Another avt150 - diyAudio
Go Back   Home > Forums > Live Sound > Instruments and Amps

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

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 August 2013, 10:03 PM   #1
Lochy is offline Lochy  Scotland
diyAudio Member
 
Join Date: Mar 2013
Location: Lochwinnoch
Default Another avt150

Hi guys
I'm trying to fix a avt150. It's blown the tda7293s and the 2.2r resistors.
Which seems to be a common thing. The resistor had up to 16k.
Did an initial check but blew the new chips a 23volts on a variac. The chip popped over the signal in pin. I'm obviously missing something.
Anyone else had this problem.
Thx
  Reply With Quote
Old 29th August 2013, 10:29 AM   #2
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
Common? If an AVT blows up it is likely this, but most do not blow up.

The 2 ohm resistors are limiters in the low voltage supplies, and are not usually involved in blown 7293s. Leave the power ICs out and make sure those low voltage circuits are right before moving on.

Always work with no speaker load until you know the amp is stable and not making DC.

The power modules have two connectors, the three pin carries the power rails. NEVER connect or disconnect the power modules if there is any charge in those power supplies. ALWAYS check for voltage on the pins before plugging it in.

If one power module blows, replace both. One bad one stresses the other "good" one. Note their outputs are hard-wired together.

I forget which is which in the AVT series, but in some the heat sink is grounded to chassis, in others the heatsink is insulated - mounted to the plastic fan housing. The heatsink tab on the IC is hot, and so must be insulated from grounded heat sinks. If that is yours make sure your insulating wafer is intact.
  Reply With Quote
Old 29th August 2013, 11:58 AM   #3
Lochy is offline Lochy  Scotland
diyAudio Member
 
Join Date: Mar 2013
Location: Lochwinnoch
Thanks Enzo
I think it's the way They link that's confusing me. I have the schematic. But the 7293's are a different beast.
I'm going to retest the voltages. Would you remove the chips from the boards and test voltages at the pin outs?
I'll check and post my findings.
  Reply With Quote
Old 29th August 2013, 04:02 PM   #4
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
You can buy whole new modules, but I always replace the chips. The little caps on the module boards never seem to be bad, and unless the copper is burnt of the board, a new 7293 does the job.

The amp is happy as can be with the modules unplugged, so you can operate the amp without them to verify everything else is OK. If you want to plug in empty modules to see if voltages are there, go ahead. I'd probably just probe the cable connector myself.


The same board the 150 uses is also used for the stereo 275 model. The schematic has a box for each model listing which links, resistors, and caps are to be installed or left out. So keep those in mind when trying to read the drawing.

Make sure zobel resistors R110,112 are not open. And speaker return resistor R111, is it OK?
  Reply With Quote
Old 29th August 2013, 08:48 PM   #5
Lochy is offline Lochy  Scotland
diyAudio Member
 
Join Date: Mar 2013
Location: Lochwinnoch
Will do thanks.
  Reply With Quote
Old 30th August 2013, 02:40 PM   #6
Lochy is offline Lochy  Scotland
diyAudio Member
 
Join Date: Mar 2013
Location: Lochwinnoch
Check r110 111 112 all ok
The voltages check on the board pins.
C230. C189
1.. 2mv. 2mv
2.. 88mv. -78mv
3.. 2mv. -49mv
4.. 6v. 6v
5.. 2mv. 2mv
6.. -1mv. -2mv
7.. 0mv. -1mv
8.. -1mv. -2mv

Each three pin has N. -49 +49.
  Reply With Quote
Old 30th August 2013, 11:42 PM   #7
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
Just make sure those 49v rails are down under a volt before doing any connecting of modules.
  Reply With Quote
Old 13th September 2013, 01:13 PM   #8
Lochy is offline Lochy  Scotland
diyAudio Member
 
Join Date: Mar 2013
Location: Lochwinnoch
New tda's installed haven't blown. But there's a
Very loud hum and the light limiter is bright.
Voltage to tda's way down at 5v. Not fans. Front of board
Is unresponsive. No sound from the fx.
But unplug the tda's voltages seem to return to normal.
Fx, fans and front of board work. But limiter light still glowing not
As bright but still glowing. I also checked the speaker wasn't shorted.
Anyone had this problem.
  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



New To Site? Need Help?

All times are GMT. The time now is 08:28 PM.


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