Sony KV8000.
 

Hi folks, newbie here. I have this nice little portable TV that was working 100%. Until it wasn't. It is totally dead, no video, no sound. The pilot light doesn't light up. I have checked both fuses and the on/off switch, all good. There is voltage leaving the secondary of the power transformer. My skills do not extend to diagnosis at the component level on the boards- nor do I have much in the way of test equipment. I don't have a schematic, either. I don't have the accessory battery pack for this set, so can't tell if the fault is in the AC or DC power supplies. Anyone got suggestions as to what I can do? I hate to bin it, but at the moment it's a doorstop.

Hi to all,
Hi Jayjaydub,

Cute! little 8" Trinitron, end of 1970s.

You're in luck! the full Sony KV-8000 service manual is downloadable for free on ElektroTanya, BTW once of the best worldwide sources for service data :

https://elektrotanya.com/sony_kv-800.../download.html

Please state your skill level in repairing vintage electronics so that we can help you.
Do you have a Volt/Ohm/Ampmeter; digital? analog?

If AC volts on transformer secondary, probably a shorted rectifier and dry/shorted filter Caps.

Once you have the Service Manual, see if there is +22V DC at the output of the main regulator board (Q901 power transistor).
See block diagram below.

The Pilot light is a miniature Neon tube powered by a voltage derived from the Horizontal power Scan section.

Keep us informed....

Best Regards
jhalphen
Paris/France

Sony’s we’re common to have the high voltage block arc and crap out. Look for carbon arc tracking. The HV block we’re usually red epoxy and had the hv lead out of it go to the anode of the picture tube. Sony was well known for using derived voltages to power other parts of the set from the flyback i. e. sound video color circuitry. That’s at least a start. Use your nose to see if anything smells burnt and good luck.

Find Q901
Its chassis mount near the power cord.
All 3 terminals should have APX 22 VDC on them.
While there if the power socket is mounted on a PCB check it
for cold solder joints.
Report back.....

73 Zeno:smoke:
LFOD !

Btw
 

BTW this set uses a hoz design most will never see.
Output # 1 runs the HV & scan supplies.
Output # 2 runs the hoz sweep & pin
Sony & Panasonic both did it. Maybe others.

Zeno

Hi to all,

additional data from the Service Manual :
- Physical location of Q901 (red circle)

Best Regards
jhalphen
Paris/France

Sony KV8000
 

No sign of dry joints. I have 22v B-G, 22v C-E, 22v C-Ground. Does this sound like the transistor (D476A) is faulty?

Well done power supply is running.
Now check volts on
Q502 - C
Q503 - C
d504 - Cathode
d505 - Cathode
Probably all on the main PCB
Check the main PCB for bad joints especially on T502
That will narrow it to a stage.

Zeno

Sony KV8000 (cont)
 

No volts on any of these. In fact, can't find any power on the main PCB except the outputs from the power transformer. I guess that this is a clue! Whatever supplies/distributes power on the board is AWOL.

The 22 V from Q901-E is the main B+ for the hoz out Q503.
Only thing between the 22V & the FBT is R631
If that opened Q503 may be shorted.