| |
G8MNY > TECH 13.11.24 11:05l 244 Lines 12204 Bytes #999 (0) @ WW
BID : 19850_GB7CIP
Read: GUEST
Subj: DEL 7000815 SMPSU 12V 75A Mods
Path: IW8PGT<IZ3LSV<DB0ERF<DK0WUE<PI8ZTM<CX2SA<GB7CIP
Sent: 241113/1002Z @:GB7CIP.#32.GBR.EURO #:19850 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Update Jun 16)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I bought this DEL server SMPSU at ham car boot sale. I needed 75A @ 13.8V for
my T500M HF linear. So this seemed to meet my requirements, instead of floating
a battery in the shack. But I have always wondered if a SMPSU would be RF quiet
enough for this application?
<- - - - - - - - 12" - - - - - - - ->
____________________________________ _
/// /³ /| /|\ SPEC
Jacking/// / ³ 3"
in ///___________________________________/ ³ |/ | 100-240V AC
Frame|_[------------------------------------³ ³rear ~ 930W
|³~ ³ ³ |
MAINS³ ³ /³intake 6" 3.3V @ 6.0A
IEC ³ ³/ ³ 12V @ 75.7A
LEDs³ ³ ³fans |
³ ³ ³___
ÀÄ¿ ³ / /³ \|/
Air³ ³ / / /rear
Vents³ ³/__/ /connector
³_______________________________________³/
Powering up the 930W PSU gives just the power connected green LED, until the 2
external links are put in, then 12V green LED lights. A fault yellow LED
indicates overload trip etc.
The rear connector links needed are 1-4 for +3.3V then (0V)2-23 for the +12V.
REAR CONNECTOR (my Nos)
1 5 9 13 17 21 0V 0V 0V +12V +12V +12V
.---------------------------------------------------.
| : : : : : : Û Û Û Û Û Û Û Û Û Û Û Û|
| : : : : : : Û Û Û Û Û Û Û Û Û Û Û Û|
'---------------------------------------------------'
4 8 12 16 20 24 \ _ _ _ _ _ _ 75A _ _ _ _ _ _ _ /
Pin Identified use
1 3.3V PSU control (+ve = on)
2-3 0V
4 Start voltage (+6V) link to pin 1
7 Fan speed link to 0V for slow
8 Earth wire drop compensation, put to a +Ve for +0.6V more.
9-12 0V (3.3V rail)
13-16 +3.3V output (@ 6A from small SMPSU)
23 12V PSU control (0V = on, once 3.3V is on)
SCHEMATIC (something like this?)
ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄ>+6V Start
ÚÄÄÄÄÄÄ¿Start ÚÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄ¿³ÚÄÄÄÄÄÄ¿
mains>´FilterÃÂÄ\___³Bridgeô Caps ôSmall SMÃÁ´ 3.3V ÃÄÄ<on
IEC ÀÄÄÄÄÄÄÙ³ ³ÀÄÄÄÄÄÄÙÀÄÄÄÄÄÄÙ³ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÂÄÄÄÁÂÄ>+3.3V @ 6A
100- ÀNTCÄÙ ³ ÚÄÄÄÁÄÄ¿ ³
250V R 140V @ 8A³ FANS<´PW REGÃÄ)Ä<Speed REAR
AC to 350V @3A³ ÀÄÄÄÂÄÄÙ ³
³ ÚÄÄÁÄÄÂÄÙ CONNECTOR
³ ³ 12V ÃÄÄÄ<on
ÀÄÄÄÄÄÄÄÄÄÄÄ´SMPSUÃÄÄÄ<add 0.6V
ÀÄÄÄÄÄÁÄÄÄ>+12V @ 75A
MOD TO RAISED 12V OUTPUT TO 13.8V
This involves disconnecting the mains, removing the steel cover, locating the
control IC (large surface mount IC pins) & also the voltage protection circuit
where some very fine soldering is needed! For good access, unplug the 2 cable
connectors.
== == == == == == == == ==
____ ____ ____ == == == == == == == == ==
/ \ / \ / \ 4 MAINS FETS 2 MAINS FETS
/ \/ \/ \
MAINS HT CAPS |
\ /\ /\ / ÚÄÄÄÄÄÄÄ¿ 12
\____/ \____/ \____/ ³| ± | ³ 16,,,,,,,,9 Carefully solder a 39R between
== == == == == == ³| ± | ³ ÚÄÄÄÄÅÄÄÄ¿ the 12V SMPSU IC's feedback pin
== == == == == == ³| ± | ³ ³Ú39KÙ ³ 1 & 0V pin 12, the output is
4 MAINS FETS ÀÄÄÄÄÄÄÄÙ ³³ IC ³ then raised to 13.8V but...
FET ÀÅÄÄÄÄÄÄÄÙ
ÚÄÄÄÄÄÄÄ¿ 1''''''''8
DRIVER³| ± | ³ ___________________
³| ± | ³ [ o o o o o o o o o ]
TRANSFORMERS³| ± | ³ ³"""³ ~~~~~~~~~~~~~~~~~~~
ÀÄÄÄÄÄÄÄÙ ³ ³ r
ÀÄÄÄÙ rc
ÚÄÄÄÄÄÄÄ¿ """ ³"""³c
³ ³ rr³ ³ crr r
³ ³ _______________ rcÀÄÄÄÙ
ÀÄÄÄÄÄÄÄÙ [ o o o o o o o ] """ rcrcR <-Modify
~~~~~~~~~~~~~~~ c
³"""³
³ ³
ÀÄÄÄÙ
To stop the over voltage trip, a very small SMD 10K resistor R that needs a
270R put across it, for the trip just over 13.8V. Or even a short (fine 2A fuse
wire) or a solder blob for no trip. (SMPSU rarely go over voltage, they usually
just blow up!)
Be aware when testing, some of the components are at mains potential! Use a
mains isolation transformer if doing live testing.
Result is a very stable 13.8V that trips out just over 75A, ideal for full
performance from ham gear & floating with 12V batteries etc. N.B. With an
external battery (SMPSU OFF) the fans spin slowly, battery drain is 400mA !
MOD TO SLOW DOWN & CONTROL FAN SPEED
The two 3 wire 12V 0.45A fans, run from 3.3V or 12V via a pulse width speed
controller. So to thermally control the fan, I used a 100kê thermistor (old
telephone bell circuit type) in a heat-shrink sleeve, placed near the front of
the PSU exiting air to gently control the fan speed with the aid of a high gain
NPN.
nearby PCB pad A 2M2 sets the temperature that the thermistor just
+13.8V<ÄÄÄÄÄÄ¿ lets the high gain NPN conduct to keep the fans slow.
2M2 A wire under the little rear PCB picks up pin 7.
pin7<ÄÄÄÄ¿ ³
Fan \³ ³u1 Components are mounted on the back of the connector &
Speed NPNÃÄÁÂÄÄÄÄ¿ positioned so as to not to foul the fan/plate!
e/³ === Therm
0V<ÄÄÄÄÁÄÄÄÄÁÄÄÄÄÙ When hot exit air warms the thermistor, it turns off
the NPN & the Fans slowly speed up to full speed.
AF noise is very low on slow speed, & the air temp hardly rises on SSB mode.
But for full continuous rating, say on CW modes like FSTV, QRO PSK31 & or with
a hot ambient, the faster fan speed might be needed.
MOD FOR A SMALL DVM DISPLAY
A small 3 digit LED IC sized DISPLAY can be mounted next to the status LEDs
behind the front grill, & wired up to the rear 13.8V large pad (wires threaded
into the heatshrink) care must be taken not to sort out the DC!
screw post (o)mains earth screw
__ LEDs __ ______________
³O ³______³Oo³³O ³[] [] []³ O³
³ ()()() ³À¿ ³[] [].[]³ ÚÙSMALL DVM
STATUS ³ ³\\~~~~~~~~~~~~ DISPLAY PCB
LED PCBÀÄÄÄÄÄÄÄÄÄÄÄÄÙOverlap
Front PCBs holes Behind
A "hard wire tie" through the small LED PCB hole next to the locating LED PCB
hole, is enough to support the small display behind it. Make sure neither the
case or mains earth screws foul display PCB. (bend "post" as needed,)
MOD FOR MAINS SWITCH
I put in a small mains switch behind the existing front panel hole, but there
is not much room. Paralleling contacts gives the switch better reliability at
this power.
I also turned around the shrouded IEC filtered mains socket 180ø, so that a
right angle IEC plug lead now goes under the PSU (large feet). To removed the
IEC socket (needed to free the main PCB) the 4 metal corner springs have to be
pressed in & socket worked out at the same time.
switch ===== (Caps with bleed Rs) Fuse Start Relay
LùÄÄo\oÄ>>Ä(((()ÂÄÄÂÄÄ¿ ÚÄÄÂÄÄ¿ ÚÄÄÂÄÄÂo-oÄÄÂÄ\_____ =====
IEC ³ === (((() === (((() === ³ ³ ³ ~ +Ä(((()ÄÂÄÄÂÄÄÂÄ>
Filtered === ³ ===== ³ ===== ³ === ÃÄNTCÄÙ BRIDGE === ³ ===
Socket u1³ ³ (((() ³ (((() ³ ³u1 VDR RECTIFTER ³ === ³
NùÄÄÄÄÄÄ>>ÄÄÄÄÄÄÁÄÄ)ÄÄ´ ÃÄÄ)ÄÄÙ ÃÄÄ)ÄÄÁÄÄÄÄÄÁÄÄÄÄÄÄÄ~ -ÄÄÄÄÄÄÄÁÄÄÁÄÄÁÄ>
Spade ³ === === ³ === ³ (MOS) 3x 330uF 450V
EùÂÄÄÄ¿ ÃÄÄÁÄÄÄÁÄÄÁÄÄÄÄÄÄÁÄÄÙ ____
_³_ _³_Earth _³_PCB rear PCB_³_ 0V DC
/// ///screw ///screw connector screw///
The mains plug IEC lead must be fused @ 5A (UK 13A 240V plugs), as an arcing
mains plug will take out a 3A fuse when suddenly charging up the 990uF (Xc=1R5
@ 100Hz!) if the start cycle relay is still closed, or the NTC Rs have not
cooled down!
On a small generator it wants to take 1kW, so if the mains dips at all, the
SMPSU increases the mains current, presenting a negative Z mains load! This can
overload the generator & dangerous "stop start mains oscillation" occures.
MOD TO SWITCH ON 12V FROM PTT
As I only use this SMPSU for my 400W HF PA & it is 0V controlled.
___ _______
Mic>Ä´RIGÃÄÄÄÄ´400W PAÃÄ>ANT
³pttÃÄÂÄÄ´ptt ³ So it can be directly connected
ÀÄÂÄÙ R ÀÄÄÄÄÂÄÄÙ (via a resistor & diode if needed) to
_³_ ³ __³__ the rig PTT-PA control line for less
³PSU³ À´<ÃÄ´SMPSU³ QRM on Rx. (N.B. 3.3V SMPSU still runs!)
ÀÄÂÄÙ onÀÄÄÂÄÄÙ
MainsÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÙ
But this may not be quick enough? However I found the RFI levels are too low to
bother with this option, & I can always power down the PSU leaving the Rx on my
linear PSU if needed.
FINNISHING OFF
I took off the front jacking in frame, & cut off the front steel lobes & filed
edges smooth. Rubber feet were glued on after grinding some "key" into the
surface. Then I took off the steel case, I cleaned & painted it, masking off
the metal-metal facing edges to make good RF case to case contact.
/ / / REAR /
/ FRONT / / ______________/
/________________/ /_/³o o o o³
³ LEDs 13.8 ³ / ³±³³ Air Filter ³ /
³ ³ / ³ð³³ ³ /
³ IEC SW ³ / ³ð³ß\ o o o³/
³___ Ý__________³/ ³ð³ß\\~~~~~~~~~feet
feet \\ feet ~ 75A Leads
mains cable tied together
I made an air filter from plastic scouring pad, cut to size & 8 holes burnt
into it to match rubber fan stalks.
For DC leads, I burnt 2 holes in the side of the PCB connector by the Fans to
take the 2x 75A DC 30cm long flex cables. Splayed their wire ends to fill
between the 3 copper spade grips & quickly soldered up with a hot heavy iron,
so not to melt the PCB connector. Then I melted in some heat glue to protect
the high current connections. This gives some cable support as well as cables
ties too.
ON AIR
The RF QRM from the 110kHz 12V inverter switching is very low level, due to the
complex mains filter. With a spectrum analyser & ferrite ring pickup, the mains
cable RFI was very low too. But magnetically quite loud near the box case, as
the earthed steel case is very thin. (originally in use it had a 2nd metal
shroud in a rack)
A wobbly RF carrier is only very slightly noticeable on 160/80/40m with a
nearby wire aerial (not at all heard on distant garden dipole aerial) & mostly
well below my neighbour's TV/PC QRM. But a further "mains filter adapter" did
remove nearly all traces of the wobbly carrier on my shack noise aerial wire.
All seems every good, DC is better regulated than my float battery system & 30A
PSU.
Power consumption with no load & fans on slow it was 26W (45VA).
SPARE SMPSU
At another Ham rally, I bought a second one as a spare & that has been modified
OK too, with no problems.
Also see my Tech buls "DEL A870P7 SMPSU 12V 70A", "Switch Mode PS Principles"
"Clip on QRM Probe", "Mains Plugtop Filter Adapter",
"Reducing Electronic RF QRM", & "T500M 12V 500W HF Linear"
Why don't U sent an interesting Bul?
73 De John, G8MNY @ GB7CIP
Read previous mail | Read next mail
| |
