BK Precision 9130 PS dim display - Page 1
Forum section: electronics / repair

author: Cyclotron
author_rank: Unknown
timestamp: July 06, 2025, 11:55:07 pm
content: So, I have been working to improve the brightness of my BK 9130 power supply. The AC voltage at max on the filaments is 4.3v AC and that seems low to me.I have improved the display by cycling filaments at 10v DC .20 amp a few times as has been community knowledge for VFDs for a while.I'm looking for a schematic or other docs that might help me in an effort to bump up the AC voltage to about 5v which is the most common voltage I see for these types of displays.If someone has experience with this unit and improving a dim display, I'm in your debt if you can share the knowledge.

author: Cyclotron
author_rank: Unknown
timestamp: July 07, 2025, 05:33:49 pm
content: I have identified the VFD controller as a PCT (Princeton Technology Corp.) PT6314https://newhavendisplay.com/content/app_notes/PT6314.pdfThe VFD itself is a 2 line 24 field each made up of 5x8 dots. I'm looking to source a VFD module to test.https://www.aliexpress.us/item/3256803601466594.html?gatewayAdapt=glo2usa4itemAdaptThis module is over 100USD currently on AliExpress but Taobao it looks closer to a couple USD.https://www.taobao.com/list/item/43628341372.htmI need to figure out how to order stuff from Taobao. My typical sources do not list any VFDs that appear to be similar.

author: floobydust
author_rank: Super Contributor
timestamp: July 07, 2025, 06:03:57 pm
content: I could write a lot about troubleshooting dim VFD displays.How is the display dim? All digits and segments equally dim? Dim rows away from the filament wires? A pic could help.This can tell you if the phosphor is burnt or aged, or it's low emission etc. - but you did try rejuvenate the filaments.Any repair, first thing you do is verify the power supply voltages are in spec. Before you fully blame the tube.There's three for most VFD's - the +HV anode rail say 25-50VDC going to the driver IC.This rail can be made using a capacitive multiplier with electrolytic caps that don't last due to the high ripple currents they experience. This is a big problem in appliances. Or the filter cap dries out and mains ripple shows up. There can be a discrete HV regulator as well to check. See what your HV rail measures.The filament voltage - these are Kovar pins and fractured solder joints are common. It usually causes the display to intermittent fade out or just appear dead. I think 4.3VAC is reasonable although I don't know how long this tube is, or if you measured at the VFD pads or pins. There will be an inrush limiting resistor in series usually.The filament is usually biased negative to say -6VDC so there is a zener/cap for that but if it failed there would be ghosting and other effects seen where segments don't fully turn off.It's common in test benches where these get left powered on 24/7 and the displays age fast when not used part time in a lab.I would hit up BK for the service manual or schematic, see if there are replacement VFD options. I find them very helpful at least you have a chance to repair their test equipment.The VFD is likely not a custom part? Although 24 characters wide seems special. I would see if it's an off the shelf module or not,NewhavenorMatrix Orbitalofferings etc.

author: Cyclotron
author_rank: Unknown
timestamp: July 07, 2025, 06:22:09 pm
content: The dim parts are just the dots in the matrix that remain lit all the time. It really has improved a lot since I cycled the filaments but its still very obvious when bars or long text are shown. I can certainly "live" with what I have.The 2 lines by 24 does appear to be fairly rare. NewHaven used to sell one with the same driver chip per what I can tell but no longer do.The image of the display appears to look better than it does to the eye. I forced it to loading firmware mode so the bottom matrix show a bar where you can see the ghosting of the dots that are used by the idle display.Thanks for jumping in!

author: Cyclotron
author_rank: Unknown
timestamp: July 07, 2025, 08:29:25 pm
content: Quote from: floobydust on July 07, 2025, 06:03:57 pmI just got word back from BK that the display parts are no longer available from them.I'll see if they might provide a set of schematics.

author: floobydust
author_rank: Super Contributor
timestamp: July 07, 2025, 10:02:24 pm
content: The bottom row I can see some characters burnt in the phosphor (not really"burnt" but just aged more) for some dots.Also the dots are fuzzy around the edges which is usually due to low emission, you could increase the filament voltage a bit or make sure it's not lower than it should be. Not sure if they use a dedicated transformer winding with series resistor, or this is a DC-DC converter or what is powering it or the board for the VFD is custom BK.Maybe same display used in IEE (Industrial Electronic Engineers) S03601-48A-048 module which ended up in some expensive machines. You'd have to see your old tube's markings who makes it. 24 char is uncommon.

author: Cyclotron
author_rank: Unknown
timestamp: July 08, 2025, 01:09:42 am
content: I think I'll pull the display off as I have the tools to desolder it easily enough. Document what's there and the components.If I can't find an easy way to boost the filament voltage I'll let it ride for now till I get annoyed with it.I have plenty of projects that actually need to be repaired before use.I very much appreciate your knowledge, commentary, and suggestions.