Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Instruments and Amps Everything that makes music, Especially including instrument amps.

AVT50 Repair
AVT50 Repair
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 30th June 2012, 06:39 PM   #1
j4976 is offline j4976
diyAudio Member
 
Join Date: Jun 2012
Default AVT50 Repair

I have a Marshall AVT50 that keeps blowing fuses. I unplugged the leads to the TDA7293 board, and the fuse does not blow, but I removed that board and inspected it very carefully, and I can't find any sign of abuse, heat, or other distress. It looks new.

Should I replace the TDA7293 chip anyway, or can I test it first? Do they sell some that don't have the mute function, or will I be ok as long as the chip is a TDA7293?

Is there a cheap place to get these fuses?

Thanks.
  Reply With Quote
Old 30th June 2012, 08:01 PM   #2
geraldfryjr is offline geraldfryjr  United States
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
Check the chip with an ohm meter.
Or any diodes or bridge rectifiers if there is any on the board.
Most likely it is shorted otherwise it wouldn't be blowing any fuses !!

Replace it with the required chip ,I.E. TDA7293


jer

Last edited by geraldfryjr; 30th June 2012 at 08:05 PM.
  Reply With Quote
Old 30th June 2012, 08:24 PM   #3
j4976 is offline j4976
diyAudio Member
 
Join Date: Jun 2012
So, is there a key somewhere that tells me which leads to check impedance across? Also, would I have to remove the chip from the board to get an accurate impedance reading?
  Reply With Quote
Old 1st July 2012, 05:16 PM   #4
geraldfryjr is offline geraldfryjr  United States
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
The power supply pins to ground and the output pin as well.
if any of these combinations show a dead short then the chip is bad.

VS2000 AVT 150h, replacing TDA7293 w/ pics & schematics - Marshall Amp Forum

tda7293 marshall - Google Search


No,you don't have to remove the chip from the board to do this test.

jer

Last edited by geraldfryjr; 1st July 2012 at 05:22 PM.
  Reply With Quote
Old 1st July 2012, 05:23 PM   #5
j4976 is offline j4976
diyAudio Member
 
Join Date: Jun 2012
Ok. Yes, I have a pinout diagram.

So, its ok to test on the board? Just looking for dead shorts?

I'll get it done.
  Reply With Quote
Old 1st July 2012, 06:05 PM   #6
j4976 is offline j4976
diyAudio Member
 
Join Date: Jun 2012
Ok. Pins 6, 7, 8, 9, 10, 11, 13, 14, and 15 all have less than 2 ohms resistance between them, and to the heatsink. That's the threshold for my continuity setting.

The other pins are all above that level.
  Reply With Quote
Old 1st July 2012, 06:37 PM   #7
geraldfryjr is offline geraldfryjr  United States
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
Sounds like it is shorted to me !!

I have a friend that has one of those amps and he just had the power amp chips replaced.
And it is now working fine.
I didn't do the repair on it but I good friend of mine did as he does this stuff in my area.
We are not exactly sure of the cause but I guess it happens quite often as he keeps these chips in stock.

jer
  Reply With Quote
Old 1st July 2012, 07:14 PM   #8
j4976 is offline j4976
diyAudio Member
 
Join Date: Jun 2012
Its good that they are so cheap.
  Reply With Quote
Old 1st July 2012, 09:29 PM   #9
geraldfryjr is offline geraldfryjr  United States
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
Yes,They are amazing little chips for the money !!!

jer
  Reply With Quote
Old 2nd July 2012, 02:04 AM   #10
j4976 is offline j4976
diyAudio Member
 
Join Date: Jun 2012
Hey, do you know what kind of stuff Marshall put between the chip and the metal plate? It seems to have been some kind of adhesive, and it doesn't look at all like the white conductive heat sink stuff I'm used to using.

Some thread said the chip needed to be insulated from the metal plate, but I think the plate helps cool the chip. Is the adhesive some kind of special thermally conductive, but non electrically conductive stuff?

Thanks. Don't want to overheat or short the new one.
  Reply With Quote

Reply


AVT50 RepairHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Marshall AVT50 Mods JakeAC5253 Instruments and Amps 6 18th December 2014 12:46 AM
Marshall AVT50 Pops when Switching Channels morta Instruments and Amps 2 7th October 2010 04:13 AM
Marshall AVT50 Pops when Switching Channels morta Instruments and Amps 0 1st October 2010 12:50 AM
Getting better EQ on a Marshall AVT50 Fr_3_aK Instruments and Amps 15 3rd January 2009 10:01 AM
MARSHALL AVT50 mod. Vahagn Instruments and Amps 4 28th January 2006 06:52 PM


New To Site? Need Help?

All times are GMT. The time now is 04:36 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki