Technics SA 626 blowing fuse before transformer - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

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
Reply
 
Thread Tools Search this Thread
Old 24th July 2014, 03:51 PM   #21
diyAudio Member
 
Join Date: Jan 2014
Location: New Hampshire
Default Sanken 2SA1295/2SC3264

I am heading in the direction of buying a pair of Sanken 2SA1295($6.55)/2SC3264($6.80) from Digikey.

Too many fakes of the existing Toshiba being offered along with the NTE products. The $2 and $3 NTE chips from China can not be genuine.

I know this unit is not worth the investment but I look at it as a learning project.

Any thoughts or comments?

Last edited by rfitts46; 24th July 2014 at 03:58 PM.
  Reply With Quote
Old 24th July 2014, 08:56 PM   #22
diyAudio Member
 
Join Date: Jan 2014
Location: New Hampshire
Actually found them cheaper at Newark. $4.54 and $3.90.
  Reply With Quote
Old 25th July 2014, 11:32 AM   #23
diyAudio Member
 
Join Date: Jan 2014
Location: New Hampshire
removed output IC's on one channel. Reconnected secondary, Using DLB powered amp up and the bulb glowed brightly and then decreased. Relay clicks.The bulb still seems to glow substantially. The amp did power up without blowing a fuse. Connected speaker up to see if any evidence of output on the one good channel and no evidence.
  Reply With Quote
Old 25th July 2014, 12:47 PM   #24
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Test the assembly in simple stages.
Power on via Mains Bulb Tester until you haved proved that all modules and all wiring is all operating correctly.

First test the transformer alone.

Then test the transformer plus rectifier.

Then test the transformer plus rectifier plus one pair of smoothing capacitors. Use a pair of small (around 100uF to 470uF) electrolytics with a voltage rating above what the previous test showed as output voltage.

Then test the transformer plus rectifier plus original smoothing capacitors.

Then test the transformer plus rectifier plus original smoothing capacitors plus one amplifier.
Remove that amplifier and repeat the test with the other amplifier.

Then test the transformer plus rectifier plus original smoothing capacitors plus both amplifiers.

Then test the transformer plus rectifier plus original smoothing capacitors plus both amplifiers plus one speaker or dummy load.

Then test the transformer plus rectifier plus original smoothing capacitors plus both amplifiers plus both speakers or dummy loads.
__________________
regards Andrew T.
  Reply With Quote
Old 25th July 2014, 02:01 PM   #25
diyAudio Member
 
Join Date: Jan 2014
Location: New Hampshire
AndrewT, This receiver has one integrated regulator, driver, and power circuit board. The only hard wiring that can be removed is the AC from the transformer secondary.

I have confirmed the transformer secondary for the amplifier section is not shorted or open by removing load upstream. Cut wires.

Then removed output IC's(one PNP and one NPN, MT200 case) on one channel that had hard short emitter to collector, removed hard short, the receiver can now be powered on with DLB in place. The dimness of the bulb after capacitor charge up makes me suspicious of a soft short?

Now that the side that had the hard short is powered I can measure voltage on rails, measure voltage at transistor bases, etc?

To test section by section I assume the transistor upstream must be unsoldered and removed from the board?
  Reply With Quote
Old 27th July 2014, 07:35 PM   #26
diyAudio Member
 
Join Date: Jan 2014
Location: New Hampshire
tested the transistor rail voltages they are ok. checked out the two transistors one stage back from the shorted output IC's and they check ok. ordered a pair of the Sanken transistors from Newark.

did power the receiver with out the output IC's on one side installed using straight 120 VAC without the DLB in place and it was ok.
  Reply With Quote
Old 28th July 2014, 02:02 PM   #27
diyAudio Member
 
Join Date: Jan 2014
Location: New Hampshire
I am assuming without the output IC's in place on one channel that it goes in to protect mode?

Can anyone help describe how the self protect mode works?

I see IC801 with nine inputs does the function.
There is a large relay 801 near IC801 that is clicking. It appears it opens or closes the final stage output.
The 48VDC rail voltages are present.

There are two inputs on IC801 monitoring output of final stage...without the output IC's on one channel in place, the IC is not happy?
Attached Images
File Type: png technics sa 626 schematic protect circuit.png (620.1 KB, 41 views)

Last edited by rfitts46; 28th July 2014 at 02:07 PM.
  Reply With Quote
Old 28th July 2014, 10:32 PM   #28
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
you can measure the voltage before the relay contacts.

A high DC here should be detected and prevent the relay closing.
__________________
regards Andrew T.
  Reply With Quote
Old 1st August 2014, 12:41 PM   #29
diyAudio Member
 
Join Date: Jan 2014
Location: New Hampshire
replaced the output IC'S and the unit is up and running. I used the Sanken IC's. I will have to comment at a later date when I get time to listen well to see if there is any difference in the sound of the original ICS on one channel and the replacement IC's on the other.

the volume level indicators I'm not working so I will fool with that next. Any Ideas?
  Reply With Quote
Old 5th August 2014, 11:27 AM   #30
diyAudio Member
 
Join Date: Jan 2014
Location: New Hampshire
The volume range indicator, as it is called on the schematic, is a plastic sheet that rotates using the volume motor shaft. It is a belt. Inside the housing is a #44 6v .25 amp bulb. The bulb was blown waiting for a replacement. It was difficult to get to but will post images of this contraption.
  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
SA-W2500 Sub blowing fuse 2dbit Solid State 14 27th February 2013 06:33 AM
Technics 1210 Mk2 Internal Fuse keeps blowing dunksterp Analogue Source 5 21st October 2011 07:52 PM
Fuse housing melting but fuse not blowing, ppi amp rawadia Car Audio 21 2nd August 2008 11:39 AM
Transformer fuse nuisance blowing halfgaar Parts 16 10th September 2006 11:53 PM


New To Site? Need Help?

All times are GMT. The time now is 01:28 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