Philips FW41 Mini Hi-Fi Display Has Faded

[ian.hindle]

philips fw 41

Can you help.


The display on my hi-fi has faded away in just one week. This is clearly not just the display itself fading due to age, because of the speed its gone. I can just see the characters in the dark, but there is a significant amount of flashing going on, so looks like the multiplexing of the characters is still working.

If any one has a service manual / circuit diagram I’d be most appreciative.

Ian

 

[btbass]

philips fw41

Check the power supplies. Fluorescent displays usualy have three, a 3 Volt ac supply, a negative bias supply of about -15 to -24Volts and a 5 volt supply. Sounds like the negative supply is zapped, normally just a diode popped.
Good luck.

 

[aldodj]

mini hifi 43 philips

hello i need circuit diagrams philips fw 41 , because i have the same problem that you have , about the fluorescent display.

aldodj - thank

 

[E-design]

capasitor 1000mf/10v

Check the power supplies. Fluorescent displays usualy have three, a 3 Volt ac supply, a negative bias supply of about -15 to -24Volts and a 5 volt supply. Sounds like the negative supply is zapped, normally just a diode popped.
Good luck.

Often a doubler setup using a multivibrator and 2-electrolytic caps produces the -ve supply (-20 to -30v) for these displays. I have found these caps going bad or drying up in similar applications.

 

[sunny]

hi fi with 7 display

There is a 30V negative bias for the two display tubes. If the display is too dark or flickering check the 1000MF 10V capacitor for leakage. If the cap. is ok then check the BD236 transistor connected to a heat sink. Also, check the safety resistor near that transistor.
- Sunny

 

[jmglp]

fw41 display

Thank you very much sunny.
I changed the 1000MF 10V capacitor, and it worked very well.
Attach file of the diagram of the power supply.
-jmglp