Black Hole
Gottlieb, 1981ok, i measured power supply voltages using the test points.
the 5v test point reads 6v and i can get it ss low as 5.88v using the trim pot
the 42v test point reads 60v!!
the 60v test point reads 84v!!
Im making a assumption that this isn't normal or good?
what steps should I take to rectify this?
Quoted from itsab67:ok, i measured power supply voltages using the test points.
the 5v test point reads 6v and i can get it ss low as 5.88v using the trim pot
the 42v test point reads 60v!!
the 60v test point reads 84v!!
Im making a assumption that this isn't normal or good?
what steps should I take to rectify this?
no one has any info?
Could be several things but all in the same area.
Q1 is either shorted... or being held high by the biasing circuit.
Cheapest and easiest is the biasing circuit. With meter ground to TP3 -- what voltages do you get at E1 and E3?
E1 will probably be close to your 84V reading.
E2 measures CR5 voltage which is what sets the output voltage and *should* be close to 62V.
Quoted from G-P-E:Could be several things but all in the same area.
Q1 is either shorted... or being held high by the biasing circuit.
Cheapest and easiest is the biasing circuit. With meter ground to TP3 -- what voltages do you get at E1 and E3?
E1 will probably be close to your 84V reading.
E2 measures CR5 voltage which is what sets the output voltage and *should* be close to 62V.
Sorry, been on Holidays, i had hoped to answer you much sooner.
E1 measures 106v! and E2 measures 86v! would replacing cr5 be a good place to start? voltage seems way to high.
Quoted from G-P-E:E1 is quite high but could be due to a no load condition.
The E2 at 86V is wrong, should be at about 62V. CR5 is what sets that voltage so first thing I would suspect is CR5.
what would be the best way to measure so i can determine if E1 is a no load condition or not?
Are you measuring the voltages with or without load on the supply? Nothing plugged onto J3 = no load. Something plugged onto J3 = loaded (unless cables are disconnected at other end).
You could also have a meter that's measuring Vpeak instead of Vdc. Majority of digital meters out there will measure Vpeak if there is no real load on the supply.
To curb things a bit - *temporarily* tie a load resistor between E1 and TP3 using aligator clips. Do you have something like a 4.7K 5W resistor handy? See if that'll bring things more in line. If so, then it's a non-issue and we're just chasing our tails with the high E1 voltage.
Not sure I would mess with this, though. Just replace CR5 and give it a shot.
A better replacement for CR5 would be a 1N5372B.
Original CR5 was a 1N4759A which is a 1 watt part. During normal operation - that part continuously dissipated 0.715 Watts ... 71% of rated load => HOT! The 1N5372B is a 5W part. Larger physical size and will stay cooler.
When I do new boards - I use 1.8K resistors paired with 1N5372B's to keep heat down. I try to keep part loading at 10% or less to keep things cooler. This would bring the 1N5372B's dissipation down to 0.51W on a 5W part.
Quoted from G-P-E:Are you measuring the voltages with or without load on the supply? Nothing plugged onto J3 = no load. Something plugged onto J3 = loaded (unless cables are disconnected at other end).
You could also have a meter that's measuring Vpeak instead of Vdc. Majority of digital meters out there will measure Vpeak if there is no real load on the supply.
To curb things a bit - *temporarily* tie a load resistor between E1 and TP3 using aligator clips. Do you have something like a 4.7K 5W resistor handy? See if that'll bring things more in line. If so, then it's a non-issue and we're just chasing our tails with the high E1 voltage.
Not sure I would mess with this, though. Just replace CR5 and give it a shot.
A better replacement for CR5 would be a 1N5372B.
Original CR5 was a 1N4759A which is a 1 watt part. During normal operation - that part continuously dissipated 0.715 Watts ... 71% of rated load => HOT! The 1N5372B is a 5W part. Larger physical size and will stay cooler.
When I do new boards - I use 1.8K resistors paired with 1N5372B's to keep heat down. I try to keep part loading at 10% or less to keep things cooler. This would bring the 1N5372B's dissipation down to 0.51W on a 5W part.
im measuring with all connections comected, so loaded i guess. all my voltages are high everywhere. even right at the bridge rectifiers in the bottom powersupply are all measuring more than what they should be... so the power supply board up top is being feed a higher voltage then it should could be why im measuring high up there?
The game works, and seems fine, but, i reluctant to use it if things are being overloaded. id feel better if my 5 volts to the mcu board was 5 volts. im getting 5.8 volts with the trim pot turned all the way up {500 ohm trim pot). ive replaced all caps, zenors, transistors and rectifiers on the upper power supply board and rectifiers, caps, resistor on lower power supply.... yet all voltages everywhere are high.
5 vokt is 5.8 volt
40volt is 54 volt
60 volts is 84 vokts
30 volts is 34 volts
Quoted from G-P-E:Check your transformer voltages. You might have the transformer input jumpers wrong.
Everything checks out ok with the transformee, ive replaced all components on both lower and upper power supplies.... still everything measures to high. So, i went out and bought a new voltmeter.... and with the new meter ALL my voltages and bang on. Im pleased all is good, but i sure wasted lots of time trying to figure out the problem. Thanks so very much for your help. And the old meter is going in the trash.
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