RICHARD STETSON
- Aug 13, 2017
- 5
- Joined
- Aug 13, 2017
- Messages
- 5
I need a comparable display for this vfd. Any help appreciated.
Hi all,
I know this is an old thread, but maybe my findings can still be useful.
I own an old but perfectly working Mettler AE240 balance; like all the AE series balances (which share the same display board), its main problem is the VFDisplay getting dim with age.
Currently, it's virtually impossible to find a new replacement VFD unit, so I bought a couple of 9-BT-28 displays on eBay to give a try.
There are quite a number available for sale at low prices.
Compared with the original Futaba 9-BT-26 VFD, the 9-BT-28 shares the same pinout and length; its case is a little bit narrower, but the digits are identical - so a one-to-one replacemente is easily feasible. It looks like the only significant difference is in the filament: the 9-BT-26 measures a cold resistence around 55 ohms, while the 9-BT-28 is only 12 ohms (this is between the extreme pins).
I replaced the VFD on the balance's display board and - after a little fiddling, I found that a 47 ohms 1W resistor in series with the filament does the trick (this is about the minimum series resistance under which the digits' brightness does not increase noticeably).
Now the balance shows off a beatiful, bright and uniform turquoise reading, like it has to be.
P.S.: the 47R has to be placed in series with the first (leftmost) or last (rightmost) pin of the VFD. No PCB modifications are required, and plenty of space is available underneath the VFD body.
Hope this helps.