Hi, and thanks for your time and knowledge!
Struggling a bit with this foldover issue as seen here:
As you can see, it starts "drawing" before the beam has returned to its correct position, therefore the top lines are inverted (verified with the mouse pointer).
Also, the scan lines start vertically far apart but gets progressively closer at the end of the scan.
I suspect both the vertical flyback timing, the ramp/sawtooth curve, possibly generated by a marginal Sony PSU (not recapped, but OK Voltages present).
Disclaimer:
This is the first time I actually attempt repairing a CRT circuit on a deeper level, but I'm not unfamiliar with digging inside CRTs and repairing electronics in general on a professional level (High voltages an so forth).
Still not sure what NOT to put a scope probe onto in a CRT, so keep that in mind.
What has happened so far:
I started digging around on the analog board because an initial jittery / jumpy (a few pixels) horizontal deflection, worsened by HDD activity, appeared after years of storage.
After unsoldering the HOT and verifying that it was still a transistor with a tester, not a partial blob of conductive metal, resoldering it back in circuit fixed the horizontal issue.
Dry joints more or less verified.
In between that and the current issue, I resoldered a bunch of grey / dull solder on the Digital board around where all the capacitor juice once lived (Yes, recapped and cleaned about 5 years ago, also battery was removed long time ago by previous owner).
I also have phase error issues with the SCSI HDD at the end of formating in Lido 7, but that is an issue for later.
Important note: I made a mistake during resoldering the ICs and shorted two pins on UH7 (Red circle, last attached image), causing a temporary no boot / black screen.
During that situation, I also reflowed most, if not all solder points on the Analog board and verified that the electrolytic caps where still somewhat within spec (lifted one leg on difficult ones).
Also important note: During the no boot and black screen situation, I forgot to resolder one leg on C7 (Analog board), making that section of the Horizontal circuit not complete.
Since the Digital board did not start, the H/V signals where not present, so I believe that last mistake has not caused an issue (hopefully).
What has been done and verified on the Analog board:
+5, -12V and both +12V rails verified with DMM with not too much (<100mV) ripple in AC mode.
Scoping them is a good idea at some point.
The Analog board has been mostly recapped now (Panasonic NHG and FM mostly), except the Horizontal circuit related axial caps (measures fine) and the 10uF / 160V (not in stock) which measures marginally with a slightly high ESR (4ohms ish according to memory).
No leaking caps found.
Most of the resistors in the Vertical section verified, apart from the 68k (R7 and R8?) resistors which measure 34k both ways in circuit.
Is this possibly a hint that the C4 cap is shorted? I rarely suspect non-electrolytic caps for shorts.
Yoke coils measured within spec with my not-a-Fluke DMM.
TDA1170N replaced with a year younger NOS. No change.
CR1 (1N4001) replaced with a fresh 1N4007. No Change.
Suspects:
Marginal 74LS38 ?
PSU 12V Sweep and Disk voltage sag during retrace?
The smaler non-electrolytic caps in the Vertical section?
Something wrong in the Horizontal circuit making it appear as a Vertical issue?
Any hints and tips are welcome, also where to probe with my scope and especially what to expect there is very helpfull.
Struggling a bit with this foldover issue as seen here:
As you can see, it starts "drawing" before the beam has returned to its correct position, therefore the top lines are inverted (verified with the mouse pointer).
Also, the scan lines start vertically far apart but gets progressively closer at the end of the scan.
I suspect both the vertical flyback timing, the ramp/sawtooth curve, possibly generated by a marginal Sony PSU (not recapped, but OK Voltages present).
Disclaimer:
This is the first time I actually attempt repairing a CRT circuit on a deeper level, but I'm not unfamiliar with digging inside CRTs and repairing electronics in general on a professional level (High voltages an so forth).
Still not sure what NOT to put a scope probe onto in a CRT, so keep that in mind.
What has happened so far:
I started digging around on the analog board because an initial jittery / jumpy (a few pixels) horizontal deflection, worsened by HDD activity, appeared after years of storage.
After unsoldering the HOT and verifying that it was still a transistor with a tester, not a partial blob of conductive metal, resoldering it back in circuit fixed the horizontal issue.
Dry joints more or less verified.
In between that and the current issue, I resoldered a bunch of grey / dull solder on the Digital board around where all the capacitor juice once lived (Yes, recapped and cleaned about 5 years ago, also battery was removed long time ago by previous owner).
I also have phase error issues with the SCSI HDD at the end of formating in Lido 7, but that is an issue for later.
Important note: I made a mistake during resoldering the ICs and shorted two pins on UH7 (Red circle, last attached image), causing a temporary no boot / black screen.
During that situation, I also reflowed most, if not all solder points on the Analog board and verified that the electrolytic caps where still somewhat within spec (lifted one leg on difficult ones).
Also important note: During the no boot and black screen situation, I forgot to resolder one leg on C7 (Analog board), making that section of the Horizontal circuit not complete.
Since the Digital board did not start, the H/V signals where not present, so I believe that last mistake has not caused an issue (hopefully).
What has been done and verified on the Analog board:
+5, -12V and both +12V rails verified with DMM with not too much (<100mV) ripple in AC mode.
Scoping them is a good idea at some point.
The Analog board has been mostly recapped now (Panasonic NHG and FM mostly), except the Horizontal circuit related axial caps (measures fine) and the 10uF / 160V (not in stock) which measures marginally with a slightly high ESR (4ohms ish according to memory).
No leaking caps found.
Most of the resistors in the Vertical section verified, apart from the 68k (R7 and R8?) resistors which measure 34k both ways in circuit.
Is this possibly a hint that the C4 cap is shorted? I rarely suspect non-electrolytic caps for shorts.
Yoke coils measured within spec with my not-a-Fluke DMM.
TDA1170N replaced with a year younger NOS. No change.
CR1 (1N4001) replaced with a fresh 1N4007. No Change.
Suspects:
Marginal 74LS38 ?
PSU 12V Sweep and Disk voltage sag during retrace?
The smaler non-electrolytic caps in the Vertical section?
Something wrong in the Horizontal circuit making it appear as a Vertical issue?
Any hints and tips are welcome, also where to probe with my scope and especially what to expect there is very helpfull.
