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Discussion Starter #1 (Edited)

Left: Original Scosche TA-03 (came w/BlueBox) <------> Middle: Scosche TA-03HB (harness only/no BlueBox) <------> Right: Best Kits BHA8113 identical to orig TA-03 (search eBay)
Note: orig harness (left) doesn't have a shell covering the pins so it's easy to mod, newer harness (middle) has the extended shell covering the pins making it difficult to mod, and BHA8113 harness (right) is identical to the original TA-03 so GET THIS ONE!

20-Pin Toyota Wiring Harness w/RCA for 2K & Up Premium 8-spkr w/FactoryAmp Mod for:

The Scosche TA-03A & TA-03B Harness
and BestKits.com BHA8113 Harness


(update 1/05: This mod fits 2000 & up GT's & GTS's w/optional Premium 3-in-1 AM/FM ETR/Cassette/CD w/8 spkrs & separate amp)
= click to jump to post about which GT's this will fit & about TA-02 harness vrs. TA-03 =


(update 7/07: Latest notes on the new TA-03B Harness, BestKits.com BHA8113 harness, Metra TYTO01 harness)
1) Some time ago the original Scosche TA-03 was superceded by a newer TA-03B harness which uses a different connector that has an extended shell covering the pins, making it more difficult to mod.

2) When selecting resistor values from the Termination Resistor Table for the newer TA-03B, add +16% to the value from the table, or use the following calculator to find the exact value, substituting 2200 ohms for R1 (the TA-03A uses 1900 phms for R1): Voltage Divider Calculator

3) There are many wiring harnesses out there which claim to be compatible with the 00-02 / 03-05 Celica's but members have discovered are not compatible. We know the original TA-03 was the easiest to modify and absolutely works, as well as the newer TA-03B, even though it's a bit more difficult to mod. We also know the BestKits.com BHA8113 Harness also works, and may still have the original Scosche TA-03 style connector that's easier to work with.

4) Recently members have been asking me about a new "compatible" harness called the Metra TYTO01. At this time all I can say is that it looks like it might work with later JBL-equipped vehicles which use the Toyota databus to control Turn-On. Other than that, I don't know yet whether it needs the mod or not. Note: Metra does not list any Celica's in their TYTO01 compatibility table.

(update 8/07: )
1) Confirming: the BestKits.com BHA8113 Harness is identical to the discontinued original TA-03 harness, including long pins making it easy to modify compared with the newer Scosche, so I'd recommend you use the BHA8113 instead of the Scosche TA-03B.

2) If your HU only has two RCA outs (L&R) you can use an RCA Y-Cable to connect to the StockAmp's Rear RCA's, but you'll need to roughly double the value of the termination resistors to avoid double-terminating the signals. For example if the table says use 600 ohms, use 1000-1200 ohms instead.


PacificBlue
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You might think installing an aftermarket head-unit and hooking it up to the existing FactoryAmp would be a piece of cake, esp. using Scosche's TA-03 wiring harness and matching Toyota connector. Not so, and like just about everyone else here who's tried it I got loads of ECU noise, power-window buzz, dimmer buzz, and the worst: alternator whine. After installing and removing my HU about a dozen times trying things, I was about ready to throw that fancy HU out the window and put the stock unit back in, until...

I love my Celica like most everyone here does, and cuz I got so much help from reading the posts on this board, I'm posting this to give a little back. So I hope I do this right...

I'm an electronics engineer, but after re-checking everything it all looked like it was hooked up ok, aw crap. Like everyone else I thought it must be a grounding problem. Well, yes & no. And what's with the blue box Scosche gives you with the switch on the side? I wasn't about to give up because I know how good the stock GTS Premium Stereo can sound, so that FactoryAmp can't be all that bad... so I kept going.

In a nutshell... I found out our GTS Premium 4-channel FactoryAmp has high-impedance inputs with virtually no input termination. This means when you hookup most head-unit's PreAmp Outs (which have virtually no output termination) the RCA cables and the Celica's own HU-to-FactoryAmp wiring harness act like radio antennas picking up every little electrical noise generated by the car. Have you ever stuck your finger on the end of a guitar cable with the amp cranked up? Same thing.

On top of that, the TA-03 has a 1.9k resistor in series with every RCA cable. If you feel the heatshrink, you can feel the resistor inside each cable.

Solution... Terminate the inputs of the FactoryAmp to match the output impedance of the head-unit being installed. Doing this effectively dumps most of the electrical noise picked-up by the RCA's & wires to ground while allowing the higher-level audio signals to pass on to the FactoryAmp's inputs.

Click Here: If you don't see pics (goes to Tripod clone site) (updated link: 3/06)


Remove heatshrink from audio pins (notice hidden resistors in black shrink, also 4 new resistors in front



Back of TA-03 showing 4 audio pins - (Red Wire is Right Channel & Top Row is Front)



Unsolder the 4 RCA wires from the connector pins and twist termination resistors onto them before soldering


Add heatshrink tubing (yel) to prevent shorts & add structural support, then tin the ends and solder
them back to the pins

["tin the ends" means melt some solder into each twist first, then when you solder them back to the pins they've
already got plenty of solder so you don't need 3-hands to add more. Use one hand to hold the twist onto the pin
then touch the soldering iron just long enough to make the connection melt back to the pin.]




Add more heatshrink (blu) then twist the ends of the resistors together and tin with solder



Add larger heatshrink to Analog GND wire & solder it to the twisted end of the resistors



After applying heatgun to shrink tubing - (Top Row is FRONT Left & Right)



Completed Mod - tie-wrap all power leads together, then separately tie-wrap all audio & gnd's together



Scosche TA-03 FactoryAmp Noise Fix Mod - Basic Pictorial Diagram & Notes


The output impedance of my head unit is 60ohms at 5vrms, so the 1.9k (1900 ohm) series resistors don't hardly reduce any level and it's easier to leave em in. Basically what you're doing is adding a terminating resistor from each signal wire to ground, closest to the FactoryAmp's inputs. (Ideally you would do this right inside the amp, but this won't be necessary unless you plan on listening to your stereo while driving thru an MRI Scanner or past some military radar dish)


----------------------------------------------------------------------------------------------------------
|__________________SCOSCHE SLC-4 "BLUEBOX" SPECS
|____________( comes w/TA-03 Kit - features & notes below )
|
| * 4-channel HV LINE LEVEL to 4-channel LINE-LEVEL converter
|__( don't need SLC-4 for HU's w/Preamp Outs - Only use TA-03 Conn w/Mod )
|
| * 4-channel SPEAKER LEVEL to 4-channel LINE LEVEL converter
|__( up to 80 watts max per channel )
|__( use SLC-4 together with TA-03 Conn w/Mod - adjust trimpots on SLC-4 to match levels )
|
| * Transformer circuit for noise cancellation.
|
| * Common ground adapter.
|
----------------------------------------------------------------------------------------------------------


So what's with the blue box Scosche provides? Well in an ideal noise-free world you would set the switch to "Line" and plug your RCA's into it and wire the other end into your amp, but if you don't have a HU with high-level preamp outs you can connect your HU's speaker outputs into it (thru the screw terminals) and it will drop speaker-level down to line-level to feed the FactoryAmp. Will you still need to do this mod? Uhm, yeah probably... it's because inside the SLC-4 BlueBox are 4 level-dropping circuits and impedance matching/isolation transformers. What's great about transformers is that they can match the impedance of one circuit to another almost perfectly, plus they can isolate DC path between two devices and only pass the audio signal, but what's not so great is that they can also act like guitar pickups when designed to be connected to high input-impedance amps like ours.

Ever hookup a Scosche SLC-4 BlueBox and wave it around the inside of the dash with the ignition on? Acts like a Theremin doesn't it? That's cuz its transformers are picking up the noise from the data bus running all thru the Celica wiring harness. Ever play with a telephone pickup coil? Almost the same thing.

Notice the TA-03 has 3-ground wires coming out of it. Make sure you connect the ends of the 4 resistors (tied together) to the wire labeled Analog GND in the photos & diagram. The other two GND wires can be tied together and connected to your HU's GND wire. Believe it or not, once you terminate with resistors, your grounding problems will pretty much disappear.

I forgot to mention that when you terminate audio lines with the matching impedance of your HU, your frequency response will probably be restored more closely to what it's supposed to be too. In otherwords if it sounded too bright & tinny before, your bottom end (bass & lows) should come back to life again and you won't have to subtract your treble & max your bass eq settings anymore.

thanks for the help on the board & enjoy your FactoryAmp, I hope it helps...


ps ~ i want to give some credit to EvilED who posted a msg way back in 10-12-2002 about a mod for the factory amp. I found it while searching to make sure the TA-03 Noise wasn't a topic already covered. It just goes to show that doing thorough research pays off if you bother to do it (and no, I didn't find it until it was too late cuz I was lazy too... crap!)

Click Here: EvilED's factory amp mod

Click Here: If you don't see pics (goes to Tripod clone site)

Click Here: For a table of Termination Resistor Values and Final Test Results

Click Here: To jump to post about which GT's this will fit & about TA-02 harness vrs. TA-03

Click Here: Wanna hear a simulation of what the Scosche TA-03 Harness sounds like -without- the mod? [updated 4/2017: sample mp3 file moved to Tripod]
 

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cool write up, i was actually about to buy an amp to get rid of the noise, but i guess i'll try this mod....
is there any way you can make the pics show?
so far, are there any drawbacks to this mod?
 

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Yeah, host your pics somewhere else besides image station.

I just got rid of my whine, but I did something different. I cut the speaker leads away from the stock amp and hardwired them to my HU, running the front speakers in a series. Unfortunately this destroyed the power in the front speakers, they were really weak and sounded terrible, so then I got an idea... I reconnected the larger front speakers to the stock amp (my HU has both pre-outs and speaker leads) and left the front tweeters and rear speakers connected straight to the HU. This way I keep my power and almost completely remove any whine or humm. If you listen really close there is a slight whine, but the speakers are mid-range only so it's not noticable over any other normal cabin noise. I'm very pleased with the way it's turned out.
 

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Discussion Starter #5
Thanks everyone.

01blkgts, nope no drawbacks so far. Before the mod I could tell my bass was missing and the mids & highs were way too loud & out of proportion when my volume control was barely cranked up. Now it's nice & loud while the volume sits right in the middle of its range with plenty left to go plus now the "Loudness" button works like it's supposed to. Just make sure the termination resistors match the HU's output impedance: My HU's high voltage preamp outs are 5v @ 60 ohms, some HU's are 2.5v @ 200 ohms, in that case you'd substitute 200 ohm resistors in place of the 60's that I used.

Sorry about the Imagestation thing, I know it can be a pain. I used to not be able to see stuff on the boards until I finally gave-in & registered. Ever since then I guess it set a cookie in my browser so I automatically get access to pics from their site. I thought about moving them over to a Yahoo account but I'm not sure what their policies are about inactivity & traffic loads.

The pics were originally shot in 1600x1200 by an Exilim w/closeup adapter lens but I didn't want to offend the board by posting Jurrasic-sized pics in the thread so I shrunk them down to 640x480. If there's enough interest maybe I'll upload the monsters to an album on Imagestation and post a link in the thread.

SQ GT-S thanks, I sent you a PM. I tried dropping the ".orig.jpg" but the pics shrank even smaller so I put em back the way they were.
 

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Discussion Starter #9 (Edited)
The Imagestation thing is weird, on some computers the post comes up w/empty Imagestation boxes instead of pics and on others it comes up with pics even tho those computers have never been registered on Imagestation (no previous cookie).

Anyway, I copied the post to Tripod and put a link to it near the top & bottom of the original post, or you can just click the same thing here:

Click Here: If you see Imagestation boxes instead of pics

(let me know if the empty Imagestation thing is still happening in the original post and if you like, maybe I'll just hook the pics directly to Tripod instead)
 

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I'm still new at this and plan on installing my system next week. Anways, if I have an aftermarket amp and HU, will I still hear a whine when I install it. Which is a better method? Hardwiring it to the stock harness or buy a new one that is an adapter made specifically for the Alpine(where can I get one that is good).
 

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Does anyone know how many wire harness there is for the stock radio? Also, is the stock wire harness connected to another wires then goes to the fuse? I'm asking this because my lights dont' work anymore for the stock radio but it still play music though. I might be the grounding because my cig light and my ac control grounding is burn/shorted out.
 

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Discussion Starter #13 (Edited)
tripnotic - I don't know if your Alpine HU is terminated inside, but from reading the posts of others on the board likely not. You'll just have to get a Scosche TA-03 kit and try it out. If you get noise you'll definitely need to do the mod.

(please note: this mod is only for the Scosche TA-03 which mates w/Toyota's 8-speaker 4CH premium stereo HU connector)

Technically, if you buy a HU that comes with high-voltage preamp outs (2.5 - 8.0 volts) plus a built-in or external power-amp, the best way to hook it up is to use the HU's own amp which is designed to match it. Of course this means bypassing the factory amp by disconnecting the speaker wires from the amp and splicing into them or running new wires to every speaker. (don't wire your HU's speaker outs across the factory amp's speaker outs - disconnect em from the factory amp)

If you're happy with how the premium factory amp sounds (w/stock or upgraded speakers) but just want to install a different HU, then get the Scosche TA-03 and mod it if necessary.

The last thing you want to do with any decent sound system is to drive a power amp off another power amp. I mention this only because there are products out there like some of the OEM Interface Adapters (aka speaker-to-line level converters including the bluebox that came with the TA-03) which take speaker level from your aftermarket's HU and drop it to line-level to feed the inputs of another power amp. Sounds innocent, but all power amps add some distortion & noise to the output signal. This is because they switch large amounts of voltage & current thru power transistors, coils, and transformers which in turn overshoot, undershoot, hiss, and throw spikes into the output. Why add that into the signal you're going to feed your power amp esp. when your HU's manufacturer gave you 4-clean HV preamp outs to use?

To answer your question about whether the 8-speaker 4CH Toyota HU connector & harness has a wire going to the fuse: Yes it does, and GND too. I keep reading about people losing their radio & cigarette lighter lights. This may be a little late but...

(Warning: Never use the ground of any illumination lights to ground your HU or (anything else)! This includes the following lights: Cigarette Lighter, A/C Switch, Hazard Switch, a/t Shift Lever)

This is because their brightness is adjusted by varying their connection to ground by a dimmer circuit on the Combination Meter. If you fry it, you'll lose all those lights but your gauges will still work cuz they're on a separate dimmer circuit.

Don't know if it's a replaceable part, maybe someone can tell us this, otherwise you may have to get a new Combination Meter.

There's a dirty fix for this but I don't think this is the place to post it, maybe in a new thread if there's interest.
 

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Discussion Starter #16 (Edited)
Noise Mod for those without HU Connectors

The Scosche TA-03 Wiring Harness Kit is great if you want to do a clean install that's pre-wired to the right pins & right grounds, already has built-in attenuators for HV outs, is easy to hookup, & easy to remove. To keep it that way I stuck the 4 terminating resistors inside the TA-03 harness for the Mod. Later if you want, you can remove your HU in its original condition, disconnect the TA-03 and replace the stock radio, or connect the same TA-03 to a new HU and drop it in. Clean, simple.

But if you've already cut off the Toyota HU connector there's still hope. You can order a replacement R4 connector from your Toyota dealer (I've never ordered one so I'm not sure if comes with pins in it, if not I think they sell pins w/pigtails in small packs of 10 for repairs, see below). Or you might drop by a junkyard and cut the connector off of some GT-S or Lexus. For R4 Pinouts & Color Code see below.

Again this is a little long, but then it's for everybody else who's ever wanted to get rid of that noise but already hacked-off their Toyota HU connector, so here goes...

1) You'll need to find each audio line coming from your HU: FrtL, FrtR, RrL, RrR.

2) You'll need to find the ANALOG GROUND wire in the Toyota harness and free it up from any other ground wire it may be twisted together with.

3) You'll need to find the Output Impedance of your HU (specified in ohms).

4) You'll need 4 terminating resistors (1/8 watt to 1/2watt size) that match your output impedance, 20" of small hookup wire, some heatshrink tubing (or electrical tape), and some solder and a soldering iron.

5) You want to add some wire to the ends of the terminating resistors, so twist a short 4" wire onto the end of each resistor & solder it. Leave the other end of each resistor exposed for a 1/2" and slip some heatshrink over it and shrink it. Strip the end of the 4" wire and set it aside.

6) Find the centerwire of one of the 4 audio lines from the HU. Twist the centerwire onto the exposed end of one of the terminating resistors and solder it. Do this for all 4-lines. Go ahead and heatshrink or tape-up the exposed connections.

7) You should now have 4 short wires from the terminating resistors hanging loose. Twist all 4 wires together then connect them to the ANALOG GROUND wire you separated from the Toyota harness earlier.

8) Now take all 4 braided shield wires (from each audio line) twist them together, and connect them to the ANALOG GROUND wire too.

Which one's the ANALOG GROUND wire? It's been awhile since I had my dash apart so I'm trusting the manual which sez: SOLID BLACK (You'll know if you use the wrong one: it'll still be noisy)

Double-check your work, turn key to IGNITION, power-up your HU, listen for ECU noise, run your power-windows up/down, then start the Celi and listen for alternator whine. If you still get noise check you work again: make sure you're using the correct wire for ANALOG GROUND, make sure only the 4 short wires from the terminating resistors & the shields from the audio lines are connected to it, nothing else. --> don't connect the ANALOG GROUND wire to the car's ground, radio's ground lead, or radio's chassis <-- Connect the radio's ground lead to a ground bolt on the car.

If you don't have a soldering iron you can find inexpensive soldering irons at Radio Shack good enough to do the job, some RS's stock heatshrink.

Since each manufacturer designs their HU & Amp specifications differently (some have 2V, 4V, 5V, 8V PreampOuts with output impedances like 60ohm, 200ohm, 330ohm, 10Kohm, and 47kohm outs) matching them to the Toyota Premium Stereo Amp ideally means selecting the right values for the attenuating resistors (already in the stock TA-03 harness) and terminating resistors (added by the Mod).

Generally, the terminating resistors should match the output impedance of the HU, so that's easy. The only reason why you might want to add series antenuating resistors in each audio line (or replace the ones Scosche already put in their TA-03 harness) is if the sound gets too-loud & distorts when barely cranked up, or isn't not loud enough. Compare it to how loud your stock radio radio got. The stock amp won't go much beyond that, so your new HU should at least be able to match it if everything's right.


Wiring Harness Color Codes & Pinout for Toyota HU 20-pin R4 Connector:

1 BATT = BLU w/Yel Stripe*
2 ILLUM = GRN*
3 AMP ON = RED*
7 Mute = Brown
8 FrtR = Red
9 FrtL = White
10 Shield (drain wire)
11 ACC = Gray*
12 FACTORY RADIO ONLY = WHT w/Grn Stripe* (Don't use! Cover w/tape!)
16 SGND = Black (ANALOG GROUND)
17 Beep = Green
18 RrR = Blue
19 RrL = Yel
20 GND (car chassis) = BROWN*

*1, 2, 3, 11, 12, & 20 (in caps) are individual wires, the rest are shielded together (pin 10)

(I think I got the pinouts right, lemme know if I screwed anything up)


'00-'02 Celica GT-S R4 connector: PN 90980-12038

Note: I'm not sure if these are the right pins for our R4 connector, but give your dealer the PN to point him in the right direction and maybe he can tell. Toyota calls them "Terminal, Repair":

Pack of 10 Prewired Female Pins w/6" Pigtails:
Terminal, Repair PN: 82998-12340
 

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Hey everybody,

Well, this is my first official post. I'd like to thank PacificBlue for the Mod. It works to about 95%.

I did everything like Blue said and the stereo works way better than it used to with that awful whine. However, the "whine" is still faintly there. I was wondering if anyone else still hears the faint whine and if so how (if possible) can I take care of it. My girlfriend can't hear it; but I can, I guess I am making a huge deal out of something so tiny. The slight whine is alternator whine, because when accelerating the pitch jumps. Like I said, it is so slight, it is almost not even worth bothering about but if there is an easy way to fix it, I'd like to know.

The stereo settings are perfect now. Without the mod I would play the volume on about 5 (out of 40) and the audio would be blasting. The resistors really helped tune down the sound. Now, I can jam at a comfortable 15-20.

Thanks Again PacificBlue and everyone else who has been posting car audio help,

Kevin
 

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Sweet...I got everything fixed...COMPLETELY!!!

If you have your head unit completely pulled out of the dash and held far from the center console, there is absolutely no whine. The closer you move the unit, the louder the whine gets.

After doing the mod, the noise was dramatically reduced but not eliminated. What I did to rid myself of this final noise is mount the harness and the SC-4 box just behind the HU and above on the crossing piece of plastic.

No noise now.
 

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Discussion Starter #20 (Edited)
Nice feeling to be rid of that god awful noise isn't it?

Don't use the SLC-4 BlueBox Level Converter if you're going to connect your HU Preamp Line Outs directly to the Toyota Factory Amp, you don't need it - like I said, hang it on the wall and turn it into a dart board. The TA-03 wiring harness connector emulates the one on the back of the stock radio and mates directly with the connector in the Toyota GT-S harness. Use the SLC-4 only if your HU doesn't have PreOuts or LineOuts and you're forced to use the speaker outputs. The SLC-4 has transformers in it that unfortunately tend to pickup the electrical noise around it (that's why it's sensitive to careful placement behind the dash).

If you do the direct Mod without the SLC-4 BlueBox and crank your headunit up to max (during silence), all you should hear is some HU & amp hiss and very little else. There should be -zero- alternator whine, power window motor buzz, or ECU hash.

If you're in a hurry, you can try your local Radio Trash Store for resistors, or ask them where there's a decent electronic parts supply store. I used tiny 1/8 watt 5% tolerance carbon-film resistors so they'd fit neatly inside the heat shrink tubing and keep things tight. You can use 1/4 watt resistors which are a little bigger if you like. Here's a link to Radio Trash if you want to get 'em right away: 1/4 watt Carbon Film Resistors. (8/07 updated link -PB)

"...dude, what'cher hearin' now is 1.21 gigawatts of silence"

PacificBlue
 
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