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 22nd January 2011, 05:32 AM   #11
Dr Zeus is offline Dr Zeus  United States
diyAudio Member
 
Dr Zeus's Avatar
 
Join Date: Oct 2010
I thought so too. Its a JRC 2068. Maybe I'll order a dozen and give U107 and U106 new ones.
  Reply With Quote
Old 22nd January 2011, 09:17 PM   #12
Dr Zeus is offline Dr Zeus  United States
diyAudio Member
 
Dr Zeus's Avatar
 
Join Date: Oct 2010
I removed U107 and powered the amp up. The pads under U107 are measuring as follows:

Pin 1: 0
Pin 2: 0
Pin 3: -12
Pin 4: -12
Pin 5: 0
Pin 6: 0
Pin 7: 0
Pin 8: 12

U106 is still in place. Its measuring as follows:

Pin 1: 0
Pin 2: 0
Pin 3: 0
Pin 4: -12
Pin 5: 0
Pin 6: -12
Pin 7: -12
Pin 8: +12


Would -12 on Pin 6 of U106 make it defective?
  Reply With Quote
Old 22nd January 2011, 09:26 PM   #13
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
When op-amps are used for audio, they virtually always work to make the inverting input have the same voltage as the non-inverting input. Since pin 5 (the non-inverting input) is at 0v, the op-amp should drive the output to bring the inverting input (pin 6) to 0v. Since it isn't doing that, it's likely defective. I'm assuming that nothing (external to U106) is driving the output to -12v.
  Reply With Quote
Old 22nd January 2011, 09:42 PM   #14
Dr Zeus is offline Dr Zeus  United States
diyAudio Member
 
Dr Zeus's Avatar
 
Join Date: Oct 2010
I'd say we nailed it.

Since its tough without a schematic to really see what was driving the inverted input pin 6 to -12v, I used process of elimination.

Removing U106 revealed the following pad voltages measured with the DVM

U107:
Pin 1: ~0
Pin 2: ~0
Pin 3: ~0
Pin 4: -12
Pin 5: ~0
Pin 6: 0.325*
Pin 7: 0.325*
Pin 8: 12

*Pin 6&7 are tied together on the PCB. Do you think 0.325vDC on here is too much?

U106
Pin 1: ~0
Pin 2: ~0
Pin 3: ~0
Pin 4: -12
Pin 5: ~0
Pin 6: ~0
Pin 7: ~0
Pin 8: +12
  Reply With Quote
Old 22nd January 2011, 09:48 PM   #15
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
Whatever U106 is driving is likely producing the 0.325v.

The output of U106 is driving the inverting input of U106. In this configuration, the op-amp is simply a buffer (output = input to non-inverting input).
  Reply With Quote
Old 22nd January 2011, 09:54 PM   #16
Dr Zeus is offline Dr Zeus  United States
diyAudio Member
 
Dr Zeus's Avatar
 
Join Date: Oct 2010
Very well. What else is cool is that I'm actually seeing audio now on what looks like all of the input and output pads where the JRC2068 opAmps on U106 and U107 were. Before I was seeing mostly nothing or +-12vDC.

Looks like last night's order of opAmps may provide some positive outcome.

Thanks!
  Reply With Quote
Old 22nd January 2011, 10:13 PM   #17
Dr Zeus is offline Dr Zeus  United States
diyAudio Member
 
Dr Zeus's Avatar
 
Join Date: Oct 2010
I'm assuming I need U106 and U107 for something, otherwise the amp is able to produce a sine wave at the speaker terminal outputs. I wonder if those opAmps are for the RCA outputs - supposedly the other amp in line with this one really blew up from what the owner told me.
  Reply With Quote
Old 22nd January 2011, 10:33 PM   #18
diyAudio Member
 
Join Date: Nov 2003
Location: Louisiana
If the transformer shorted in the other amp or a speaker wire shorted to ground (assuming cheap amps with floating secondary), it could have damaged the op-amps feeding the outputs on this amp.

Does the output RCA produce audio?
  Reply With Quote
Old 23rd January 2011, 01:37 PM   #19
Dr Zeus is offline Dr Zeus  United States
diyAudio Member
 
Dr Zeus's Avatar
 
Join Date: Oct 2010
The output RCAs produce audio as expected. I think these opAmps have something to do with the LP crossover as that control does not seem to be affecting the audio output correctly. This amp's crossover cannot be disabled, and even setting it to ~50hz allows the amp to play frequencies way above at equal volumes. The crossover is just not working right now. I'll post up when I receive and put new parts in.
  Reply With Quote
Old 27th January 2011, 09:41 PM   #20
Dr Zeus is offline Dr Zeus  United States
diyAudio Member
 
Dr Zeus's Avatar
 
Join Date: Oct 2010
This amp is FIXED! Two 2068 JRC opAmps and she's good to go. Cost was only about $0.60 to fix, but I ordered a few extra for the next amp
  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
kicker 450.2 timwebb Car Audio 5 26th May 2010 05:59 AM
Kicker 600.1 mike49504 Car Audio 3 25th March 2009 04:10 PM
Kicker SX650.1 help shagone Car Audio 12 19th March 2008 07:35 AM
Kicker Vs. Memphis irokpierce Car Audio 1 23rd August 2005 03:12 PM
adire? kicker? anybody? jadenlinkletter Car Audio 5 22nd April 2005 01:37 PM


New To Site? Need Help?

All times are GMT. The time now is 12:31 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