diyAudio

diyAudio (http://www.diyaudio.com/forums/)
-   Solid State (http://www.diyaudio.com/forums/solid-state/)
-   -   Pioneer A400 faint distortion on right channel (http://www.diyaudio.com/forums/solid-state/32364-pioneer-a400-faint-distortion-right-channel.html)

Growers 16th April 2004 11:49 AM

Pioneer A400 faint distortion on right channel
 
Hi everyone,

I have recently purchased a 2nd hand A400 on ebay and unfortunately there is a slight but audible distortion on the right hand channel when signal is present. The distortion sounds like a partially blown speaker (I spent an hour or so checking my speakers over before realising it was coming from the amp!) a sort of signal dependant mechanical buzzing. It is most apparent with a low level mid-range signal such as an a bass guitar note and is present using all inputs and also on the right headphone output.

Does anyone have any suggestions as to what may be causing the distortion?

Also, I did a search on this forum and found a thread regarding A400 schematics. Would anyone be kind enough to email me the schematics?

Thanks,
Duncan

SVI2004A 16th April 2004 12:17 PM

possible o/c transistor - tried cheching output transistor(s)

subwo1 16th April 2004 12:21 PM

Two things I would check for are bad transistors and dried up electrolytics.

K-amps 16th April 2004 08:49 PM

Also no bias can be audible as crackling. Check bias too.

lucpes 16th April 2004 11:41 PM

Had some similar problems and the culprit was a blown diode :) but in your case it could be almost anything. Take a digital VOM and compare against the 'good channel', whilst shut down first and then when fired up, taking G R E A T care not to slip connectors, but first read:

http://sound.westhost.com/articles.htm

check these first: http://sound.westhost.com/troubleshooting.htm

http://margo.student.utwente.nl/el/audio/amphelp.htm

Growers 18th April 2004 11:55 AM

Thanks for your replies. Since my initial post I've had a closer inspection of the PCB and noticed some evidence of electrolyte leakage which could have come from one of two caps which I will try replacing.

Without schematics (and with little familiarity of amp design) I find it quite difficult to do fault diagnostics on a good channel vs faulty channel basis.

Thanks again.

lucpes 18th April 2004 03:20 PM

Replacing all the low value electrolytics you find on both L/R PCBs isn't a bad idea at all + it's cheap.

mudan 30th April 2004 11:14 AM

Hi all,

I've replaced the old PSU smoothing Elna black/gold caps with Panasonic TSUP as I couldn't source any better of the same spec.

I'm soon about to replace the coupling caps with Audyn MKP QS , hoping this will make a worthwhile improvement. I'm also replacing some of the larger Elna/Nichicons for the L/R channels with Black Gates.

Any recommendations for mods to the A400, including my choice of the Audyn MKP QS would be appreciated.

Thanks,

Dav


All times are GMT. The time now is 12:19 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