Forums
New posts
Search forums
What's new
New posts
Latest activity
Members
Registered members
Current visitors
Log in
Register
What's new
Search
Search
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Install the app
Install
Audio and Video Talk
The Vintage Audio Section
Any amp geniuses here willing to give advice?
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Help Support AVForums:
This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Message
<blockquote data-quote="Rick" data-source="post: 847086" data-attributes="member: 17143"><p>It might help if I post some specific questions about the schematic.</p><p></p><p>1) Q409 serves what purpose?</p><p></p><p>2) Q427 and Q429 are not a complimentary pair in fact they are even different packages, were the designers trying to compensate for something?</p><p></p><p>3) If I remove Z401 the output resistor pair (in a package) so it doesn't short, I can power up the amp feed it a sine wave and get clean signals on the base of Q423 and Q424. Put it back, and thermal runaway and boom the smoke leaks out, well used to, now the 100W light bulb goes on full.</p><p></p><p>4) Right channel totally distorted left channel plays, nothing is blown I even measured every single capacitor and resistor. After initial repairs I keep replacing only Q423 and Q425. Working backwards from Q419 and Q421 voltages are virtually identical on both left and right channels, I even swapped components between left and right on the SUP 15251 A board just in case (took ages) Right channel still distorted, its something on the SUP 15251 A board after Q401/3/5 and before the SUP 15251 B board I "suspect" .</p></blockquote><p></p>
[QUOTE="Rick, post: 847086, member: 17143"] It might help if I post some specific questions about the schematic. 1) Q409 serves what purpose? 2) Q427 and Q429 are not a complimentary pair in fact they are even different packages, were the designers trying to compensate for something? 3) If I remove Z401 the output resistor pair (in a package) so it doesn't short, I can power up the amp feed it a sine wave and get clean signals on the base of Q423 and Q424. Put it back, and thermal runaway and boom the smoke leaks out, well used to, now the 100W light bulb goes on full. 4) Right channel totally distorted left channel plays, nothing is blown I even measured every single capacitor and resistor. After initial repairs I keep replacing only Q423 and Q425. Working backwards from Q419 and Q421 voltages are virtually identical on both left and right channels, I even swapped components between left and right on the SUP 15251 A board just in case (took ages) Right channel still distorted, its something on the SUP 15251 A board after Q401/3/5 and before the SUP 15251 B board I "suspect" . [/QUOTE]
Insert quotes…
Verification
Post reply
Audio and Video Talk
The Vintage Audio Section
Any amp geniuses here willing to give advice?
Top