I think you have a short in the board. Maybe look for anything burnt or a metal chip laying across some traces or something.
Jim Dawson
Sandy, Oregon, USA
I just had another thought. I think you said FU9 and FU10 were 6 amp fuses. Are you sure you are not installing 0.6 amp fuses? I made that mistake once.
Jim Dawson
Sandy, Oregon, USA
I think it's time to take a hard look at the AUF board, something is not right with it. A close inspection is in order.
Jim Dawson
Sandy, Oregon, USA
I wish I could tell you. I have never seen one. I would be looking for shorted diodes or something like that. Since you have 50 ohms across the 24V input terminals, I would be looking for something that turns on at power up. Maybe a relay or something.
Jim Dawson
Sandy, Oregon, USA
Jim
The fuses blow even when nothing else attached to board except dc pwr??
Do you think it could be the pwr supply itself?
Maybe the different power from the rpc was enough
to damage it?
Is it possible for a pwr supply to put out dc voltage but still have a damaged bridge rectifier or capacitor?
It's possible, maybe one of the diodes in the bridge rectifier is bad. It's cheap to replace, about $5 or so. One that's rated 50V or higher will work fine.
It could I suppose, but that would be pretty unusual.Maybe the different power from the rpc was enough
to damage it?
Maybe, I guess it would depend on exactly how the rectifier failed. The capacitor could be damaged by going way over voltage, but I can't figure out how that would affect FU9, maybe FU10 if the cap was shorted.Is it possible for a pwr supply to put out dc voltage but still have a damaged bridge rectifier or capacitor?
On thing you could try is to connect two 12V light bulbs (tail light?) in series, and test the PS that way. That would tell you if the PS operates correctly under load.
Jim Dawson
Sandy, Oregon, USA
Yes, I would have expected them both to light to normal brightness. Try that again, but measure the voltage across the bulbs or at the cap. You should see around 24 volts. If it's a lot less, maybe the bridge rectifier is bad.
Jim Dawson
Sandy, Oregon, USA
the bulbs have to be identical
other wise one will heat up faster so most of the voltage is dropped across its filament
and the other will remain cold and dark
depending on the fuses used for FU9 & FU10
it may be normal for a short circuit to blow both fuses
do you have a link to a PDF manual with a schematic showing the connections to the AUF board ?
a photo of the power supply and AUF board would be helpful
having only worked on a bridgeport once to help a member trace a fault that was blowing fuses -
with the aid of the schematic I had predicted 3 possible faults in advance including
as it turned out a short between the armature of a servo motor and earth that proved to be the problem
John
PS
I note both fuses are 6A so I would expect a short will blower both fuses
PPS
the only photo of a AFU board does not show enough detail
Attachment 391736
but I guess at the top leff is a 5V regulator for the logic devices
top right 9 transistors for outputs
and at the bottom of the board 4 solid state relays
if you have two transistors connected as a totem pole output
then only one can be on at a time other wise the supply will be short circuited
one to switch the output to ground
and the other to switch the output to the positive supply (+24V ?)
the only part number that's just readable is the 70M-OAC5A solid state relay
looking at the power supply
the capacitor looks in good condition
the black rubber seal is OK and the grey vent plug in place and the blue plastic sleeve shows no sign the capacitor has over heated
I can not read any more part numbers for the components on the AUF board
what is the part numbers on the 9 devices I expected in post 34 could be 9 transistors connected to the output terminals ?
assuming they are for open collector outputs to drive 24V relays or solenoids
thing don't add up as I can only see 8 diodes next to the connectors
I assume the voltage regulator U4 in your photo will be a "7805" regulator
Fairchild for instance add a "LM" prefix so their part number will be LM7805
with such a small heatsink I would not expect its supplying any thing near the 1A that a "7805" regulator can supply
since it appears to be only supplying the 52 pin Motorola controller , 20 pin 74 series data buffer (74245 ?) and
four 8 pin IC's that may be optp-isolators
I assume the AC transformer connections 1 & 2 are connected to the four solid state relays
john
PS
relay driver
Attachment 391752
with some controller IC's they can limit the output current so you don't need a resistor between the IC output pin and the transistor base
PPS
to follow up the reference in post 34
AdeV's bridgeport with the faulty servo motor can be found here
https://www.cnczone.com/forums/bridg...ing-fuses.html
by post 10 , I had worked out what needed to be tested,