3.4mV
both should be nearly equal to TP23 TP23= 0.4mV
What are voltages at TP14,16? TP14= 1.18V
TP16= 3.48V
And the output voltage?
For this I didn't know what you wanted Positive out on the front = 0
Negative out the front = -40.17
S- = 40.17
Assuming it doesn't respond to the Voltage Control pot, report
It didn't
-S= 40.17
TP 17= 2.86V
TP 18= 1.48V
TP 19= 2.47V
TP 20= 3.49V
TP 22= 0.65V
TP 23= 5.6mV
TP 24= 45.7mV
TP 26= 1.48V
TP 27= 0.74V
TP 38= 26.00V
TP 41= 6.11V
measure resistance of R18//R19-select pair R18= 9.68 KOhm
R19= 9.68KOhm
confirm -6.2V at A4? A4= 6.11V
A3= 3.4mV
should be same voltage as A1= 3.4mV
both should be nearly equal to TP23 TP23= 0.4mV
What are voltages at TP14,16? TP14= 1.18V
TP16= 3.48V
And the output voltage?
For this I didn't know what you wanted Positive out on the front = 0
Negative out the front = -40.17
S- = 40.17
Assuming it doesn't respond to the Voltage Control pot, report
It didn't
-S= 40.17
TP 17= 2.86V
TP 18= 1.48V
TP 19= 2.47V
TP 20= 3.49V
TP 22= 0.65V
TP 23= 5.6mV
TP 24= 45.7mV
TP 26= 1.48V
TP 27= 0.74V
TP 38= 26.00V
TP 41= 6.11V