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PS Audio PS3 preamp power supply help

JimmyNeutron

JimmyNeutron

Super Member
I ordered a PS Audio PS3 from that place and it arrived today. I have a few questions and am hopeing someone here can help me.

There isin't much info about this vintage phono preamp on the web, but the 2 photos I did manage to find show a standard 2 prong type A/C cord comeing out from the rear of the unit. My unit, however, has a 4 pin screw type power adapter. This has me confused. I'm not sure if it uses an external power supply and then feeds a DC voltage to the PS3, or if it is still a special AC type plug feeding AC into the unit. I opened it up and took some pics of the guts to see if anyone here can shed some light by looking at it's insides. It looks to me like this PS3 uses an outboard power supply and then feeds a DC voltage via 3 of the 4 pins to the unit. The inside pins of the adapter show 2 are RED, or positive, and 1 is BLACK, or negative. There is also an etching on the board that says +V and -V on each half of the board. This I'm sure proves it's DC voltage. There is also no transformer or any other AC step down device inside. So, if this unit does require an outboard AC to DC power supply ( of which I have many ) then the next question would be how much DC voltage is needed? 5 volts? 12 volts? 18 or more volts? Does anyone have one of these PS3's that can look and verify how much power they require?

Any help would be greatly appreciated.

Thanks, and Merry Christmas!!!

Jimmy

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Hi I went throught the same problem with my 5.0. I was lucky to find an external power supply. I'll try and find a pic of the one I believe you need. I know it could be converted over to a power cord but it's expensive. I had contacted Cullen Curcuits about that very thing as in my case Rick Cullen helped design the 5.0
if you send me a PM I can give you all the info I received when I did my search.
Also try PS Power forum over at Audio Asylum as Paul McGowen posts there and was very helpful to me.
 
A big thanks goes to Zenith2324. He sent some nudie pics of his PS3 and he helped confirm my suspicions. It seems I have a modded PS Audio III. Whether this is a good thing or a bad thing I don't know. The plot thickens at this point. Mine has a new power supply board inside instead of the lone tranny from the OEM. I have no idea the design or voltage in/out of this board. It looks like a newer board and of a different design than the OEM PS Audio circuit board so I don't believe it was done by PS Audio. Also, the main circuit board has also been modified. The cartridge impeadance selector wires have been removed so that is no longer functional. There is a lot of diodes, caps, and resistors added to the board. My guess is it was modified for 1 type of cartridge. I'll tell you what, someone went thru a lot of work to do this. The work looks very well done and very professional. I don't know if I should persue trying to get a correct power cord or to try to revert this back to an OEM version. I guess without knowing what the original user wanted or used it for it's gonna just be guessing. First step would be to try to see what kind of voltage is required to power the unit. Looking at the "new" power board it has 2 red and one black wire. But I don't know if it's AC or DC input. I did, however, try connecting a 12, 18, and a 32 volt DC power supply here and the unit will not pass audio. I then bypassed the power supply board and connected the DC votage directly to the main boards power input, but also no sound ( the power LED does light, however ). Am I right in assuming that this circuit requires DC and not AC to run? The power board appears to be a beefier type power filter/regulator type with the big caps and power rectifiers. I'm assuming DC in and filter/regulated DC out. I say this because of the power wire colors and number - 2 red and 1 black. Another question is do the 2 RED power wires carry the same voltage in or different? Still, if I bypass the power board altogether should'nt I at least be able to get audio if I hook up power to the main boards leads directly?

I'm stumped. I've heard many great things about this vintage preamp. I'd love to get this to work, but the modifications have me vexed. I want to know the history. Does anyone know something about this unit's past? Are these mods OEM?

Jimmy
 
Am I right in assuming that this circuit requires DC and not AC to run?
Click to expand...
AC...What voltage I have no clue.. What is the part number on these two voltage regulators (the ones with the winged heatsinks?)also what voltage is printed on the two smaller electrolytic capacitors?
 

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Well Zenith confirmed the voltage of his PS3 at the tranny out going into the main board - 28 volts negative and positive. His unit has a smal tranny inside where mine has this power board. CDfac is most probably correct in the linked power supply as the listing mentions 28 volt AC out. OK, so now what I need ( at least ) is a small tranny that is 120 AC in and +28 and - 28 volt out and if I connect this to my board as shown in Zenith's pic I should have mine working - that is *IF* more modding wasen't done to the power section input of the main board. On the underside of my board I notice there are 4 missing long caps at the power input. I don't know if Zenith's also has these missing or if they are important.

I may have bought a lemon here. Even if I get this to work I'm still left with the modded cartridge capacitance. Mine is hardwired for 1 single type of cart and trying to get it back to OEM would require a similar unmadded unit for side-by -side comparisons. Oh well. FRACK!
 
JimmyNeutron said:
Well Zenith confirmed the voltage of his PS3 at the tranny out going into the main board - 28 volts negative and positive. His unit has a smal tranny inside where mine has this power board. CDfac is most probably correct in the linked power supply as the listing mentions 28 volt AC out. OK, so now what I need ( at least ) is a small tranny that is 120 AC in and +28 and - 28 volt out and if I connect this to my board as shown in Zenith's pic I should have mine working - that is *IF* more modding wasen't done to the power section input of the main board. On the underside of my board I notice there are 4 missing long caps at the power input. I don't know if Zenith's also has these missing or if they are important.

I may have bought a lemon here. Even if I get this to work I'm still left with the modded cartridge capacitance. Mine is hardwired for 1 single type of cart and trying to get it back to OEM would require a similar unmadded unit for side-by -side comparisons. Oh well. FRACK!
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Would be a piece of cake to DIY a AC power supply...:yes:
 
MJE172
Not a regulator..high voltage/current switching transistor.
 
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avionic said:
Would be a piece of cake to DIY a AC power supply...:yes:
Click to expand...

Found a transformer....:D Only $44.. 28-0-28 @ 400VA
OK, so now what I need ( at least ) is a small tranny that is 120 AC in and +28 and - 28 volt out
Click to expand...
Nope.transformers are AC only. You just need a tranny wth 117 primary and either a 56 VAC CT or 0-28,0-28 VAC secondary. That small circuit board rectifies the AC to a + and - DC voltage.
 
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I bought that unit several weeks ago and returned it to the seller when I saw all the work that was done under the hood.
 
Bluespower said:
I bought that unit several weeks ago and returned it to the seller when I saw all the work that was done under the hood.
Click to expand...

PSaudio stuff sounds excellent..Once you figure out the stuff..:yes:
Stanton681EEES --and I have been down this road..


PSaudio corporate is next to no help....they supplied me with hand scribed circuit diagrams a 5th grader would be able to do a better job drawing .No published service manuals.
 
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avionic said:
PSaudio stuff sounds excellent..Once you figure out the stuff..:yes:
Stanton681EEES --and I have been down this road..


PSaudio corporate is next to no help....they supplied me with hand scribed circuit diagrams a 5th grader would be able to do a better job drawing .No published service manuals.
Click to expand...

Yes Dave we certainly have. What you described as to his problem is what I was told about mine had I not been fortunate enough to find a power supply from a 4.6 pre. I really enjoy mine. And yes there schematic does look like a 5 year old drew it.:scratch2:
 
I have seen that socket on other PS Audio gear, so I would think that the change is factory, and put in when they went from internal power supplies to external power supplies, and this was the regulator board that they installed. It could have been retrofitted to existing units at the factory by someone who is not that good with a soldering iron, so it still could be stock.

If you have a bench variable supply, you could try feeding in the power figures that Zenith2134 quoted and see what happens.
 
Well.....so now we have some history here. It seems it has traveled thru some hands before landing in mine. I now must decide what to do. I originally bought the unit because .......well...it was a PS Audio phono preamp. They're reputation on phono pre's is rather high so I thought I can just hook up a power supply to it and I'd have a nice pre ( I ASSumed it would take a standard 12 DC external brick ). It seems that a new DIY or OEM power supply will cost me between $75.00 and $100.00. Do I want to invest that into what I already have in the unit? I'll ba at the price of a Cambridge 640p at that point. But the PSIII does have it's strengths. It IS a PS Audio after all. It has a strong history. It has now an improved (over the original) power supply section. And it can be modded a bit further with better RCA connectors and caps to further tweak some more out of it. This could be a nice little project. One thing that needs to be done though is to reconnect the 2 front panel switches, and remove the hacked together diodes/caps that were done for 1 type of cart. I don't know what components were removed, if any, so a schematic may be in order, however I understand they are unobtanium since McGowen guardss his toys with more reverance than my son playing a game of Super Mario Bros.

So........should I take the high road and commence this project and see what a 25 year old PS Audio III preamp performs like? Or should I just get rid of it?

Jimmy
 
I showed the unit to two of my audio buddies (who are both electrical engineers) and they backed away like the thing had the plague. It may indeed work the way it is but I'm not sure you would ever know what values are built into it at this point. If you choose to tackle it I wish you all the best. I'm waiting on a Gram Amp 2 SE I bought off that site and have my fingers crossed that it has lead an un-modded life.
 
Been talking to McGowen from PS Audio and another fellow who appears to have a lot of design experience with this unit. Apparently it was either retrofitted at the factory when PS Audio stated to tackle high current power supplies in their units, as is evident by the beefy power supply voltage regulator board. This is a good thing - a very good thing as most PS3's don't have this mod and many people swear by this 25 year old piece as one of the best pre's made for the price - still today beating some very big names ( I'm just quoting as I've never heard a PS Audio phono pre ). The cartridge selector mod will have to be fixed back to OEM ( Zenith has been most kind sending me nudie pics of his unmodded PS3 which I can use to find the correct values and locations of the solder points). So the only thing really that I will need to do is replace all caps with higher quality ones, add better RCA connectors, add a DIY outboard power supply, repair the selector switch and I should be in business with this baby.

Jimmy
 
Well Jimmy if it sounds anything like my 5.0 then I'd say go for it. When I got mine it as I said was missing the power supply and the unit was pretty much non working. A trip to Avionic and he did his stuff on it and it's been a good well worth it project.
Sounds really good plus it gave me the chance to try an AT OC9 do to the 5.0 having adjustable gain settings, as well as loading.
 
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