Well, at least it didn't go up in smoke when I brought it up on the variac!
And now we go into troubleshooting the Power Amplifier Board, the original problem that brought the receiver here.
This board has six undocumented changes from the schematics in the Service Manual.
1 - Four 10uF capacitors, two each on the STK-0080 "Darlington Power Packs".
2 - Two small inductors on the bottom of the board.
3- An "extra" transistor on each driver transistor
4- An extra resistor in each channel.
5 - A resistor that doesn't go to the designated pad in each channel.
6 - A capacitor/resistor network mounted to the chassis, with "flying leads" going to the board. The capacitor is the out-of-focus blue cylinder handing in midair.
Things like this, along with the haphazard layout of the board (parts are scattered everywhere, part numbering is odd, etc) makes troubleshooting tedious.
This shows "Q17" with an extra resistor, and an extra transistor stuck into some of the holes for Q17. Resistor "R03" is also not going to where it looks like it should go. These are most of the major changes Sanyo made that I have to figure out.
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Yes, it needed a lot more work than I anticipated, but that's why people bring me these things to fix. At least I'm down to one circuit board, which to me is the Light At The End Of The Tunnel.
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Reminds me of the wire I was chasing behind the dash of a mid 70's Ford one time. I actually had the diagram for it but it didn't show me that the wire color changed FIVE TIMES in the space of less than 15 inches inside the harness. The wire doubled back on its self every time it changed colors. I have never seen anything like that since.
ReplyDeleteYou my man, have a very seriously under rated and hard to find skill set.
Phil, buddy! Good to see you're feeling better.
DeleteI've got a ton of posts to do about the Supra. One of the things I'm doing is upgrading the charging system with new, bigger cables, and a bigger alternator. ALL of the split loom tubing in the engine bay has gotten to the point was falling apart, so I'll be rewrapping the harness, but yow....Toyota sure doesn't wire up a car the way I would! Got splices in the main power lead all over the place, and it doubles back on itself a couple of times. I'm getting rid of some of that, but figuring it out took a while.
Happy Weekend! Damsel and I (mostly I) look forward to seeing the completion of the Fisher mega-project.
ReplyDeleteThe tuner is working fine, but needs an alignment and dial calibration (part of the alignment), which is easy. The last thing left to rebuild is the Power Amp Board. Should be fun!
DeleteVery interesting. Working electronics to me is close to magic. I mean, it makes sense and I understand the theory but past that all I hear is "Wah, wahwahhhwah wahhh."
ReplyDeleteI, of course, discovered this when I was in college for an electrical engineering degree. Got the good old brain beyotch-slapped by reality. So I am happy to pay other people to do what they do.
I can fix simple issues, like a busted cord or easily identifiable problems, but doing the canoodling and cafudging and fuzting around, yeah, I can watch someone else do that all day long. Happily watch someone competent do it all day long.
I started "experimenting" with electricity when I was around 10 years old, so I've been doing it well over 60 years. Been my whole life. Well, except for the forays into Road Racing, Hot Rods, Engine Building, and a few other things. I don't grok all of it, but enough to get by!
ReplyDelete