Newall Digital Readout troubleshooting

[R Lamparter]

This is a DP7 digital readout for a milling machine and the reader shows no display.  The only indication of power is the green LED for in/mm glows when turned on.  The manual says that this is an indication that "the voltage of the power source is too low".  There is a corroded 3.6V battery on the mainboard, but the net says that this battery only affects memory, and the corrosion hasn't damaged any nearby traces.  The battery is not likely the cause.  I scanned the power supply and I don't spot any bulged capacitors or burned components.  It has a 6 wire output cable, but I have no idea how to even test the outputs from that.  The wire labeled #1 has a black stripe, so I assume that's the ground.  I have an email in to Newall, but from scanning around on the web, they have a reputation of not releasing their schematics and requesting that the devices be sent for service.  I am an electronic novice.  Where / how do I start troubleshooting this switch mode power supply?  I have available a multimeter and one of the multifunction transistor, diode, ESR, etc. testers.  I have an HP 54601 oscilloscope, but don't really know how to use it yet (it was too cheap not to buy it).

[Seekonk]

I just might have a couple new 3 axis ones.  I was going to import them from China and then Newell found out.  I'm always suspicious of those connectors.  I just worked on another readout and I had to solder the wires directly to the pins to get it to work. I had done the same thing to the other end of the cable just about five years ago.  I'd look for familiar voltages to see if they were there.  The 5V can get low if the output caps dry out.

[R Lamparter]

Is it safe to put one probe of the multimeter on pin #1 (wire with the black stripe) and touch each of the other pins in sequence to see what the voltages are, or will that cause problems?

[R Lamparter]

I checked the voltages  on the output pins.  With Pin 1 as the ground, I got the following values
Pin 2: -7.5v
Pin 3: -7.5v
Pin 4: -12.7v
Pin 5: -12.7v
Pin 5: -24.8v

I assume the next step is to desolder all of the electrolytic capacitors on the secondary side and test them, right?

[Seekonk]

Pins 4 & 5 are common.  I'd start looking elsewhere.

[R Lamparter]

Pins 4 & 5 are common.  I'd start looking elsewhere.

Pins 2&3 have a common trace also.  I wondered if they were supposed to be -12v or -5v rather than -7.5v.  If looking for something other than replacing the electrolytic capacitors, where else would you look or what other tests should I do?

[Seekonk]

+5 & +12.   I'd look to see if the power actually made it to the other board.

[lowimpedance]

 One other thing are those resistors in the photo top left burnt ?.(cant tell well enough from the pic.). Near the power connector.
I have repaired two Newall readouts at work and it was the supply in both cases, (both completely dead though). Maybe excessive ripple with yours as you seem to have some life.
 Any away you should be able to get similar replacement types at the usual places like RS , Element 14, etc. Dont trust Ebay ones.

[R Lamparter]

+5 & +12.   I'd look to see if the power actually made it to the other board.

Hmmm.  I need a little more instruction on taking voltages - a real newbie question.  I had the black lead on Pin #1 (wire from this had a black stripe), assuming that was ground and where the black lead should go.  How do you know whether to place the black or red lead on the pin with the black stripe?

I'll check to see if the power is getting to the end of the connecting cable and report back.

[R Lamparter]

+5 & +12.   I'd look to see if the power actually made it to the other board.

I checked.  Directly from the pins at the mainboard end. 
Pins 2&3 -6.8v
Pins 4&5 -12.1v
Pin 6 -25.5v

[R Lamparter]

One other thing are those resistors in the photo top left burnt ?.(cant tell well enough from the pic.). Near the power connector.
I have repaired two Newall readouts at work and it was the supply in both cases, (both completely dead though). Maybe excessive ripple with yours as you seem to have some life.
 Any away you should be able to get similar replacement types at the usual places like RS , Element 14, etc. Dont trust Ebay ones.

They looked odd to me when I first took the head apart, but I glossed over them because they weren't black.  I looked more closely today and they must have heated to the point where their values are no longer readable.  I didn't have time to take that board out and unsolder them to check resistance.  Closeup of the mainboard resistors in question below.  Any idea what their values should be?

[lowimpedance]

Can you still measure them with your multimeter, at a guess they are 10  1 watt. As for the supply post a pic of both top (connector end with the ribbon con. removed) and the solder side.
I cannot remember exactly but the +5 and 12 volt supplies sound right. What you are getting is either wrong ref 0v (reason for more pics of the supply), or the supply is stuffed.

[R Lamparter]

Can you still measure them with your multimeter, at a guess they are 10  1 watt. As for the supply post a pic of both top (connector end with the ribbon con. removed) and the solder side.
I cannot remember exactly but the +5 and 12 volt supplies sound right. What you are getting is either wrong ref 0v (reason for more pics of the supply), or the supply is stuffed.

I unsoldered the two burned looking resistors.  They each measured 33 ohms.  That value fits with what remains of the color bands - orange, orange, black, gold for both of them.  I wasn't sure if they were red, red, black, but the 33 ohms suggests they were orange rather than red.  Photos of the power board in a second post.

[R Lamparter]

As for the supply post a pic of both top (connector end with the ribbon con. removed) and the solder side.
I cannot remember exactly but the +5 and 12 volt supplies sound right. What you are getting is either wrong ref 0v (reason for more pics of the supply), or the supply is stuffed.

Here are top and bottom photos of the power board.  I have closups of the triacs/scr's if needed.  Pin #1 was my reference and I connected the black wire of the multimeter to that.

[lowimpedance]

Okay , Measure again (being real careful here as mains is nearby!) using pins 4 and 5 as GND or common and see what pin 1, 2 and 3, and 6 have on them.

[Seekonk]

Using pins 4 and 5 as GND or common and post what voltages are on each side of those burnt 33 ohm resistors.  I wouldn't concentrate on the external power supply.  Your problem is on the main board.

You should have mentioned those resistors first off.

[R Lamparter]

Thanks lowimpedance & Seekonk.

Pins 4/5 (black=common) to 2/3 = +5.1V
Pins 4/5 Comm to 6 = -12.1v
Pins 4/5 Comm to 1 = +25.0 V

I hadn't carefully examined the two resistors on the main board because I was looking for something blackened, my inexperience. I just noted they looked a little funny.  It wasn't until I looked at them again when lowimpedance pointed them out that I noticed that they were cooked.   I had also jumped to the conclusion that I must have a power supply problem based on what the manual said about insufficient voltage.

I looked at the undersurface of the board to see what might make you guys say that 4/5 was the common/ground.  The only thing I note is that there's an almost continuous trail of solder on that trace.  Is that a hint that something is the ground?

I picked up a pack of 33 Ohm 2% tolerance, 1 Watt resistors at the local electronics supply today.  We're lucky to have a real electronics shop in in the area.

[lowimpedance]

Actually I would concentrate on the supply and if the +25v measured (under load??)was correct then its certainly stuffed. That rail should be +12V.
The 33 ohm resistors are in parallel and form a minimum loading on the +5V rail so one side will be 5 ish V and the other 0V.
Did you measure those voltages when the readout unit was plugged in?.

[R Lamparter]

I checked the pins on the mainboard when under load.  Using 4/5 as the common/ground
4/5 to 2/3 = +5.3v
4/5 to 1 = +12.3v
4/5 to 6 = -13.6v
The two new 33 ohm resistors got hot and I unplugged it.  After I reread the posts from yesterday and went back to check the voltage on either side of the new resistors the main fuse to the power cord was blown.  I need to find another fuse.  I'll do that and report back - hopefully tomorrow.

[Seekonk]

5V on 33 ohms is 3/4W.  5V is not turninig them into a charred mess. What are those heat sinked transistors doing?

[lowimpedance]

The resistors do get quite hot and the appearance is more long term baking leading to the paint peeling .
The two readouts at work that needed new supplies both had the BBQ d resistor's as well. After supply and resistor replacement they have been running years powered on 24/7. The resistor's were changed as a matter of course ,both had not gone open but still measured okay.
It appears you're supply is okay by your measurements thus if still no display then the problem is on the main board..
Check the output of each regulator with the heatsinks, close up pic to see what part no. They have will hell.

[R Lamparter]

I'm providing closeup photos of the four heat sinked transistors.  I've identified them as best I can using the numbers.  What I don't know are details on how to check them.  Do I unsolder them from the board to test them or do I test them on the board?  I've done a little looking so I know that each will be tested like diodes if out of the board.  Or were you guys requesting voltage readings from their leads while under power?

[Seekonk]

Close up heatsink area of the main board, not the power supply.  I'm curious about what those two heatsinked parts do on the main board and L1. Doesn't seem like there is any further need for regulation as it is too old for 3V3 parts.

[R Lamparter]

Close up heatsink area of the main board, not the power supply.  I'm curious about what those two heatsinked parts do on the main board and L1. Doesn't seem like there is any further need for regulation as it is too old for 3V3 parts.

They are a 12v and 5v regulator.  Closeup of the chips and basic data attached.  Getting a shot of the opposite side will be problematic, but may have to be done eventually if they need to be removed for testing.  A display board is (*I think*) soldered in place over the area of  the back side of the regulator area.

Also.  I'm held up a little bit on the fuse.  The counter person at the electronics shop had a pack of the T1A 250V fuses in Buss brand for between $13 - $14.  He suggested that he could get the generic brand for $6 a pack for me by early to mid week, if one of the other stores had them in stock.  At half the price, I went with his suggestion.

[Seekonk]

They may have decided to separate the power to the glass slides, having them powered by power supply and the board itself powered by the on board regulators.  Since the board is dead, likely one of those is bad.  Check what is going into them and if anything is coming out.  If the 5v is bad it could have been from a tantalum cap shorting.  Before just replacing the regulator, check resistance to ground. It should be at least a couple hundred ohms.

When I have a bad cap on a board, I generally power it with an external supply that is capable of a couple amps current limited. Regulators are supposed to get hot and go into current limiting. The bad cap often will heat up a little.  Measuring the voltage across each cap on the mv range can also get you close.  If you have lived a good life it won't be a chip. Start with low currents so the chips don't go up in smoke if bad.  Write down the part numbers to be safe. 

[R Lamparter]

They may have decided to separate the power to the glass slides, having them powered by power supply and the board itself powered by the on board regulators.  Since the board is dead, likely one of those is bad.  Check what is going into them and if anything is coming out.  If the 5v is bad it could have been from a tantalum cap shorting.  Before just replacing the regulator, check resistance to ground. It should be at least a couple hundred ohms. 

Again, my newbieness showing.  Just to be clear.  When you talk about testing "resistance to ground" , that means I would put the black lead of my meter on the center lead of the regulator and touch the red lead to each of the outside leads.  Right?

When I have a bad cap on a board, I generally power it with an external supply that is capable of a couple amps current limited. Regulators are supposed to get hot and go into current limiting. The bad cap often will heat up a little.  Measuring the voltage across each cap on the mv range can also get you close.  If you have lived a good life it won't be a chip. Start with low currents so the chips don't go up in smoke if bad.  Write down the part numbers to be safe. 

Below is a photo of the only external power supply I have, an old analog one that was intended for a Caswell plating setup.  The meters give results that are close, but outputs aren't exact.  Is it safe to use this type of power supply for the testing?  If I'm understanding correctly, I'd start out with settings of 5v and less than an amp of output and do my testing of the tantalum capacitors near the power regulators, such as C26, C17 & C18 in the photos.

[lowimpedance]

One thing I forgot about till now is the supplies in the two DP7 Newalls here are +/-15V and 5V whereas yours is 12V , 5V   .
So question did you have this unit before in working condition ? or have you obtained it as a faulty one? thus not having seen it previously working.
Does it appear as if some one else has been in there if you received it in this non working condition?.
Your readout appears to be only X and Y, no Z, for a lathe perhaps instead of a mill !.
As for measuring the regulator outputs with respect to the 0V, do a google on the part number to get the pin outs of that package and then check the voltage going in and coming out.

[R Lamparter]

One thing I forgot about till now is the supplies in the two DP7 Newalls here are +/-15V and 5V whereas yours is 12V , 5V   .
So question did you have this unit before in working condition ? or have you obtained it as a faulty one? thus not having seen it previously working.
Does it appear as if some one else has been in there if you received it in this non working condition?.

It was given to me by a neighbor.  The company he works for was pitching it and he thought it worked.  I don't know if it was worked on previously. The only indication that it could have been worked on previously is that there is a hand written ID for the fuse of F2A 250V (fast blow 2 amp?) seen near the input power connector in the photo below.
With regard to the proper voltages, I wonder if the marking on my power supply board is the same as yours "60-03215 Rev. L"  seen on the soldered side of the board and if we both have DP-7 display units. 

As for measuring the regulator outputs with respect to the 0V, do a google on the part number to get the pin outs of that package and then check the voltage going in and coming out.

The diagrams for both voltage regulators showed the middle pin as the ground so I assumed that's where you'd put the black multimeter lead to test the voltage/component.

[lowimpedance]

As for measuring the regulator outputs with respect to the 0V, do a google on the part number to get the pin outs of that package and then check the voltage going in and coming out.

The diagrams for both voltage regulators showed the middle pin as the ground so I assumed that's where you'd put the black multimeter lead to test the voltage/component.
[/quote]
 That will do.

[R Lamparter]

They may have decided to separate the power to the glass slides, having them powered by power supply and the board itself powered by the on board regulators.  Since the board is dead, likely one of those is bad.  Check what is going into them and if anything is coming out.  If the 5v is bad it could have been from a tantalum cap shorting.  Before just replacing the regulator, check resistance to ground. It should be at least a couple hundred ohms.

For the 12v regulator
Ground to Input = no reading/infinity
Ground to Output = starts ~100 ohms and increases (a capacitor seems to be charging)

For the 5v regulator
Ground to Input = Starts at 15 ohm and increases like a capacitor charging
Ground to Output = Starts about 100 ohms and increases like a capacitor charging.

The tests between ground and input for the two regulators behave differently, so possibly one of these is bad; however, I don't know if these measurements are meaningful.

[lowimpedance]

Now power up and measure the volts on the inputs and outs with respect to the gnd, and post results.

[R Lamparter]

I discovered that both voltage regulators are being fed by pins 4/5 to 1, the 12v power supply.  The 5v power from 4/5 to 2/3 doesn't go to either of the voltage regulators.

With 12.3v being fed to the board from pins 4/5 to 1
5v regulator Ground to In = 10.64v
                    Ground to Out = 4.97v

12v regulator  Ground to In = 12.3v
                       Ground to Out = 11.94v

While I had it powered, I checked the nearby tantalum capacitors  C26=12.14v,   C17 & C18 both = 4.97v
The board was pulling less than half an amp on the power supply's analog meter.

It would appear that both regulators are working.  Now what?

[Seekonk]

At this point power likely isn't a problem.  Do you have a scope?  I would be looking on the pins of the micro to see if it is clocking.   The display is matrix driven.  If the micro is working then there have to be some display bits that are toggeling.

[R Lamparter]

At this point power likely isn't a problem.  Do you have a scope?  I would be looking on the pins of the micro to see if it is clocking.   The display is matrix driven.  If the micro is working then there have to be some display bits that are toggeling.

I do happen to have a HP 54601a scope (because I got it cheap).  My experience using it is getting the square wave pattern built into the unit.  I'm lost when you say looking at the pins of the micro.

[techineer]

I have been working on one of these for a client, with the exact same symptoms and readings, and may have your solution if you are still trying to solve it.

The switchmode power supply for this unit is supposed to put out +5V, +15V and -15V.  (Look for the label on the side of the big can capacitor near the input power connector.) The readings you indicated were +12V.   This is too low.
The processor board has a circuit that compared the input voltage to the output of the 12V regulator.  If the input voltage is low, it holds the CPU in a reset state, so there is no activity. 

The problem I found on the one I have is that the filter caps in the switchmode power supply are going bad and not filtering the output voltage properly.  I would recommend replacing all of them.  The unit was probably built during the "capacitor plague" era.  (Google it!)  If you look closely at the tops of the capacitors, you may see that one or more is bulging slightly.

These capacitors can be ordered from Mouser Electronics (www.mouser.com)

You will need:
Quan     Mouser#                       MFR PN#                           Mfr name                              Description
2 - 661-EKYB160E102MJ16S   EKYB160ELL102MJ16S   United Chemi-Con (UCC)      Aluminum Electrolytic Capacitors - Leaded 16V 1000uF 20% Tol.
1 - 661-EKZN100E222MJ25S   EKZN100ELL222MJ25S   United Chemi-Con (UCC)      Aluminum Electrolytic Capacitors - Leaded 10V 2200uF 20% Tol.
2 - 661-EKYB250E471MJC5S   EKYB250ELL471MJC5S   United Chemi-Con (UCC)      Aluminum Electrolytic Capacitors - Leaded 25V 470uF 20% Tol.
1 - 661-EKYB350E331MJC5S   EKYB350ELL331MJC5S   United Chemi-Con (UCC)      Aluminum Electrolytic Capacitors - Leaded 35V 330uF 20% Tol.
1 - 647-UPM1H470MED1TA   UPM1H470MED1TA   Nichicon      Aluminum Electrolytic Capacitors - Leaded 47UF 50V 105c
1 - 647-URZ2G680MRD   URZ2G680MRD   Nichicon      Aluminum Electrolytic Capacitors - Leaded 400volts 68uF 20x25 20% 10LS

Carefully unsolder the leads from each capacitor using a 30 - 40 watt iron.  Use a vacuum bulb to slurp up the excess solder, then use a knife or tool to straighten the leads and pull the cap out.  Note the direction of the stripe on the side.  The new cap will have to go back in the same way. Solder the leads to look like the original, then clip the excess lead.  Be careful not to burn the board.  Remove and replace one cap at a time.  Mark the tops of the old ones so you can tell which ones to remove.

When you are done, the power supply should again be putting out + and - 15V on the end pins, and there is a very good chance the display will work.  If it is not connected to its sensors, it will display "SIG FAIL" on both windows.

[R Lamparter]

Thanks for the help.  It will be a while until I can get back to the Newall project.  I'm sure your information will be helpful to others as well.

[DanLins]

Techineer,

I have a Newall DP7 here with the same power supply readings measured by R Lamparter. I've ordered the caps you mention, fairly cheap, so no big loss if they do not fix it. However, I'm reading right around 2 vdc on the onboard battery, which is a GP 3.6 volt, 70 mAh NiCad. (GP70BVT X3 G4)

I think these retain memory for setup and some parameters. However, I cannot find a source for this battery replacement. Any ideas?

Thanks,

Dan Linscheid

[Seekonk]

I don't see any reason you couldn't just put a Li battery in it.  So it only charges to maybe 3.8V, that would be fine.

[DanLins]

Just wanted to follow up on this. I replaced the battery as discussed, as well as every single electrolytic capacitor on the power supply board and the display now lights up!

With no scales connected (they are over at my brothers shop on his lathe), it goes through some kind of bootup and displays SET U, whatever that means.

Thanks,

Dan L

[Graham S]

Sorry to drag this thread up but it was very helpful to me and I want to add to it for anyone else searching for the same.

My PSU also stopped working but I found that this style of PSU is quite common, I was able to buy a replacement from RS (radio spares), part 183-0054

This is a Artesyn LPT45 but there were several others that would have worked.

It fitted the mounting holes and the connectors too. Note that it needs a load to regulate properly, that confused me when I was testing it.

Cheers,

Graham

[lowimpedance]

Sorry to drag this thread up but it was very helpful to me and I want to add to it for anyone else searching for the same.

My PSU also stopped working but I found that this style of PSU is quite common, I was able to buy a replacement from RS (radio spares), part 183-0054

This is a Artesyn LPT45 but there were several others that would have worked.

It fitted the mounting holes and the connectors too. Note that it needs a load to regulate properly, that confused me when I was testing it.

Cheers,

Graham

Keep an eye on the battery condition , leakage will cause PCB damage. Also some settings may need to be re entered at startup (either a 'hidden' button or 'button sequence' to get to the menus), if you change the battery. Scale type/corrections etc , cant remember exactly but differ between models.

[Rui Loureiro]

Hello !
 I have same problem with one Newall Dp7, that came with one old machine !
One friend of mine with knowledge in electronics is helping me .
In my case the mm/inches led powers up but then nothing happens. We already checked power  levels , tested some capacitors changed battery...
My friend thinks the problem is in the transistor down the battery. Old battery may have leaked some acid to the board and killed it . The transistor is in TR12 position on board.
Can any help me with the reference of this transistor ?
Thanks

[lowimpedance]

 There is quite a bit of damage to the PCB traces which needs to be fixed first, ie scraping off whats left of the solder resist  on the affected traces and CLEAN all areas where battery leakage has gone. Next check for open PCB traces and bodge in a bridge wire where required. Note any components in the 'damage zone' should be removed and /or replaced after PCB clean and repair.
 The transistor is possibly the buzzer driver !?., there should be a part number printed on it which hopefully will produce a search result !. (most likely a generic part , just a guess though without any further information.). If you do manage to get it to work you will need to set some settings for the scales used etc , see the relevant manual for details.

[Rui Loureiro]

The problem is that the acid erased the reference...We only can see " 354 "      but we need to know the letters before .
If anybody have one opened DRO and can see it for me , I will be very grateful ! 
Thanks

[Rui Loureiro]

There is the transistor that is damaged. One diode is damaged too but we can see the reference
My friend put the transistor  under microscope, only can see ...C54?? (it is in TR12 position on the board ...)
Anyone can help ? The reference is stamped in the transistor

Thanks

[ericscott]

This post likely is too late to help, but in case needed, TR12 is a C546 PH36.

I have the same issue with my Newall DP7, where the PSU is good, but the pcb tracks around the battery and buzzer have corroded.

Did you have any success in repairing the board tracks?  Were there any additional damaged components?

[Graham S]

 Keep an eye on the battery condition , leakage will cause PCB damage. Also some settings may need to be re entered at startup (either a 'hidden' button or 'button sequence' to get to the menus), if you change the battery. Scale type/corrections etc , cant remember exactly but differ between models.

This was good advice that I didn't see or ignored (can't remember which). The display started to go haywire yesterday, obviously wrong pulse/mm setting or something now "SET UP" appears on boot. Battery is dead and the PCB is somewhat corroded, the tracks were still OK, just, but I have reinforced them with wire and ordered a new battery pack.

[ddrumguy]

I know this is an older thread but hoping someone can assist. I too just received a used Newell X/Y DRO and it will light up the little green light but i have nothing in the displays. It appears that the battery IS corroded and the two resistors in the upper left corner look like they got warm and the paint is chipping off of them, i haven't pulled the circuit board to look at traces underneath. I am not an electronics guy but could possibly solder on new resistors and a battery. Also where is everyone sourcing the battery for these things? I haven't been able to find one. If anyone would be willing to hold my had through this i would greatly appreciate it. Thanks in advance

[ddrumguy]

was hoping someone would respond so in the meantime i measured voltage or at least thought i did - will have to check again not realizing pin4/5 were common (i was using black stripe wire as common). Anyway, i saw this video on youtube ( ) where he turned a potentiometer to get more power on the outputs. I did this and the displays lit up and it did increase the power on the outs a bit (going to recheck these though). Any danger in turning this pot up to get things working? or is it just a sign that the PS is going bad (i assume). Also was able to get the battery unsoldered. any reason why a guy couldnt solder wires in those pins and have a battery off the board so the issue of leaking on the board could be mitigated?

anyway just some random thoughts - hopefully someone will weigh in.. feel like im talking to myself here.