PS cap for Electrocompaniet Otala 25W amplifier - 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 23rd March 2012, 10:41 AM   #1
Tube747 is offline Tube747  Hong Kong
Account disabled at member's request
 
Join Date: Jan 2012
Default PS cap for Electrocompaniet Otala 25W amplifier

My friend is seeking PS supply cap for refurbishing this amplifier, Is RIFA a good choice since both are made in scandinavian.

Any good option??
  Reply With Quote
Old 4th April 2012, 08:34 PM   #2
Sorscha is offline Sorscha  Netherlands
diyAudio Member
 
Join Date: May 2009
Location: Hoofddorp
Hello Tube747,

Forgive me but I don't quite understand this. I can think of two possibilities:

"PS supply cap" Do you mean the power supply electrolyte capacitors ?
If you do, those are Philips capacitors. In fact, every electrolyte in the original two-channel is Philips. For the filters, Styroflex-red is used. Decoupling: Wima red or blue.
..
But I can also imagine that you mean "Powerswitch" with "PS" and the capacitor that is mounted over it. It doesn't quite matter much as long it's not the "old" transparant series.

"Is RIFA a good choice since both are made in scandinavian. Any good option??"
What do you mean with both ?

Cheers!
Johan
  Reply With Quote
Old 4th April 2012, 08:56 PM   #3
AMV8 is offline AMV8  United Kingdom
diyAudio Member
 
Join Date: Jan 2005
Location: near london
Hi
I refurbished two of the 25 watt amps some years ago. Both amps needed attention to the same areas.
The emitter resistors on the output transistors, that were fitted by electrocompaniet, needed replacing by ones of the same ohm value but 5 watt instead of 2 watt. Also the pcb around those resistors needed attention due to overheating around those resistors. I also reduced the bias slightly so that I could just keep my hand on the heatsinks when the amp had fully warmed up.
I found that the electrolytic capacitors on the pcb's needed replacing but not the power supply capacitors for the amp output or amp front end supplies.
I also found that a number of joints on the pcb were cracking and needed resoldering.
At one time Electrocompaniet suggested it might be worth experimenting with more modern output transistors ( I think this might help a lot ) and improved input transistors possibly using jfets on the front end.
Don
  Reply With Quote
Old 9th April 2012, 12:25 AM   #4
Tube747 is offline Tube747  Hong Kong
Account disabled at member's request
 
Join Date: Jan 2012
Don,
Can I replace those 5W emitter resistors with either Mills MRA-5 or MRA-12?

Mills MRA-5 Resistors

Mills MRA-12 Resistors

Thanks!
  Reply With Quote
Old 9th April 2012, 12:35 AM   #5
Tube747 is offline Tube747  Hong Kong
Account disabled at member's request
 
Join Date: Jan 2012
Hi Johan!
Thanks!

Yes, I'm talking about power supply electrolytic cap. But Philips getting hard to find. My friend told me it's under BC components instead of Philips logo now.

What is Styroflex-red? Can I replace all Wima red and blue with Wima Black box series??

Sorry, I mean "both" RIFA and EMC Otala amp also made in Scandinavian.

At first I suspects someone has modded the amplifier from Rifa to Philips since the amplifier I get is not from the original owner. I always think the Otala amplifier "should" have RIFA there. The reason is that just like some Italian equipment like to put Kendeil cap there and British gear has BHC cap. So I assume the Otala amplifier should have RIFA in the power supply.

Thanks again!


Quote:
Originally Posted by Sorscha View Post
Hello Tube747,

Forgive me but I don't quite understand this. I can think of two possibilities:

"PS supply cap" Do you mean the power supply electrolyte capacitors ?
If you do, those are Philips capacitors. In fact, every electrolyte in the original two-channel is Philips. For the filters, Styroflex-red is used. Decoupling: Wima red or blue.
..
But I can also imagine that you mean "Powerswitch" with "PS" and the capacitor that is mounted over it. It doesn't quite matter much as long it's not the "old" transparant series.

"Is RIFA a good choice since both are made in scandinavian. Any good option??"
What do you mean with both ?

Cheers!
Johan
  Reply With Quote
Old 11th April 2012, 07:36 PM   #6
AMV8 is offline AMV8  United Kingdom
diyAudio Member
 
Join Date: Jan 2005
Location: near london
Tube 747
I checked my notes on the electro rebuild to make sure I am giving you the correct information.
I find that in I replaced the 1 ohm 5 watt resisters on the output transistors with 1 ohm 12 watt resistors. These seem to work fine and I would recommend the 12 watt resistors.
I also found that I increased the value of the resistence of the variable potentiometer that sets the bias current by 50%, from 300 ohms to 450 ohms. ( This is only given for guidance. You will need to check the value on the potentiomer on your amp. I reset the value of the potentiometer to lower the temperature of the heatsinks . )
Hope this helps
Don
  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
Electrocompaniet 25W class A GIRAFON45 Solid State 10 26th September 2012 01:58 PM
Matti Otala - An Amplifier Milestone. Dead or Alive lineup Solid State 775 25th September 2012 08:47 PM
Link on Otala, Electrocompaniet mlloyd1 Solid State 1 9th December 2002 03:39 PM


New To Site? Need Help?

All times are GMT. The time now is 07:25 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