DRO display problem

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DRO display problem

This topic has 9 replies, 7 voices, and was last updated 1 March 2023 at 00:42 by John Doe 2.

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26 February 2023 at 23:41 #635201
Roderick Jenkins
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@roderickjenkins93242
The DRO display on my mill has a problem with the top line of the X display. On switch on, the very top line of the display is missing. After being on for about 5 minutes the top line appears and all is normal. However, yesterday the problem persisted all day. I'm guessing there is a dodgy contact somewhere that used to sort itself out once the display warmed up but now it's permanent. The system is a good umber of years old and way out of warranty. Any advice before I start taking it apart and ruining it permanently?

Cheers,

Rod
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26 February 2023 at 23:41 #34181
Roderick Jenkins
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@roderickjenkins93242
27 February 2023 at 00:34 #635205
Ady1
Participant
@ady1
bright light, headband magnifyer, patience and luck

Look for dodgy ribbon cables first was my old computer method, they can look fine but are shot
27 February 2023 at 07:03 #635209
David George 1
Participant
@davidgeorge1
Ring M DRO. They have a service engineer who will sugest where to look evan out of warranty.

01992 455921

David
27 February 2023 at 07:51 #635212
John Doe 2
Participant
@johndoe2
The top display seems to have lost contact with the common rail of the top segment of the display.

Depending how good you are at tackling electronics, you will need to disassemble the unit and with luck the displays will be in sockets. If so, very gently and carefully prise the top display out of its socket – a millimetre at a time and keeping it square as you do so. When the display is free, spray some proper electronic contact cleaner (NOT WD40), onto the terminals of the display and the socket. Then replace the display – making absolutely certain that all the pins are correctly into the socket, it can be easy to bend one over – and once plugged fully in; gently push and pull the display in and out by just a millimetre a few times to thoroughly clean all the pins and sockets. Leave for an hour or so for the contact cleaner to evaporate, and you should be back in business.

Alternatively, the display might have a ribbon cable rather than a built-in plug/socket arrangement, but the same methodology will apply.

If the displays are soldered in, you will have to melt and allow to re-solidify each soldered connection of the display on the PCB, since there will be a dry joint somewhere.

Actually, quick and dirty : if the displays are in sockets move each display without withdrawing it from its socket – just gently angle it ; pushing very slightly side to side and up and down by a millimetre or so. That might do it.

If it has a ribbon cable, ditto with the ribbon connector still in its socket. If the display is soldered in to the PCB, this won't do anything.

Edited By John Doe 2 on 27/02/2023 08:05:24
27 February 2023 at 09:39 #635218
SillyOldDuffer
Moderator
@sillyoldduffer
As per John Doe. First thing I would try is easing and reseating any plugs and sockets with a squirt of Servisol switch cleaner. Physical plugs and sockets depend on metal to metal contact, usually spring loaded, and they're vulnerable to dirt, corrosion, and coming loose due to vibration and heat expansion / contractions. (The latter is consistent with the symptoms – a intermittent contact due to tiny movements as the head heats up.)

The connectors that clamp the end of thin ribbon cables are more reliable in my limited experience, but may also be worth reseating.

Rarely, you might find a cable that's pulling a connection apart due to poor installation, or something else fouled the wire when the unit was built.

Last 'easy' thing to look for are faulty solder joints. Maybe a pin that should have been soldered was missed, or the solder failed to flow properly because of a flux or dirt problem, or a 'dry joint'. Look for joints with no solder, dirty solder not fully flowed over the connection, and solder with a cloudy crystalline look. Bad joints are obvious once spotted, the only problem is the need to hunt through a multitude of solder connections with an eyepiece! Once identified, mostly easy to fix – just clean the area and remake the joint with a dash of fresh solder. Although the same fix in principle, I struggle with modern electronics because sub-miniature components are too small for me!

Dave
27 February 2023 at 11:03 #635234
Ian P
Participant
@ianp
As far as I can recall each 7 segment display is soldered to the main PCB as are 95% of all the components and keypad switches. So a large PCB and the PSU module are the two main contents of the enclosure.

Since the fault is affecting the top segments of only one section of the display the fault is not likely to be just in one character. Probably all the top segments in that row will be connected to the same PCB track and connected to a pin on whatever chip is driving them.

Careful inspection (with a very strong loupe) of the soldered joints on the PCB might be rewarding.

Ian P
27 February 2023 at 11:24 #635235
Dave Halford
Participant
@davehalford22513
Dry joints can work for years and then give up.

They look more bead like and dull, good joints are bright and spread out on the track.

It's just as likely to be a connector that just needs reseating, even gold contacts can benefit. To be clear reseating means fully remove and replace plugs, I wouldn't go spraying anything on them.
28 February 2023 at 23:09 #635428
Roderick Jenkins
Participant
@roderickjenkins93242
Thanks for the comments chaps. The wretched thing has reverted to being fully functional after 5 minutes but I will open it up and have a look round when I've finished a couple of present projects.

Cheers,

Rod
1 March 2023 at 00:42 #635435
John Doe 2
Participant
@johndoe2
Posted by Dave Halford on 27/02/2023 11:24:35:

It's just as likely to be a connector that just needs reseating, even gold contacts can benefit. To be clear reseating means fully remove and replace plugs, I wouldn't go spraying anything on them.

Many of the BBC television outside broadcasts you watched and listened to in the 80s and 90s were courtesy of a cleaner spray called 'Colclene' that we used to clean electronic contacts on cable interconnects between OB vehicles, and other electronic devices in the signal chain…….Seemed to work just fine.

Edited By John Doe 2 on 01/03/2023 00:43:30
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