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HRC
03-28-2012, 11:10 PM
First off, I just bought my '01 Prostar 205V at the first of March. The P.O. had installed a cheap amp, a Mitzu. Anyway, I was messing around last week and noticed that the stereo was sounding crappy with distortion and buzzing noise. I started poking around thinking the gain on the amp was up too high. The sound from the speakers faded out and that was it. I decided to pull the amp out because I couldn't really see any of the writing on it and when I un-hooked the blue remote power wire from the stereo unit, the speakers that were wired to it (the head unit) started working. If I put the remote wire back on they would quit.
I took the amp to work and we hooked it up to a power supply and a signal generator and a speaker and when I jumped 12v to the remote terminal it seemed to work fine. I put it in the boat and hooked it up and jumped 12v to the remote terminal again and every thing worked fine. I then hooked it back to the remote wire from the head unit and it went quiet. Sounds like there is a problem in the head unit to me. Have any of you ever seen this before?

Sorry for the long post.

rspiecha
03-29-2012, 12:43 PM
Not sure if this is your problem, the dealer connected the power antenna lead to my boat amp. So it only worked when I used the tuner on the head unit. Switching to CD or AUX turned the amp off. Turns out there are two blue leads off the head unit. Connected the correct remote blue wire, and all is good :)

carlsonwa
03-29-2012, 12:56 PM
Do you have access to a multimeter? You should have 12Volts on the blue remote turn on wire from you headunit (when turned on) place the other lead of your meter on ground at the battery or the ground wire at the headunit..

You should have a contant 12 volts on the main power wire to the amplifier at all times. Could be a fuse.

jk13
03-29-2012, 01:16 PM
Add a relay. We need to do this with systems that have many pieces to turn on regularly.

Sounds like your HU doesn't have enough power on the remote turn on for that amp, no matter which piece of equipment is at fault. Do this:

HRC
03-29-2012, 02:14 PM
Add a relay. We need to do this with systems that have many pieces to turn on regularly.

Sounds like your HU doesn't have enough power on the remote turn on for that amp, no matter which piece of equipment is at fault. Do this:

That's exactly what I've done for now. Just wondering what might be the problem.
Thanks for the replies.

EarmarkMarine
03-29-2012, 07:11 PM
If the voltage threshold out of the HU remote turn on trigger is high enough to trip the relay then it should also be high enough to engage the amplifier. But if the relay works go with it and never look back. If it does not pan out then you can go with a signal or voltage sensing module that should work automatically even if the HU has an internal issue.

David
Earmark Marine

HRC
04-02-2012, 10:56 PM
Ok, now I'm frustrated. Everything was working fine until a few minutes ago. We're heading to the lake tomorrow and I was vacuuming the boat and now the amp isn't working again.

EarmarkMarine
04-03-2012, 10:34 AM
Taking a few concise measurements with a multimeter is the first step in going from speculation to meaningful diagnosis.

HRC
04-09-2012, 03:50 PM
Earmark,
I'm open for suggestions. I have checked and it's getting 12 volts to the remote terminal and 12 to the B+ terminal. Is there a way to make sure I'm getting a signal out of the RCA jacks coming from the stereo?

EarmarkMarine
04-09-2012, 07:24 PM
Okay, most contemporary HUs will have a buffer transisitor sending out the remote turn on lead. That output could be intermittent. So if you jumper it and it works consistently then the problem is either the HU transistor failing when it heats up or there is a problem with the amplifier circuit (possibly corrosion) that is causing the circuit to draw too much current and heat up the HU transistor. So look inside the amplifier and see if there is a build up of residue. If so try a little tuner wash and a very soft bristle toothbrush. You might look inside the HU chassis also. If you use a relay as a permanent solution then I would place a .1 amp fuse on the supply to be safe. Also, there is a module available from PAC that will manage the process via signal sensing. Or, you can use a switch to turn on/off the HU and amplifier simultaneously. Most amplifiers have a muted input so you won't have a turn on/off thump. Again, the PAC can manage this problem too.
To verify the amplifier is getting an input then convert the HU RCA preout to a stereo 3.5mm jack via an adapter and plug in a headphone set. To verify the amplifier is processing a signal then run an ipod or MP3 directly into the amplifier inputs.
Through the process of elimination and confirmation, as long as you have verified voltage at the equipment terminals, then I feel we have just about covered all bases. The real culprit should emerge.
Now roll up your sleeves and go fix it.

David
Earmark Marine

JimN
04-09-2012, 08:46 PM
Earmark,
I'm open for suggestions. I have checked and it's getting 12 volts to the remote terminal and 12 to the B+ terminal. Is there a way to make sure I'm getting a signal out of the RCA jacks coming from the stereo?

Do you have an old cassette deck or a boombox with line input? You could connect it to that. Another cheap way is to go to Radio Shack and get a battery powered amplified speaker plus an RCA - 1/8" adapter. It was about $15 the last time I saw one. If you have a stereo in your garage, use that.

Disconnect the remote lead from the head unit AND the amp, then check from that wire to the radio's chassis for continuity. If that lead is shorted to ground, it can shut the head unit down if it was designed that way. If that part of the head unit isn't protected, it will either damage that circuit or blow the radio's fuse. I would also disconnect the remote lead from the radio and amp. If it turns on, look at the amp for a switch that may determine how the turn-on is activated- it may have a +/- designation for this. Set it to +. If you get nothing after you turn the head unit on, connect a wire from the power amp's + terminal to the remote terminal. It should turn the amp on.

You referred to the remote terminal and B+. Is this on the amp? How is the amp getting 12V to the B+ terminal and what is it grounded to?

HRC
04-10-2012, 08:16 PM
Remote terminal is on the amp. It's what the stereo head unit would normally connect to but I rewired it through a relay like shown on page 1. The B+ is also on the amp and comes from the battery through a fuse. The amp is grounded back to the battery - terminal.
1 other problem though. The boat is now at the lake so all this will have to wait until I get back up there.

JimN
04-10-2012, 09:27 PM
Remote terminal is on the amp. It's what the stereo head unit would normally connect to but I rewired it through a relay like shown on page 1. The B+ is also on the amp and comes from the battery through a fuse. The amp is grounded back to the battery - terminal.
1 other problem though. The boat is now at the lake so all this will have to wait until I get back up there.

How old is that amp, and what kind of terminals does it have for power? If it's really old, and I haven't seen a Mitzu amp- is that the whole name, or is it a Mitsubishi amp? That remote terminal may have been meant for a wire that comes from the ignition switch's accessory lead. This means it would draw a lot more current than a FET-triggered turn-on circuit.

HRC
04-10-2012, 11:03 PM
Mitzu is the full name. I can't find any info on it, just that they sell for about $89 on Ebay. The terminals are just the standard small screw type.

JimN
04-11-2012, 12:16 AM
Mitzu is the full name. I can't find any info on it, just that they sell for about $89 on Ebay. The terminals are just the standard small screw type.

Never heard of it and I did car audio for over 20 years.