RMI-FC100, a single stage audio power amplifier - Page 76 - 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 10th April 2009, 09:18 PM   #751
Sheldon is offline Sheldon  United States
diyAudio Member
 
Join Date: Dec 2003
Location: San Diego
Gotta get some more fuses. All OK, until I start probing the front end. Doesn't like that much. I don't know exactly where I did it, so I'll have to track it better next time.

Sheldon
  Reply With Quote
Old 10th April 2009, 10:58 PM   #752
Sheldon is offline Sheldon  United States
diyAudio Member
 
Join Date: Dec 2003
Location: San Diego
I'm gonna make the fuse company happy if I do too much more testing. I'll poke around with the output unpowered. Amp seems stable on its own, but it's hard to find where the problem is. If I just unplug the input from the signal generator, and try to plug it back in with the amp on, the rail fuses go. Yes, I know, not generally considered good practice to connect and disconnect with the amp on, but it shouldn't oscillate severely, that easily. I'm not sure how to check without the fuses going.

Do these look legit? Got them here: http://www.bdent.com/search/part.jsp?partnum=2SA1360#



Sheldon
Attached Images
File Type: jpg toshiba drivers.jpg (47.7 KB, 1027 views)
  Reply With Quote
Old 11th April 2009, 02:27 AM   #753
Sheldon is offline Sheldon  United States
diyAudio Member
 
Join Date: Dec 2003
Location: San Diego
With the output unpowered, all the voltages/currents check out for the front end. Currents for the back cascode/mirror (R15-18) with the outputs powered are very close to the unpowered state. Didn't dare poke around to much in front of that with output power, as that's when the fuses go.

Sheldon
  Reply With Quote
Old 11th April 2009, 05:34 AM   #754
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
Your A1360 seems to be fake
This could be a problem if the chip inside don't have low Cob
  Reply With Quote
Old 11th April 2009, 07:46 AM   #755
diyAudio Member
 
nelsonvandal's Avatar
 
Join Date: Nov 2006
If B&D Enterprises sells fake trannies, who the hell can we trust?
  Reply With Quote
Old 11th April 2009, 03:08 PM   #756
Sheldon is offline Sheldon  United States
diyAudio Member
 
Join Date: Dec 2003
Location: San Diego
Quote:
Originally posted by roender
Your A1360 seems to be fake
This could be a problem if the chip inside don't have low Cob
This, of course, begs the question: Anyone know where I can get genuine parts, this time Y versions?

Sheldon
  Reply With Quote
Old 11th April 2009, 03:27 PM   #757
housing is offline housing  Hong Kong
diyAudio Member
 
Join Date: Nov 2006
My 2SA1360/2SC3423's. Over 15 years old.
Attached Images
File Type: jpg dscn3254a.jpg (94.5 KB, 923 views)
  Reply With Quote
Old 11th April 2009, 04:05 PM   #758
Banned
 
Join Date: Apr 2005
Location: Stockholm
Hi,
Quote:
Your A1360 seems to be fake
Looks very genuine to me.
  Reply With Quote
Old 11th April 2009, 04:15 PM   #759
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
I have powered up the front end successfully. Checked voltages and feedback using the suggestons here a what I did before and all worked OK.

I have since powered up the output stage succesfully, but without a bias voltage coming from the unpowered front end. Again voltages appear to be OK.

BUT,
if I power up both stages from a common PSU in turn supplied by a light bulb tester, it motor boats.

Back to a gentler start up.
Power up the output stage and very slowly bring up the input stage using a variac and lightbulb tester and it comes on OK.

Power up the front end and slowly bring up the output stage and I can see the two stages hunting with the current swinging in the output stage from near zero amperes to near fuse rating. Turn it up a little too quickly and the fuse blows.
Turn it up VERY SLOWLY and I can get full voltage on it.

I dare not remove the light bulb tester which comes on and off at ~0.3Hz cycles for fear of damaging the amp.

That all came happened about a month ago and I have left it aside while I re-think how to get it safely up to working quiescent voltage without killing all Roender's good work.

This symptom of fuse blowing seems very similar to what Sheldon is experiencing.

Any thoughts from the ether?
__________________
regards Andrew T.
  Reply With Quote
Old 11th April 2009, 06:15 PM   #760
roender is offline roender  Romania
diyAudio Member
 
roender's Avatar
 
Join Date: Sep 2006
I have no idea what is gowning on Never happened to me
Someone with this problem and with a very good scope may trace it. First place to look is at cascodes and if everything is ok then at the CFP.
  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
Single stage amplifier Skorpio Pass Labs 33 5th January 2011 02:03 AM
RMI-FC100 MKII, single ended folded cascode VAS roender Solid State 27 9th July 2010 10:56 PM
single stage common-drain amplifier Music_Sg Solid State 4 4th July 2006 05:45 PM


New To Site? Need Help?

All times are GMT. The time now is 09:04 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