musical fidelity synthesis - 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 22nd July 2006, 05:08 PM   #1
latala is offline latala  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: staffordshire
Default musical fidelity synthesis

I have a friend who has given me his amp for repair !
has any one got the schematic for this
problem is a distorted right channel dc offset etc seems to be ok
regards Trev
  Reply With Quote
Old 24th July 2006, 08:51 AM   #2
latala is offline latala  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: staffordshire
I have opened the amp up Its a mess right channel has burned up drivers and burned out resistors It seams to be a mosfet unit.
The later hitachie plasic ones luckily i have a few sets of these!
Does any one out there have a shematic of the output stage ?
regards trev
  Reply With Quote
Old 25th July 2006, 09:15 PM   #3
latala is offline latala  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: staffordshire
I am looking at this amp at the moment To be honest in my opinion it does not seem to be of a great build quality! The pc tracks around the driver /output pair seem to be very fine in fact too fine!!!
The output stage is mosfet driven by a mj350/mj340 pair in a source follower mode ?
Does anyone no of a similar output stage ?
I have contacted MF to be told they are all on a 2 week holiday
just my luck
regards trev
  Reply With Quote
Old 26th July 2006, 09:40 PM   #4
latala is offline latala  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: staffordshire
Looks to me as I am all alone with this one all though i have received a leade fom an ex engineer from MF he tells me it a basically the hitachie mosfet circuit !
What a poor piece of equipment this is I have found that a neg rail decoupler capacitor has gone short and litterally blown the print off the board!!!
I am glad i never purchased one of these all though it did sound quite nice
the drivers seem to be in some sort of cascode configuration does any one have a drawing ?
regards Trev
  Reply With Quote
Old 27th July 2006, 08:48 PM   #5
latala is offline latala  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: staffordshire
The circuit is derived from the hitachie application note
However the diif input pair are fed from a constant current circuit
The output from the diff pair go to a cascode connected set of drivers an improvement in the classic active sink source hitachie circuit ?
but to be honest it about the worst board I have ever seen !
I still would like a circuit though to see if my diagnoses is correct
Regards Trev
The adventure goes on
ps I still want to prove my high voltage driver but untill I get this out off the way I can not go forward
  Reply With Quote
Old 28th July 2006, 12:19 AM   #6
anatech is offline anatech  Canada
diyAudio Moderator
 
anatech's Avatar
 
Join Date: Jun 2004
Location: Georgetown, On
Hi Trev,
If it is the old Hitachi circuit, why not search for the app notes that may be on line? I don't have anything on it at all, sorry.

-Chris
  Reply With Quote
Old 28th July 2006, 07:40 AM   #7
jaycee is offline jaycee  United Kingdom
diyAudio Member
 
Join Date: Apr 2004
Location: Norwich, UK
You could always e-mail MF and ask them if they'd be nice enough to send you the schematic.

Perhaps it is similar to AmpsLab Lm60 amplifier - this is very close to the Hitachi schematic. Take a look at http://www.ampslab.com/lm60_schematics.htm
  Reply With Quote
Old 28th July 2006, 02:45 PM   #8
latala is offline latala  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: staffordshire
Thanks for your kindness Gentlemen
The schematic is derived for the Hitachie but has a lot of major differences hence the request !
I know the hitachie circuit very very well and I can draw it from memory !
I have contacted MF who tell me there tech dept is on Holiday for a few weeks so I suppose I will have to wait or press on the hard way
Regards Trev
  Reply With Quote
Old 29th July 2006, 11:45 PM   #9
latala is offline latala  United Kingdom
diyAudio Member
 
Join Date: Feb 2006
Location: staffordshire
Well its done
The amp is now repaired and tests out well! The problems
faulty power supply decoupler at the board 100 uf 63 vdc short this then vapourised a piece of earth track this had the effect of diconnecting the Zobel network and the bottom leg of the feedback network.
A diode in the protection to the gate of the sk fet was also leaky causing the amp to be assymetric .
Also the string of 4 diodes (1n148 )that held the bases of the driver cascodes mje340 were either OC or sc this caused the mje340 to turn on fully and blow the bottom of the cascodes bc184 to catch fire
Schematic ?
Its a version of the Hitachi circuit but has the following changes
The first diff pair are fed from a constant current circuit that is also coupled to the preamp section psu in order to give a silent turn on/off.
The driver stage is a cascode formed from a pair of bc184and mje 340
On replacing the above components its a winner and now works well.
Conclusions?
Very nice sounding
Poor PC board
Typical of the amplifiers in its price range(450) and time
I think esoteric is another way of overcharging for poor build quality'
Regards Trev
  Reply With Quote
Old 10th July 2013, 10:43 AM   #10
diyAudio Member
 
Join Date: Aug 2009
Location: Kaunas
Hello, would anyone happen to have a service, user manual or any other information regarding this amplifier?

I would be very grateful for any help.
  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
Musical Fidelity A1x or A 120 which one is better ? Bernhard Solid State 4 9th December 2012 09:24 AM
Musical Fidelity Synthesis - Loud pop - Help Needed! Audiofirst Solid State 2 9th September 2010 11:45 PM
MUSICAL FIDELITY a1 cd pro gio_b Digital Source 0 4th June 2009 03:30 PM
Musical fidelity b1 abiedoodles Solid State 6 20th October 2007 09:29 AM
Musical Fidelity B1 NamWong Solid State 1 29th April 2004 01:46 PM


New To Site? Need Help?

All times are GMT. The time now is 06:11 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