Alpine MRV-1507 - RCA Ground Floated - Need help - diyAudio
Go Back   Home > Forums > General Interest > Car Audio

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 28th May 2008, 07:29 PM   #1
diyAudio Member
 
Join Date: Oct 2007
Default Alpine MRV-1507 - RCA Ground Floated - Need help

Hello!
Recently bought a Alpine MRV-1507.

Protection light blinks Red indicating "RCA Ground Floated"
according to Owners manual.

Doesnt matter if i have an input signal or not.
(have an solid state cd player connected to the RCA)

I have checked the ground, and its connected to the
+-15V regulator circuits ground. OK

And now the funny thing, THE AMP PLAYS MUSIC!

No DC at the outputs...

Someone please help me, what should i look for?

http://www.itxpress.se/MRV-1507.pdf <-- schematic here
  Reply With Quote
Old 28th May 2008, 08:00 PM   #2
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
If you're using a home cd player, the RCA shields are floating. If you connect them to the chassis ground, the indicator should go back to green.
  Reply With Quote
Old 28th May 2008, 08:17 PM   #3
diyAudio Member
 
Join Date: Oct 2007
I allready tried to ground the RCA shields to chassi.
No difference... what is the next step?

Im not sure if there is any fault or not.

I noticed that if i measure from Battery ground to RCA shield
i have almost 2 Volts.

But this is just normal since its not the same ground reference?

The RCA shields should be connected to 2nd Ground directly
according to schematic.

In the 15 volt regulator ground i have a direct connection.

But then i measured from the centertap of the secondary
winding of the transformer to RCA shield, looks like a
cap is charing as i measure Ohm.
  Reply With Quote
Old 28th May 2008, 09:56 PM   #4
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
You'll need to have the shields grounded to the chassis ground. Confirm that the shields are at 0v DC.

If the amp still indicates that there's a fault, go to Q703 (on page 21 of the PDF file). Is the base-emitter voltage 0v?

If it is, is the voltage on its collector near 8v?

What is the voltage on pin 13 of IC703.

The secondary ground is not tied to the secondary center taps of the power transformers in this amp.
  Reply With Quote
Old 29th May 2008, 04:39 AM   #5
diyAudio Member
 
Join Date: Oct 2007
Those Alpines are tricky..But i love them =)

When you mean chassi ground...where is the best
place for this? It should be the same as Battery Ground
or am I at the wrong side of the road?

So after I connect them to ground i should have
0VDC refering to (chassi/battery)Ground?

Before i had nearly 2VDC when measuring from
battery ground to RCA.

I will check the voltages on the transistor when i come home
from work

Where is the "real" measuring reference for the secondary
ground.

And where is the "real" reference point for the chassi ground.

Cant find any star ground point its just symbols on schematic.

Thanks perry!
  Reply With Quote
Old 29th May 2008, 06:12 AM   #6
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
chassis ground = battery ground

After connecting the shield ground to the chassis ground, the difference should be 0.0v.

Ideally, all of the points on the secondary ground are the same. The shields of the RCA connectors are the most accessible.

Use the ground terminal on the amp as the reference point for the chassis/battery ground.
  Reply With Quote
Old 31st May 2008, 11:17 AM   #7
diyAudio Member
 
Join Date: Oct 2007
yes if i ground the RCA shields to chassi ground i have
a 0V reading on them.

Q703
The base-emitter voltage is 0,13V

IC703
Pin 13 has a reading of 8 volts with
a small pulsing difference about 7,8 volts to 8 volts.

Strange thing is that Pin 1 has 10 volts pulsing on it.
Exactly the same frequency as the LEDs are flashing.


I am starting to think that some Elyts are leaky in the
protection/led driver circuits?
  Reply With Quote
Old 31st May 2008, 02:23 PM   #8
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
The pulses on pin 1 are the clock pulses and are normal.

If Vbe for Q703 is 0.13v, Q703 should not be on so Vbe for Q721 should be ~0v. If that's the case in your amp, Q721 should not be conducting and the voltage on pin 13 of IC703 should be ~0v.

Since you're seeing pulsing in pin 13, the IC may have failed and is leaking internally. Confirm that the supply voltage feeding IC703 is steady (not pulsing). If it is, I'd suspect the IC.

If possible, lift 2 legs of Q721 to remove it from the circuit. If there are pulses remaining on pin 13 and the supply voltage is steady, the IC is almost certainly defective.
  Reply With Quote
Old 31st May 2008, 11:17 PM   #9
diyAudio Member
 
Join Date: Oct 2007
Ok I will try that tomorrow!
But isnt it very odd if the IC have failed without reason?

One more thing I noticed is that the Power LED is blinking
Red indicating that the Battery Voltage is below 10Volts.

Thought that it just was my battery that was weak.
But after charing it for several hours i measured
the voltage above 11Volts with the amp powered.
Should be enough i think...

So maybe the IC is defective and causing this LED
to blink as well?

One more question, what component is making the Pulses?
And what is the FLIP-FLOW thing?
Looks almost like a current mirror with two elyts.

Why are they doing it this complicated :P
A whole circuit for three small leds....
  Reply With Quote
Old 1st June 2008, 01:29 AM   #10
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
A defective IC could possibly make the other LED blink also.

I don't think there was a reason for the failure (if it has failed). Sometimes semiconductors fail.

The flip flop is a free running oscillator. They used to use them to drive switching power supplies but the caps were smaller so the oscillator ran at a much higher frequency.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Should I directly connect my signal ground to chassis ground? Bricolo Solid State 4 18th March 2014 09:42 PM
Parallel LM3886, input ground, power ground, safety resistor and oscillations. markiemrboo Chip Amps 5 9th August 2007 03:50 PM
DC filament ground and high voltage ground mikeyho Tubes / Valves 0 15th September 2005 05:52 PM
Chassis Ground = Circuit Ground --&gt; Problems? rhildenbrand Pass Labs 5 23rd April 2004 01:08 AM
does connecting mains ground with circuit ground create a ground loop? jarthel Everything Else 0 25th June 2003 12:55 PM


New To Site? Need Help?

All times are GMT. The time now is 08:52 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2