Repair Vintage DC Power Supply, Sorensen DCR-B series 2700-Watt 600-4.5B - Page 1
Forum section: electronics / repair

author: mancoast
author_rank: Newbie
timestamp: October 06, 2018, 09:52:29 pm
content: Greetings,I seek relevant forums and communities to document my issue and to formulate structured dialogs. With respect to the repair and restoration of a vintage DC power supply from the early 1980's, I need advice and direction. Majority of my experience exists on the computer designing systems, but this project sparks a new curiosity with vintage electronics restoration.The Sorensen DCR 600-4.5B DC Power Supply, 0-600V, 0-4.5A, 2700W rests on my workbench with the system input voltage supplied from 208V 3-phase 20A because the Sorensen factory default M1 configuration needs 208 VAC for DCR-B series 2700-Watt models. The manual for this vintage Sorensen power supply exists on the internet (Document No. 165042 Rev F), however I am not sure if we can post external links here. Additionally, I have concurrently formed similar threads across a plurality of electronics forums, so know that there exists cross-posting.When initially getting the device, the system's chassis fan activated with a flip of the main breaker, however little else occurred in the 7" high chassis. Troubleshooting at the component-level initialized by tracing the supply line voltages. The schematic reflects line voltage to a large transformer, so I verified voltage at those nodes. However, at this point I seek advice and directions. The service manual states, “DCR-B series supplies are phase controlled type with SCR's (Silicon Controlled Rectifiers) or Triacs at the input to the transformer, followed by a passive LC filter … Low dissipation transistors and diodes are located on a single printed circuit board while high dissipation devices are heat sinked to aluminum brackets and heatsinks.”Replacement of the single printed circuit board (DCR control board P/N 586955-1) returned some progress. Now, the system generates variable voltage output when the main breaker activates, however I cannot reach the required 600V specified by the manual. What are your thoughts and advice?Sincerely,Mancoast

author: coromonadalix
author_rank: Super Contributor
timestamp: October 07, 2018, 03:45:14 pm
content: If you are not under NDA (non disclosure agreement), you can share your documentationThe service manual is available, i found it : SORENSEN DCR-B2 2700W Operation and Service.pdfhttp://manuals.repeater-builder.com/te-files/SORENSEN/SORENSEN%20DCR-B2%202700W%20Operation%20and%20Service.pdfIs your programming rear jumpers are a the good place ? you have 3 of them ?On the pin 3-4 "short" the voltage will vary 0-10vdc for the full 600v scale (600v=10vdc)What are the max voltage you get ? Do you have an OVP adjustment who will limit the output voltage ? I think you have one hole in your front panel ?Does it have M1 M2 M3 otions ?? (220 230 vac options) ??some infos:https://www.ntecusa.com/docs/DCR80-33B_data.pdfhttps://www.ntecusa.com/docs/DCR600-9B_data.pdf

author: mancoast
author_rank: Newbie
timestamp: October 09, 2018, 12:49:50 pm
content: Quote from: coromonadalix on October 07, 2018, 03:45:14 pmHello coromonadalix,These are the exact PDF's I have been using. The three jumpers are correctly installed in the back of the chassis. The system is wired to 208VAC input voltage. When I return from travel in two weeks I will confirm the M1 (208VAC) transformer wiring and post plenty of pictures. I am getting a maximum voltage around ~190V when tested with a DMM and have not been able to locate the OVP. What does the OVP look like?Thanks,Mancoast

author: coromonadalix
author_rank: Super Contributor
timestamp: October 09, 2018, 08:45:08 pm
content: Sometimes it is an small hole in the front panel, with mine i limit the ovp voltage and it affects the maximum output voltage if i set it too low. If you seat in front of it, the small hole should be on the front panel left sidenot far away of the meters and current potentiometers.Normally you have ''ovp adjust'' written near the hole, it is a small 1 turn trimpot, be gentle lolll you may strip or break it.Turn it to the max ''clockwise'' and check if it works better than 190v ?

author: mancoast
author_rank: Newbie
timestamp: November 02, 2018, 07:58:40 pm
content: Hello coromonadalix,I cannot locate the OVP. Pictures attached.What do you suggest to further troubleshoot?Thanks,Mancoast

author: coromonadalix
author_rank: Super Contributor
timestamp: November 02, 2018, 08:38:41 pm
content: Damn thats a beast, the ovp is normally on the front panel near the coarse voltage adjustment, but you dont have one on this model it seems, since you got a new board, is the (black 11 screws terminal) screws jumpers are corectly placed ?Maybe you have half the main supply voltage ? i would check the p1-51 p1-52 p1-53 p1-54 pins with an isolated ground oscilloscope to see when you adjust the output voltage if the signal phase is more complete when "dialing up" / cranking up the voltageIs the pcb is configured for your model if you check all the corresponding chart vs parts values ?

author: AllTheGearNoIdea
author_rank: Unknown
timestamp: November 03, 2018, 01:09:49 pm
content: That’s a fantastic power supply. My only not useful comment is please be careful. You have a lethal combination of stored energy. I shall follow your progress with interest.

author: precaud
author_rank: Frequent Contributor
timestamp: November 03, 2018, 02:01:34 pm
content: I've worked on a number of those beasts. OVP was an option on the DCR series, yours doesn't appear to have it. When installed, the board was mounted in that rectangular opening in the inner rear panel, and there was a small hole on the rear trim panel to access its adjustment. As always for older power supplies, check all the lytics, especially on the regulator board, for open. That's where most of the problems I found were. (I see a 1980 date code on one of yours...) Oh, and make sure you have + and - sense lines connected to their respective output terminals.You can change the transformer jumpers (there are two separate ones) from 208 to 230 VAC, I believe that is detailed in the service manual.

author: mancoast
author_rank: Newbie
timestamp: November 09, 2018, 10:29:27 pm
content: Greetings,Thank you very much for the pointers and direction. Reconfiguration of the resistors on the control PCB enabled an output voltage of 600V. This required removing the (4) 150k resistors from the old board and populating them on the "new" board.Now I would like to perform a load test. Below are pictures of a very large 5.5 OHM resistor. What is the recommended procedure for load testing this PSU. What size wires are required from the terminal block to the resistor?Thanks,Coast

author: coromonadalix
author_rank: Super Contributor
timestamp: November 09, 2018, 11:23:41 pm
content: What is the wattage of the 5.5 ohms load ?You can check if the supply is stable say at : 5.5 volts in 5.5 ohms will get 1 amp, 11v = 2 amps, 22v = 4 amps, 55volts = 10 amps, any awg 14 or awg 16 gauge can do ...I would test current with an clamp ammeter, dont use an multimeter, i case of a failure the meter can blow something.If the supply output stay stable, and the meters are following the given ouput, unless all adjustments trimpots were played with ? follow the calibration procedures ...First i would check the meters needles if they are mecanically at zero with no ac power in the supply, but i see you have an broken one on the front ? Normally you have to find one with the same impedance coil ? The meters normally have an 2 to 3 % tolerance / precision unless marked differently on the front lower corners with small text or numerical characters.Second after the mecanical adjustment of the needle meters, i would do the calibrations ....