Need help to restore Sansui 500A - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 11th December 2010, 12:56 AM   #1
diyAudio Member
 
Join Date: Jan 2005
Location: montreal
Default Need help to restore Sansui 500A

I am restoring a Sansui 500A amp sections.
Use a cd player to play a 1Khz sinewave.
Measure waveform from output transformer with 8ohm load, distortion found.

Installed 2 6aq8, measure waveform at C707, C716, waveform looks good.

Installed 2 6bl8, measure waveform at C804, C805, C809, C810, the waveform looks different between R&L channels. The voltage I got is quite some different from reference voltage from the schematic.

Voltage after the rectifier measure good according to schematic.
If I want to replace C804, C805, C809 and C810, what type of capacitor to use?

Sansui 500A Service Manual
  Reply With Quote
Old 11th December 2010, 01:18 AM   #2
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Sansui used oil caps., which are known to become leaky. Replace the interstage coupling parts with Soviet surplus 0.33 μF. K40s, which are paper in oil (PIO). The Russian stuff is modestly priced and WELL made.
__________________
Eli D.
  Reply With Quote
Old 11th December 2010, 02:52 PM   #3
diyAudio Member
 
Join Date: Jan 2005
Location: montreal
Is Polypropylene Capacitor ok to use?
  Reply With Quote
Old 11th December 2010, 03:53 PM   #4
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Assuming the value and WVDC rating are correct, it is electrically fine. The unit may be bright sounding, with polypropylene dielectric in those positions.

BTW, don't use metalized film construction. Use film and foil parts.
__________________
Eli D.
  Reply With Quote
Old 11th December 2010, 11:43 PM   #5
diyAudio Member
 
Join Date: Jan 2005
Location: montreal
Are C804, C805, C809 and C810 can cause distortion?
VR001 - VR004 pots are these use to adjust bias? and how to adjust.
I got -17v at test point C1,C2,C3,C4.
  Reply With Quote
Old 13th December 2010, 09:31 PM   #6
diyAudio Member
 
Join Date: Jan 2005
Location: montreal
How to adjust bias?
  Reply With Quote
Old 19th December 2010, 02:20 PM   #7
diyAudio Member
 
Join Date: Jan 2005
Location: montreal
Quote:
Originally Posted by fastvideo View Post
Are C804, C805, C809 and C810 can cause distortion?
VR001 - VR004 pots are these use to adjust bias? and how to adjust.
I got -17v at test point C1,C2,C3,C4.
any help?
  Reply With Quote
Old 19th December 2010, 06:30 PM   #8
diyAudio Member
 
Join Date: Aug 2008
Hi, fastvideo,

Although I don't have Sansui 500A, but rather Sansui AU-70 (waiting for restoration), and AU-111 (to be completely rebuilt), advices you are asking for are common for vintage equipment restorers.

I would advise you to learn tube schematic a little bit to avoid common problems and mistakes.

I have comprehensive walk-through in my blog, for Pioneer SM-83 and Fisher 400. Sansui 500A is very close to these two.

Pioneer SM-83 Vacuum Tube Amplifier Restoration | MacGuru HQ
Fisher 400 Vacuum Tube/Valve Tuner/Amplifier Restoration | MacGuru HQ
  Reply With Quote
Old 5th January 2011, 12:34 AM   #9
diyAudio Member
 
Join Date: Jan 2005
Location: montreal
Quote:
Originally Posted by LinuksGuru View Post
Hi, fastvideo,

Although I don't have Sansui 500A, but rather Sansui AU-70 (waiting for restoration), and AU-111 (to be completely rebuilt), advices you are asking for are common for vintage equipment restorers.

I would advise you to learn tube schematic a little bit to avoid common problems and mistakes.

I have comprehensive walk-through in my blog, for Pioneer SM-83 and Fisher 400. Sansui 500A is very close to these two.

Pioneer SM-83 Vacuum Tube Amplifier Restoration | MacGuru HQ
Fisher 400 Vacuum Tube/Valve Tuner/Amplifier Restoration | MacGuru HQ
Thank you, it is very useful.
On the Pioneer Amp, you replaced 7189A with 6P14P-EV.
I just got 4 6P14P-EV, but it did not work with my unit.
Is this pin to pin replacement tube?
  Reply With Quote
Old 5th January 2011, 12:41 AM   #10
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
The Russian 6П14П-ЕВ (6p14p-ev), AKA EL84M, is a genuine 7189 (no "A") equivalent. There are socket wiring differences between the 2.

In any event, your Sansui unit uses 6BM8s, not 7189s.
__________________
Eli D.
  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
Sansui 500EA vs. 500A rwm8088 Tubes / Valves 3 16th April 2010 05:16 AM
WTB : ICEPower 500A module YCLee Swap Meet 3 15th October 2009 01:53 AM
Sansui 500a Output Transformer KIERANPHILLIPS Tubes / Valves 0 26th March 2002 09:53 PM


New To Site? Need Help?

All times are GMT. The time now is 03:51 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