Spectra missing audio

Conundrum · Post by **Conundrum** » Mon Sep 12, 2005 8:14 am

Well, heres the story.
A friend was using my spectra and decided to hook it up to their car audio system, they rewired the audio plug to go
1. a car audio amp
2. a tape adapter for a car audio system

during this ordeal at some point they blew something in the radio and there is now no audio at any time, whether it be receiving something, or the beeping from raising the volume.

I have seen on here that leaking caps can cause this, but is there anything else that it could be because it was an instant thing due to their stupidity, and not to extended use. on top of that the radio seams to operate fine, other than the fact that there is no audio.

Thanks,

Conundrum

kcbooboo · Post by **kcbooboo** » Mon Sep 12, 2005 8:19 am

Is there a jumper on an accessory plug, like on a MaxTrac, that enables the internal speaker? If so, is it in the right positions? If not, it seems that they probably let the smoke out of some component inside the radio.

Bob M.

Conundrum · Post by **Conundrum** » Mon Sep 12, 2005 9:57 am

the spectra is hooked up to the accessory plug that is connected to the external speaker, there is no internal speaker. I had assumed that something internal was blown, but wanted to know if anyone had any idea of what.

copcarguy · Post by **copcarguy** » Mon Sep 12, 2005 11:02 am

You could have blown the audio chip, #TDA7256 ...89143 on the chip. It looks like an Ic chip, pins only on the bottom (15 pins) glued to a piece of steel with a hole drilled in it for mounting and heat sink applications (complete with di-electric white grease). They unsolder pretty well. Torx screw to unmount. I have 2 of them brand new in stock. $25.00 includes shipping each. Hope this helps...

jackhackett · Post by **jackhackett** » Mon Sep 12, 2005 11:28 am

Yup, probably the audio amp chip. What probably happened (about a 99.9% chance) is that when your friend hooked it up to the car stereo he hooked the speaker leads to something that was grounded.

The spectra has a floating output, which means that unlike many stereos, neither speaker lead is connected to ground. Both speaker leads normally have about 6 volts on them, and grounding one will short it out and blow out the chip.

Replacing it isn't hard for a qualified tech, might be a bit tricky for a novice though.

When connecting to something, such as the input to a stereo amp, that has one lead grounded you need to use some type of isolation, such as a transformer or capacitors. Probably the best solution is not to lend it to your friends ;)

kcbooboo · Post by **kcbooboo** » Mon Sep 12, 2005 5:37 pm

GTX mobile radios do the same thing. This is the way they get more power to the speaker, by driving both leads. When one lead goes positive, the other goes negative, and vice versa. Grounding either lead is a bad thing, and will certainly let what little smoke there is, out. MaxTracs and equivalent have the speaker referenced to ground, so you can hook it up to other stuff without blowing it up.

Bob M.

kc7gr · Post by **kc7gr** » Tue Sep 13, 2005 3:00 pm

copcarguy wrote:You could have blown the audio chip, #TDA7256 ...89143 on the chip. It looks like an Ic chip, pins only on the bottom (15 pins) glued to a piece of steel with a hole drilled in it for mounting and heat sink applications (complete with di-electric white grease). They unsolder pretty well. Torx screw to unmount. I have 2 of them brand new in stock. $25.00 includes shipping each. Hope this helps...

I would concur with other posters. It is very easy to blow up the Spectra's audio amp by grounding either speaker output lead, and it can happen in milliseconds.

If you do go shopping for replacement chips, though, beware! Motorola did NOT use the stock TDA7256A audio chip (made, BTW, by ST Microelectronics, formerly SGS-Thomson). They had one specially made just for them that has more leads, and a closer lead spacing, than the stock chip you can buy off the shelf.

I'm assuming that CopCarGuy has the actual Motorola-supplied chips. The price looks about right.

Keep the peace(es).

copcarguy · Post by **copcarguy** » Tue Sep 13, 2005 4:52 pm

Yes, I have Factory motorola ones..

GradyMedic · Post by **GradyMedic** » Tue Sep 20, 2005 6:47 am

Wow, I'm glad I did a search.. I am having the same problem with my Spectra, only the audio is not completely gone all of the time.. it just fades out after the radio has been on for a minute or so. The louder you have the audio set, the quicker it fades. Radio still works fine, scans, receives, only after you've had it on a minute or so (less if you have it turned up loud) it loses audio. I called the Motorola shop and they said to also try a different speaker, which I did with the same results.... THey said to bring it by.. Repaired while I wait.. $75.00. I was debating about fixing it myself, or atleast taking it apart and seeing if I see a broken solder point somewhere....

Spectra missing audio

Spectra missing audio

You could have blown the audio chip

Re: You could have blown the audio chip

Yes, I have Factory motorola ones

Same Problem