11 Oct
2015
11 Oct
'15
6:19 p.m.
On Sun, Oct 11, 2015 at 12:07 PM, Brent Hilpert <hilpert at cs.ubc.ca> wrote:
On 2015-Oct-10, at 8:44 PM, Josh Dersch wrote:
. . .
Awesome, thanks for the detailed writeup. Things make sense, or at least
more sense.
I went to take a look at the +13V supply and of *course* once I did things
started working, mysteriously. The relay clicks over and I get +13V and it
looks like the bias voltages are present as well. All I did was tack on a
wire to the 10/L header pins on the bias/interface board (+13V)...
So that's... good, but I have no idea what the actual problem is/was.
Going to clean the connectors and look for cold solder joints (again :))
just to rule that out. I'll get a dummy load hooked up and see if anything
happens when I throw the front panel switch.
Thanks again, all.
- Josh
Thanks for the explanation. I tacked on some
wires to the bias board (to
bring them out for safe probing); the wires are connected to the 5V logic
supply and the +12V bias supply and I get nothing at all out of them when
the H7140 is turned on.
I'm slowly coming to terms with the schematic but I'm not quite clear
where
these two voltages are being generated. I note
from the block diagram
that
the +15 and +12 are rectified on the motherboard
(backplane) -- which
should make it GREAT fun to probe. So it looks like some careful
disassembly is now required (unless there's a trick to probing things on
the backplane...)
Note that the "+13V" supply must also be present, and it's generated and
referenced on the Mains side of everything.
In summary, for the relay to activate:
1) The Mains is rectified and filtered to produce Mains +300V via
bridge LNS-CR1 and caps LNS-C1,C2.
2) MOB-D1,D2,R1,R2 form a voltage divider / balancing network to
produce Mains +150VDC.
They also balance the voltage across the Mains filter caps
(LNS-C1,C2) when in 220VAC mode.
** 3) Mains +150V is regulated via MOB-R3, BIB-Q6, BIB-C4, BIB-D11 to
produce Mains +13V, referenced
from MOB-D2 feeding ("START-UP DRIVE") the base of BIB-Q6.
16V zener BIB-D12 additionally clamps this level.
4) Mains +13V supplies 555 oscillator BIB-E2, LM393 comparator
BIB-E3b and associated circuitry. These form a SMPSU with MOB-T1.
5) The output from MOB-T1 is half-wave rectified in both
polarities to produce BIB +12V (MOB-D6,C3) and BIB -15V
(MOB-R4,R5,R6,D4,C2,D5).
6) BIB +12V produces BIB +5V via regulator BIB-E1.
7) BIB-E3a forms a voltage level sensor with reference zener
BIB-D13 and voltage divider BIB-R3,R4,R27 that must detect an adequate
level on
the Mains +300V to turn on the relay via BIB-Q11, BIB-E5,
BIB-E4a.
LNS = Line Supply section PDF.146
MOB = Motherboard PDF.162
BIB = Bias & Interface Board PDF.166-168
** There appears to be something inconsistent in the schematic here in
that the base of BIB-Q6 is fed by +10V from MOB-D2, which would leave the
Mains +13V at more like +8V.
Am I missing something? - is there anywhere in that doc that explicitly
declares the association between the 2-dozen connectors, for example, that
Line Supply P1 & P2 connect to Motherboard J5 & J4, and that Bias and
Interface Board J1 & J2 connect to Motherboard J7 & J6?