misterg
Active member
I put a copyright statement on any that I've designed, and often notice one on other PCBs - I guess it's the track pattern / artwork that's being copyrighted, rather than the board itself.
Andy
navtex clipper problems
- Thread starter bikedaft
- Start date
I put a copyright statement on any that I've designed, and often notice one on other PCBs - I guess it's the track pattern / artwork that's being copyrighted, rather than the board itself.
Andy
bonny
New member
Nasa navtex clipper pro
Hi,
I had a similar problem, where my battery died. I replaced it with an easily obtainable cordless phone battery 3.6V 760mah (original was about 400mah - anything upto about 1000mah will do), simply cut off the plug and soldered it in. Cost about £2 on ebay.
I also had a problem with corrosion in the bottom corner (below the battery) and cleaned this up then laquered the pc board (masking off the connector first). This was done in may 2010.
Last year 2011 I had a problem that the display went black and could not be adjusted with the contrast. This turned out to be a broken 39k resistor (bottom left corner near where the corrosion was. I spent some time figuring out the circuit and this works as follows.
The display board requires a negative supply of around -15V (3rd pin on the 16 pin connector) this is supplied by a pump charge circuit (technically a buck-boost converter) which uses a BC327 transistor and the inductor (which gets a bit warm). This inductor has nothing whatsoever to do with the battery. The transistor switches on and off rapidly (driven by the BC550 from pin 13 of the PIC), energising the inductor which provides a back emf which is rectified by the small diode on the bottom left edge of the board. This charges a capacitor (bottom left corner (1uF 63V). The voltage is monitored by the 39K resistor to the PIC microcontroller (big socketed 28 pin IC bottom left). The PIC monitors this voltage on pin 2. The normal voltage for the display is around -15V which results in about 1.7V pin 2 of the PIC. (The 39K is in series with a 10K to the +6V regulator).
The battery is charged by a 47R resistor via 2 1N4148 diodes from the 6V regulated supply. The battery also provides power through the same 47R resistor to the PIC and another IC. If the battery is short circuit this will pull down the supply to the PIC. If the battery is suspected it can be disconnected and the unit should then work (but will not retain messages onces switched off).
Problems that can occur with the display are:-
Too dark - display voltage is to high (-ve) if this is around -17V check the 39K resistor - could be open circuit - rare.
Too light - display voltage too low (-ve) if this is below about -13V and the inductor gets hot - (ouch hot) try replacing the 10uF 63v capacitor (may have gone leaky).
also try replacing the diode on the left edge (1N4148 should do) You could also try replacing the BC327 and the BC550 (can use BC547) - these are all low cost items - pence.
Mapiln codes for components - prices as of 13th Aug 2012:-
1N4148 - QL80B 49p
BC327 - QB66W 39p
1uF 63V - DT52G 29p (high temp type)
BC547 - QQ14Q 39p (slightly better spec than BC550)
For information, the display normaly draws about 5mA from the -15V supply.
Hope this helps with anyone else having similar problems.
Hi,
I had a similar problem, where my battery died. I replaced it with an easily obtainable cordless phone battery 3.6V 760mah (original was about 400mah - anything upto about 1000mah will do), simply cut off the plug and soldered it in. Cost about £2 on ebay.
I also had a problem with corrosion in the bottom corner (below the battery) and cleaned this up then laquered the pc board (masking off the connector first). This was done in may 2010.
Last year 2011 I had a problem that the display went black and could not be adjusted with the contrast. This turned out to be a broken 39k resistor (bottom left corner near where the corrosion was. I spent some time figuring out the circuit and this works as follows.
The display board requires a negative supply of around -15V (3rd pin on the 16 pin connector) this is supplied by a pump charge circuit (technically a buck-boost converter) which uses a BC327 transistor and the inductor (which gets a bit warm). This inductor has nothing whatsoever to do with the battery. The transistor switches on and off rapidly (driven by the BC550 from pin 13 of the PIC), energising the inductor which provides a back emf which is rectified by the small diode on the bottom left edge of the board. This charges a capacitor (bottom left corner (1uF 63V). The voltage is monitored by the 39K resistor to the PIC microcontroller (big socketed 28 pin IC bottom left). The PIC monitors this voltage on pin 2. The normal voltage for the display is around -15V which results in about 1.7V pin 2 of the PIC. (The 39K is in series with a 10K to the +6V regulator).
The battery is charged by a 47R resistor via 2 1N4148 diodes from the 6V regulated supply. The battery also provides power through the same 47R resistor to the PIC and another IC. If the battery is short circuit this will pull down the supply to the PIC. If the battery is suspected it can be disconnected and the unit should then work (but will not retain messages onces switched off).
Problems that can occur with the display are:-
Too dark - display voltage is to high (-ve) if this is around -17V check the 39K resistor - could be open circuit - rare.
Too light - display voltage too low (-ve) if this is below about -13V and the inductor gets hot - (ouch hot) try replacing the 10uF 63v capacitor (may have gone leaky).
also try replacing the diode on the left edge (1N4148 should do) You could also try replacing the BC327 and the BC550 (can use BC547) - these are all low cost items - pence.
Mapiln codes for components - prices as of 13th Aug 2012:-
1N4148 - QL80B 49p
BC327 - QB66W 39p
1uF 63V - DT52G 29p (high temp type)
BC547 - QQ14Q 39p (slightly better spec than BC550)
For information, the display normaly draws about 5mA from the -15V supply.
Hope this helps with anyone else having similar problems.
Last edited:
OMTRX
New member
Hi,
I also have recently been struggling to get a liquid damaged receiver going. Mine is the Navtex Standard Plus which is quite similar internally to misterg's however it has a few extra components. After extensively cleaning it, the problems I am having are quite similar to the ones described here - the board is getting power but nothing is appearing on screen. I have checked the battery (which appeared corroded) but it seems fine and I have tested the board with three rechargeable AA batteries of which have made no difference. What I can say is that over the last few days poking around with it the display has came on twice. The first time it came on with the welcome screen but faded off after a few seconds; the second time (a few hours later) it came on with garbled text. From looking at the troubleshooting section in the manual this seems to be symptoms of a discharged or faulty battery, however as I say it seems fine. Has anyone any ideas as to what may be the issue? Bonny's post was particularly interesting but the components mentioned are not present on this board from what I can see.
The board looks rally damaged, but everything is in fact making contact
I also have recently been struggling to get a liquid damaged receiver going. Mine is the Navtex Standard Plus which is quite similar internally to misterg's however it has a few extra components. After extensively cleaning it, the problems I am having are quite similar to the ones described here - the board is getting power but nothing is appearing on screen. I have checked the battery (which appeared corroded) but it seems fine and I have tested the board with three rechargeable AA batteries of which have made no difference. What I can say is that over the last few days poking around with it the display has came on twice. The first time it came on with the welcome screen but faded off after a few seconds; the second time (a few hours later) it came on with garbled text. From looking at the troubleshooting section in the manual this seems to be symptoms of a discharged or faulty battery, however as I say it seems fine. Has anyone any ideas as to what may be the issue? Bonny's post was particularly interesting but the components mentioned are not present on this board from what I can see.
The board looks rally damaged, but everything is in fact making contact
misterg
Active member
The battery isn't essential to make it work.
A screen full of garbled characters is normal until you clear the memory.
The negative bias voltage for the LCD is crucial to make the display readable, and is sensitive to contamination, etc. on the pcb. It is generated by the gubbins at the top centre of the lower board in the picture. The lacquer has lifted in this area and the battery juice, etc. will have got underneath it and be allowing current to leak between components in this area which will play havoc with its operation.
I would carefully clean up the PCB and all that loose lacquer so that the battery juice under it can be removed. You should end up with clean, green lacquer or bright copper. When you do this, you may well find that component leads have been eaten through by the battery juice (which is alkaline, btw.). Even if not, cleaning up the board will likely fix things.
Fibreglass pencils are handy for this sort of thing:
Andy
A screen full of garbled characters is normal until you clear the memory.
The negative bias voltage for the LCD is crucial to make the display readable, and is sensitive to contamination, etc. on the pcb. It is generated by the gubbins at the top centre of the lower board in the picture. The lacquer has lifted in this area and the battery juice, etc. will have got underneath it and be allowing current to leak between components in this area which will play havoc with its operation.
I would carefully clean up the PCB and all that loose lacquer so that the battery juice under it can be removed. You should end up with clean, green lacquer or bright copper. When you do this, you may well find that component leads have been eaten through by the battery juice (which is alkaline, btw.). Even if not, cleaning up the board will likely fix things.
Fibreglass pencils are handy for this sort of thing:
Andy
Last edited:
winsbury
New member
Navtex pro plus exhibited blank screen until powered on 5 minutes or so. Then gradually text started to appear but many horizontal lines ( individual pixels) missing on screen. Left it powered up for a full 2 days and display returned completely to normal. Opening the case revealed minor battery leakage; not as bad as many of the photos above. Removed the battery and the unit continued to work perfectly except loses its memory and resets on each power cycle so am currently awaiting a new battery via ebay. I also left the unit off without the battery for a few hours and powered back on and the missing pixels problem recurred and gradually fixed itself. I figure one or more of the electrolytics has gone awol too so have a new set on order. I'll update the thread once Ive fitted the parts and fingers crossed it will be good for another 20 years
winsbury
New member
As promised: all new electrolytic capacitors fitted and a 3.6v 3x short AA NiMh rechargeable telephone battery fitted. It was a bit fiddly but if you are decent with a soldering iron and desolderer its not that hard. Total cost around £6 for parts and took about 40 minutes and it works beautifully again. Just one line on the lcd is a fraction lighter than the rest but once its warmed up for 5 mins it looks perfect.I'll update the thread once Ive fitted the parts and fingers crossed it will be good for another 20 years
nigel1
Active member
Just had a similar issue with my Nasa Clipper Navtex. When switched on, completely blank screen.
Removed the display unit and brought back home for investigation.
Opened up the casing, no apparent damage noted, but based on this thread, ordered a new battery BT NiMH 3.6V 650mA T279, - original battery is 3.6V 350mA, but could not find one, but as it turned out, the replacement is just about the same dimensions as the original, cost including postage £6-70.
BT NiMH 3.6V 600mAh Cordless Telephone Battery T279 4LR3WS
I thought rerplacement would be easy, snip off the original battery leads close to the old battery, remove battery, and then use small connectors to connect the new battery to the original leads. However, when stripping back the insulation on the original negative wire, it detached itself from the board, and on closer examination, it appears that slight battery leakage had wicked down the wire and corroded the whole length.
Ended up soldering the new battery leads to the board, and secured the new battery in place with a double sided sticky pad.
Refitted the display on the boat , powered up, and it came back to life immediatly.
I would suggest that anyone with a Clipper Navtex with original battery check the condition of the battery, as I have seem some pictures of the damage that a leaky battery can cause to the board and components.
Removed the display unit and brought back home for investigation.
Opened up the casing, no apparent damage noted, but based on this thread, ordered a new battery BT NiMH 3.6V 650mA T279, - original battery is 3.6V 350mA, but could not find one, but as it turned out, the replacement is just about the same dimensions as the original, cost including postage £6-70.
BT NiMH 3.6V 600mAh Cordless Telephone Battery T279 4LR3WS
I thought rerplacement would be easy, snip off the original battery leads close to the old battery, remove battery, and then use small connectors to connect the new battery to the original leads. However, when stripping back the insulation on the original negative wire, it detached itself from the board, and on closer examination, it appears that slight battery leakage had wicked down the wire and corroded the whole length.
Ended up soldering the new battery leads to the board, and secured the new battery in place with a double sided sticky pad.
Refitted the display on the boat , powered up, and it came back to life immediatly.
I would suggest that anyone with a Clipper Navtex with original battery check the condition of the battery, as I have seem some pictures of the damage that a leaky battery can cause to the board and components.
Refueler
Well-known member
This is interesting as I have a Nasa Navtex that has been dead for ages ... tried leaving it powered for days ... nothing.
I did take apart and didn't see anything untoward - but will check again once home after travels.
It is an old unit though ... wonder if it really worth it !!
I did take apart and didn't see anything untoward - but will check again once home after travels.
It is an old unit though ... wonder if it really worth it !!
nigel1
Active member
Replacement unit about £260, so I thought changing the battery was worth a try.
From what found out through internet searches, symptons of a dead/shorted battery is that the display goes completely blank. At first glance, my unit appeared fine, no signs of damage to the PCB's.
Refueler
Well-known member
I gathered that from this old thread ....
My query now is whether my very early Navtex unit will actually be worth the effort ? Its the basic model from the early Nasa days ... before the Pro.
With the Active antenna
