11 Oct
2015
11 Oct
'15
12:07 p.m.
On 2015-Oct-10, at 8:44 PM, Josh Dersch wrote:
. . .
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?