11 Jun
2008
11 Jun
'08
2:31 a.m.
Hello all,
just tried to power up one of my 11/34a and found it's console dead:
Power on LED and adresse display are not lit.
The PSU fans are running. Using the field maintenance print set for the
11/34a and docs provided at bitsavers I checked the voltages at the
backplane and found the +5V Voltage seems to be out of range.
Are there any docs, advices and procedures to check an repair a H7441
Powersupply?
Looking at the bottom side of the PSU untit there are three PSU's, two
H7441 with a red LED, the LED of one H7441 is lit, and a H755 with a
bulb, which is not lit. What is the meaning of these LED and bulbs?
Andreas
10 Jun
10 Jun
10:43 p.m.
Hello all,
just tried to power up one of my 11/34a and found it's console dead:
Power on LED and adresse display are not lit.
The PSU fans are running. Using the field maintenance print set for the
11/34a and docs provided at bitsavers I checked the voltages at the
backplane and found the +5V Voltage seems to be out of range.
What voltage are you getting there?
Are there any docs, advices and procedures to check an repair a H7441
Powersupply?
The H7441 is a switching regualtor which takes in about 20-30V AC from
the large transformer in the middle of the PSU chassis and gives out 5V.
It has overcurrent protection (of course), so a short somwhere else in
the machine may cause the supply to shut down.
These supplies will, in my experience, run without any load. Maybe try
unplugging the backplane power conenctors (the 6 pin and 15 pin
mate-n-lock ones) and seeing what you get then.
Looking at the bottom side of the PSU untit there are three PSU's, two
H7441 with a red LED, the LED of one H7441 is lit, and a H755 with a
bulb, which is not lit. What is the meaning of these LED and bulbs?
The indicators are simply connected across the ouytput of the PSU block
(from the output rail to ground). If it's lit, it means that block is
giving out _something_. If it's out, then either there's no output, or
the bulb has failed (!).
-tony
12 Jun
12 Jun
6:38 a.m.
Tony and Christian,
thank you for your advices.
The measured voltage is about 1,5V.
I'll pull all boards and measure again before trying to dismount the PSU
(Its the middle one).
Andreas
Hello all,
just tried to power up one of my 11/34a and found it's console dead:
Power on LED and adresse display are not lit.
The PSU fans are running. Using the field maintenance print set for the
11/34a and docs provided at bitsavers I checked the voltages at the
backplane and found the +5V Voltage seems to be out of range.
What voltage are you getting there?
Are there any docs, advices and procedures to
check an repair a H7441
Powersupply?
The H7441 is a switching regualtor which takes in about 20-30V AC from
the large transformer in the middle of the PSU chassis and gives out 5V.
It has overcurrent protection (of course), so a short somwhere else in
the machine may cause the supply to shut down.
These supplies will, in my experience, run without any load. Maybe try
unplugging the backplane power conenctors (the 6 pin and 15 pin
mate-n-lock ones) and seeing what you get then.
Looking at the bottom side of the PSU untit there
are three PSU's, two
H7441 with a red LED, the LED of one H7441 is lit, and a H755 with a
bulb, which is not lit. What is the meaning of these LED and bulbs?
The indicators are simply connected across the ouytput of the PSU block
(from the output rail to ground). If it's lit, it means that block is
giving out _something_. If it's out, then either there's no output, or
the bulb has failed (!).
-tony
11 Jun
11 Jun
11:03 a.m.
On Wed, 11 Jun 2008, Andreas Holz wrote:
Are there any docs, advices and procedures to check an
repair a H7441
Powersupply?
The docs are in the 11/34 printset. The usual fault (at least with our DEC
power supply bricks) is the big capacitor having a short and thus blowing
the fuse. Either replace the capacitor or "repair" it with a high current
pulse which burns away the short.
Looking at the bottom side of the PSU untit there are
three PSU's, two
H7441 with a red LED, the LED of one H7441 is lit, and a H755 with a bulb,
which is not lit. What is the meaning of these LED and bulbs?
The LED (or light bulb) is connected to the output to indicate the
presence of the output voltage. The light bulbs are usually broken; I
replace them with LEDs when I have to repair these power supplies.
Christian
5879
days inactive
5880
days old
3 comments
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