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HOW-TO: SC300/SC400 Install Aftermarket Head Unit, OEM Speakers and Sub Working!

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Old 12-15-14, 01:10 PM
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HOW-TO: SC300/SC400 Install Aftermarket Head Unit, OEM Speakers and Sub Working!

 
Old 12-15-17, 12:27 PM
  #586  
idp1
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Thanks so much Raine.. appreciate the support. Yeah, I will do this as Phase-1 & Speakers in Phase-2. True, as you said it perhaps makes no difference putting in the amp, but, I wanted to do the ground work - installs & wiring - for enhancing the stock. Would not have planned but for the Nak amp death. I did not want to change the stock when I bought the car a year ago, but, the radio was DOA. I bought a used Nak amp which was water damaged as well. Using both I tried to replace components - spending 4-5 days on de-soldering/soldering - cannibalizing 1 to fix the other! In the end the only thing I achieved was when I hooked up the amp, the sub woofer was making thumping sounds with no audio from other speakers! That was the most depressing moment in that whole week. So, I waited couple of weeks to steel myself and started looking around for ideas - then came across your DIY post which is the adrenaline I needed from the sordid/failed amp-repair-nut job!

First I thought of keeping the stock radio with an aftermarket amp, but, no matter how much I explored it sounded as ridiculous as my first exercise of attempting to revive a dead Nak amp. So here I am seeing some light at the end of tunnel. There is not a day my wife throws those funny looks whenever I head to the garage...
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Old 12-15-17, 07:12 PM
  #587  
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Honestly at this point, with a vehicle that old, I wouldn't have done it again - I would have gone full aftermarket current tech. I only did this write-up because I was low on funds at the time
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Old 12-18-17, 12:27 PM
  #588  
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I see what you mean... thanks
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Old 02-18-18, 10:33 AM
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Got a 1992 Soarer with what appears to be the same audio system. Decided to go full aftermarket after the stock speaker amp died.

Used your diagrams to confirm that a locally available harness would give me ACC, +12, illumination, antenna etc. The wires were exactly the same as yours. The ground didn't work (tested with multi meter) but it seems to be an issue with both Lexus and Toyota.

So your write up is still helpful after all these years, even for those who don't intend to follow the whole thing.
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Old 02-18-18, 11:59 AM
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Originally Posted by UncleFungu View Post
Got a 1992 Soarer with what appears to be the same audio system. Decided to go full aftermarket after the stock speaker amp died.

Used your diagrams to confirm that a locally available harness would give me ACC, +12, illumination, antenna etc. The wires were exactly the same as yours. The ground didn't work (tested with multi meter) but it seems to be an issue with both Lexus and Toyota.

So your write up is still helpful after all these years, even for those who don't intend to follow the whole thing.
Good to hear!
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Old 07-07-18, 05:08 PM
  #591  
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Okay so I followed this step by step with a friend of mine and the front speakers spun perfect but the sub, and the 2 rear deck speakers are not working, I am getting power to the sub but there is no sound. Have not checked for a signal from the rear speakers yet. Please help itís hot and I just wanna figure this out
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Old 07-08-18, 08:00 AM
  #592  
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Default sub woofer connection causing noise

I am replacing Nakamichi amp with Kenwood KAC-7005PS 5-Channel Amp, Nakamichi head unit with JVC KW-V40 BT & speakers (front & rear - Kicker 44KSC404 & 44KSC6504) . Thanks to Raine & others who posted their work I was able to successfully hook up head unit, amp, Nak sub & speakers,. Can hear sound from sub & all speakers except Front left, which I tried trouble shooting without much success: I switched left & right speakers, but, still have issue. Switched amp out to speaker wires without success. I will work something later about front left speaker but, need help with following issues:

1. Used noise filters for both RCA outs to Amp from head unit and looks like there is no noise. But, when I hook up RCA out to Amp from head unit, I hear high static which drowns out with some music, but, at low volume I hear the 'hissing'. If I unplug sub RCA outs at head unit the noise is gone. I read we don't need filters for sub, but, do you guys think I should add filter to sub outs at head unit as well?

2. I hooked up a rear view camera to head unit ( a $15 purchase from Amazon.com) and followed instructions for wiring. Head unit display does not switch to Rear Cam in reverse gear: I have to manually switch display. There is a trigger wired on head unit which is hooked up as per cam instructions, but, it triggers camera when in reverse. But, display does not switch to rear cam - I have to be in rear camera mode and then in reverse rear image comes up. When not in reverse gear the image goes out. Any suggestions on how to get head unit display to switch to rear cam when in reverse?

3. As suggested by many I did not use Metra adapter, but, spliced wires - following color codes - to hook up Battery, Ignition, Antenna (A1 & A8 combined), Ground etc but I am not getting constant 12v from Blue/White lead! As a work around I hooked up constant 12v from Cigarette lighter harness. The unit works now, but, memory settings are not retained since it is getting 12v from cigarette lighter harness which is powered, I assume, when Ignition is on. Following are the 'ground connections' I made.

3.a. Grounded head unit lead & ground lead from Lexus head unit harness to a chasis bolt.
3.b. Joined ground wires from both amp harness (sub out & speaker out).
3.c. Connected a ground lead to Head unit chasis at rear and brought it all the way into trunk to connect to a rear screw of Amp underside.
3.d. Amp is powered by direct battery connection from engine compartment through its own dedicated heavy fuse as instructed by others here with its own ground lead going to a chasis bolt in trunk. Amp is not heating up and apparently working fine.

Do I need any additional ground connections and/or add noise filter to amp out RCA leads at head unit? Appreciate your help/suggestions. It has been exhausting, but, rewarding... started this project in Dec when it was really freezing cold, put it off for 6 months and picked up this weekend. Hearing sound coming through speakers for the first time - nak amp was DOA - since I bought the car in Dec 2016 was really thrilling.

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Old 07-08-18, 02:31 PM
  #593  
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I resolved noise on sub outs by adding 1 more ground loop filter. I forgot to mention, but, I can't get my stock antenna down.
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Old 07-21-18, 08:18 AM
  #594  
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I am not getting constant 12 v from any of the wires in 'A' jack - including blue/yellow (A4). I joined A1 & A8 (pink+sliver & pink+blue/green) to antenna lead of my JVC head unit, inserted larger black antenna lead (from Nakamichi HU) to antenna jack on JVC head unit, but, there is no antenna moving up or down when JVC HU is powered from alternate 12v (cigarette lighter for testing purpose: eventually I will need to establish a more permanent solution). My speakers & work from new Kenwood amp. Can some one suggest ways to resolve constant 12+v & antenna issue please?
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Old 10-01-18, 05:35 PM
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Anyone done this swap and saved your stock radio? Im looking for a stock 93 SC400 radio, Lexus/Pioneer brand. Mine has an odd issue that the low volume FM sound is very distorted, like the pre-amp is bad, but CD's sound fine. The distortion sometimes totally clears up after I go over a bump or just out of the blue. Ive jiggled the harness and pounded on the dash with no affect. I like the cassette feature as I've got quite a few mix tapes. I have resoldered all the ground points in the radio itself looking for a cold solder joint but no change, Could it be the amp? Does not explain why the CD changer sounds fine unless the CD changer outs go directly into the amp but then what about the volume control? Puzzled. May just get a double DIN and adapt it but I really like the Dolby B-C cassette on this unit. Dolby C is somewhat rare on a car audio cassette.
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