Author Topic: DIY power supply  (Read 7111 times)

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Offline MarkF

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Re: DIY power supply
« Reply #25 on: August 13, 2018, 12:59:13 pm »
on the topic of function generators, i do have some ICL 8038 ICs that i could build one with.
i also have various arduinos and one of those cheap arduino starter kit LCD displays, as well as a small tft screen.

how would u rate the challenge level of such a project?

incidentally i have put together that XR2206 thing and BOY does it suck! lol
i might try to implement those improvements in those videos posted, but i'm not sure it's worth it.
prolly end up using it in some project for some specific task or something...

It looks like the ICL8038 works in a similar fashion to the XR2206.  I would predict a similar result.  But, it maybe a worth while exercise to gain experience since you already have the chips and they only need a few external parts and NO microprocessor required.

If you want to build a function gen, I still feel a modern DDS like the AD9834 will give you better results.  However, they are $12.00 each and have a SPI interface.  Since you already have an Arduino and some small displays, you could start by just programming the display and controls with no initial monetary investment.  Here is the display I did for my function generator to give you a starting point (There is a PIC hidden under the display):

You are definitely going to need a scope to do some debugging.

   
« Last Edit: August 19, 2018, 01:44:03 pm by MarkF »
 

Offline Pirateguy

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Re: DIY power supply
« Reply #26 on: August 13, 2018, 08:06:49 pm »
i'm not sure what is more practical, but for limited room for jacks n stuff i think i am gonna
go with the rotary switch.

my ATX has lots of red, black and yellow, but only 1 white, blue and orange wire.
there is a thick shielded bundle of wire connected to the board and power jacks that has a big switch on the other end
to be mounted in the PC case.
maybe the sense wire is in there?

i also read something about having a load resistor on one of the outputs for some reason.
thinking about pulling one off this $1 usb dummy load thing i have.

if i ever put in a high voltage output i intend to have a separate transformer, inside it's own compartment in the housing,
fully isolated from all other stuff.
maybe something like a halogen ballast or a neon sign transformer or something like that. though more likely it will just a ZVS driver,
keeping the actual high voltage stuff external.
my ATX is just a 200 watt one.


---

on the topic of fin gens: from what i understand the xr2206 is not that terrible up to 12v, and it is mainly design flaws in the
board that make this module crappy, aside from already being cheap.
hopefully i wouldn't make those mistakes and maybe i could use multiple chips for better performance.
like dedicate a chip to each waveform, or have different chips for frequency ranges or something like that...

unfortunately i don't have a proper scope.
i do have a OSD nano (first gen) but i think maybe i should hold off on this till i get a proper bench one.
 

Offline MarkF

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Re: DIY power supply
« Reply #27 on: August 14, 2018, 04:56:43 am »
I think you have that backwards -
  • Power Supply  I can think of lots of projects that would require multiple voltages. Essentially, any analog project that includes a microcontroller.  A function generator for example could require +5V, +12V and -12V.  I currently have six power supplies on my bench.

    Old ATX Power Supplies required a load on the 5V rail to start. An adapter I bought (never used) included a 10 ohm 10 watt resistor.  The adapter also included fuses.  An ATX power supply DOES NOT have any current limiting and can ruin your day.   http://dangerousprototypes.com/docs/ATX_Breakout_Board   

    IMHO: An ATX power supply is not a replacement for a proper lab supply.

  • Function Generator  In almost every case you will only use one signal at a time.  The only case I can think of would be if you needed some kind of modulation.
« Last Edit: August 15, 2018, 05:24:48 pm by MarkF »
 

Offline Pirateguy

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Re: DIY power supply
« Reply #28 on: August 14, 2018, 09:51:04 am »
well i have some 0.9A poly switches, but i also have some breakout boards
with step down converters for arduino. they have 3.3 and 5v.

also the rotary switch i have has 12 positions :D
 

Offline MarkF

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Re: DIY power supply
« Reply #29 on: August 15, 2018, 11:18:40 am »
I do like these little HP Supplies.  Not a lot of power but without a fan, they are quiet and don't take up much space.
   HP 6216A Power Supply

Also, an AD9834 DDS Signal Generator Sine/Triangle/Square Wave Generator module that you could interface your Arduino to.
   AD9834 Module
« Last Edit: August 15, 2018, 12:05:09 pm by MarkF »
 

Offline Old Printer

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Re: DIY power supply
« Reply #30 on: August 15, 2018, 12:41:24 pm »
I do like these little HP Supplies.  Not a lot of power but without a fan, they are quiet and don't take up much space.
   HP 6216A Power Supply

Ditto on the little HP's. The 6216A is good for about a half amp at 24 volts. Has both voltage and current modes, each having coarse and fine adjustments. Very well documented which is easily available online. Operation, service & schematics. With a little patience they can be had in nice shape for $50 shipped on ebay. I bought three last winter like that for my bench in a spare bedroom. Quiet and compact, built like a tank and easy to repair.
 

Offline Pirateguy

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Re: DIY power supply
« Reply #31 on: August 15, 2018, 01:09:00 pm »
 |O
 

Offline Jwillis

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Re: DIY power supply
« Reply #32 on: August 15, 2018, 03:47:51 pm »
Seems when you start to make progress you get cornered by more salesmen .I feel your pain.....Anyway.
Ok so your +5V and +12 volt will give you the most current .3 volt will probably only be a few miliamps .You can load one of the +5 volt lines with a 5 to 10 Watt power resistor connected to ground.
Difficult to say what the potential current is. Current limiting is nice to have, but not completely necessary.Unless you create dead shorts your projects will only draw as much current as it requires .You can always put in short circuit protection later if you like.
We can start by tying the yellow wires together and the black wires together.tie all the red ones together except one .We'll use that for the 5-10 Watt 10 Ohm resistor.If  yours has a switch you can use that one or shorten the bundle and use a similar switch put through the ATX case.You can use a LED and a 1 or 2k resistor for each voltage if you like to indicate which voltage you switched to.Will also indicate power on.For variable power try a buck boost variable regulator..
Maybe consider a larger enclosure than the stock enclosure.Things will most likely get pretty cramped inside.
 

Offline MarkF

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Re: DIY power supply
« Reply #33 on: August 15, 2018, 06:02:32 pm »
Seems when you start to make progress you get cornered by more salesmen .I feel your pain.....Anyway.
Ok so your +5V and +12 volt will give you the most current .3 volt will probably only be a few miliamps .You can load one of the +5 volt lines with a 5 to 10 Watt power resistor connected to ground.
Difficult to say what the potential current is. Current limiting is nice to have, but not completely necessary. Unless you create dead shorts your projects will only draw as much current as it requires .You can always put in short circuit protection later if you like.
We can start by tying the yellow wires together and the black wires together.tie all the red ones together except one .We'll use that for the 5-10 Watt 10 Ohm resistor.If  yours has a switch you can use that one or shorten the bundle and use a similar switch put through the ATX case.You can use a LED and a 1 or 2k resistor for each voltage if you like to indicate which voltage you switched to.Will also indicate power on.For variable power try a buck boost variable regulator..
Maybe consider a larger enclosure than the stock enclosure.Things will most likely get pretty cramped inside.

Fuses or No Fuses?

An ATX Power Supply has almost the same current capabilities as my MIG Welder!  If you drop a wire into a project you're testing, short the wrong pins with a probe, or a wire comes loose on a solderless breadboard -- FIREWORKS.  Accidents happen.  The polyfuses the OP has would be a must in my book.  As I mentioned earlier the ATX Breakout board has the polyfuses, ATX power connector, load resistor (if needed), On/Off Switch and LED power on indicator.  Just plug and play. No need to modify the power supply or cutting off connectors and dealing with tying off unused wires.

   

From everything the OP mentioned, the ATX power supply would probably be the cleanest way to go over the wall-warts.  I can also envision projects that require multiple voltages.  NOT a rotary switch with a single output.

The OP has a lot of suggestions of what "to do" and "not do".  Plus several options of low cost items that are available to purchase.  If this all seems like too much to take in, I would stay far away from the high voltage projects mentioned!  I'm sorry if this comes off mean spirited.  It's not meant to be.  Just trying to point out the dangers.
« Last Edit: August 19, 2018, 01:43:14 pm by MarkF »
 

Offline Pirateguy

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Re: DIY power supply
« Reply #34 on: August 15, 2018, 11:55:02 pm »
well my ATX is onlu 200watt, but that still plenty to set my projects (and me) on fire.
some years there was a death in the family and i inherited a bunch of electronics stuff from this person.
including a bunch of fuses.

do those things age when not in use?
and what kind of values am i looking for?

to clarify: i want BOTH a selectable fixed voltage that i can dial in with a switch AND
a variable output that i can set with a pot.
the variable output at least will have a little panel v/a meter to tell me what is going on and the unit will have a temp display.

if i understand correctly you are saying it is better to have each output with it's own binding posts
cuz i might need to use several at the same time?

i have some breakout boards for stepping down to 3.3 and 5v for arduino. i am considering including one of those
and drawing the 3 and 5v from there instead of directly from the atx.
and for the variable output i have 317 and 338 regulators.

maybe i should make it so i can switch between a 5amp 338 one and another limited to lower current?

right now the only high voltage stuff i am screwing around with is all powered by those cheapo stun gun modules off ebay:
particularly these 2:
https://www.ebay.com/itm/15KV-High-Frequency-Inverter-Generator-High-Voltage-Electric-Ignitor-Coil-Arc/382475346892?ssPageName=STRK%3AMEBIDX%3AIT&var=651230490166&_trksid=p2057872.m2749.l2649
https://www.ebay.com/itm/High-Voltage-Pulse-Generator-Inverter-Module-Super-Arc-Pulse-Ignition-Coil-DH/362195494965?ssPageName=STRK%3AMEBIDX%3AIT&var=631407328312&_trksid=p2057872.m2749.l2649

neither of those have the cap built in and they are basically like arc lighters and will run off 2xAA.

what i want right now is to see how i can incorporate sparks as special effects for dioramas, so
it's gotta be low power anyway. dioramas tend to be fairly flammable :P
so part of the scope of my high voltage projects is to see how low i can get the amps and still have cool looking sparks.

this stuff is indeed overwhelming, especially for me as i have ADD.
that's kinda why i came here; to plan things out ahead of time (after having it checked for stupidity)
and work systematically, 1 step at a time.
 

Offline Pirateguy

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Re: DIY power supply
« Reply #35 on: August 16, 2018, 03:23:24 am »
just remembered: i still have a couple of UK wall plugs.
harvested 2x 3A fuses from those.
 

Offline MarkF

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Re: DIY power supply
« Reply #36 on: August 16, 2018, 04:34:39 am »
well my ATX is onlu 200watt, but that still plenty to set my projects (and me) on fire.

Mine too.  Just trying to drive home the point with those who think fuses are not necessary.   ;D

Quote
to clarify: i want BOTH a selectable fixed voltage that i can dial in with a switch AND a variable output that i can set with a pot.
the variable output at least will have a little panel v/a meter to tell me what is going on and the unit will have a temp display.

if i understand correctly you are saying it is better to have each output with it's own binding posts
cuz i might need to use several at the same time?

Exactly.  Separate posts for each voltage.

Quote
i have some breakout boards for stepping down to 3.3 and 5v for arduino. i am considering including one of those
and drawing the 3 and 5v from there instead of directly from the atx.
and for the variable output i have 317 and 338 regulators.

Why?  Just use the 3.3V, 5V, +12V and -12V directly from the ATX supply.
You could tap off one of the ATX +12V lines to drive a LM317/LM338 to create a 0 to 10V variable output. (I believe the cutoff for the LM317 and LM338 is around 2V.  So, you won't be able to go above 10V with a 12V input.)

Quote
maybe i should make it so i can switch between a 5amp 338 one and another limited to lower current?

You can go a long way with the ~1A polyfuses (or normal fuses) on each output voltage.  I would wait a see what your real needs are and proceed from there with something more at that point.  You may wish to buy a proper lab power supply with current and voltage adjustments.
 

Online rstofer

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Re: DIY power supply
« Reply #37 on: August 16, 2018, 04:34:55 am »
Difficult to say what the potential current is. Current limiting is nice to have, but not completely necessary.Unless you create dead shorts your projects will only draw as much current as it requires .You can always put in short circuit protection later if you like.

I would think that adjustable over-current protection would be the second most important criteria for a power supply right after voltage.  I don't always care if voltage is adjustable, I just need +- 15V and 5V but current limiting at a low level seems terribly important.  Having current foldback on a 5A supply doesn't do much to protect things.

The other day I was bringing up a Z80 project and there was an address conflict.  In effect, two sources were driving the data bus at the same time.  Not good!  I had set the current limit to 100 mA and, sure enough, the limit kicked in and the output voltage dropped to about 1V.  This potentially saved a lot of chips.

Even adding fuses doesn't do much good if they are of some high value.  I want to limit current at low mA, not low Amps.

If I didn't have the money for a real lab supply, I might try these $6 Chinese supplies just to see if they would work.

https://www.ebay.com/itm/Red-0-30V-2mA-3A-Continuously-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-PCB/201751652278

There are dozens of these supplies around, maybe some of them are satisfactory.

 

Online rstofer

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Re: DIY power supply
« Reply #38 on: August 16, 2018, 04:37:33 am »
well my ATX is onlu 200watt, but that still plenty to set my projects (and me) on fire.

Mine too.  Just trying to drive home the point with those who think fuses are not necessary.   ;D

Quote
if i understand correctly you are saying it is better to have each output with it's own binding posts
cuz i might need to use several at the same time?

Exactly.  Separate posts for each voltage.


Spaced exactly 3/4" on centers so that double plugs will fit.
 

Offline Pirateguy

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Re: DIY power supply
« Reply #39 on: August 16, 2018, 05:45:56 am »
i was thinking i would have a selector switch between differently rated fuses.
one limited to something appropriate for micros and something a little stronger for motors n stuff like that.

i was thinking of using the breakout boards cuz they come with a regulator for each output.
isn't that also a way to limit the current?
 

Offline MarkF

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Re: DIY power supply
« Reply #40 on: August 16, 2018, 09:37:18 am »
i was thinking i would have a selector switch between differently rated fuses.
one limited to something appropriate for micros and something a little stronger for motors n stuff like that.

I don't know if that would be worth while.  If you really want different current capability outputs, I would have separate output jacks.  It is far too easy to overlook a switch position. 
You could put a high current output and the variable voltage output off to the side to distinguish the difference.

Quote
i was thinking of using the breakout boards cuz they come with a regulator for each output.
isn't that also a way to limit the current?

The current limiting capabilities of those breakout boards is probably only a thermal shutdown.  Far too late to save you.  Just stick with the ATX outputs and fuses.  Just speculation not knowing the exact boards you are referirng to.

I prescribe to the K.I.S.S. (keep it simple stupid) theory.
 

Offline MarkF

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Re: DIY power supply
« Reply #41 on: August 16, 2018, 10:01:02 am »
Here's is a possible panel layout:

   

I agree with having a 3/4" horizontal spacing between the jacks. 
There is a high chance you would use the double banana plugs at some point.
« Last Edit: August 19, 2018, 01:45:33 pm by MarkF »
 

Offline sureshot

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Re: DIY power supply
« Reply #42 on: August 16, 2018, 10:21:10 am »
Once you've done your wire grouping and or binding posts, preload options...
If you choose the atx route how about this below.
Rotary switch is break before make configuration.
 

Online rhb

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Re: DIY power supply
« Reply #43 on: August 16, 2018, 10:33:53 am »
I suggest visiting thrift stores and looking for an old piece of audio gear that's cheap.  Those will usually have a good transformer for a linear supply.  Another option is to rewind the secondary of a microwave oven transformer.  That will certainly give you 0-40V at 5 A provided you add a *large* pass transistor to the LM317 with a big heatsink. For the fixed stuff just use the ATX.

Adjustable current limiting is not difficult.  For the ATX, use a comparator, a sense resistor voltage divider pot and flip flop so if overcurrent is detected it toggles the flip flop and disables the PSU power enable line until you press a reset button.

I think it would be wise to start with the ATX as a base, but in a large enough case that you can add an adjustable linear supply later.  The layout by MarkF looks very practical.  Get some cheap DMMs and add switching to monitor voltage and current using those minus the cases.
 

Offline Pirateguy

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Re: DIY power supply
« Reply #44 on: August 16, 2018, 11:37:43 am »
these are the boards i was talking about:
https://www.ebay.com/itm/5Pcs-DC-DC-12V-To-3-3V-5V-Buck-Step-down-Power-Supply-Module-For-Arduino-/352280409059?var=&hash=item0

my thinking was that instead of blowing a fuse when u use too much this would just limit the current and not deliver more then it can.
seems to make more sens then replacing fuses... although i would include those too in case of anything malfunctioning in the PSU or something like that.

so i went over the fuses i have, and looked up the codes n stuff.
apparently they come in speed ratings, are the slow ones ok for this?

also lemme see if i got anything wrong here:
remove access wires, combine multiple rails of the same output, run a wire for each output to a fuse, and from there to the jacks?
and for the variable the fuse goes between the atx and the regulator?

I suggest visiting thrift stores and looking for an old piece of audio gear that's cheap.  Those will usually have a good transformer for a linear supply.  Another option is to rewind the secondary of a microwave oven transformer.  That will certainly give you 0-40V at 5 A provided you add a *large* pass transistor to the LM317 with a big heatsink. For the fixed stuff just use the ATX.

Adjustable current limiting is not difficult.  For the ATX, use a comparator, a sense resistor voltage divider pot and flip flop so if overcurrent is detected it toggles the flip flop and disables the PSU power enable line until you press a reset button.

I think it would be wise to start with the ATX as a base, but in a large enough case that you can add an adjustable linear supply later.  The layout by MarkF looks very practical.  Get some cheap DMMs and add switching to monitor voltage and current using those minus the cases.

could i just yank the whole setup out of an extension cord that has that feature?

with large pass transistor, do you mean one that lets through a lot of current?
i have some 2N3055 ones that look pretty beefy...

for power monitoring i have a couple of panel units that show volts and amps at the same time.

for now i think i will build it all into the original ATX case as i don't have anything else right now,
and i want to take my time finding something that looks nice.
there is enough room though for a regulator circuit to do a limited variable output of 10v as suggested below.
 

Offline MarkF

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Re: DIY power supply
« Reply #45 on: August 16, 2018, 02:52:19 pm »
DO NOT TAKE THE ATX CASE APART.
The extra space is needed for air flow.

Just use the wires on the connector for the motherboard.
Cut out the wires you want to use from the connector and leave the rest.
You may wish to use the leftover wires in a future mod. Or power your function generator.
Leave the disk drive connectors alone.

You said you have polyfuses. 
I would recommend them for the low current outputs and the variable output.
They reset after the load is removed.

I would save your breakout boards for something else. 
They don't have any special current limiting.
You're not going to gain anything over using the ATX outputs with some polyfuses.

The slow-blow fuses will react slower and will take a little more current.
I would suggest 0.5A for the low current outputs and 5A for the high current output.

Something in the 0.5A to 1A range for the variable output.
Put the fuse on the output of the variable supply. Also, you will need a heat sink and cooling.
You will need to carefully consider the grounds for this if you drive the input from something other than the +12V of the ATX supply.

You are probably okay not having fuses for the internal things you power from the ATX.  Just for lines leaving the box.

You also need to be careful how you wire those volt/amp panel meters. 
You especially need to check the low sides of the input power, volt meter and amp meter. 
Some have the low sides tied together and will short what you're trying to measure if connected wrong.

Like I said before, I would not get overly ambitious for a first project with unknown needs.  Just the basics for now.
« Last Edit: August 16, 2018, 03:11:42 pm by MarkF »
 

Offline Pirateguy

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Re: DIY power supply
« Reply #46 on: August 16, 2018, 05:01:35 pm »
lol i already cut off the connectors, but no worries, i may be a noob but this isn't the first time i heat up a soldering iron.
(and i have several half finished robots to show for it :P)
and don't worry, i know all about discharging the caps n stuff. u could safely shower with this thing right now.
i intend to desolder the wires i don't need instead of cutting them, and will have no trouble adding new ones if needed.
and the case, once i find a larger enclosure for it all, i will ditch entirely.

with the room i have available, and some reworking of the wiring, changing yuge connectors for solder connections,
i think there is more then enough room for air flow and the circuit for the regulator for the variable output
shouldn't take up too much space.
only the interface will take up space, and it's not too terrible (again after taking care of some unnecessarily bulky plugs n stuff.)
also there will be a thermometer on the thing, so if i run into trouble i should get fair warning, and i can always drill some holes and add another fan if needed.

also i think right now i will just do the fixed outputs in the ATX box, and make the variable a separate unit for now until i find
a proper housing for it all. i have a nice looking HP 32V 1.550A linear psu with what looks like ample protection.

also there is a yuge heatsink already in the atx and i was thinking of making use of that. though i do have other heatsinks if needed, incl specific to220 ones.

once my brain gets done booting up ill post some pics.
 

Offline Pirateguy

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Re: DIY power supply
« Reply #47 on: August 16, 2018, 05:19:23 pm »







 

Offline MarkF

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Re: DIY power supply
« Reply #48 on: August 16, 2018, 06:55:13 pm »
The 32V HP Supply and a LM317 would make a very nice variable supply.
However at low output voltages and a 1A load, the LM317 would need to dissipate 30W. 
You could use a bypass transistor to handle the load. There is a two transistor configuration in the datasheet if you want to use the 2N3055.

I saw a thread last week discussing a LM317 and a TIP36C PNP bypass transistor.  I would opt for the PNP single transistor.
   https://www.eevblog.com/forum/beginners/lm317hv-and-heatsink/

I would also use a 10-turn potentiometer to adjust the voltage.
   https://www.mouser.com/ProductDetail/Bourns/3590P-2-103L/?qs=sGAEpiMZZMvygUB3GLcD7uCOAMig3YAGHWGOtVZsEa0%3d
 

Offline Pirateguy

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Re: DIY power supply
« Reply #49 on: August 16, 2018, 09:23:30 pm »
what about lm338?
i have some of those coming my way.

edit:
that pot is a bit pricey for my budget, how about this one:
https://www.ebay.com/itm/1PCS-3590S-Precision-Wirewound-Potentiometer-Pot-10Turn-500R1K2K5K-10K-20K-50K/302098816720?hash=item46567e1ed0:m:mEC_-G0YRedjCMHo_CI84VQ
« Last Edit: August 16, 2018, 09:39:25 pm by Pirateguy »
 


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