Equipment Display Types

[Mark R]

Most Displays I have worked with are of course LCD Or Blueish Fluorescent Types. I Have a Marantz PMD800 tuner with sort of a white display. The display area is a sealed rectangular shape in a Glass Case. Looks like some sort L.E.D. display only not your typical section number type. I picked up this Tuner cheap as the display is very Dim. In front of the circuit is a dull red Plastic lens.

The display is very week and hard to see. I've got my DC 5 Volts allover and also a DC 32 Volt that runs some other section. Power supply looks good front to back. Not familiar with this type of display. Don't know if the Chemical Element of the display itself has burnt down or exactly how this display works.

Their is a Large Postage stamp chip that runs this display. Their is 5 Volts on the Operating input pin. The display works in all functions. But it is hard to see.

No Clue? Any thoughts?

[stj]

probably a VFD, so you need to look for a schematic and it will probably be a bad cap causing the dim output

[Mark R]

probably a VFD, so you need to look for a schematic and it will probably be a bad cap causing the dim output

Thanks Great Sage,

So it is a vacuum fluorescent display. It's made up of many small dots that form the Letters and numbers. As far as a Schematic goes , Its hard to find.
I'll have to search for one again. I assume that Bad Cap.. Should be on the main Display Board behind the front panel with the Postage Stamp Driver IC Chip.

Did a quick look at the caps and nothing bulging up. Got My Sencore LC 103 Cap checker so it'll be pull and check if I can narrow the location down of the cap. Wonder what kind of voltage is used to drive the VFD??

Any Ideas? Also... Cool Name...."MONKEY KING" L.O.L.

[stj]

so,
look at the display pins, the outermost ones are the heater and have about 3v AC on them - they often feed through a cap.
also check the soldering - it often cracks on VFD panels - no idea why unless it's because they are heavy.

[Mark R]

so,
look at the display pins, the outermost ones are the heater and have about 3v AC on them - they often feed through a cap.
also check the soldering - it often cracks on VFD panels - no idea why unless it's because they are heavy.

Thanks 齊天大聖,

Thank you for the starting place. I have had my share of cold joints. Wave soldering does it every time. I have a PACE MBT 250 Solder-De Solder Station and a Hot Air Unit for SMD Devices. So I should be able to locate the problem.

Interesting that they use a heater in the VFD. Now I can see why. If I locate a 3 Volt AC rail in the chassis plug feeding the Main front panel display board I should be able to run it down to a Cap as you say.

I didn't notice an AC feed after the ac to dc conversion in the back end. I'll check the back end PS again. I'll rip the unit apart tomorrow or the next day.

Thanks Again:
Regards: Mark R

[stj]

https://www.noritake-elec.com/techno.../vfd-operation

[Mark R]

https://www.noritake-elec.com/techno.../vfd-operation

Great ..Got it... Will review and Operate on the Patience...

[sam_sam_sam]

Just replace all of the capacitors around the display and around the display ic chip as well especially the low uf values ones under 100uf
Also very carefully redo and display pins that look dull or are have rings around the soldering joints or cracked soldering joints because there have been a lot of issues with these displays after many years of use and service

One note be extremely careful with ribbon cables between circuit boards do not be tempted to remove them if you do not need to because some of them are not remove-able even if they appear to be able to be removed this is the type that needs to be desoldered instead and to remove this type is not easily removed either I have been there and done it before and should have left it alone I would have been better off in the long run

One other note about ribbon cable there is a flat type that has a locking tab mechanism that is a nightmare to get into the connector and to get the device to work properly again this type is another one that if you do not have to remove it do not do it make your life easier if you can

[Mark R]

Just replace all of the capacitors around the display and around the display ic chip as well especially the low uf values ones under 100uf
Also very carefully redo and display pins that look dull or are have rings around the soldering joints or cracked soldering joints because there have been a lot of issues with these displays after many years of use and service

One note be extremely careful with ribbon cables between circuit boards do not be tempted to remove them if you do not need to because some of them are not remove-able even if they appear to be able to be removed this is the type that needs to be desoldered instead and to remove this type is not easily removed either I have been there and done it before and should have left it alone I would have been better off in the long run

One other note about ribbon cable there is a flat type that has a locking tab mechanism that is a nightmare to get into the connector and to get the device to work properly again this type is another one that if you do not have to remove it do not do it make your life easier if you can

Thanks For the reply Sam Sam Sam

As you say Been there done that..L.O.L. The ribbon cable is the removable type or plug in with a release tab on the main board. So no problem there.
I am able to remove the entire front panel complete. It's held in place by about 10 screws. Luckily I have a good Small power Screw driver...
( Panasonic) which works great.

Also...Yep... the dreaded cold cracked solder joints. I also have a 10" screen LCD Microscope for working on SMD's. So I can see a small SMD Resistor which the scope makes it look like the size of a Foot Ball. L.O.L.


Iv'e had my share of cracked cold joints. This unit is a Japanese Marantz PMD800. It's well made and super easy to service. All the components are marked as well as voltages on the boards. Thanks for your tips, and I have run into those pesky ribbon cables that are soldered into the board!
That's called cheeping out because the plastic connector cost to much $.02....LMAO.

Regards: Mark R

[sam_sam_sam]

Let us know if you are able to fix the issue with the display

[Mark R]

Let us know if you are able to fix the issue with the display

Will do Sam Sam Sam ,, Been busy running around. Haven't been at the bench. I'll try and rip into it tomorrow. I hate when guys help you out and then that person who needed the help never answers back. That's Not me. I appreciate you guys and I will keep you posted. I'll take a few pic's when I find the problem. Thanks Guys..

Regards: Mark R

[Mark R]

Let us know if you are able to fix the issue with the display

Ok Sam Sam Sam.. Here are some Pic's showing the unit broken down. There are a bunch of caps on one side of the board. Also I don't see any indication of 3 Volts A C on the board . Just 5 Volts and I think 31Volts. But it does read as DC Voltage.
So Next step is to get out the LC103 Cap Checker and Fire up The MBT-250 De solder station.

I'll check back after I check these caps.

Regards: Mark R

[stj]

you need to clean up that potential solder-bridge you created on the display pcb

[Mark R]

you need to clean up that potential solder-bridge you created on the display pcb

At the time of the pictures I had not touched or soldered anything. Where are you indicating?

As of this time 12:05 AM EST I located the problem. It was a 6.3 Volt 1000 MFD cap on the display board. The LC103 showed Leakage and also showed high Dielectric Absorption. I replaced the cap and the display now is much brighter. I used a 1000 MFD @10 Volt cap. Seems to be working ok.

Now what is really ticking me off is one button fell out of the front panel which I have been looking for over 1 hour. Can't reassemble the unit until I find the button!!!!!!!!!!!

I'll report back with Pic's if I can find the dam thing!!

Thanks for the help to All. I'm not done here. I will tare my shop apart till I find it. LMAO Back soon.

[stj]

look at the right side of the display controller in your pictures - there are 2 joints manually soldered - the lower one has some "splash" effect

[Mark R]

you need to clean up that potential solder-bridge you created on the display pcb

Are you speaking about the Main Multi pin IC? Between Pin 51 and 50? Post a picture from mine so I know which photo your speaking about.

Also: The unit seems to be working now since I changed out two caps... Thanks for leading me to that area and the link to The VFD display site and every one here who helped me.

Here is a pic of the now brighter display. Why they shove a Hunk of Red filter in front doesn't make sense to me. I guess they want to hide the circuitry in and around the VFD. It looks better in it's Natural color.

[sam_sam_sam]

Probably still a good idea very closely look at the soldering joints on the VFD display and any of them that look questionable redo them so you do not to revisit this issue again I would also recommend that you replace the capacitors around the VFD display and the display ic chip for good measure especially if the this device has a lot of use and age because both are hard on capacitors for this type of use

I am not suggesting that you recap the tuner section or anything like that because then you would have to have special equipment to be realigned tuner

The reason for the red filters is so it is easier to read in the dark and very low light settings I would recommend reinstalling them so it be like it originally was when new

[Mark R]

look at the right side of the display controller in your pictures - there are 2 joints manually soldered - the lower one has some "splash" effect

You call it the display Controller???? Are you speaking about the large Postage stamp IC Chip? Can you post a pic from mine that indicate what you are talking about?

Also All solder joints on the VFD are perfect. They were looked at with a Jewelers Loop. All caps were changed out after testing. Two were bad. All solder joints are perfect on the front panel control board.

[stj]

this - or is it flux?

[Mark R]

this - or is it flux?

Ok..Now Ise what your talking about. Ok I'll pop the cover since it's back together and take a Look. Thanks for the Photo and location. Get back to you soon