Power Designs 6150 Universal DC Power Source Restoration

Restoring a Power Designs Inc. 6150 power supply

Power Designs 6150 front panel meters
Power Designs 6150 front pan­el meters

PD6150 Repair Front Panel
PD6150 Front Panel after clean­ing and pol­ish­ing meter faces
PD6150 Shipping with loose capacitor top view with cover removed
PD6150 Shipping with loose capac­i­tor top view with cov­er removed

The Power Designs Inc. 6150 pow­er sup­ply is the high­est wattage unit in the low volt­age sin­gle out­put series. It is a lin­ear pow­er sup­ply designed to out­put 0 to 60 volts DC in 4 decreas­ing amper­age ranges from 15 to 2 amps as the volt­age is increased.
It uses the Power Designs UNIPLY® cir­cuit design (Patent #3,699,352) to accom­plish this.
It uti­lizes dual meters for out­put volt­age and amper­age with dual ranges for each meter. The volt­age and cur­rent lim­it con­trols are sin­gle turn wire wound poten­tiome­ters that also change range set­tings with the asso­ci­at­ed meter range switch­es.
The pow­er sup­ply was a bit dusty inside, but not near­ly as bad as sev­er­al units that I have worked on in the past. I was able to find all the loose hard­ware inside the enclo­sure with the excep­tion of one nut. I was wor­ried that a stud mount­ed diode had pos­si­bly been dam­aged by the loose 110,000 uF 16 volt elec­trolyt­ic capac­i­tor. But it and the capac­i­tor checked out good.

Also described in the Ebay PD6150 listing was a bent handle that may require some adjustment.
Also described in the Ebay PD6150 list­ing was a bent han­dle that may require some adjust­ment.

Most of the restora­tion involved clean­ing and mechan­i­cal repairs. I did end up replac­ing the 15 volt sec­tion elec­trolyt­ic capac­i­tor, but sur­pris­ing­ly the loose 6 volt sec­tion capac­i­tor test­ed good. I will still end up replac­ing it when I make my next big parts order.

PD6150 cleaned up and parts reinstalled before testing
Power Designs 6150 cleaned up and parts rein­stalled before test­ing
PD6150 Power input and UNIPLY bridge rectifiers
Power Designs 6150 Power input and UNIPLY bridge rec­ti­fiers
PD6150 main board top
Power Designs 6150 main board top
PD6150 main board angle view
Power Designs 6150 main board angle view

All the elec­trolyt­ic capac­i­tors on the main board looked great and test­ed fine in-cir­cuit. I still haven’t decid­ed if there is a need to replace them yet. I am still try­ing to fig­ure out the man­u­fac­ture date for this unit, so far my best guess for this units vin­tage is 1984.

PD6150 front panel On set to 3.3 volts

Power Designs 6150 front pan­el On set to 3.3 volts on 6 volt range with no load

PD6150 at full load. 15 amps at 5.6 volts. With PD6050D on top for comparison
Power Designs 6150 at full load. 15 amps at 5.6 volts. With PD6050D on top for com­par­i­son

Under full load at the upper volt­age in each of the 4 ranges, volt­age reg­u­la­tion was bet­ter than 0.002% and volt­age rip­ple-noise was less than 0.16 mV P‑P. Current noise was less than 2 mA at a 3 amp load.

I have not yet found an online ser­vice man­u­al for this pow­er sup­ply, so I do not know the design spec­i­fi­ca­tions. Drop me a com­ment if you know where I can find one.

I decid­ed to pho­to­graph this unit exten­sive­ly since there was not much in the way of pho­tos and doc­u­men­ta­tion avail­able.
More pho­tos: (click on pho­to to view at full res­o­lu­tion)

PD6150 Back Panel
PD6150 Back Panel
PD6150 Left Side Power Transistors cover removed
PD6150 Left Side Power Transistors cov­er removed
PD6150 Left Side Power Transistors cover on
PD6150 Left Side Power Transistors cov­er on
PD6150 Right Side Power Transistors cover removed
PD6150 Right Side Power Transistors cov­er removed
PD6150 Right Side Power Transistors cover on
PD6150 Right Side Power Transistors cov­er on
Power Designs 6150 Main Board bottom
Power Designs 6150 Main Board bot­tom
Power Designs 6150 Main Board Top Backlight
Power Designs 6150 Main Board Top Back-light
Power Designs 6150 Main Board closeup top left
Power Designs 6150 Main Board close­up top left
Power Designs 6150 Main Board closeup top left
Power Designs 6150 Main Board close­up top left zoom
Power Designs 6150 Main Board closeup
Power Designs 6150 Main Board close­up top right 1
Power Designs 6150 Main Board closeup
Power Designs 6150 Main Board close­up top right 2
Power Designs 6150 Rear Terminal solder connections and components
Power Designs 6150 Rear Terminal sol­der con­nec­tions and com­po­nents
Power Designs 6150 UNIPLY Stage 25V and 60V capacitors
Power Designs 6150 UNIPLY Stage 25V and 60V capac­i­tors
Power Designs 6150 Transformer connections and Stage 16 volt capacitor
Power Designs 6150 Transformer con­nec­tions and Stage 16 volt capac­i­tor (New)
Power Designs 6150 Voltage potentiometer back
Power Designs 6150 Voltage poten­tiome­ter back
Power Designs 6150 Top Back View with cover removed
Power Designs 6150 Top Back View with cov­er removed
Power Designs 6150 Bottom Front View with cover removed
Power Designs 6150 Bottom Front View with cov­er removed

Power Designs 6150 Instruction Manual with Schematics
cour­tesy of “gto 4ben”

9 Replies to “Power Designs 6150 Universal DC Power Source Restoration”

  1. I have a Power Designs 6150 (no man­u­al nor schemat­ic) and resis­tor R48 on the main board burned. Would you please ohm out R48 and R47 and send me the val­ues. I still need to fig­ure out why R49 smoked, but the lack of a schemat­ic is hin­der­ing me.

    Thanks

    1. Hi Edward,
      Resistor R48 is 0.75 ohms, and R47 is 0.216 ohms accord­ing to what is actu­al­ly print­ed on them.
      Also print­ed on both resis­tors “PD305” and “411”.
      Both resis­tors con­nect to R46, which i believe is the large resis­tor just behind the front pan­el. Possibly the main cur­rent sense? and these two resis­tors are pos­si­bly for the 1.5 amp and 15 amp ranges?
      I doubt that I would get a valid resis­tance read­ing on them in-cir­cuit with­out remov­ing a lead any­way.

      Greg (Barbouri)

      1. Hi Greg,
        On sec­ond thought, would you mind ohming out R47 & R48 in-cir­cuit? If they real­ly are that low of a resis­tance, what­ev­er is in par­al­lel with them won’t make that much dif­fer­ence.
        Thanks,
        Edward

        1. In cir­cuit resis­tance checks with Range switch set to 15A.
          R48 = 0.058 ohms (labeled val­ue 0.75)
          R47 = 0.134 ohms (labeled val­ue 0.216)
          R46 = 0.033 ohms, 25 watts
          Cable resis­tance from “TO R46‑2” to R46 ter­mi­nal = 0.0140

          Greg (Barbouri)

  2. Hi Greg,

    Thanks for the infor­ma­tion con­cern­ing the resis­tors. My prob­lem with the unit is in the con­stant cur­rent sec­tion, but I do not know if I can trou­bleshoot it with­out a schemat­ic.

    Sincerely,
    Edward Eison

  3. Your unit is very clean! I’m hap­py you got it work­ing. Thank you for all your pho­tos.

    I also have a PD 6150. I just fin­ished trou­bleshoot­ing it. First prob­lem was that the pow­er switch did not turn off due to stuck con­tacts. The sec­ond was that the out­put volt­age does not go above 3.125V at 0A on the 6V range. It also trig­gered a high cur­rent on the meter with no load at >19V on the 60V range. Once trig­gered, it imme­di­ate­ly set­tles back and repeats unless I low­er the out­put volt­age below 19V.
    After replac­ing the pow­er switch S1, I dis­cov­ered C19 & C20, 1000uF, 70V, out­put caps were faulty (6 ohms across) and the C3, 60uF, 75V cap that fil­ters the pow­er for the ref­er­ence sec­tion was open result­ing in only 20V across it instead of 53.5V. A loss of ref­er­ence volt­age down­stream would explain the low out­put volt­age range. Replacing C3 restored oper­a­tion.

    To cel­e­brate my good for­tune, I’d like to offer a scanned man­u­al with schemat­ic if you or your read­ers are still inter­est­ed.

    1. Hi gto4ben,
      Congratulations on get­ting your PD 6150 up and run­ning. I end­ed up replac­ing all elec­trolyt­ic fil­ter caps on my unit.
      I am sure that many of us would love to have a scanned copy of the man­u­al. I still need to cal­i­brate the cur­rent meter on mine, but am unsure which pots to adjust.
      Thanks,
      Greg(Barbouri)

  4. If you send me an email to the email address I pro­vid­ed here to com­ment, I’ll glad­ly respond & attach a copy of the man­u­al (pdf 2.5MB size)

    For cur­rent adjust­ment, this is what I did.
    1st, set the cur­rent range pots (1.5A-R49, 15A-R32) for each respec­tive range to 10% over rat­ing.
    2nd, set the pan­el cur­rent meter pot R57 for one of the ranges to cal the cur­rent. 15A will heat the load caus­ing the resis­tance to change (unless you have an elec­tron­ic load) and may make a con­stant 15A dif­fi­cult to attain so I cal­i­brat­ed the meter using the 1.5A range which will be good enough for the 15A range.

    This is my inter­pre­ta­tion of all the pot adjust­ments based on both the 6050 and 6150 man­u­als:
    R23-Voltage Max for flash­ing lim­it lamp. Set up to 2V above max per­for­mance rat­ing (62V).
    R32-Current Max 2 (15A) for front pan­el flash­ing lim­it lamp. Set to 10% above max per­for­mance rat­ing. (16.5A)
    R34-Front Panel Voltage Limit Control
    R39-Front Panel Current Limit Control
    R57-Panel cur­rent meter Cal
    R49-Current Max 1 (1.5A) for front pan­el flash­ing lim­it lamp. Set to 10% above max per­for­mance rat­ing. (1.65A)

    My volt­age pan­el meter lost the grey mechan­i­cal zero adjust­ment in the front that you use a screw­driv­er to zero the point­er when off. Would you know where I can get a replace­ment, per­haps from a bro­ken meter?

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