Sony STR-DB795 dim display

[vidtek]

I have one of these I use as my home theatre amp, it sits in my loft together with my HTPC above the room where the display (Samsung ES8000 55" smart tv) sits.
When I went into the loft the other day, I noticed the display was dimmed, I thought I'd pressed the dim switch by accident, but had another look today and there is no display at all.
Did a quick google, but the only results were pretty inconclusive.

Anyone had this with this older amp? Caps or fluro itself? In my experience could be either.

Cheers, Tony.

[CapLeaker]

Re: Sony STR-DB795 dim display

check the voltage supply to the display.

[Longbow]

Re: Sony STR-DB795 dim display

If you have a VFD, there are 2 possibilities. They usually need about 30 volts multiplexed on the segments to operate. The filter capacitor(s) on the 30 volt line are the first to smoke during a power surge. Sometimes the 30 volts comes from the main supply and sometimes there is a small switching supply near the display. A VFD has filaments with a separate filament supply that needs to be checked. The second reason is aging of the tube itself. Schematics?

[jiroy]

Re: Sony STR-DB795 dim display

It could be also bad solder on display screen's pins , Sony is famous in bad soldering , lol ..

[budm]

Re: Sony STR-DB795 dim display

Service manual.
Check the -28V, C1014, C1071, D1071
See page 51 DC1 board connector CN907 SCH for the -28V source,
Page 29 (Digital bd.) connector CN1110, CN1105.
Page 49 (display bd.) connector CN1001.

[vidtek]

Re: Sony STR-DB795 dim display

check the voltage supply to the display.

My first thought.

All within normal range.

When I left Aussie I donated my 'scope to the sally army, wish I hadn't could have seen the ripple on the supply if any. sigh...

Thanks for your reply CapLeaker

Tony

[vidtek]

Re: Sony STR-DB795 dim display

If you have a VFD, there are 2 possibilities. They usually need about 30 volts multiplexed on the segments to operate. The filter capacitor(s) on the 30 volt line are the first to smoke during a power surge. Sometimes the 30 volts comes from the main supply and sometimes there is a small switching supply near the display. A VFD has filaments with a separate filament supply that needs to be checked. The second reason is aging of the tube itself. Schematics?

I have a nasty feeling about the tube, thanks for this detailed response Longbow.

Tony

[vidtek]

Re: Sony STR-DB795 dim display

It could be also bad solder on display screen's pins , Sony is famous in bad soldering , lol ..

Had a good look at the joints and floated some more suspect ones... Sony dry joints were famous on their Trinitron 19" early 1970's receivers. They used expensive scr's in the psu and timebase circuits which were exceedingly easy to blow up on replacement.
A variac and swift hand near the off switch was essential.

Tony.

[vidtek]

Re: Sony STR-DB795 dim display

Service manual.
Check the -28V, C1014, C1071, D1071
See page 51 DC1 board connector CN907 SCH for the -28V source,
Page 29 (Digital bd.) connector CN1110, CN1105.
Page 49 (display bd.) connector CN1001.

Budm- Thanks for the links and suggestions, I have a bad feeling about the tube though......

Cheers, Tony.

[Longbow]

Re: Sony STR-DB795 dim display

No need to give up now. It would be unusual to have the tube fail outright. They tend to grow dimmer and dimmer with time. Who knows, maybe you can find a spare online.

[jiroy]

Re: Sony STR-DB795 dim display

Had a good look at the joints and floated some more suspect ones... Sony dry joints were famous on their Trinitron 19" early 1970's receivers. They used expensive scr's in the psu and timebase circuits which were exceedingly easy to blow up on replacement.
A variac and swift hand near the off switch was essential.

Tony.

Variacs are life savers ..Good luck .

[Longbow]

Re: Sony STR-DB795 dim display

Just out of idle curiosity, what does a variac have to do with a dim VFL display?

[R_J]

Re: Sony STR-DB795 dim display

Did you check for 6 volts a/c right on the display (pin 2 and 41/42) It is posible R1011 or R1012 increased in value droping the filiment voltage to the display, just a thought