[Info-vax] BA23 Cooling and Power Supply Questions

[vaxorcist]

I have several BA23 enclosures with differing cooling assemblies and
power supplies.
I'm not sure everything is still as it once was when it was sold.

Questions concerning the BA23 cooling and PSUs:

Where/when and in what combinations were the following cooling options
used:

- With/without fan speed control (70-22643-01; regulates from 5.9 V
[cold] to 10.3 V [warm] with 12 V input)

- With/without front fan baffle/cowling (70-21506-01)

- Full/reduced fan voltage (4 possible H7864 settings; 12.2 V, 11.5 V,
10.8 V, 10.1 V)

What are the differences between the three PSU versions (besides the
known 12 V 6A/7A)?

Known facts:

A sticker under the PSU tells that the fan speed control is to be used
with the 12 V setting only
(which makes sense)

Assumptions:

The front fan baffle/cowling accomplishes that most of the front fan
cooling effect is concentrated on the PSU and card cage; the cooling
of the two drive bays at the front of the BA23 will get worse because
of that.

A fully loaded card cage with power consuming modules might be a
reason to use the baffle.
Using an RD53 and a TK50 in the front drive bays might require more
intensive cooling directed to the bays by not employing the baffle.

Quotes on the baffle:

EK-186AA-MG-001 BA23 Enclosure Maintenance.pdf (10/88)

Page 3-24:
"On some systems, remove the fan baffle and baffle holder from the
front fan."

Page 3-31:
Figure 3-20: Accessing the Front Fan: "OLDER SYSTEMS ONLY" [relates to
the baffle removal]

EK-MIC11-SG-001 MicroPDP-11 Systems-2.pdf (09/85)

Page 8-32:
"Remove the fan cowling and cowling holder (if present)."

Three versions of PSU H7864:

H7864   (30-20444-00) 5V, 36A / 12V 6A
H7864-A (30-21749-01) 5V, 36A / 12V 7A
H7864-B ???

Quotes on the PSU versions and fan voltage settings:

EK-186AA-MG-001 BA23 Enclosure Maintenance.pdf (10/88)

Page 1-14:
"There are three variations of the power supply, depending on the
enclosure model number: H7864, H7864-A, or H7864-B."

"The power supply has also two +10 Vdc at 0.45 A fan outputs for the
front and rear dc fans. You can increase the fan voltages to 12 Vdc by
changing a power supply jumper. However, the KA630 CPU module's
thermal and acoustical specifications are based on the +10 volt
setting."

Page 3-2: Table 3-1 BA23 FRUs

??? Who can shed some light on this ???


Regards,

Ulli