Novice interested in electronics - diyAudio
Go Back   Home > Forums > Member Areas > Introductions

Introductions Welcome to the DIYaudio Community. Introduce yourself here so we can get to know you better!

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 6th March 2013, 10:52 PM   #1
tvissoc is offline tvissoc  United States
diyAudio Member
 
Join Date: Mar 2013
Default Novice interested in electronics

I pretty much a novice when it comes to really understanding or testing electronics. I've built some circuits (board etching, soldering, etc) but never designed circuits. I have a basic understanding of electronics, but transistors and their magic smoke always trip me up. :-) I'm basically here to gain some knowledge on testing circuits, especially audio amplifiers. I have some vintage electronics (is '80s really vintage?) that I'd like to resurrect and/or maintain. I still have the receiver and speakers that I bought with my first tax return back in the '80s. A Realistic STA-785 receiver and a pair of Realistic Mach Two speakers that need re-foamed.
  Reply With Quote
Old 7th March 2013, 12:52 PM   #2
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Welcome to the forums tvissoc

Some of the older gear can be well worth saving and a quick once over checking for poor soldering and replacing old electrolytic caps can work wonders.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 8th March 2013, 01:51 AM   #3
tvissoc is offline tvissoc  United States
diyAudio Member
 
Join Date: Mar 2013
Quote:
Originally Posted by Mooly View Post
Welcome to the forums tvissoc

Some of the older gear can be well worth saving and a quick once over checking for poor soldering and replacing old electrolytic caps can work wonders.
Thanks. I'm suspecting the Sanyo audio amp in the receiver. Just don't know how to test it.
  Reply With Quote
Old 8th March 2013, 03:07 AM   #4
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Blog Entries: 1
You will need at least a multimeter.

One cool thing about stereo amplifiers is that they have two identical channels. The circuitry for the two channels should be identical to each other. So you can take measurements from both channels, at the same point in each channel. If there's a problem, then the measurements will differ, where a problem is affecting only one channel's circuit. Or, the problem could be elsewhere. A typical first type of measurement to try would be the resistance between each test point and a convenient ground point, somewhere, with the unit unplugged.

If it's close to 30 years old, I would just start by replacing every electrolytic capacitor, large and small. You can buy new ones from places like mouser.com or digikey.com . Just make sure you use a cap with an equal or higher voltage rating, and roughly the same capacitance. Certainly +/- 20% would be good enough, for the capacitance value, and even more of a tolerance range would almost always be close enough. Usually, erring on the high side would be the best way to go, if you had to choose one way or the other. If you feel the need, values can be added together by wiring the caps in parallel. Watch out for any non-polarized ones. And make sure that you try to get caps that have similar lead spacings, and can dimensions that will fit where the old ones were.

Last edited by gootee; 8th March 2013 at 03:11 AM.
  Reply With Quote
Old 8th March 2013, 07:31 AM   #5
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Quote:
Originally Posted by tvissoc View Post
Thanks. I'm suspecting the Sanyo audio amp in the receiver. Just don't know how to test it.
That sounds as if you mean an STK type module. They can suffer with poor soldering externally on the pins.

Depends exactly what the fault is really. Speaker relays (if it has them) can be a source of problems (tarnished contacts).
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 8th March 2013, 08:58 AM   #6
JMFahey is offline JMFahey  Argentina
diyAudio Member
 
JMFahey's Avatar
 
Join Date: Mar 2009
Location: Buenos Aires - Argentina
Just what is it you are suspecting?
Meaning: do you think "this stuff is 30 y.o. , surely something must be worn/old" or you have some specific symptom?
The approachn is not the same.
If preventive maintenance, yes, do what was suggested above.
If you have some specific problem, you'll have to troubleshoot it.
Anyway, start googling around, maybe you can get the schematic.
You might even have an original manual, if so scan and post it.
Good luck.
  Reply With Quote
Old 8th March 2013, 02:18 PM   #7
tvissoc is offline tvissoc  United States
diyAudio Member
 
Join Date: Mar 2013
Quote:
Originally Posted by JMFahey View Post
Just what is it you are suspecting?
Meaning: do you think "this stuff is 30 y.o. , surely something must be worn/old" or you have some specific symptom?
The approachn is not the same.
If preventive maintenance, yes, do what was suggested above.
If you have some specific problem, you'll have to troubleshoot it.
Anyway, start googling around, maybe you can get the schematic.
You might even have an original manual, if so scan and post it.
Good luck.
Realized I didn't specify in this thread what my problem was... Realistic STA-785 receiver. Just recently producing almost no audio. Crank the volume all the way and I can barely hear sound from speakers... Speakers are fine hooked to another receiver. Unit has an STK4182II.

On eBay right now, there is a schematic and manual. I'll probably buy it. I already have a manual that I can scan in.

Thanks,

Tony
  Reply With Quote
Old 8th March 2013, 05:46 PM   #8
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
If both channels are the same, very faint sound... wild guess but worth checking... make sure no preamp out to poweramp in "links" are missing on the back (if it has that) or, that the correct input is selected and not looped through a tape monitor or something.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 8th March 2013, 06:09 PM   #9
tvissoc is offline tvissoc  United States
diyAudio Member
 
Join Date: Mar 2013
Quote:
Originally Posted by Mooly View Post
If both channels are the same, very faint sound... wild guess but worth checking... make sure no preamp out to poweramp in "links" are missing on the back (if it has that) or, that the correct input is selected and not looped through a tape monitor or something.
Yeah, I'm going to go back and check some of the "obvious" things. I'll try another audio source too.

Tony.
  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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Novice Here stefer Introductions 8 2nd August 2012 06:15 AM
ESL electronics 101 for the electronics challenged markusA Planars & Exotics 12 29th April 2011 06:19 PM
Novice looking for first design aps Full Range 19 26th February 2010 09:01 AM
Could anyone help a novice? sunnycue Full Range 8 4th August 2006 06:45 AM
Novice in need of help skiermurph Solid State 2 22nd December 2004 02:52 AM


New To Site? Need Help?

All times are GMT. The time now is 03:18 AM.


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