So, I first took these steps to try fix the collapse, in this order:
- Replaced IC401 LA7832 with LA7833 (haven't got LA7832)
- Installed socket and replaced IC103 HA11423 just in case (not sure if it could be related)
- Measured a bunch of components around the vertical area (ZD401, ZD501, both 6.2v zener are good), and after desoldering and closely measuring 2 transistors that seem related to vertical, multimeter displays some voltage (diode test) between C-E, got replacements, they don't have that weird reading, put them into the chassis but nothing changed (still same collapse):
- Q402 PNP 2SA1408 Y - only found an O one to replace it with but hFE looks quite similar, maybe it doesn't even matter.
- Q401 NPN 2SC3621 Y
B+ is quite adjustable, goes from 80-something to 104v, left it at 94 which is around where the silicone blob kept the pot.
I was doing a bit more of research since it seems the MS8-29 is quite the same (unlike the MS8-26), found this one https://www.aussiearcade.com/topic/9842 ... ting-down/ , mentions the same odd transistors readings that I had, and then his issue was a bad fusible resistor R438, so went and checked mine, it is bad too!, measures megaohms.
His is 2.2 Ω, I guess because it's a MS8-29, mine is red/violet/green/green, so 2.7 Ω?
- Replaced it with a Vishay PR02FS0202708KR500 (Fusible 2W 2.7ohm), turned it on and still nothing, I guess because there's the shutdown issue
- Also got all capacitors and did a full recap (minus the filter one).
- Turned it on again and nothing.
- Took out and measured the HOT D1887, Vreg C3306, Diode thing C021M-15, C2688 Q532, all fine with TC-01 tester.
- Took the HOT out and hooked up the bulb between TP2 (gnd) and TP1 (b+), it turned on
- Then connected it between gnd and HOT collector, turned on too
- Then desoldered the FBT B+ pin (2nd one) connected it between the pad of that pin and gnd, turned on too, voltage is same as B+
I found on this thread viewtopic.php?t=45856 :
- to check for R562, took it out, depending on which lead I put in the multimeter it reads between 391.5k or 392.5k so I guess that's right?
- Also from the thread I took out and checked ZD903, ZD904, tested the zener voltage with a 10v psu, both work fine at 6.2v
Any assistance appreciated!