OE stereo install 75 280z

[Dave WM]

My Z only has the one speaker on the driver side, I really want to have stereo as close to OE as possible. Currently there are a 3 after market speakers, all in plastic enclousers that are mounted 2  in the back (left channel) and one in the front by the passenger side hung under the dash. That has to go. So anyway I managed to get a passenger side speaker mount (hole were in the pass rear trim already but no mount and no wire harness connection) and some new matched period correct speakers. It looks like I will at least have to remove the quarter glass trim to get access to the factory location of the body harness that would be where the speaker wire should go. If any one else has had this off to look over the wiring, please let me know if that would be enough or do I need to remove more trim (lower piece that is aft of the door and under the quarter trim, looks like a vinyl covered piece. I am hope I can fish the pass speaker wire down behind that and follow the body harness.

[Dave WM]

some video of the progress so far

 

[Dave WM]

Worked on it some more last nite, got all the wiring for the new speaker routed and tucked away. Adding some bullet connectors, will clean up the dirt etc and button up the trim parts later today. I have to do something with the carpet. The OE rubber backing on the rear deck is dry/cracking and falling apart. The carpet itself looks fine. I am thinking of flexing it and seeing how much of the spent rubber I can get off and then maybe use a spray on rubber like flex seal or something like that to apply to the back side. Only real issue I can think of is I don't want it to come of the carpet and foul the prestine paint underneath it. So I may just remove the rubber to end the mess and leave it at that. The radio came in yesterday, I am just waiting on the plugs to fit the harness and the radio so I can make the adapter. Sticking with the bullet connector for the sake of originality, plus considering the power I expect to be pushing thru them (4 watts max), I am sure they will be up to it.

[Dave WM]

wow, that was a let down, got it all wired up and silence completely dead (well the lights worked).

So dug up a schematic, Noted that I could get a hum if I touched the hot side of the volume pots, so power amp is good. Voltage checks of the 1st transistor in the AM (easy to get at) showed zippo for voltage. Ah the power amp does not have a regulated power supply but the tuner does. Its a transistor that is biased on with a zener diode in the base circuit. Collector has full B+ (13v) base 0 (should be about 6v) emitter (output from the regulator) 0 should be about 7v. Ok so why is the Base zero, only 3 parts in there, a couple resistors, a electro cap and a zener. resistors tested ok, pulled the cap out hoping it was shorted, tested ok, darn that leaves the zener. shows about 5 ohms both ways. Tried to pull in out but broke so never could test it in circuit (just in case I missed something that could account for the short). Hey great I have one in my stash, hey darn I broke it bending the leads to fit the pcb (7.4v). so a 1 am I found a 5.1v and used it. sure enough the voltages pop back up at the tuner and the radio roars to life (AM anyway, may still have issues with FM but want to get all the shielding back in place and the correct voltage to make sure). drove across town to skyjunk and dig thru the stash of zeners, of course they are not marked for values but they had a ref manual that let me look up the 1N number. So now I will do a quick function test just to confirm the ratings and install the proper 7.4v rated diode.

Edited July 23, 2016 by Dave WM

[siteunseen]

Dang!  I just got a haircut reading that.  You know, it went right over my head.

[Captain Obvious]

Haha! Me too! I know where I'm going to send my old electronics for repair!!

So what do you think would short a Zener like that? It's not like it was passing a lot of current.

[Dave WM]

Good question, and I have no idea. Its only function is to provide bias voltage, and the transistor is not shorted.

I did some more testing I was hoping putting the shielding back on I could get some FM but no joy. I do get a lot of white noise so I am guessing the LO is working just nothing to beat against, so my guess is the JFET RF is bad on the front end of the tuner. Prob is its BURIED deep inside the tuner and appears to be integrated with the actual tuning slugs. No way I can get in there to even do a voltage test. So next up to try and confirm it will be to get my sweep generator and start with the IF (10.7) and TRY to get some signal down near the board so see what is going on with the gain. My guess is the IF is fine due to the loud hiss. I could confirm it with an RF signal but like I said its going to be nearly impossible to get at. I could try signal tracing with a scope prob as well but again access will be the killer. I am so sure its the JFET I am tempted to just disassemble as needed and forget testing just see if I can get to it and replace that one part. A clue was I was able to tune a local strong FM channel with some careful positioning of an antenna, and I do mean a very strong channel that I could just hear at full volume. The clue was it was tuning so I assume the LO is working but just not enough signal from the RF to work with. In the mean time I put my old AM/FM stereo 8 track back in and it sound great with the new speakers in the correct stock location. So the pressure is off for now. I have not pulled the Z out of the garage in 4 days and starting to get antzee. I don't know how some guys can have their cars down for long periods of time, that would make me crazy.

[Captain Obvious]

Well it's definitely in the right hands. I'll bet you're the only guy willing to go that deep into a project like that. Accounting, huh?

There was another thread a little while ago where a bunch of diodes (maybe the Zeners?) had turned to fuzz and had actually pretty much completely disintegrated. It sounds like they may have a longevity issue. Maybe internally shorting is the first step, or maybe the fuzz is conductive. Silver oxide or something from the tarnished old school silver coated leads?

Is the Zener you found shorted a spherical ceramic looking body style or a cylindrical glass body? The fuzzy disintegrated ones were the spherical ceramic looking ones.

I know what you're saying about getting itchy to drive the car. I'm the same way, although (not living where you are) I get the winter months to take the Z off the road. Not sure that's a benefit or a drawback? Wonder if your neighbors missed seeing you cruising the neighborhood these past four nights. 

[Dave WM]

Yea I even do that same route I did with you every day, I think they use it to confirm the atomic clock is correct.

I think it was spherical, but it was very hard to get at, I broke it just trying to get to it. I did some reading up on zener, seems the most  common failure mode is indeed shorting. Guess that is a good thing since it would tend to protect overvoltage of whatever they are trying to regulate.

Accounting, just a way to make money to spend on other stuff for sure.

[Captain Obvious]

Haha! Consistency!

Good luck with the radio. I have no doubt that you'll get it working. And make money, almost at the same time!   

[hr369]

"stereo datsun radio thats coming"     You said at the end of your video.  What kind of radio is this new one?

 

Your first radio you bought has FET's ?  what kind of radio is this?

The OE hitachi i have has NPN's 

Edited July 25, 2016 by hr369

[Dave WM]

Well its working, two issues 1st was the power supply to the radio tuner, this fixed the AM the FM sounded like a dead RF FET but messing about with it I was able to push on the tuner board (buried deep in radio enclosed mostly with a shield integrated with the tuning slugs. I look a bit closer and thought I could see a crystalized solder joint on one of the coils. got my solder iron and reflowed that, put it together messed with it some more and think I got it. I will ruff handle it some to see if that issue pops up again.

 

HR its a Datsun hitachi  KMS2501B I got off ebay. Guy said it was not a z but think a truck or 710 or something like that. My existing radio is a audio vox or some after market branded AM/FM stereo 8 track. I really wanted the old style push buttons and not some current junk that fakes the push buttons. has a single JFET as an RF amp in the FM tuner. rest are conventional bipolar transistors AND some IC's in the MPX and power amps. The hitachi service manual says oct 1976.

I got a video on the works its pretty ruff since I do my hobby work at nite (still have a day job).

Prob is I was so frustrated with having my car all apart that I spent today (daytime) putting the old radio back in. I do have the speakers installed and all the trim panels back up. I like the way it sounds a lot better than the goofy 3 speaker pod mounted (2 4.5" for left in the back and 1 5.25" mounted on the tunnel on the passenger side up front for right). I spent a lot of time routing the added speaker along the same path as the body/console harness (inside some of that wire loom plastic to protect the speaker wires and provide a channel if I ever wanted to run any other wires back there) taped the new speaker wire along the console harness with some electrical tap so it looks pretty much factory. I used some bullet connector so I can alter harness easy, fabricated a wire harness to take the stock Datsun (power/lights/single speaker) 6 pin connector to the 3 pin speaker/6 pin radio harness used by the 2501B. I will prob just wait to put the KMS radio in when I do the trans swap (and have the center console out again.

One thing is for certain, those radios on Ebay selling for $$$ better have new zeners if used like this one in the power supply. I have read up on them and found its not uncommon for them to fail shorted (protects against overvolt that way) and they can fail from age not use. Working on car radios is a real bugger, but I can see how if you did one brand (like the common Z radio) you could get good at it as far as how to take apart and what to look for. One thing for sure, its not a shot gun recap deal like I see done so often in other vintage electronics. Better to diagnose the issue and fix the ONE part that need fixing, limit the abuse to the pcb's and interconnecting wires from overhandling.

 

 

 

 

 

Edited July 25, 2016 by Dave WM