Modding my Soundcraftsmen - 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 November 2004, 07:14 AM   #1
splsaab is offline splsaab  United States
diyAudio Member
 
Join Date: Oct 2004
Location: Fairfax County, VA
Send a message via AIM to splsaab Send a message via Yahoo to splsaab
Default Modding my Soundcraftsmen

Hi all, First time poster

I have a Soundcraftsmen RA7503 amplifier that I am planning to modify. I have the schematics and have done some lurking here plus some preliminary reseach. The amp is a Class H design with constant 62V rails and 93V variable rails controlled by a darlington pair. The output transistors are T03 type, and currently a mix of origonals plus some MJ15023 and MSJ 6343. This amp has obviously been repaired multiple times.

So the first two things I want to do is replace all the output transistors and beef up the power supply. Transistor options I am looking at are MJ15022/23, MJ15024/25, MJ21193/94. But I am looking for suggestions on the best transistors to use.

As for the power supply, I modified the schematic in photoshop. All the parts in red would be added.
http://umsis.miami.edu/~rcarter/Soun...owerSupply.JPG

It seems the filter caps are way too small, esp when the 93V rails are used. If I calculated it right, about 92,000uF would be ideal when the 93V rails are used. Oh, maybe I should state that the amp is rated at 750 WRMS @ 8ohms bridged. Unfortunately I have no clue what the rating of the transformer is, but for now I don't think I'll be replacing it.

So what would be reasonable for C2 an C3? I was thinking about just ditching the old caps, I seriously doubt the 24 year old caps in there now are as good as you can get today.

For the transformer caps C4 & C5 would 100nf be good?

For the series RC filters I'm not even sure the way I drew it on the schematic would work right, since the extra rails complicate things. So would this work ok and if so what values should I use?

Thanks so much any help you can give me.

Robert Carter
  Reply With Quote
Old 20th November 2004, 07:20 AM   #2
splsaab is offline splsaab  United States
diyAudio Member
 
Join Date: Oct 2004
Location: Fairfax County, VA
Send a message via AIM to splsaab Send a message via Yahoo to splsaab
ok, so I know I'm a noob but all the more reason to help me right?
Please, if you can give any input at all, by all means do so. I know there are lots of smart people on this board! I only understand about 50% of what I read here! If you need more info, ask, and I'll try my best to deliver.

Thanks,
Robert
  Reply With Quote
Old 31st July 2006, 05:28 PM   #3
diyAudio Member
 
Join Date: Aug 2005
I know I am bringing a really old thread back from the dead but I wanted to hear how the modifications went.

I am also thinking about doing some modifications to my Soundcraftsmen Class H amplifiers.
  Reply With Quote
Old 31st July 2006, 08:27 PM   #4
splsaab is offline splsaab  United States
diyAudio Member
 
Join Date: Oct 2004
Location: Fairfax County, VA
Send a message via AIM to splsaab Send a message via Yahoo to splsaab
Hi SleeperSupra!

At long last someone is interested in my post!

well, I did swap out the big caps, and that is as far as I have gotten. I replaced the old 11,000uF caps with Aerovox M series 41,000uF caps, and the the 22,000uF caps were replaced with Aerovox M series 39,000uF caps. I also rewired the whole amp, rerouting wires to make runs shorter, neater, and increased the size of the wires between the AC input and the power supply transformer. The amp looks beautiful inside now, but more importantly, Just these mods alone made a huge difference in the performance. Like most people say, the bass was a lot more forceful, but it just all around sounds better. I do have a full set of transistors and the small bypass caps to go into the thing when I have time.
What Soundcraftsmen model(s) do you have?
  Reply With Quote
Old 31st July 2006, 08:43 PM   #5
Netlist is offline Netlist  Belgium
diyAudio Moderator Emeritus
 
Netlist's Avatar
 
Join Date: Jan 2003
If only we could find some schematics.
My old buddy (RA7501) is still collecting dust due to lack of data.

/Hugo
  Reply With Quote
Old 1st August 2006, 06:20 AM   #6
splsaab is offline splsaab  United States
diyAudio Member
 
Join Date: Oct 2004
Location: Fairfax County, VA
Send a message via AIM to splsaab Send a message via Yahoo to splsaab
The schematics are available. I bought mine online for around $25USD I believe. I don't remember where, but I can find out for you.
  Reply With Quote
Old 1st August 2006, 07:04 AM   #7
Netlist is offline Netlist  Belgium
diyAudio Moderator Emeritus
 
Netlist's Avatar
 
Join Date: Jan 2003
That would be nice, thank you. I believe more members are on a quest for schematics over here.

/Hugo
  Reply With Quote
Old 1st August 2006, 07:45 AM   #8
diyAudio Member
 
Join Date: Aug 2005
My system consists of:

Audio/Video Gear
Hitachi Ultravision 60SBX72B 60" Rear Projection TV
Mitsubishi HSU780 S-VHS Stereo Hi-Fi VCR
Sony DVP-CX985V 400 DVD/SACD Player
Onkyo Integra TXDS939 AC3/THX Surround Receiver
Soundcraftsmen MA5002A Power Amplifier
2 (two) Soundcraftsmen PA5001 Amplifiers
Soundcraftsmen TG3044R Third Octave EQ
Monster Interconnects and Cables
Thiel CS2 Coherent Source Speakers (for two channel)
JBL HT1F THX Surround Speaker System (has two passive 12" subs, three MTTM speakers, and two dipole TM/MT surrounds)
Custom Center Channel Speaker (one 3 1/2" fiberglass mid tweeter with a phase plug, first order crossover, two 10" mid bass drivers and a 15" passive radiator)...

I also have an NAD 2400 PE Power Amplifier and a pair of Linn LS150 Helix's that I am using in my secondary system.
  Reply With Quote
Old 1st August 2006, 10:49 PM   #9
oPossum is offline oPossum  United States
diyAudio Member
 
oPossum's Avatar
 
Join Date: May 2005
Location: Michigan
Quote:
Originally posted by Netlist
If only we could find some schematics.
My old buddy (RA7501) is still collecting dust due to lack of data.

/Hugo
I have the old Class H schematics here:

http://soundcraftsmen.info/Class%20H/
__________________
Possum - the other white meat
  Reply With Quote
Old 20th February 2007, 12:57 AM   #10
diyAudio Member
 
Join Date: Aug 2005
splsaab,

Any updates?

Where did you get the larger Aerovox caps?

I plan to do the same modds with my MA5002A.
  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
soundcraftsmen pcr 800 schematics artcarmo Solid State 11 9th September 2008 06:16 AM
Soundcraftsmen Pre-amp enzedone Solid State 2 27th March 2007 01:07 AM
Soundcraftsmen MA-5002a mhirvon Solid State 0 17th May 2005 09:52 AM
Soundcraftsmen 220 mig-ru Tubes / Valves 2 16th July 2002 06:11 AM


New To Site? Need Help?

All times are GMT. The time now is 12:51 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