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Advice to troubleshoot Ground Zero GZTA2.500TX
Advice to troubleshoot Ground Zero GZTA2.500TX
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Old 27th February 2019, 10:02 AM   #1
mariadumitruiulian is offline mariadumitruiulian  Ireland
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Location: Limerick, Ireland
Default Advice to troubleshoot Ground Zero GZTA2.500TX

Hi everybody,

I have a very strange behavior on my Ground Zero amplifier... Very often the volume is automatically lowered and the sound gets distorted, then it comes to normal again, and so on... In the last couple of days this happen much often.

I used it with 2 different subwoofers (dual 4ohm coils) connected in parallel; (i also tried series, to increase the impedance, but is even worst) .

I tried to rotate the potentiometers while the sound is distorted (thinking of a bad potentiometer) or to toggle the switches for LPF / phase / bass boost / subsonic filter , but didn't influence in a positive way distorsions .

I checked it on a different car and i get the same behavior;

I checked my ground and is OK (other amp is working OK in my car) .

I just want some hints of what and where to check, maybe some of you had the same problem with your amplifier and can guide me in the right area.

An electrical schematic of this would be very helpful as well.

Sorry for my english, but i tried to make myself as clear as possible.

Thank you all for your help!

Last edited by mariadumitruiulian; 27th February 2019 at 11:02 AM.
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Old 27th February 2019, 01:10 PM   #2
Perry Babin is offline Perry Babin  United States
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If you don't get any answers. post a photo of the board.
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Old 28th February 2019, 06:31 AM   #3
mariadumitruiulian is offline mariadumitruiulian  Ireland
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Location: Limerick, Ireland
Hi!

I think I found the problem. The steps I did:
I opened the amplifier, connected an 8 ohm bookshelf speaker and played music at low volume.

I observed that when I push on the board the sound starts to distort / is clear again, so I was thinking at a bad contact. I disconnected input signal and pushed the board again, and every time I was pushing on the hoard, a crack(strange sound) could be heard in speaker.

I took out the board, disconnected input signal and started to move components / push pins with a plastic lever( and amp connected to power supply) until I found a pin of a strap which looked like it had a bad solder/cracked solder (see 3rd picture) .

I re-soldered the pin and problem looks to be solved , amplifier doesn’t distort anymore when I push on the board. I will mount it tomorrow in the car to make a proper test.

The strap is visible in the picture on the amp side of the board: close to input connector there are 2 5W resistors (green ones) , 2 zenner diodes, one strap, 2 big electrolytic capacitors(C21 abd C22) and then, right next to capacitors the strap covered with some black silicone/glue. This is the trouble-giver strap.

PS:
I made the scratch on the board just to make sure that there is no connection between traces, as this was the area with the fastest response when i was pushing the board, and there was a scratch on the board already.

I will keep you updated after few days of playing in the car.

@Perry Babin , next time i will start with a more detailed post, and i will include also pictures. Thanks!
Attached Images
File Type: jpg image1.jpg (817.4 KB, 31 views)
File Type: jpg image2.jpg (641.6 KB, 29 views)
File Type: jpg image3.jpg (320.8 KB, 29 views)
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Old 28th February 2019, 06:43 AM   #4
Perry Babin is offline Perry Babin  United States
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Join Date: Nov 2003
Location: Louisiana
When repairing connections like this, for the best reliability, you need to...

add new solder
desolder
stand leads up straight in the hole
scrape the lead if all oxidation wasn't removed during desoldering
resolder

You should do this to all similar jumpers.
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Old 6th March 2019, 08:27 AM   #5
mariadumitruiulian is offline mariadumitruiulian  Ireland
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Location: Limerick, Ireland
@Perry Babin i did as you adviced, and the amp is now working for the last couple of days without any issue.

Thank you!
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