Yamaha A 720 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

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
Thread Tools Search this Thread
Old 21st November 2008, 03:31 PM   #1
diyAudio Member
Join Date: Nov 2008
Default Yamaha A 720

Hello everybody

My longtime friend has been sick lately and I'm hoping someone here can help me
When using the cd or tuner I often get static/cutouts mainly from the right channel.
Changing cables and speaker wires did not help.
I accidentally discovered that if I lightly touch or hold the corresponding button on the front I can recreate the problem.
After 20+ yrs. could he just need a good cleaning or is it something more serious?

Also his tuner buddy (T 720) never remembers his radio presets.
Is their an internal battery or something that I could replace?

Thanks in advance
  Reply With Quote
Old 21st November 2008, 03:56 PM   #2
diyAudio Moderator Emeritus
Iain McNeill's Avatar
Join Date: Oct 2007
Location: Santa Cruz, California
I think you're on the right track on both counts.

An intermittent switch eh? Has it had a lot of use? If so the only solution may be to replace it.

Cleaning everything out won't hurt and may fix it

And on the tuner - yes, I'd expect to see a very old battery somewhere.

Good luck!
  Reply With Quote
Old 21st November 2008, 11:55 PM   #3
diyAudio Member
Join Date: Nov 2008
Yeah, He's been a workhorse. Easily over 10k hrs

Very little if any dust inside.
I used some compressed air and when I put it back together it still does it though not quite as much.
I also noticed that if I lower the loudness or volume knob (more so on loudness) the left channels will create alot of static/cutouts.
Right side does not seem affected now

Think some electrical contact cleaner might help?

As for the turner I could find no battery
  Reply With Quote
Old 22nd November 2008, 03:17 AM   #4
rabbitz is offline rabbitz  Australia
diyAudio Member
rabbitz's Avatar
Join Date: Jul 2003
Location: Newcastle, Australia
The tuner probably has a super cap that provides the backup power. Look for a fat short cap 0.01-1F about 13dia x 7 high. Yeah, that's F and not uF.
No longer DIY active
  Reply With Quote
Old 22nd November 2008, 04:37 AM   #5
diyAudio Moderator Emeritus
Iain McNeill's Avatar
Join Date: Oct 2007
Location: Santa Cruz, California
Like Rabbitz says, it'll be the same size as a battery. Can you post a picture? Is there a silkscreen? What's the reference designator? More info will get you better advice.

If you can consistently reproduce the problem by manipulating the pots then they must be #1 candidate for remedial action. I find that vigorous exercise (rotate the pot 0 - 10 - 0, 10 times quickly) scrapes most of the crud up to past full scale wiper action and provides temporary relief (just like me, you need to work out every day to keep those pots quiet)

Failing that, there's the cranolin and De-oxit specialty sprays but you need to get one that cleans *and* lubricates. It has to be a formulation for volume pots. WD-40 and the likes will just ruin everything. You don't want an oil, you want a solvent that doesn't leave more residue than it clears out.

edit, the PCB batteries can be very unusual shapes/sizes not aa/aaa etc. Look for some big blob with 2 (maybe 4 ) pins and usually a bright colored shrinkwrap plastic exterior.
  Reply With Quote


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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Yamaha AX-930 jleaman Analogue Source 6 21st November 2010 11:43 AM
Yamaha cdx 900 stex Digital Source 4 23rd January 2010 11:44 AM
Yamaha RX-777 quasi Solid State 4 15th November 2007 12:58 PM
Yamaha A-550 angel Solid State 4 18th January 2006 01:22 AM
Yamaha CDX-490 newbie123 Digital Source 1 3rd December 2005 03:31 PM

New To Site? Need Help?

All times are GMT. The time now is 10:33 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2