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I have a DPO70804 scope. The display is dark. I have determined that the fluorescent backlight tubes are not lit. I connected an XGA monitor to the XGA socket on the rear, and the XGA monitor displays the scope display and all functions are working correctly.
I have been trying to determine if the display tubes or the voltage supply for those tubes is bad, or if the problem is elsewhere. The service manual I have for the unit contains no schematics nor any info on a way to test the fluorescent display circuit.
The power supply board has a 20-pin plug with voltages on the pins. All the voltages are correct as per a drawing in the manual, except for the -5 volt pin (pin 18). That measures 0 volts. But on the drawing, there is an asterisk next to the -5 volt pin, with no explanation I can find anywhere of what the asterisk means. The PS-ON pin measures 0 volts and the PW-OK pin measures +5 volts.
Can anybody give me any guidance or suggestions?
Zack
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That probably uses LED backlighting, and that may have a separate power connector. So look for that¡ I doubt it¡¯s got the old CCFL backlight, but that would certainly be a separate connector as the voltage is too high to include with signals. Good luck and keep us posted. dan ?
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From: [email protected] <[email protected]> On Behalf Of Zack Widup via groups.io
Sent: Tuesday, April 16, 2024 1:42 PM
To: [email protected]
Subject: [TekScopes2] DPO70804? I have a DPO70804 scope. The display is dark. I have determined that the fluorescent backlight tubes are not lit. I connected an XGA monitor to the XGA socket on the rear, and the XGA monitor displays the scope display and all functions are working correctly. I have been trying to determine if the display tubes or the voltage supply for those tubes is bad, or if the problem is elsewhere. The service manual I have for the unit contains no schematics nor any info on a way to test the fluorescent display circuit. The power supply board has a 20-pin plug with voltages on the pins. All the voltages are correct as per a drawing in the manual, except for the -5 volt pin (pin 18). That measures 0 volts. But on the drawing, there is an asterisk next to the -5 volt pin, with no explanation I can find anywhere of what the asterisk means. The PS-ON pin measures 0 volts and the PW-OK pin measures +5 volts. Can anybody give me any guidance or suggestions?
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Thanks. The backlight consists of two very small diameter glass tubes about 10 inches long and somewhere around 1/16 inch in diameter. There are two pink wires and one yellow wire coming out of that assembly and going to a plug on a board that appears to be a high-voltage power supply. The power supply board is even labeled "high voltage." I don't think that is an LED backlight. The pc board patterns going from a module on the power supply board are covered with epoxy up to the connector. I cannot figure out a way to measure the voltages out of the connector to the pink and yellow wires without cutting the wires.
Zack
That probably uses LED backlighting, and that may have a separate power connector. So look for that¡ I doubt it¡¯s got the old CCFL backlight, but that would certainly be a separate connector as the voltage is too high to include with signals. Good luck and keep us posted. dan ? ? I have a DPO70804 scope. The display is dark. I have determined that the fluorescent backlight tubes are not lit. I connected an XGA monitor to the XGA socket on the rear, and the XGA monitor displays the scope display and all functions are working correctly. I have been trying to determine if the display tubes or the voltage supply for those tubes is bad, or if the problem is elsewhere. The service manual I have for the unit contains no schematics nor any info on a way to test the fluorescent display circuit. The power supply board has a 20-pin plug with voltages on the pins. All the voltages are correct as per a drawing in the manual, except for the -5 volt pin (pin 18). That measures 0 volts. But on the drawing, there is an asterisk next to the -5 volt pin, with no explanation I can find anywhere of what the asterisk means. The PS-ON pin measures 0 volts and the PW-OK pin measures +5 volts. Can anybody give me any guidance or suggestions?
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Okay yes so that¡¯s a CCFL (cold cathode fluorescent) backlight. You will most likely find the backlight driver on a separate board (because of high voltage AND noise). CCFL initially goes up to a high ¡°strike¡± voltage, then after the tube conducts the voltage drops. And it¡¯s AC voltage, keep that in mind if you try to measure it. The CCFL driver may shut down if it detects that the tubes do not fire. But most likely that driver has fried. I guess make sure the driver has DC input power, and maybe look for AC voltage on the output when you apply power. It¡¯s not 60Hz, so keep that in mind. Your DMM may or may not give you an accurate reading. You can buy generic CCFL drivers but of course OEM is best if you can get it. Maybe Tek still sells it? If you need to use a generic driver, try to find someone on the group that knows what voltage you need. I don¡¯t know if there is much difference in CCFL voltages. Dan ?
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From: [email protected] <[email protected]> On Behalf Of Zack Widup via groups.io
Sent: Tuesday, April 16, 2024 2:19 PM
To: [email protected]
Subject: Re: [TekScopes2] DPO70804? Thanks. The backlight consists of two very small diameter glass tubes about 10 inches long and somewhere around 1/16 inch in diameter. There are two pink wires and one yellow wire coming out of that assembly and going to a plug on a board that appears to be a high-voltage power supply. The power supply board is even labeled "high voltage." I don't think that is an LED backlight. The pc board patterns going from a module on the power supply board are covered with epoxy up to the connector. I cannot figure out a way to measure the voltages out of the connector to the pink and yellow wires without cutting the wires. ? That probably uses LED backlighting, and that may have a separate power connector. So look for that¡ I doubt it¡¯s got the old CCFL backlight, but that would certainly be a separate connector as the voltage is too high to include with signals. Good luck and keep us posted. dan ? ? I have a DPO70804 scope. The display is dark. I have determined that the fluorescent backlight tubes are not lit. I connected an XGA monitor to the XGA socket on the rear, and the XGA monitor displays the scope display and all functions are working correctly. I have been trying to determine if the display tubes or the voltage supply for those tubes is bad, or if the problem is elsewhere. The service manual I have for the unit contains no schematics nor any info on a way to test the fluorescent display circuit. The power supply board has a 20-pin plug with voltages on the pins. All the voltages are correct as per a drawing in the manual, except for the -5 volt pin (pin 18). That measures 0 volts. But on the drawing, there is an asterisk next to the -5 volt pin, with no explanation I can find anywhere of what the asterisk means. The PS-ON pin measures 0 volts and the PW-OK pin measures +5 volts. Can anybody give me any guidance or suggestions?
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re: measuring the voltages:?? DON'T unless you like 1500 volts. That's about 1000 volts at about 3-5 ma.? Definitely enough to be highly dangerous.
The backlights are CCFL lamps, evacuated tubes with some? mercury in them.? They work like standard fluorescent lamps without a heater.
If the lamps show signs of darkening, they are likely suspect.
Unless you have a high voltage AC probe, (for a scope), don't do anything with them.
There are some low voltage LED replacement kits on the market.
There are also replacement lamps available, specific to that display, I'd think.
One thing to do is to take a scope probe and see if you can? pick up? a magnetic field (use a small loop of insulated wire) by getting NEAR the inverter transformer.? Another is to see how much low voltage current you're pulling.? It might be a bit.
Inverters can also be had.
Another trick might be to get an ungrounded neon lamp (plastic rod! for a handle) near the HV lines, or near the transformer.
Yet another would be to expose enough of the lamps (when installed in the display), run the equipment in darkness, and see if you can see any light from the tubes.? Keep your distance from the tubes, though and the inverter.? There's a reason why the inverter has a nice coating of insulating epoxy on it.
Be careful.
Harvey
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On 4/16/2024 3:18 PM, Zack Widup wrote: Thanks. The backlight consists of two very small diameter glass tubes about 10 inches long and somewhere around 1/16 inch in diameter. There are two pink wires and one yellow wire coming out of that assembly and going to a plug on a board that appears to be a high-voltage power supply. The power supply board is even labeled "high voltage." I don't think that is an LED backlight. The pc board patterns going from a module on the power supply board are covered with epoxy up to the connector. I cannot figure out a way to measure the voltages out of the connector to the pink and yellow wires without cutting the wires.
Zack
On Tue, Apr 16, 2024 at 1:45?PM dan.meeks222@... via groups.io <> <dan.meeks222@...> wrote:
That probably uses LED backlighting, and that may have a separate
power connector. So look for that¡
I doubt it¡¯s got the old CCFL backlight, but that would certainly
be a separate connector as the voltage is too high to include with
signals.
Good luck and keep us posted.
dan
*From:*[email protected] <[email protected]> *On Behalf Of
*Zack Widup via groups.io <>
*Sent:* Tuesday, April 16, 2024 1:42 PM
*To:* [email protected]
*Subject:* [TekScopes2] DPO70804
I have a DPO70804 scope. The display is dark. I have determined
that the fluorescent backlight tubes are not lit. I connected an
XGA monitor to the XGA socket on the rear, and the XGA monitor
displays the scope display and all functions are working correctly.
I have been trying to determine if the display tubes or the
voltage supply for those tubes is bad, or if the problem is
elsewhere. The service manual I have for the unit contains no
schematics nor any info on a way to test the fluorescent display
circuit.
The power supply board has a 20-pin plug with voltages on the
pins. All the voltages are correct as per a drawing in the manual,
except for the -5 volt pin (pin 18). That measures 0 volts. But on
the drawing, there is an asterisk next to the -5 volt pin, with no
explanation I can find anywhere of what the asterisk means. The
PS-ON pin measures 0 volts and the PW-OK pin measures +5 volts.
Can anybody give me any guidance or suggestions?
Zack
|
There's a fair amount of difference in CCFL voltages depending on the size of the tubes.
If the OP doesn't want to play with high voltages (and those are nasty!), then I'd look for a replacement LED strip made for that display.? It would come with a control board.
The current through the CCFL lamps is limited by the driver and board circuitry, so the board is matched to the lamps.
Harvey
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On 4/16/2024 3:26 PM, dan.meeks222@... wrote:
Okay yes so that¡¯s a CCFL (cold cathode fluorescent) backlight.
You will most likely find the backlight driver on a separate board (because of high voltage AND noise).
CCFL initially goes up to a high ¡°strike¡± voltage, then after the tube conducts the voltage drops. And it¡¯s AC voltage, keep that in mind if you try to measure it.
The CCFL driver may shut down if it detects that the tubes do not fire. But most likely that driver has fried.
I guess make sure the driver has DC input power, and maybe look for AC voltage on the output when you apply power. It¡¯s not 60Hz, so keep that in mind. Your DMM may or may not give you an accurate reading.
You can buy generic CCFL drivers but of course OEM is best if you can get it. Maybe Tek still sells it?
If you need to use a generic driver, try to find someone on the group that knows what voltage you need. I don¡¯t know if there is much difference in CCFL voltages.
Dan
*From:*[email protected] <[email protected]> *On Behalf Of *Zack Widup via groups.io
*Sent:* Tuesday, April 16, 2024 2:19 PM
*To:* [email protected]
*Subject:* Re: [TekScopes2] DPO70804
Thanks. The backlight consists of two very small diameter glass tubes about 10 inches long and somewhere around 1/16 inch in diameter. There are two pink wires and one yellow wire coming out of that assembly and going to a plug on a board that appears to be a high-voltage power supply. The power supply board is even labeled "high voltage." I don't think that is an LED backlight. The pc board patterns going from a module on the power supply board are covered with epoxy up to the connector. I cannot figure out a way to measure the voltages out of the connector to the pink and yellow wires without cutting the wires.
Zack
On Tue, Apr 16, 2024 at 1:45?PM dan.meeks222@... via groups.io <> <dan.meeks222@...> wrote:
That probably uses LED backlighting, and that may have a separate
power connector. So look for that¡
I doubt it¡¯s got the old CCFL backlight, but that would certainly
be a separate connector as the voltage is too high to include with
signals.
Good luck and keep us posted.
dan
*From:*[email protected] <[email protected]> *On Behalf Of
*Zack Widup via groups.io <>
*Sent:* Tuesday, April 16, 2024 1:42 PM
*To:* [email protected]
*Subject:* [TekScopes2] DPO70804
I have a DPO70804 scope. The display is dark. I have determined
that the fluorescent backlight tubes are not lit. I connected an
XGA monitor to the XGA socket on the rear, and the XGA monitor
displays the scope display and all functions are working correctly.
I have been trying to determine if the display tubes or the
voltage supply for those tubes is bad, or if the problem is
elsewhere. The service manual I have for the unit contains no
schematics nor any info on a way to test the fluorescent display
circuit.
The power supply board has a 20-pin plug with voltages on the
pins. All the voltages are correct as per a drawing in the manual,
except for the -5 volt pin (pin 18). That measures 0 volts. But on
the drawing, there is an asterisk next to the -5 volt pin, with no
explanation I can find anywhere of what the asterisk means. The
PS-ON pin measures 0 volts and the PW-OK pin measures +5 volts.
Can anybody give me any guidance or suggestions?
Zack
|
Thanks Harvey. I figured out how to measure the output voltages by pushing wires into the socket connector pins on the output of the 121PW181 module. I also found a manual for that module. It appears all the voltages on the input are correct for operation of the module. But the output voltages are 0 volts AC. Also, the ends of the FLD tubes are also slightly discolored.
I ordered this kit:
This appears to be a replacement kit, but using LED's instead of the FLD tube.
Zack
|
|
?
re: measuring the voltages:?? DON'T unless you like 1500 volts. That's
about 1000 volts at about 3-5 ma.? Definitely enough to be highly dangerous.
The backlights are CCFL lamps, evacuated tubes with some? mercury in
them.? They work like standard fluorescent lamps without a heater.
If the lamps show signs of darkening, they are likely suspect.
Unless you have a high voltage AC probe, (for a scope), don't do
anything with them.
There are some low voltage LED replacement kits on the market.
There are also replacement lamps available, specific to that display,
I'd think.
One thing to do is to take a scope probe and see if you can? pick up? a
magnetic field (use a small loop of insulated wire) by getting NEAR the
inverter transformer.? Another is to see how much low voltage current
you're pulling.? It might be a bit.
Inverters can also be had.
Another trick might be to get an ungrounded neon lamp (plastic rod! for
a handle) near the HV lines, or near the transformer.
Yet another would be to expose enough of the lamps (when installed in
the display), run the equipment in darkness, and see if you can see any
light from the tubes.? Keep your distance from the tubes, though and the
inverter.? There's a reason why the inverter has a nice coating of
insulating epoxy on it.
Be careful.
Harvey
On 4/16/2024 3:18 PM, Zack Widup wrote:
> Thanks. The backlight consists of two very small diameter glass tubes
> about 10 inches long and somewhere around 1/16 inch in diameter. There
> are two pink wires and one yellow wire coming out of that assembly and
> going to a plug on a board that appears to be a high-voltage power
> supply. The power supply board is even labeled "high voltage." I don't
> think that is an LED backlight. The pc board patterns going from a
> module on the power supply board are covered with epoxy up to the
> connector. I cannot figure out a way to measure the voltages out of
> the connector to the pink and yellow wires without cutting the wires.
>
> Zack
>
> On Tue, Apr 16, 2024 at 1:45?PM dan.meeks222@... via
> <> <dan.meeks222=[email protected]> wrote:
>
>? ? ?That probably uses LED backlighting, and that may have a separate
>? ? ?power connector. So look for that¡
>
>? ? ?I doubt it¡¯s got the old CCFL backlight, but that would certainly
>? ? ?be a separate connector as the voltage is too high to include with
>? ? ?signals.
>
>? ? ?Good luck and keep us posted.
>
>? ? ?dan
>
>? ? ?*From:*[email protected] <[email protected]> *On Behalf Of
>? ? ?*Zack Widup via <>
>? ? ?*Sent:* Tuesday, April 16, 2024 1:42 PM
>? ? ?*To:* [email protected]
>? ? ?*Subject:* [TekScopes2] DPO70804
>
>? ? ?I have a DPO70804 scope. The display is dark. I have determined
>? ? ?that the fluorescent backlight tubes are not lit. I connected an
>? ? ?XGA monitor to the XGA socket on the rear, and the XGA monitor
>? ? ?displays the scope display and all functions are working correctly.
>
>? ? ?I have been trying to determine if the display tubes or the
>? ? ?voltage supply for those tubes is bad, or if the problem is
>? ? ?elsewhere. The service manual I have for the unit contains no
>? ? ?schematics nor any info on a way to test the fluorescent display
>? ? ?circuit.
>
>? ? ?The power supply board has a 20-pin plug with voltages on the
>? ? ?pins. All the voltages are correct as per a drawing in the manual,
>? ? ?except for the -5 volt pin (pin 18). That measures 0 volts. But on
>? ? ?the drawing, there is an asterisk next to the -5 volt pin, with no
>? ? ?explanation I can find anywhere of what the asterisk means. The
>? ? ?PS-ON pin measures 0 volts and the PW-OK pin measures +5 volts.
>
>? ? ?Can anybody give me any guidance or suggestions?
>
>? ? ?Zack
>
>
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Good, the CCFL tubes are rated perhaps 5000 hours, the LEDS are effectively infinite, and lots easier to deal with.
Harvey
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On 4/16/2024 5:28 PM, Zack Widup wrote: Thanks Harvey. I figured out how to measure the output voltages by pushing wires into the socket connector pins on the output of the 121PW181 module. I also found a manual for that module. It appears all the voltages on the input are correct for operation of the module. But the output voltages are 0 volts AC. Also, the ends of the FLD tubes are also slightly discolored.
I ordered this kit:
<>
This appears to be a replacement kit, but using LED's instead of the FLD tube.
Zack
On Tue, Apr 16, 2024 at 2:54?PM Harvey White via groups.io <> <madyn@...> wrote:
re: measuring the voltages:?? DON'T unless you like 1500 volts.
That's
about 1000 volts at about 3-5 ma.? Definitely enough to be highly
dangerous.
The backlights are CCFL lamps, evacuated tubes with some mercury in
them.? They work like standard fluorescent lamps without a heater.
If the lamps show signs of darkening, they are likely suspect.
Unless you have a high voltage AC probe, (for a scope), don't do
anything with them.
There are some low voltage LED replacement kits on the market.
There are also replacement lamps available, specific to that display,
I'd think.
One thing to do is to take a scope probe and see if you can pick
up? a
magnetic field (use a small loop of insulated wire) by getting
NEAR the
inverter transformer.? Another is to see how much low voltage current
you're pulling.? It might be a bit.
Inverters can also be had.
Another trick might be to get an ungrounded neon lamp (plastic
rod! for
a handle) near the HV lines, or near the transformer.
Yet another would be to expose enough of the lamps (when installed in
the display), run the equipment in darkness, and see if you can
see any
light from the tubes.? Keep your distance from the tubes, though
and the
inverter.? There's a reason why the inverter has a nice coating of
insulating epoxy on it.
Be careful.
Harvey
On 4/16/2024 3:18 PM, Zack Widup wrote:
> Thanks. The backlight consists of two very small diameter glass
tubes
> about 10 inches long and somewhere around 1/16 inch in diameter.
There
> are two pink wires and one yellow wire coming out of that
assembly and
> going to a plug on a board that appears to be a high-voltage power
> supply. The power supply board is even labeled "high voltage." I
don't
> think that is an LED backlight. The pc board patterns going from a
> module on the power supply board are covered with epoxy up to the
> connector. I cannot figure out a way to measure the voltages out of
> the connector to the pink and yellow wires without cutting the
wires.
>
> Zack
>
> On Tue, Apr 16, 2024 at 1:45?PM dan.meeks222@... via
groups.io <>
> <> <dan.meeks222@...> wrote:
>
>? ? ?That probably uses LED backlighting, and that may have a
separate
>? ? ?power connector. So look for that¡
>
>? ? ?I doubt it¡¯s got the old CCFL backlight, but that would
certainly
>? ? ?be a separate connector as the voltage is too high to
include with
>? ? ?signals.
>
>? ? ?Good luck and keep us posted.
>
>? ? ?dan
>
>? ? ?*From:*[email protected] <[email protected]> *On Behalf Of
>? ? ?*Zack Widup via groups.io <> <>
>? ? ?*Sent:* Tuesday, April 16, 2024 1:42 PM
>? ? ?*To:* [email protected]
>? ? ?*Subject:* [TekScopes2] DPO70804
>
>? ? ?I have a DPO70804 scope. The display is dark. I have determined
>? ? ?that the fluorescent backlight tubes are not lit. I connected an
>? ? ?XGA monitor to the XGA socket on the rear, and the XGA monitor
>? ? ?displays the scope display and all functions are working
correctly.
>
>? ? ?I have been trying to determine if the display tubes or the
>? ? ?voltage supply for those tubes is bad, or if the problem is
>? ? ?elsewhere. The service manual I have for the unit contains no
>? ? ?schematics nor any info on a way to test the fluorescent display
>? ? ?circuit.
>
>? ? ?The power supply board has a 20-pin plug with voltages on the
>? ? ?pins. All the voltages are correct as per a drawing in the
manual,
>? ? ?except for the -5 volt pin (pin 18). That measures 0 volts.
But on
>? ? ?the drawing, there is an asterisk next to the -5 volt pin,
with no
>? ? ?explanation I can find anywhere of what the asterisk means. The
>? ? ?PS-ON pin measures 0 volts and the PW-OK pin measures +5 volts.
>
>? ? ?Can anybody give me any guidance or suggestions?
>
>? ? ?Zack
>
>
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