Designing and building a replacement display for the Power Designs, Inc. 6010D power supply, and other Power Designs D‑series supplies.
After restoring my Power Designs 6010D and using it for a short while, I was missing having the extra digit of resolution from the upgraded PD 6050C display.
Luckily one of my readers, Ron Metcalf adapted my 6050C display boards for use on his 6050D power supply. He started with my original design, and updated it by using a card edge connection, removing the power supply section and voltage divider, and changing the range to 200 mV.
It seems that most of the Power Designs D‑series power supplies use this style of edge-connector display. The OEM display utilizes a 200 mV input range to display three digits on it’s red LED display. For the 6050D and 6010D models the maximum display input voltage is around 60 mV for the maximum voltage output of the supply. The OEM module uses a Intersil ICL7117 3½ digit integrating ADC and LED driver IC, which is also available as a Maxim Integrated ICL7117 part.
The OEM display is powered by 5 volts supplied from a linear regulator on the main board thru two pins. Two of the edge-connector pins are used for the 200 mV differential input. The other three connections to the OEM display module are a 560 Ω pulldown connection to ground, and two decimal point select input connections. The three decimal select and pulldown connections all connect to the meter V / A front panel toggle switch.
I ordered a set of Ron’s boards from OSHpark to try on my Power Designs 6050D and 6010D supplies, and built up a pair of them.
Both sets of boards were easy to assemble, and worked well. The 7 segment red LED displays that Ron picked for the display board were almost a perfect match compared to the OEM module.
The only issue that I ran into was a mechanical problem and not an electrical one, in that the parts list specified a 6–32 thread size, but the original screws and holes were a 4–40 thread size including the new boards.
I ended up using a part number 4504–440-AL‑7 hex standoff #4–40 by 7/16″ and the original screws and nuts from the OEM module.
With the extra digit of resolution I was getting some digit noise on the 10 mV display position of around 30 mV. This was happening on both upgraded supplies.
On the OEM display module with only 100 mV resolution, this noise is not a noticeable issue. I was also not seeing this behavior on my modified 6050C displays.
My theory of what maybe causing the issue is the 200 mV meter range of D‑series units compared to the 2 volt meter range of the 6050C.
Even though the Rev. 1.0 boards were working, I decided to design a Rev 2.0 board with a 2 volt input range. I also wanted to make several small changes to the input circuitry, and component spacing on the board while I was at it.
I wanted to continue using the original Rev 1.0 LED display boards designed by Ron Metcalf, but wanted the option of disabling one or both of the mode LED’s, so I added a set of jumper pads on the ADC board for the mode LED’s.
The linear voltage regulators were moved to the outer edges of the circuit board to reduce the heat transferred to MAX1447 IC and its internal voltage reference. I also increased several of the filter capacitor values to reduce noise on the power rails. The reference filter capacitor was increased to 10 uF for additional reference noise reduction.
I added a pair of low noise series 100 Ω resistors to the differential inputs, along with a 10 uF differential filter capacitor, also increasing the common mode filter capacitors to 1 uF.
Another change was switching the DPON, INTREF, LED_EN, and DPV/DPA select source to the DVDD 3.3 volt power rail. The foot print was changed for trimmer resistor R1 due to lack of availability with the Rev 1.0 500K trim resistor.
Well now I have a 2 volt input board installed in a 60 mV signal 5010D power supply.
Time to change the voltage dividers on the main board that I don’t have a schematic for.
After a hour of circuit tracing and verifying resistor values I was able to change resistor R56 in the 6010D voltage calibration circuit with a 1.74K Ω 1% 50 ppm resistor, part number CMF501K7400FHEB. This changed the ratio from 1000:1 to 100:1 and presented a 0.6 volt meter input with a supply output of 60 volts. I also changed the voltage calibration circuit trim potentiometer R54 to a 50 Ω 20 turn unit part number 3299Y‑1–500LF, for ease of adjustment.
The current calibration circuit is made up of R52 a 649 Ω 0.05% 100 ppm resistor, with R12 a 5.1 Ω resistor and R53 a 10 Ω trimmer potentiometer. After several tries I ended up replacing R12 with a 120 Ω ±0.1% resistor part number CMF55120R00BHEK. This gave me a 150 mV meter input for a output current of 1.5 amps.
After upgrading to the Rev 2.0 board all of the digit flickering stopped, and the display was very stable with no display drift after warm-up and full load testing.
Unfortunately I made many changes to the board, so I don’t know if a single or multiple changes made the difference. My suspicion is that changing to the 2 volt input range, made the biggest difference in stability but I have no way to currently prove it.
The upgraded PD 6010D is being used for an upcoming audio amplifier project, for my old Nakamichi 420 power amplifier. I am enjoying that extra digit of resolution.
I am currently looking for a PD 5015D unit which this display upgrade should also work with, along with manuals for these D‑series supplies.
EagleCad V7 board and schematic ZIP for ADC / LED driver Rev 2.0 board only
Link to OSHpark ADC / LED driver Rev 2.0 shared board page
PDF Bill Of Materials for the ADC / LED driver Rev 2.0 board
Link to Ron Metcalf’s meter project PDF page
Link to Ron Metcalf’s OSHpark Rev 1.0 4‑digit display board page
I have had several requests for a 200 mV full scale (FS) input board, which shouldn’t require any changes to the supplies main board. So here it is.
EagleCad V7 board and schematic ZIP for ADC / LED driver Rev 2.1 board 200 mV FS
I haven’t tested this board, but there are only a few small changes from Rev 2.0
If you build it, please let me know if it worked well for you, Thanks!