Author Topic: Newall Digital Readout troubleshooting  (Read 7985 times)

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Offline R Lamparter

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Re: Newall Digital Readout troubleshooting
« Reply #25 on: May 21, 2017, 05:57:56 pm »
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.
 

Offline lowimpedance

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Re: Newall Digital Readout troubleshooting
« Reply #26 on: May 22, 2017, 12:47:13 am »
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.

The odd multimeter or 2 or 3 or 4...or........can't remember !.
 

Offline R Lamparter

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Re: Newall Digital Readout troubleshooting
« Reply #27 on: May 22, 2017, 01:58:50 am »
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.
 

Offline lowimpedance

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Re: Newall Digital Readout troubleshooting
« Reply #28 on: May 22, 2017, 02:40:30 am »
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.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 

Offline R Lamparter

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Re: Newall Digital Readout troubleshooting
« Reply #29 on: May 23, 2017, 12:40:35 am »
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.
 

Offline lowimpedance

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Re: Newall Digital Readout troubleshooting
« Reply #30 on: May 23, 2017, 02:56:15 am »
Now power up and measure the volts on the inputs and outs with respect to the gnd, and post results.
The odd multimeter or 2 or 3 or 4...or........can't remember !.
 

Offline R Lamparter

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Re: Newall Digital Readout troubleshooting
« Reply #31 on: May 23, 2017, 09:00:24 pm »
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?
 

Offline Seekonk

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Re: Newall Digital Readout troubleshooting
« Reply #32 on: May 23, 2017, 11:30:11 pm »
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.
 

Offline R Lamparter

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Re: Newall Digital Readout troubleshooting
« Reply #33 on: May 24, 2017, 01:08:46 am »
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.
 

Offline techineer

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Re: Newall Digital Readout troubleshooting
« Reply #34 on: November 16, 2017, 11:39:05 pm »
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.
 
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Offline R Lamparter

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Re: Newall Digital Readout troubleshooting
« Reply #35 on: November 17, 2017, 02:06:35 am »
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.
 

Offline DanLins

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Re: Newall Digital Readout troubleshooting
« Reply #36 on: July 15, 2018, 08:16:39 pm »
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
 

Offline Seekonk

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Re: Newall Digital Readout troubleshooting
« Reply #37 on: July 19, 2018, 05:20:32 pm »
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.
 

Offline DanLins

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Re: Newall Digital Readout troubleshooting
« Reply #38 on: July 24, 2018, 06:57:51 pm »
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
 


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