Nice one Nick - you're a braver man than I am. 🤣 I finally managed to find a Keithley 2015 from a genuine UK seller and it arrived today. 🎉 It feels pristine, which is lovely, but the inevitable downside is that it cost a lot more than yours so I reckon you've got yourself a real bargain.
Hi Bob, brave maybe or stupid? But it is brighter. Good you got one, if its the one I was watching on ebay (just out of interest) then it looked far nicer than mine but out of my price range, thanks for watching
@@ptronix Yes, it was the eBay one. It got to £21 below my limit which was disappointing in a way but probably fair. My intention is to use it until I'm no longer safe around high votages ⚡and then hopefully return it to the community in similar condition. Might even get my money back if I'm very lucky. 🤣
Really hope this helps. I'm skeptical though (heard some horror stories), because increasing cathode temp will boil off the barium oxide on the filament wires even faster. I'm hoping you can find a lower hours replacement in the future.....fingers crossed for you.
Hi Danish. I'm not to bothered if I ruin it by running the filament hotter. I'll find a new display or board if I keep looking long enough. Had to drink barium liquid once at the hospital, most unpleasant that was too!
if I am not mistaken the VFD heater voltage is not just AC. It rides on top of a negative DC and you must play with (increase) that DC bias in order to get better brightness. With regard to the defective segments, have you tried to probe around the VFD driver chips on the front panel board? Those are the guys responsible for driving the segments. Look up the datasheet of those chips and probe the pins
Thank you for the very interesting comment. You obviously have a lot more knowledge than me on VFDs . I've looked on the heater with a scope and you're right its a rather distorted 50 hz sine wave which is all positive going. I don't know how I would adjust this offset or if I need too. This morning I've looked on the high voltage outputs on the driver chips and I'm getting pulses of varying width as you might expect with a multiplexed display. But there is a fair amount of jitter on them, whether this is normal I don't know. As I said in a previous video the 37 volt supply is very noisy but cleaning it up with a 10 uf capacitor makes no difference to anything. So I'm at a dead end, I've no schematics nor is it possible to get any. Thanks again
@@ptronix that negative DC bias is usually generated on the main board and added in series with the transformer secondary (look up the schematics for your 34401A, the basic design of driving a VFD is the same everywhere). If you find how the DC bias is generated you can easily change it. That is partly responsible for the initial acceleration of electrons emitted by the filament. Having schematic will not have helped you anyway. All you need is to look up the datasheet of the VFD driver chips and study them a bit. It should not be very difficult to find which pins are responsible for those commas
Hi Nick, I’m following along on this Keithley. I’m gonna say something very silly now but at some point in the video I had the sensation that there is a film to pill off of that display? I might be completely wrong . Sometimes happens when people are fetishist and leave it on. If that’s the case could explain a decrease in brightness. Diego
Hi Diego, nice to hear from you. Silly or not it's a valid point. I think it lost its film many years ago if it had one. The plastic has many fine scratches especially above the power switch. I've did a bit of polishing today but the risk is that will take off the legend. But even so I sure it doesn't effect the brightness. It is definitely a bit brighter after increasing the filament current. Then again I don't know what the original brightness was like. If it shortens the life of the VFD so be it. Hope its not too hot where you are, its anything but here. Best wishes nick
As you mentioned, you're not leaving it on all day, and actual visibility is kind of critical with a meter! Did not even occur to me that the most likely reason a display board is available on eBay is that it's been replaced with a brighter one.
Hi Joe, think I've flogged this one to death now. But I shall keep looking for a replacement display or board. By the way since I upped the filament current it may be my imagination but I think the spurious commas are less apparent. Wonder how long it will last though? Wish I'd measured the filament current before and after the mod.
Nice tweak, thanks for the video Nick 😀
Thanks Mike
Nice one Nick - you're a braver man than I am. 🤣 I finally managed to find a Keithley 2015 from a genuine UK seller and it arrived today. 🎉 It feels pristine, which is lovely, but the inevitable downside is that it cost a lot more than yours so I reckon you've got yourself a real bargain.
Hi Bob, brave maybe or stupid? But it is brighter. Good you got one, if its the one I was watching on ebay (just out of interest) then it looked far nicer than mine but out of my price range, thanks for watching
@@ptronix Yes, it was the eBay one. It got to £21 below my limit which was disappointing in a way but probably fair. My intention is to use it until I'm no longer safe around high votages ⚡and then hopefully return it to the community in similar condition. Might even get my money back if I'm very lucky. 🤣
Really hope this helps. I'm skeptical though (heard some horror stories), because increasing cathode temp will boil off the barium oxide on the filament wires even faster. I'm hoping you can find a lower hours replacement in the future.....fingers crossed for you.
Hi Danish. I'm not to bothered if I ruin it by running the filament hotter. I'll find a new display or board if I keep looking long enough. Had to drink barium liquid once at the hospital, most unpleasant that was too!
if I am not mistaken the VFD heater voltage is not just AC. It rides on top of a negative DC and you must play with (increase) that DC bias in order to get better brightness.
With regard to the defective segments, have you tried to probe around the VFD driver chips on the front panel board?
Those are the guys responsible for driving the segments. Look up the datasheet of those chips and probe the pins
Thank you for the very interesting comment. You obviously have a lot more knowledge than me on VFDs . I've looked on the heater with a scope and you're right its a rather distorted 50 hz sine wave which is all positive going. I don't know how I would adjust this offset or if I need too.
This morning I've looked on the high voltage outputs on the driver chips and I'm getting pulses of varying width as you might expect with a multiplexed display.
But there is a fair amount of jitter on them, whether this is normal I don't know. As I said in a previous video the 37 volt supply is very noisy but cleaning it up with a 10 uf capacitor makes no difference to anything.
So I'm at a dead end, I've no schematics nor is it possible to get any. Thanks again
@@ptronix that negative DC bias is usually generated on the main board and added in series with the transformer secondary (look up the schematics for your 34401A, the basic design of driving a VFD is the same everywhere). If you find how the DC bias is generated you can easily change it. That is partly responsible for the initial acceleration of electrons emitted by the filament.
Having schematic will not have helped you anyway. All you need is to look up the datasheet of the VFD driver chips and study them a bit. It should not be very difficult to find which pins are responsible for those commas
Hi Nick, I’m following along on this Keithley. I’m gonna say something very silly now but at some point in the video I had the sensation that there is a film to pill off of that display? I might be completely wrong
. Sometimes happens when people are fetishist and leave it on. If that’s the case could explain a decrease in brightness.
Diego
Hi Diego, nice to hear from you. Silly or not it's a valid point. I think it lost its film many years ago if it had one. The plastic has many fine scratches especially above the power switch. I've did a bit of polishing today but the risk is that will take off the legend. But even so I sure it doesn't effect the brightness. It is definitely a bit brighter after increasing the filament current. Then again I don't know what the original brightness was like. If it shortens the life of the VFD so be it. Hope its not too hot where you are, its anything but here.
Best wishes nick
As you mentioned, you're not leaving it on all day, and actual visibility is kind of critical with a meter!
Did not even occur to me that the most likely reason a display board is available on eBay is that it's been replaced with a brighter one.
Hi Joe, think I've flogged this one to death now. But I shall keep looking for a replacement display or board. By the way since I upped the filament current it may be my imagination but I think the spurious commas are less apparent. Wonder how long it will last though? Wish I'd measured the filament current before and after the mod.
@@ptronix Fascinating that they are less apparent. Somehow that's got to be diagnostic of something important, but here, madness lay!
Has anyone ever tried to replace the vacuum fluorescent display with a TFT or similar? Might be a nice little drop in kit someone could market.