Seventy-Eight Degrees!

 And for my friend SiG, 19% humidity!

 Just gorgeous today, and I'm out in the garage painting some small parts, and dropping the exhaust manifold off the Supra so I can get at some bolts located behind it. Good thing I decided to do this, as three of the seven bolts were almost "Finger Loose", and the two end ports were blowing exhaust out. The other four bolts came out very easily, and were soon to be loose. The manifold is mounted on studs screwed into the cylinder head, and "Prevailing Torque" nuts hold it to the studs. All seven studs came out, but the nuts stayed on them. I'm having a difficult time getting the nuts off the studs, and might just buy new ones, as they're still available from Toyota.

The infamous Last Transistor for the Fisher RS-2010 got here yesterday, so I'll be installing those later today. I saved these two for last as they have an "extra" transistor (NOT on the schematic diagram) just "scabbed in there", and I still have to document what number transistor it is, and exactly how it's connected.

Hope you enjoy the upcoming weekend, as March will be going out next week accompanied by rain and snow here.

 Keep your head on a swivel, as with the warmer weather coming, things might get spicy....!

The Fisher Saga...The Last Transistor Is On The Way!

 

Yow, this receiver was a gen-you-ine PITA to source the parts for. There are two transistors in each of the two Power Amplifiers. They're what's called a Complementary Pair, which means one is a PNP type, and the other is an NPN type, and their characteristics are matched to each other.  There are several part numbers for each pair, -BUT- while I could easily find one of the pair, the other one was nowhere to be found for any of the suitable parts I was searching for. I was finally able to hook up with a forum member who had purchased a large number of these when they were still available, and after contacting him he agreed to sell me TEN of each type I needed.

So I now have enough of the correct parts to finish the Power Amplifiers, and have some spares for future use.

Happy Birthday to Ms. Swan

 

 She's 40 years old this month. I go by the door tag that says she was built in March, 1985, but I've never tried to dig deeper to see when she was built in March. Toyota could most likely tell, but they're not saying.

She has an interesting story.......

I bought her and drove her home on New Year's Eve, 2012, so I've really had her about 12 years and a few months. I looked at about a dozen of them, and all of them either had a  rod knock, rust holes you could put your fist through, trashed interiors that looked like they'd held raccoon fights, really bad body work, missing parts, or all of the above.

She was owned by the original purchaser for 27 years, and mostly had the typical maintenance a Toyota gets. She came with a shoe box full of receipts, so I was able to determine when some of the parts had been replaced, but I considered it a spotty record at best.

The original owners lived in Redlands, CA which is in San Bernardino County, which is a very dry, hot area, so NO RUST! They sold her to a single Mom who bought it as a bribe for her teenage son. If he finished High School, got his Driver's License, and a job, she would have given him the car and taken care of the maintenance, insurance, and licensing. Needless to say, that didn't happen, so she sold it to the guy I bought it from.

He said he'd bought it "To Restore", but judging from the JDM Honda Civic he drove up in, I doubt it. He said he was being forced to sell it because his girlfriend squawked about having to park her brand new Accord in the street, while his two off-road trucks, his three motorcycles, his boat and trailer, and his two other Honda Civics were taking up all the parking spaces at their place. He wanted $3500 for her, and while he said he knew I'd take excellent car of the and fix it up, nut if I wouldn't pay the price, he had "Ten kids lined up who wanted to buy it and drift it".

OUCH! A fate worse than death for these cars!

So I coughed up the Benjamins, and brought her home.

It's been a fun ride!

The Fiser Saga: Power Amplifier Autopsy

 Yeah, it's been a few weeks, and a busy time it was with the gorgeous weather we've had for the last week.

And then I got clobbered with the cold/flu/whatever. Anywhoo...feeling much better.

Back to the Fisher RS-2010 Stereo Receiver I've now had almost a year. Yes, I'm embarrassed, but it turned out to be a LOT more work than I estimated. I'm now down to searching for ONE transistor, with all the rest having been sourced, and on-hand. The issue is that it's one of what's called a Complementary Pair, and while a sub for one of the two is readily available, it's compliment is not. Soooo....I have to dive into either finding a vendor with some in stock (NO eBay or Amazon....too many fake parts!), -OR- start going through the "sub-for-the-sub" routine, and find a complementary pair that's available. 

Bags of new transistors awaiting their long overdue compatriot.

It gets a bit tedious....

 

So what killed several transistors, and let the smoke out of three resistors? Who did the dirty, dastardly, despicable deed?

'Twas a shorted Zener Diode, it was.... that's what who dunnit! 

The diode in question is labeled "DO6" in this clip:

 In this application it's being used to develop a voltage which is 12 Volts less than the supply voltage, rather than developing "just" 12 Volts. They do this because the entire amplifier is isolated from "DC Ground", and floats between the +60 Volt and -60 Volt power supplies. The only transistor in this circuit connected to the chassis, is Q06. When the diode failed, it put Q04 into saturation (FULLY turned on), meaning it had only .65V drop across it, which in turn took out everybody connected to it by putting them into an over-voltage condition. A classic example of a Cascading Failure.

So that's where I'm at right now, changing transistors, and getting ready for a brief test when they're all replaced. After I verify all the voltages are back to where they should be, I'll be ready to run it at 50% power for a few hours while I monitor the temperatures to make sure nothing goes bonkers, and then run it Pedal-to-the-Metal for a couple of hours to see how it well it performs.

 

Gettin'n close, finally, to a resolution on this one.

Groan.....Got Clobbered By Something

 Been flat on my back since Monday. Aches like I've never had (even my knees hurt),  coughing, sneezing, going between sweats and chills, and all sorts of other things.

Finally got out of bed today for more than 30 minutes, and while I'm still a bit wobbly, at least I'm feeling somewhat better.