Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Posted to sci.electronics.repair
external usenet poster
 
Posts: 1
Default Yamaha DSP A-990

I'm hoping that there may be somebody with a 5 channel amplifier Yamaha
DSP A-990. I like my old machine, 6 years old, a fantastic sound and
video processor. Happened to short the outputs and blew most of the 14
power darlington transistors. I have repaired with newer equivalents
and all e-c-b voltages are OK, but 5 seconds after start, there is a
safety relay that switches power off. I can't figure out why and what
the sensors react on. Complicated electronics. Now I just wonder if
someone happen to have such a machine and if there is also someone who
have schematics. Yamaha don't not respond positively on my request, say
they have no service on such a obsolete amplifier.

Thanks!

  #2   Report Post  
Posted to sci.electronics.repair
external usenet poster
 
Posts: 49
Default Yamaha DSP A-990

"steve" wrote in
oups.com:

DSP A-990



Looks like the following site has free info on your unit:

http://www.eserviceinfo.com/



  #3   Report Post  
Posted to sci.electronics.repair
external usenet poster
 
Posts: 43,017
Default Yamaha DSP A-990

In article .com,
steve wrote:
I'm hoping that there may be somebody with a 5 channel amplifier Yamaha
DSP A-990. I like my old machine, 6 years old, a fantastic sound and
video processor. Happened to short the outputs and blew most of the 14
power darlington transistors. I have repaired with newer equivalents
and all e-c-b voltages are OK, but 5 seconds after start, there is a
safety relay that switches power off. I can't figure out why and what
the sensors react on.


Usually looking for a DC offset to protect the speakers. Maybe also
oscillation. A scope should tell all.

--
*Money isn't everything, but it sure keeps the kids in touch *

Dave Plowman London SW
To e-mail, change noise into sound.
  #4   Report Post  
Posted to sci.electronics.repair
external usenet poster
 
Posts: 280
Default Yamaha DSP A-990

steve wrote:
I'm hoping that there may be somebody with a 5 channel amplifier
Yamaha DSP A-990. I like my old machine, 6 years old, a fantastic
sound and video processor. Happened to short the outputs and blew
most of the 14 power darlington transistors. I have repaired with
newer equivalents and all e-c-b voltages are OK, but 5 seconds after
start, there is a safety relay that switches power off. I can't
figure out why and what the sensors react on. Complicated
electronics. Now I just wonder if someone happen to have such a
machine and if there is also someone who have schematics. Yamaha
don't not respond positively on my request, say they have no service
on such a obsolete amplifier.

Thanks!


Not finding this model number, at least not on the Yamaha's US tech site.

When the outputs blew, they probably took out one or more resistors,
sometimes a 330 ohm or so which is between the emitters of the two driver
transistors, or a series resistor going to the base of an output transistor,
usually about 4.7 ohms, an emitter resistor, usually .22 ohms at 5 watts
dual package, or, and this seems most likely to me, a resistor supplying B+
or - to the collector of a driver transistor. Usually in the one to ten ohm
range.

Mark Z.


Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
looking for component - MVC pot for Yamaha RX350 Darkpaw Electronics Repair 0 September 20th 06 03:30 PM
Yamaha IC needed (IG 02940) Tim Schwartz Electronics Repair 0 April 18th 06 10:26 PM
Yamaha R8 Receiver Tuner Problem Asimov Electronics Repair 0 February 12th 06 05:11 PM
Yamaha R-8 Receiver (Attn: Leonard Caillouet et al) Richard Steinfeld Electronics Repair 3 March 26th 04 11:35 PM
newbie - blown yamaha power amplifier ant Electronics Repair 3 August 6th 03 03:00 AM


All times are GMT +1. The time now is 05:38 PM.

Powered by vBulletin® Copyright ©2000 - 2023, Jelsoft Enterprises Ltd.
Copyright 2004-2023 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"