VIZ WP 708 Power Supply Issue

[xmx]

I bought on ebay an old Viz Triple Supplyst WP708. It's a bench power supply that also has limited voltage/current measuring capabilities.
It has 2 separate input/outputs, left & right. Everything on the right side works fine, the panel lights up, measures voltage & current correctly and the outputs are fine as well.
The left side outputs fine but the display does not work. I cannot check if it also measures fine. All connections seem ok, nothing looks disconnected or obviously busted. I looked for service manuals etc. but could not find any.
Any suggestions on how to troubleshoot? Where to start looking and suggestions on the likely culprit? Of course it would be great if someone had a manual.
In the attachments a front view of the panel (found the pic as I had taken it apart already) and a view of the problem board.
Thanks!
Antonio

[Maraakate]

Re: VIZ WP 708 Power Supply Issue

I do own the original manual.

It says for troubleshooting:

DISPLAY BOARD

1. Blinking Display: Check power supply +5V. Check U215 thru U218.

2. Improper readings: Check power supply +5V. Check regulator U213 and U214 for normal operation. Check voltages on U217/218.

3. Won't Zero: Check voltages on U217/218. Check R227/228. Check +5V supply. Check C210/211.

4. No display but power supply has output: Check power supply +5V. Check on-board regulators U213/214 for normal operation. Check continuity of all VCC paths to active chips.

5. Unstable display: Check power supply +5V. Check all voltages on U217/218. Check capacitors C203/204 for opens or leakage. Check C211/212.

6. Missing segments on displays: Check each display that exhibits a bad segment by replacement. If this does not correct the problem, checvk U215/216 for output conditions.

7. Decimal point won't move. Check S202/203. Check CR201/202 and CR210/211. Check Q201/202. Check R221/222.

If you need the part numbers that it tells you to check I can give you the list as needed as it's a full page.

I hope to scan the manual in sometime soon, but it will likely be a few weeks before I can get my scanner out of storage.

[Maraakate]

Re: VIZ WP 708 Power Supply Issue

A user sent me an email on this board, but I will share this extra info with everyone

VIZ WP-708 TRIPLE DC POWER SUPPLYST

Troubleshooting

Normal troubleshooting techniques can be used to locate defective components in the WP 708 Triple Supplyst. Reference voltages are given on the schematic diagram to aid in the repair of this instrument. An in-circuit transistor/fet tester such as the VIZ WT 524A can be used to check the semiconductor components. Listed below, by circuit board, are some possible problems which may occur.


FIXED 5 VDC REGULATOR

1. No output: Check output of CR401. Check output at Pin 5 of U401. Check to see that there is approximately 26V from pin 7 to pin 14 of U401. Check all voltages on U401. Check Q2 for an open condition from emitter to collector or base to emitter.

2. High, uncontrollable output: Check voltages on U401. Check transistor Q2. Check resistance from CR401 (-) to pin 8 of U401. Reading should be about 5K ohms. Check the special 5 VDC cable assembly and connector for an open.

3. Low uncontrollable output: Check C401, C403, for open or leakage. Check C407. Check all voltages on U401. Check the special 5 VDC cable assembly and connector for an open.

NOTE: If you are in doubt of any voltages on U401 after you checked everything else, replace U401 and retest.


DUAL ADJUSTABLE REGULATOR

NOTE: The following procedure applies to both of the adjustable regulator boards.

1. No output: Check output of CR101. Check output at pin 5 of U101. Check bias on Q101. Check to see that there is approximately 26V from pin 7 to pin 14 of U101. Check all voltages of U101. Check Q1 for an open condition from emitter to collector or base to emitter.

2. High, uncontrollable output: Check voltages on U101. Check transistors Q101 and Q1. Check resistance from CR101 (-) to pin 8 of U101. This resistance can normally be anywhere from 20K ohms on down to 0 ohms.

3. Low uncontrollable output: Check C101, C103, for open or leakage. Check C107. Check all voltages on U101.

NOTE: If you are in doubt of any voltages on U101 after you have checked everything else, replace U101 and retest.


DISPLAY BOARD

1. Blinking Display: Check power supply +5V. Check U215 thru U218.

2. Improper readings: Check power supply +5V. Check regulator U213 and U214 for normal operation. Check voltages on U217/218.

3. Won't Zero: Check voltages on U217/218. Check R227/228. Check +5V supply. Check C210/211.

4. No display but power supply has output: Check power supply +5V. Check on-board regulators U213/214 for normal operation. Check continuity of all VCC paths to active chips.

5. Unstable display: Check power supply +5V. Check all voltages on U217/218. Check capacitors C203/204 for opens or leakage. Check C211/212.

6. Missing segments on displays: Check each display that exhibits a bad segment by replacement. If this does not correct the problem, check U215/216 for output conditions.

7. Decimal point won't move. Check S202/203. Check CR201/202 and CR210/211. Check Q201/202. Check R221/222.


POWER BOARD

1. No D.C. output on either display: Check primary winding of T301.

2. No D.C. output on one display: Check to see that there is AC voltage at the secondary of T301 feeding the inoperative display. Check the diode rectifiers (CR301-304) in that section.


ADDITIONAL TROUBLESHOOTING INFORMATION

1. Instrument completely dead: Check fuse and replace if defective.

2. Supply will not rest or LED overload indicator never goes out: Check the "RESET" switch (normally open) and wires from it to the respective regulator board.

3. One or more of the voltage ranges does not work: Check the wiring to the voltage range switch.

[budm]

Re: VIZ WP 708 Power Supply Issue

Since both displays are duplicated of each other, then you can start by doing voltage comparison reading of the voltages of the IC's, Transistors, etc.

[WA9TS]

Re: VIZ WP 708 Power Supply Issue

Did you ever get a chance to scan in the service manual for the Viz WP-708?

Thanks

[saturn5tony]

Re: VIZ WP 708 Power Supply Issue

Yes, I have one of those as well, had this for probably 25 years now. My supply is working fine as well, but my right side is getting a bit flakey.... Hmm seems about time to do some cap replacements!! If anyone does have a copy of this manual and/or schematic, please chime in. It would be nice to see a few of these parts/numbs and the ability to modify this.

[Hurnst]

Re: VIZ WP 708 Power Supply Issue

I just bought one of these that seems to be in good working order. However it did not come with the 5v "sensing" output cable. There is a 4 pin DIN connection for this cable and from what I can gather from the user manual it ends in two alligator clips. The additional two pins must be providing a current feedback of some type to regulate the PS as far as I can figure. I just wonder how I can fabricate this cable without some further information that was not included in the PS schematic. Any ideas from those that still have or had one?
Thanks,

[budm]

Re: VIZ WP 708 Power Supply Issue

The 4-wire system is for compensating the voltage drops on the wires feeding the load.
http://www.acopian.com/remote-sensing.html

Do you have the diagram of the power supply?

[Hurnst]

Re: VIZ WP 708 Power Supply Issue

Yes I do.

[Hurnst]

Re: VIZ WP 708 Power Supply Issue

Sent that too fast, thanks for the link to the info, looks straight forward.
Rob

I can also scan in other parts of the manual if anyone needs it.

[budm]

Re: VIZ WP 708 Power Supply Issue

OK, If you look at the 4-pin output connector, pin 4 sensing pin is connected back to pin 10 on the board which is connected to the + side of the cap C408, the other sensing pin pin1 is connected to the negative leg of the cap. So pin4 should be connected to the load positive for sensing, pn1 is should be connected to the Negative side of the load for the sensing. By the way, the SCH shows WD-708, your post shows WP-708, so I hope the SCH does match your WP-708.

[Hurnst]

Re: VIZ WP 708 Power Supply Issue

Yes, its the right schematic, I thought I may have misnamed the file after scanning it, but I'm not seeing any reference to "WD". That's the way I read the schematic as well, but was just wanting to make sure that there weren't some passive components in the cable itself. That link you posted leads me to think not. I'll wire up a din plug and do some testing over the next couple days and see what happens Thanks for the help..
Rob

[snapcrackle]

I had the original cable here somewhere. It consists of two coaxial cables (red/black) which terminated in alligator clips. The shield and center conductor of each cable were shorted together at the alligator clip. That way WP708 sense voltage at the clip, no extra passive component.

[Hurnst]

Re: VIZ WP 708 Power Supply Issue

Sorry, now I see the WD reference. I'd guess that the WP is an update to the WD maybe? My PS says WP on every tag and lable, so should be good to go.
Once again thanks..
Rob

[budm]

Re: VIZ WP 708 Power Supply Issue

Usually on the 4-wire connection, if you are not going to use all 4 wires, just two wires o the load, the two sensing wire are usually required to be connected right at the output terminals (since it is part of the feedback to maintain the regulated output) instead of at the load point. I cannot find the user manual for the WD or the WP, you may want to find out how they should be used.

[Hurnst]

Re: VIZ WP 708 Power Supply Issue

I have the complete manual, but its vague on some some points, just referencing using the propriatory cable, which I do not have of course
Here is an example..

[Maraakate]

Re: VIZ WP 708 Power Supply Issue

Since I don't know how to convert a stack of things into PDF, here is the original PNGs of the entire manual. If someone turns this into a PDF post here and I'll mirror it.

Sorry it took a really long time to scan it, almost forgot about it!

http://dk.toastednet.org/VIZ_WP-708_...upplyst_Manual

It's 14 pages, approx 19MB download.

[budm]

Re: VIZ WP 708 Power Supply Issue

Converted to PDF.

[Maraakate]

Re: VIZ WP 708 Power Supply Issue

I went ahead and redid the PNGs to be greyscale for most of the manual and darkened the text a bit so it was easier to read then put it in CBR format.

http://dk.toastednet.org/VIZ_WP-708_...yst_Manual.CBR

File size is about 12MB.

[Mechnix]

Re: VIZ WP 708 Power Supply Issue

Hi, I hate to 'hijack' this thread but my question is related to a Viz power supply...

I have a 'VIZ WP-707 dual power'

The unit is very clean and looks like it's had little use but that's about all I know about it's past life.

The problem I'm having is with one side not behaving like the other side.

Basically I'm just using this for power for a 1/32 slot car track.

The left side works perfect without any issues and never trips the overload protection.

The right side works pretty good but sometimes when you are all the way off the throttle then fully on, the supply will instantly trip off, a touch of the reset button and it's good to go till the next time.

Seems like the more it's continuously used the more it trips.

Looking at the amp gauges it's actually tripping at lower than 1 amp

I tried setting the current level (as per the manual I found here) but it had no effect on this situation.

Seems like the right side power supply doesn't like the sudden change in current going from off to full on.

If both sides did it I'd give up but it seems like it might be a simple issue.

Any help would be greatly appreciated ...oh and if anyone had the manual for this model that would be awesome..

[fionaan]

Re: VIZ WP 708 Power Supply Issue

I do own the original manual.

It says for troubleshooting:

DISPLAY BOARD

1. Blinking Display: Check power supply +5V. Check U215 thru U218.

2. Improper readings: Check power supply +5V. Check regulator U213 and U214 for normal operation. Check voltages on U217/218.

3. Won't Zero: Check voltages on U217/218. Check R227/228. Check +5V supply. Check C210/211.

4. No display but power supply has output: Check [URL="http://www.wattcoenergy.com"]switching mode power supply[/URL] +5V. Check on-board regulators U213/214 for normal operation. Check continuity of all VCC paths to active chips.

5. Unstable display: Check power supply +5V. Check all voltages on U217/218. Check capacitors C203/204 for opens or leakage. Check C211/212.

6. Missing segments on displays: Check each display that exhibits a bad segment by replacement. If this does not correct the problem, checvk U215/216 for output conditions.

7. Decimal point won't move. Check S202/203. Check CR201/202 and CR210/211. Check Q201/202. Check R221/222.

If you need the part numbers that it tells you to check I can give you the list as needed as it's a full page.

I hope to scan the manual in sometime soon, but it will likely be a few weeks before I can get my scanner out of storage.

This helped a lot