Vintage Toshiba 330 power amp problem, possible repair? - Page 4 - 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 18th January 2013, 06:27 PM   #31
diyAudio Member
 
Join Date: Feb 2012
Ok I checked again and it actually seems to do it only on switch off. It doesnt effect the telly on switching on.
  Reply With Quote
Old 18th January 2013, 06:37 PM   #32
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
That sounds like arcing and it doesn't mean there is a problem with the amp or switch.

What happens is that when the switch breaks the connection, the transformer (being inductive) can generate a high voltage spike. The plasma TV will have a switch mode type power supply and that is probably being upset by glitch on the mains and momentarily doing a "reset" and shutting down and restarting. These things weren't around way back when the amp was current.

I assume you have them all plugged into a "good" wall socket as any high impedance problems in the mains supply can make the effect much worse. Maybe try the two on an extension lead and double adapter running from another socket in the house. Just eliminates stuff, thats all.

A fix should be a supressor and maybe a VDR (voltage dependant resistor) fitted across the primary of the transformer. It should be an easy (famous last words) and cheap problem to sort because ultimately there is probably nothing wrong as such.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 18th January 2013, 06:45 PM   #33
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Something like this for the VDR,
B72207S0271K101 - EPCOS - VARISTOR, 21.0J 275VAC | CPC

you need a 275 Vac rating for UK mains

Supressing the switch if needed involves a capacitor that MUST be Class X or Y rated (suitable for continuous mains use and self healing) and perhaps a 10 ohm resistor in series with it and these placed either across the transformer primary or across the switch contacts (depends a lot on whether the switch is double or single pole).

Another thought is to try a surge supressor plug on the amp.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 19th January 2013, 11:43 AM   #34
diyAudio Member
 
Join Date: Feb 2012
I will look into this today Mooly thanks a lot as always .

Its really strange that its started doing this after I repaired the transistors. I'm glad it doesn't sound to you like anything too serious.

When the amp switches off the TV doesn't actually 'reset' and switch itself off like it does if the power is cut properly. The picture just goes into the center and goes into a sort of bright white flash and hangs there for half a second or so and then returns to a full picture. It look a bit like a really old tube tv would look when you cut the power. Cant be to healthy for the tv I suppose!
  Reply With Quote
Old 19th January 2013, 11:59 AM   #35
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Try just unplugging the amp smartly and see if the TV still trips. The other thing, the time the amp runs on for when switched off depends how much energy is being puuled from the fully charged caps. So do those two checks... bias current as per the manual... and check the DC offset. Two minutes of a job
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  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
Vintage preamplifier power supply problem slimecity Power Supplies 5 3rd October 2012 03:17 AM
Power Supply Problem/Repair ak_47_boy Power Supplies 3 7th July 2008 10:36 PM
vintage tube amp repair help adason Tubes / Valves 25 10th December 2006 09:48 PM
NEED HELP!! Vintage B&W 800 ASW repair/modify dritter_1999 Subwoofers 2 5th April 2006 11:50 AM


New To Site? Need Help?

All times are GMT. The time now is 02:47 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