Florescent display voltage

[mikeyB]

Hi,
I'm trying to fix a Musical Fidelity A3 CD player.
Nuking fuses so I guess its the transformer shorted, took the transformer off load and sure enough still nuking fuses!!
The transformer looks to be in the region of 30-50VA size. Windings are 13-0-13 (for analog), 0-9(for digital) and 0-3Vac ,which after flipping the pcbs looks like its the drive for the florescent display. looks to be a mini tx on the display pcb.
I'll hook up bench psu to see what the analog and digital draw current wise. To test the display, i'll hook up a transformer via variac and bring it up to 3Vac output and measure the current draw.  Once I know the current requirements. I'm thinking of a dual 12v or 15V for the analog and a dual 9v for the logic and display. on the display secondary I'll dump 6V with a power resistor and have 3Vac for the display. Is this the right approach? Am I overlooking anything like switch on surge/overvoltage to the florescent  driver from a cold start. I have no experience of these and don't know of any pitfalls?!?

Thanks in advance.

ps. the service agent is next to useless in getting details of spare parts!!

 

[PRR]

> 0-3Vac ,which after flipping the pcbs looks like its the drive for the florescent display

Surely the VFD *filament*. You can more easily estimate the drain by measuring the Ohms of thoe VFD terminals that take the 3VAC. (It may be less current when hot, but they don't get red-hot; and excess capacity is fine.)

https://www.instructables.com/id/A-Simple-Driver-for-VFD-Displays/
https://medium.com/@rxseger/reverse-engineering-the-pinout-of-vacuum-fluorescent-displays-vfds-hnv11ss27-fip7fm7-and-hnv-8a00b0530b52
https://www.noritake-elec.com/technology/general-technical-information/vfd-operation

 

[mikeyB]

Thanks for the quick  reply.  I'll let you know how I get on. So the filament can be DC fed?
Aha!
I don't think there are any other supplies to the display board so the transformer on the display board must be there to get the higher voltage for the anode? - hence ac fed and not dc? Fair assumption?