Sound System and Antenna questions

[BonnieJean]

I just picked up a '90 IX with a few issues that need to be addressed. I thought I would start with some "easy" convenience stuff like the broken automatic antenna and problematic stereo. It has the Blaupunkt amplifier in the trunk with a 19 pin (4x5 -1) connector.

First the antenna - I'm fairly handy and thought I might be able to fix whatever the problem was, so I pulled the unit. The grommet was cracked which lead to water seeping into the unit and there was actually quite a bit of rust inside the motor. I pulled the motor unit apart, cleaned it up and got it working again to the point that it spins up when 12v is applied BUT, someone was obviously inside this unit before me because they removed the wheel gear from the unit so the worm gear now has nothing to turn against. I figure I can spend $40 for a new gear set, $50-100 on a complete unit that's in decent shape, or less than $30 just putting a new grommet and stubby antenna on. This is a rather long-winded way to getting to my first question...the circuit board in the antenna uinit...is it solely for powering/sensing the antenna position OR is it also a signal amplifier?

I pulled the amplifier to take a peak inside thinking that it might suffer from leaky caps due to age and was surprised to see that everything appears to be fine. There aren't any burned up resistors, no electrolyte on the board, it's all super clean. I'll work on finding a pinout and will test the outputs on my scope before putting it back in the trunk. I bought a new Frankfurt head unit to install and ASSUMING that I'm not going to discover any problems with the amplifier I'm curious how this is done. Am I assuming correctly that I'll need to use the preamp outs and will need to wire up some RCA connectors? Alternatively I could use the standard 8-pin connector provided with the Frankfurt and bypass the trunk amplifier for now.

[BSAmarc]

I am fairly certain the antenna circuitry is only there to make it go up/down.

As for the stereo, if you want to keep the factory amplifier you will use the speaker outputs out of the aftermarket HU. The factory stereo used a single shared ground for speaker -ve, so you'll need to adjust the harness to account for this. In this scenario, you can either keep the factory amp or use Brad's amp bypass harness to rely on the Frankfurt HU's built-in amp (the Blaupunkt Frankfurt has 4 x 24 watts RMS)

If you want to use an aftermarket amp, then you have both options of speaker or RCA outs (depending on the amp you choose). You will need to bypass the factory amp, either by cutting off the connector or using Brad's harness.

I installed the Frankfurt HU in my coupe using RCAs out to a 5-channel amp, then kept the factory speaker wires out of the amp. It's working well and is more tunable than the OEM stuff.

[BonnieJean]

Thank you. I spent some time yesterday chasing wires and got the head unit hooked up this morning. I have notes on the wires in the trunk to bypass the amplifier and will work on that this weekend. I have other things to sort out before investing the time into a new 5ch amp and sub but I'd like the radio to function while I'm taking care of the other things.

Still trying to figure out everything I need for a simple stubby antenna replacement but I'll focus on that next week.

[BonnieJean]

The Frankfurt has been installed for about a month and I'm still having some issues so I thought I'd pop in here again. While playing through either the front or rear USB, it drops out about every 10 min and the Frankfurt unit goes through the process of recognizing the USB before it continues playback. Also FM reception has been terrible with a known powerful station.

Supposedly, I'm getting a replacement Frankfurt unit. With any luck, it fixes both issues

However, I'm always skeptical. Today I received a new Z3 antenna base unit, grommet and antenna which I installed with no improvement in reception whatsoever. Just for clarity, I hooked up the red wire that had been connected to the old antenna. I didn't test it today, but from memory it supplies 12V while the white wire it's paired with is a signal to raise the antenna. I also grounded the black antenna wire to the chassis. That's all the electrical connection that seems possible.

Are there likely offenders that might be causing the FM reception problem? I suppose it's possible that the coax cable from the HU to the Antenna could be faulty and I imagine that a simple continuity test of the center and shield wires could eliminate it as a problem.

There's a small black box that shares the same mounting tab as the amplifier that I removed. What is its purpose?

[ghrays]

There's a small black box that shares the same mounting tab as the amplifier that I removed. What is its purpose?

The under mirror check control panel is connected to a bulb testing relay module, located in the trunk next to the antenna, sharing the bracket with the Blaupunkt Quadraboost amplifier found in E30s with the optional BMW sound system. The relay module controls 3 warning lights in the under mirror panel: (1) license plate light (2) rear and (3) brake lights.

61311368324 Bulb testing relay:

[BonnieJean]

Are there likely offenders that might be causing the FM reception problem? I suppose it's possible that the coax cable from the HU to the Antenna could be faulty and I imagine that a simple continuity test of the center and shield wires could eliminate it as a problem.

There's a small black box that shares the same mounting tab as the amplifier that I removed. What is its purpose?

If I'm reading the electrical troubleshooting manual correctly, in section 6500-0 it appears that the antenna is directly connected to the head unit. I finally had the opportunity to test to coaxial cable today and the center conductor shows infinite resistance from end to end. There's also no continuity between shield and conductor (which is good) so I'm assuming that there's a break in the coax somewhere.

For those with experience with this...is my methodology sound? I won't have the time to pull the seats and carpet anytime soon so I'm actually hoping that I'm wrong about the cable.