Zurich DPS 2512M 30 Amp Power Supply

The Zurich 30 Amp Regulated Power Supply was marketed under several other names, including MFJ. I have had mine for some 12 or 15 years now I recon. It is a ‘real’ PSU with a chunky transformer.

When it started to play up I was on air, I saw 10 Amp or more pulses of current indicated on the Ammeter. I was operating on PSK31 with a friend. When I mentioned it he said ‘does that not worry you it could damage your rig’.
No, no worries here, this was the practical demonstration of one more reason for the system of 12 Volt supply I use in the shack. The PSU float charges two 40 Amp Hour Lead Acid Batteries individually via Schottky Diode isolators. A fault like this did not apply 15 to 17 Volts to my expensive radios, it might just do the batteries a little good by giving them a few de-sulphating pulses.

‘Surely’ he said ‘your power supply is protected against Over Voltage’.
Yes it is, although not Over Current, but this fault was obviously not related to over voltage, the voltage involved must be a ‘legal’ one. Any voltage between 0 and 15 is ‘legal’ it being a variable voltage supply with a front panel adjustment pot.
This should have been a good clue to the cause of the problem, I didn’t find it instantly, adjusting the voltage set pot and wriggling it made no difference to the pulses of extra current so I ruled it out at first. Finally I substituted a large preset pot and the problem was cured. I suspect that the connection of the earthy end of the potentiometer track was intermittent possibly under the riveted tag.
I ordered three 10K Ohm pots from different sources and one turned out to be very similar physically to the original.

The original has an indent at the center 13.8 Volt point, the replacement does not. No problem I don’t use that point anyway, remember the Shottky Diodes, their forward volt drop means I set the output above 13.80. The original also has a splined shaft the new one is plain so I provided a different pointer knob.

Whilst inside I soldered the wire wrap connections on the control PCB.

Also the wire wrap connections to the load share resistors, these connections do get warm, I am much happier to see some solder on these after several years of use and possible corrosion of contact.
The Regulator Transistor connections on these boards had also had many hot /cold cycles so the joints were all re soldered.

Finally back in use on the rack, Battery Terminal Voltages set to 13.8 Volts.

I now have circuits of several (not all) models of the Zurich family of PSU’s they are stored on the cloud, go HERE.


Jim G3KAF contacted me, as have several others over the years, about a problem he had with this well loved PSU. Jim had a voltage regulation problem. The Voltage dropped when current increased.
Jim like me would have liked a circuit diagram for the PSU, he managed to identify the value of a capacitor from my photograph. The fault remained though, only a few days later he found the problem.

On the small board with all the components the diode which rectifies the low voltage ac supply (next to the 470uF 12v capacitor) was highly suspect because the 470uF was getting warm!. When I took the diode out and checked it, I found it was a dead short circuit. Having replaced it the PSU is now working superbly well. I had changed all the 8 smoothing capacitors and the bridge rectifier and now I can go from zero amps to 20 amps and the voltage only drops 10mV (0.01 of a volt). I suspect it has not performed this well for years.

Thanks Jim for the information, if anyone has a circuit diagram or other information / faults found, please contact me.


27 thoughts on “Zurich DPS 2512M 30 Amp Power Supply

  1. Hello!


    Is someone can tell me if it is possible to connect batteries on the Zurich 30 Amp power supply for a backup? if yes where I have to connect it?

    Thank you in advance.



  2. Sorry for the late reply. Yes connect a 12Volt car or leisure battery to the output terminals with a 40Amp Schottky Diode in the positive line to isolate it when the PSU is off. Once connected take the power only from the battery terminals.


  3. Skipens4 we know who you are. You are a blog pest and SPAMMER you were removed from blog.co.uk as a man 3 times do you think we are fooled by your sex change. You will be removed AGAIN.
    Go and take your Gambling habits elsewhere.


  4. I have a Zurich RPS-1012MB power supply. It has proved to be a very reliable piece of equipment. The other day it went wrong and the output transistors burned out. I replaced them as well as the regulator IC. The power supply still has a problem. I request of anyone if at all possible I can get a circuit diagram or to give me the contact details of the agents/manufacturer, so that I might approach them ditectly for a diagram.

    Any assistance will be greatly appreciated.

    From Godwin. bgrsymons@hotmail.com

    I am contacting you from Johannesburg South Africa.

    Regards from Godwin Symons.


  5. Hi Godwin

    I have a later post with links to circuits
    Search 2013/02/15 Unfortunately it doesn’t include your model, maybe there are similarities that could help you.
    If anyone does find the actual circuit I would be happy to include it in my collection or provide a link.


  6. I have an issue with my Zurich Regulated DC power supply(0-30V), model no. Z-3002A. When turned on, the voltage directly jumps to 23V. Please help me.


    1. Hi Janish I have not handled the Z_3002A unfortunately. The set voltage potentiometer goes open circuit on the DPS 2512, I would check your set voltage pot first. After that there are transistors in the regulator check that the high power ones are not short circuit. Then there are the low power devices and finally the regulator IC, if it turns out to be the IC they may be difficult to source, lets hope it is something easy.


  7. Thank you very much for your reply Marco. I have checked both Voltage and ampere pots. The voltage pot is 10Kohm and ampere pot is 100 Ohm. I feel like 100 Ohm is too low. Any comments?


  8. I don’t know about the current pot, I don’t have a circuit for your model it could be right at 100 ohm, does it have any markings to indicate its value. The only thing I can add is that the voltage pot fault may be intermittent like mine was, it measured OK when not in use, It may be a good idea to remove the wires from it and tack in another 10K of any size or type temporarily just to make sure. Have you checked the regulator transistors thoroughly ie disconnect each one and test to make sure it is not short circuit.


  9. Yes marco..Thanks alott….it worked when i replaced transistor 2N3055… but now the problems are, 1.Voltage is not going beyond 27V …not able to get 30V…..
    2. When load is applied, ampere hikes for a small increase in voltage.

    Before i had changed a blown resistor with 4.7Kohm ..since i couldnot find the value of it…


  10. now am able to get 30V when i decreased the value of resistor to 47ohms..Thus case 1 is solved.
    But case 2 , i have no idea… any help is much appreciated.


  11. Hi Janish. I am pleased you cured problem 1, I was going to suggest experimenting with the value upwards, I dare not recommend reducing the value as not knowing the circuit, that could have resulted in some destruction. Problem 2, do you mean that the current limit is not working at all ?
    My DPS 2512 does not have current limit, I am not sure if any of the models that I have circuits for have it, do you know that I have the circuits on line ? They are linked from a later post about the Zurich I will locate that and include it in this post. It may be of help for you.

    BTW If you can identify the 47 Ohm resistor by a description of location it could be useful for others to post it here. As you know there is little information about these PSU’s my posts are some of the most used and commented on in my Blog.


  12. Yes… am not able to adjust Current with Ampere adjusting pot…when load is connected and started increasing voltage, current increases as well, but i have no control over it with ampere pot to decrease or increase it…

    47 ohm resistor is located near the biggest resistor(1Kohm) in the board.


  13. OK … may be we can assume that there is a high power resistor in series with the current load or a sense circuit in the lower power stages of the regulator. This should be producing a small voltage (dependant upon the current drawn) on the set current adjust pot which will vary the voltage on its slider as you adjust it. Do you have 1) a voltage on the pot ? 2) does the voltage on the slider vary when the pot is adjusted ?


  14. 1. Ampere pot has the same voltage as voltage pot…and it changes along with voltage when we decrease or increase it…. no control over ampere pot.
    2. voltage changes only a bit like 4V to 3.4V (while adjusting ampere pot)


  15. This is difficult when just imagining the possible circuit, but those voltages sound like they may be OK.
    Let us think about resistor X, the 47 Ohm resistor again, and the nearby biggest resistor on the board is that resistor marked 1K Ohm or is it 1 Ohm ? Please do not change it I am just wondering. Did the current pot work when you had 4.7K for resistor X ? Try changing resistor X to 470 Ohms.


  16. Oh Good. Our posts crossed, you fixed it whilst I was thinking about it. Is the transistor associated with the slider of the current pot ? That was my next suggestion, look at where the slider goes to


  17. Hi Janish I don’t know about this I don’t think have ever seen it. It may be normal under no load conditions. Is it causing you a problem. I was going to measure mine but is has been in use 24/7 for several days running a QRP transmitter. If the voltage adjusts OK over the useable range I don’t think I would worry about it.


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