Powersupply (520-5047-02) - To high voltages.

DarkSide

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Hi guys.

Im trying to figure out what is wrong with my power supply from my Jurassic Park, the bridge rectifier died, and the high voltage died, bridge rectifier has been changed and +5 volt is back, found a few dead zener diodes in the high voltage D9/D10/D11, and a dead TR4 (MJE15031) transistor, checked everything else and its within specs.

Also changed a few caps, including C10/C11, changed TR6 and TR2 no change at all.

Problem is now that +68 is +67 volt, -98 is -130 volt and -110 is -150 volts. (Wihout load, im not risking my dmd to test with load.)

Whats going on here ?

Checked the voltage going in to the power supply and 90 volt ac is at 90 volt ac, and 100 volt ac is at 111 volt, a bit high maybe, but i don't think thats why the other voltages are so high.
 
Not much input.

Well im trying to change D11 and D10 again tomorrow, if it still shows the same voltages its going in the trash, and i will order a new one.
 
Did you change D6 and D8, the 3.9v Zener (1N5528). If not, you probably should. Most likely the problem would be with D8 as the -98 and -110 come off that side.

Don't trash it, power supplies are the most rebuildable part in a machine.
 
Did you change D6 and D8, the 3.9v Zener (1N5528). If not, you probably should. Most likely the problem would be with D8 as the -98 and -110 come off that side.

Don't trash it, power supplies are the most rebuildable part in a machine.

I must confess no i did not, but they are on order, and will change them as soon the parts arrive.

I think that D6 is good because the +68 is perfect, its just the other two voltages that are giving me grief.
 
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I think that D6 is good because the +68 is perfect, its just the other two voltages that are giving me grief.

It sounds like you've replaced about all the other culprits so hopefully D8 will clear up the problem. It probably also isn't a bad idea to replace the .1 uF ceramic disc caps. Have you checked any of the resistors?
 
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It sounds like you've replaced about all the other culprits so hopefully D6 will clear up the problem. It probably also isn't a bad idea to replace the .1 uF ceramic disc caps. Have you checked any of the resistors?

Yea, all the resistors was in spec except one which was a bit low so i changed that., it should have been 1.5 kohm, but it was 1.3.

I had no luck finding the .1 uF caps anywhere, but if that power supply still not works after D6 has been changed then its going to junk, and i will buy another one.
 
Good news, the power supply works, it was the D11 Zener, guess the new one ive installed was defect.

Bad news is the PPB board is blowing TIP36C, Q3 and Q4, and the coils and diodes are okay.

Q40 on the CPU board also blows, so it look like the CPU board is damaged.

Predrivers are checked and changed, and the TIP122 at Q40 still blows, and Q3 and Q4 on the PPB.
 
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Good deal, glad you got the PS going. You can find the 0.1 uF caps here, towards the bottom of the page:
http://www.greatplainselectronics.com/Category-27.asp

Are you anywhere near KC?

Not even close, but maybe i will order from that site anyway.

Any ideas regarding the cpu board, and why the coils are locking on and transistors are blowing, during coil testing some of the flashers started flashing instead, but the L/R Relay on the PPB works fine.
 
Okay, I see now that your name changed so I realize you aren't close at all. I thought this was about a different machine. Looks like you got some good advice from Rob over on RGP. Probably good to eliminate what he mentioned before digging into the CPU.
 
Okay, I see now that your name changed so I realize you aren't close at all. I thought this was about a different machine. Looks like you got some good advice from Rob over on RGP. Probably good to eliminate what he mentioned before digging into the CPU.

Looks like he was right, only one more coil to sort out, not sure if the coil itself is bad, or something else is shorted out.

Got a new coil on order, so will change it anyway, the old one has been hot, and now it stinks :)
 
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