Just powered up power supply for the first time. 18 plus 18 volt Anteks x formers, dual supply. Slowly ramping up the variac, the LEDs lite up, at 115-120 volts I measured at the outputs of the power supply, red multimeter lead to plus, black multimeter lead to minus and read 40 volts on each side quickly powered down. No sizzle, smoke or funny business.
Now, I was expecting to read much less....anxiety attack. Seems good, I was thinking I would read something less than half that, 18ish or so.....
Is something amiss, or do I just need to un fart brain function?
Russellc
Now, I was expecting to read much less....anxiety attack. Seems good, I was thinking I would read something less than half that, 18ish or so.....
Is something amiss, or do I just need to un fart brain function?
Russellc
More weirdness leaving me to believe something amiss. Measuring outputs on power supply, measurements are consistent on both sides but odd. Build guide says all outputs should measure under 18 volts. All LEDs light up fine.
However measuring from - and + side of each output is 41 volts when variac is up to 120 volts. Same on both sides, one is 41.2, one is 41.4.
When measuring from ground of out put on one side, to + is 17.18, and from ground to - is 24.08. Going to other side, ground to + is 17.41, and from ground to - is 24.07.
Oddly consistent, something wired wrong somewhere...negative sides both off? Was awful careful with correctly placing Jfets, maybe something mixed up...
Russellc
However measuring from - and + side of each output is 41 volts when variac is up to 120 volts. Same on both sides, one is 41.2, one is 41.4.
When measuring from ground of out put on one side, to + is 17.18, and from ground to - is 24.08. Going to other side, ground to + is 17.41, and from ground to - is 24.07.
Oddly consistent, something wired wrong somewhere...negative sides both off? Was awful careful with correctly placing Jfets, maybe something mixed up...
Russellc
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That is the unloaded power supply....wouldnt dare hook it up until correct. transformers are right, measuring at top of fuses DC is right going in, looks like proper resistors in proper places. I took a great deal of time checking and rechecking Jfet positions, recheck tomorrow with clear head.
something silly....odd that measuring at top of both fuses going into regulator section is just under 50 volts, and half of the output is correctly "regulated" to just a tad over 17 volts, but negative side is 24 volts, half of what is going in....like minus side isnt regulating, or at least not properly, 24 volts being half of what is going in as measured at top of fuse blocks...hoping for resistor mix up.
Russellc
something silly....odd that measuring at top of both fuses going into regulator section is just under 50 volts, and half of the output is correctly "regulated" to just a tad over 17 volts, but negative side is 24 volts, half of what is going in....like minus side isnt regulating, or at least not properly, 24 volts being half of what is going in as measured at top of fuse blocks...hoping for resistor mix up.
Russellc
I have a feeling it is either misplaced resistor or Jfet in regulator section. Exact same problem across both of the dual power supplies. At least I am consistent!
Russellc
On DCSTB negative sides check Vbe on Q3 Q4, also mV drop across R2. Let us know the readings. Look up close and verify the transistor types are correct in place for the minus voltage sides. Most likely a systematic misplacement/wrong component type or a blown Q3 on both negative sides. Check the RyJ values too. Its a dual mono mirrored PCB between polarities maybe you populated something twice in the wrong way or value.
RyJ values measure 1.0 ohm both sides. ( in circuit) I will measure mV drop across R2, checking placement of j fets. Dont know how to check Vbe for Q3,Q4? Since the problem is mirrored, I am speculating that something is misplaced...But if they were, wouldnt they be mixed with the others causing + side to be off too? hopefully not. Also not sure how I would have blown both - fets on both sides, but I can tear up an anvil with rubber hammer.
Russellc
Russellc
RyJ values are not wrong by some mistake 
Measure voltage between base and emitter in those transistors. That's Vbe and indicates operation or not. Usually 0.6V-0.75V. The JFET should be working, because the Led bars are alight thus fed with current, about Q3 and Q4 transistors I am suspicious of. Mainly Q4 (BC560). That one is the smallest, it can be knocked out easier from a probing mistake, some brief short etc.
Measure voltage between base and emitter in those transistors. That's Vbe and indicates operation or not. Usually 0.6V-0.75V. The JFET should be working, because the Led bars are alight thus fed with current, about Q3 and Q4 transistors I am suspicious of. Mainly Q4 (BC560). That one is the smallest, it can be knocked out easier from a probing mistake, some brief short etc.
The small resistors across the front of the board appear to be 3.2-3.3K, as to the small resistors alongside the regulators and heat sinks, the two on the outside edges and the two in the center are 100 ohm, the others 33.
Double checking schematic, but I think thats all correct, or am I getting schematic blind and not in right place? Next to remove heat sinks and have a look at the small Jfets. If out of place I will rotate to proper position...if not and new ones need to be purchased, Q3 and Q4 need to be matched to anything? Each other, or will matching fets be needed to replace all of them?
Thanks, I usually get parts placement correct, check, double check, triple check as I solder in, but something isnt right. All suggestions much appreciated.
Russellc
Double checking schematic, but I think thats all correct, or am I getting schematic blind and not in right place? Next to remove heat sinks and have a look at the small Jfets. If out of place I will rotate to proper position...if not and new ones need to be purchased, Q3 and Q4 need to be matched to anything? Each other, or will matching fets be needed to replace all of them?
Thanks, I usually get parts placement correct, check, double check, triple check as I solder in, but something isnt right. All suggestions much appreciated.
Russellc