Sony STR-DB795 dim vfd display

[gilly1984]

SO, i bought an amp from ebay, they said their kid hit the display with something and then it wouldnt switch on.

The whole circuit board with the display and buttons on it was cracked right near the ribbon connector is, severing all the traces

Anyway, after 4 hours of surgery i have got all the traces mended but the display is dim, pretty sure it has nothing to do with my wiring as everything works fine, all buttons work.

I have heard that vfd displays go dim after time, so is there anything i can do to make it brighter?

[gilly1984]

Re: Sony STR-DB795 dim vfd display

Just checked the pinouts and the -28v is only at -18v?

This comes from another board on the other side of the ribbon.

[vinceroger69]

Re: Sony STR-DB795 dim vfd display

has it got a dimming function on it? heres a link to the manual
http://www.sony.co.uk/product/home-c...95/manuals#tab

[tom66]

Re: Sony STR-DB795 dim vfd display

Impressive surgery!

-28V is used for the VFD, so it is important that it is correct.

[gilly1984]

Re: Sony STR-DB795 dim vfd display

yh its got dimming function but its on full brightness , and thanks tom

ive followed the -28v witch is -18v all the way to the power supply so the problem must be there.

i will upload pics soon

thanks

[vinceroger69]

Re: Sony STR-DB795 dim vfd display

service manual

[gilly1984]

Re: Sony STR-DB795 dim vfd display

Thank you Vince.

Here is a few more pics of my handy work for those who like it ghetto

Also included is some pics of the psu, i have marked the pin and some components that lead to the pin.

Also a pic or 2 of how dim it is.

[gilly1984]

Re: Sony STR-DB795 dim vfd display

Just read the schematic and it says that -18.6 is what it should be?

So what else can i try?

The vfd heater voltage is 5vac so that seems normal too?

[tom66]

Re: Sony STR-DB795 dim vfd display

Hmm... VFD voltage is normally 6.3VAC but 5VAC might be OK.
Where is -28V marked?

[gilly1984]

Re: Sony STR-DB795 dim vfd display

It is marked as -28v (fl) On the psu, it then goes to the digital board where it is also marked -28v, then from there it goes via i thin ribbon cable to the front display board, also marked as -28v.

But the service manual states it should be -18.6v (Page 51, written in red), which it is, also it goes through a 25v 100uf cap, so it cant be -28v?

[tom66]

Re: Sony STR-DB795 dim vfd display

May just be a typo, then. When they draw the schematic they could have written -28V which would have been put on all boards.

The display could be worn out.

[budm]

Re: Sony STR-DB795 dim vfd display

So does the dimming function has any affect?

[gilly1984]

Re: Sony STR-DB795 dim vfd display

yes, the dimmer function dims it more.

my current Sony receiver is much older and the display is fine?

shame really as I want to replace the 5.1 I have for this 7.1 amp, just don't think I could live with a dull display.

[gilly1984]

Re: Sony STR-DB795 dim vfd display

Replaced a few caps on the vfd line with no change in brightness, gonna keep it anyway, sell my db830.

opened up the db830 to take some readings but it uses +32 volts instead of -18.6v like the db795.

the vfd heater is the same at 5Vac, so it must be like You said, it's just dimmed through usage.

[gilly1984]

Re: Sony STR-DB795 dim vfd display

Found a sort of work around

The screen/bezel that sits in front of the vfd had a lining on it so you cant see the vfd unless it was illuminated, anyway, i have scraped that lining off and now i can see my vfd even during the day

[whitesnakebg]

Re: Sony STR-DB795 dim vfd display

Any progress with this old issue?