WG K7203 high B+ Removing HV shutdown protection does not bring back pic.

texasmame

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Long and short, having B+ issues. 160+ there. The 24 and 12 volts are both fine. Looks like lifting P13 on IC401 is the equivalent of lifting D10 on a 7000 chassis to bypass the HV shutdown to see if pic can be restored. Did that and B+ still at 160 and still no pic.

Do have heater glow and it "sounds" like the monitor is on, just no HV.

This chassis was working just recently and was hoping to find a flow chart for this model but there apparently is not one.

Suggestions appreciated and I'll keep digging.
 
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Long and short, having B+ issues. 160+ there. The 24 and 12 are both fine. Would like to lift the equivalent of D10 on the 7000 from the flow chart to bypass the HV shutdown circuit for troubleshooting.
 
Thanks but that's the block diagram or what not.

Looking for the troubleshooting flowchart.
Here ya go! Added: My bad, read your issue...not on here, Screenshot 2025-04-09 at 17-23-44 K7203 (REV A) TROUBLESHOOTING GUIDE.xls - WG K7203 (REV A) T...png
 
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Looks like @paul400 ran into your issue here and fixed it:
 
need the electrical load / bulb 40-60w on tp1
All the time to control the b+ during TS
The ic is monitoring the vcc
Voltage current control by a Zener in the ic.
It will kill the oscillator and no HDrive
Open Horizontal transformer


The FB is common failure on this chassis
Sometimes not so obvious
Just add the bulb to Tp1
So the voltage drops to 121v
 

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need the electrical load / bulb 40-60w on tp1
All the time to control the b+ during TS
The ic is monitoring the vcc
Voltage current control by a Zener in the ic.
It will kill the oscillator and no HDrive
Open Horizontal transformer


The FB is common failure on this chassis
Sometimes not so obvious
Just add the bulb to Tp1
So the voltage drops to 121v

Thank you.

Finally got around to this. Bulb trick worked: B+ at 119.

Still no pic. So flyback bad? You're right - it looks the same as it did when it was running properly; no cracks, smoke, etc.!

EDIT: I have a flyback to a 1901 chassis. Are they interchangeable as the 1901 is essentially the same design as the 7200 series?
 
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Need to keep the bulb for load on ps
Until the chassis is working

Normal shutdown is around 140 tp1 not 160 v
Your missing h-drive confirm test q502 collector it Should be around 24.
Just need to confirm the drive and voltage

Though the H-transformer t501 bad solder connection ?

Don't need a fb to get h-drive and X-ray open
You got vcc.
Need dc on vcc for the ic to work

Hdrive is a small drive pulse but would have small amount dc at the base if high then no hdrive bad ic
Hot should be correct part number and solder in good and remote bd hooked up.
Is the horizontal drive circuit working??
Ok with me to swap fly back if pins and windings match up.
With X-ray remove the flyback can't stop the hdrive most would happen it would just burnup
The fb or start acting Or short the hot
Forcing the circuit means making it work
Bypassing safety
If not need to get back to drive circuit
Until there's drive first
Luk
 
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