Threshold S300 output transistors help - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 21st June 2002, 03:11 AM   #1
diyAudio Member
 
Join Date: May 2002
Location: Plano , TX
Send a message via AIM to jewilson
Default Threshold S300 output transistors help

I need help, I have a Thresold S300 with some bad outputs transistos. Unfortunately the Motorola part number has been removed. If any ones knows the NPN and NPN part number I sure would appreciate it. Of course this amp was designed by Mr. Pass
a long time ago. It bit the dust trying to drive a pair of one ohm Apogee speakers.

Thanks
JW
__________________
Jim W.
  Reply With Quote
Old 21st June 2002, 03:23 AM   #2
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
I have schematics for S350/450/550/1600 and SA4/6/10/12 amps and all output transistors were the same: MJ15012 and MJ15011 (where the second one is NPN). For drivers they used MJ15022 and MJ15023.
  Reply With Quote
Old 21st June 2002, 05:29 AM   #3
diyAudio Member
 
Join Date: Feb 2001
Location: Columbia, SC
Outputs on the S-500 were MJ15022 and MJ15023, drivers for the bank were one of the opposite polarity. As far as I know, the S-300 was just a scaled down S-500. I had a channel pop out on me once upon a time just because of cosmic rays (woofer panels on Magneplanar T-IVs, real tame 4 ohm resistive load--just playing background music levels at the time), and got the info from the tech critter at Threshold. No schematics on hand, unfortunately. I spent a bit reverse engineering the front end to figure out what all had blown and why, 'cause when the output went, it ripped all the way back up into the front end. After replacing all the transistors and resistors, it still didn't work. Turned out it was a tantulum cap with a voltage rating of something like 25V. When the front end blew, the voltage spiked (rails on the 500s are over 70 volts) and killed the silly cap. Given that the cap was something tiny like .15uF, I just put in a 100V Mylar cap.

Grey
  Reply With Quote
Old 21st June 2002, 06:29 AM   #4
Apogee is offline Apogee  United States
diyAudio Member
 
Apogee's Avatar
 
Join Date: Feb 2002
Location: Tacoma, WA
Jim,

You might consider calling Jon (sounds like Yon) Soderberg at Vintage Amp Repair. He's an X-Threshold engineer and his side business is repairing their gear...

I've spoken to him several times and he is very knowledgeable both from a topology standpoint as well as the actual products...

He has also always been willing to share info with me but keep in mind that this is also his business so tread lightly...

I have a Ta-300 which is basically an S-250 with a different faceplate. HPotter nailed the outputs - they are exactly what mine uses... The only reason that I would check with Jon just to be sure is because your amp is actually older and may have used different outputs than the later stuff...

I know he also has parts... As an FYI he also does mods to the older stuff that are supposed to be very good!!!

http://www.rsvlonline.net/vintageamp/

One last tidbit - I converted my amp to class A by switching the transformer secondaries to the 39v (if memory serves) pair that are there but capped off (green I think...) You simply re-bias the amp up into full class a after that. It made a HUGE difference in how my amp sounded... My amp essentially became an SA-3.9 by doing this. It dropped the output power down from 150 wpc to 60 and I have cranked the bias up as far as I dare... Sonically the change was amazing... You might seriously consider doing this to yours...

Hope this helps!

Good luck,

Steve
  Reply With Quote
Old 21st June 2002, 05:14 PM   #5
diyAudio Member
 
Join Date: May 2002
Location: Plano , TX
Send a message via AIM to jewilson
Default Threshold Transistors

Thanks for the feedback, I've been going to fix this amp for years
now but started listen to another amp. I've repaired the amp several times before, but lost the transistors part numbers.

Anyway, the failure was caused by driving a pair of ONE ohm Apogee Sintilla's. I've given up on the Apogee speakers since the cat got the bass ribbon, their now room dividers.

I have the schematic for the Stasis series and wanted to share it. Mr. Pass sent it to me a long time ago. Back then, I was in the process of changing the collector output resistors from 1 to .68 ohm to to increase the output current land decrease the power loss, hoping this might increase the life of the outputs.

Thanks from your help
Attached Images
File Type: jpg threshold stasis amp1.jpg (80.9 KB, 3191 views)
__________________
Jim W.
  Reply With Quote
Old 21st June 2002, 07:21 PM   #6
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
The 3.9 was my favorite, but then I don't tend to need
a lot of power.

The Motorola 1502X complementary parts are the preferred
ones.
  Reply With Quote
Old 21st June 2002, 10:56 PM   #7
Apogee is offline Apogee  United States
diyAudio Member
 
Apogee's Avatar
 
Join Date: Feb 2002
Location: Tacoma, WA
Jim,

One last little tidbit...

Should you decide that you want your room dividers to create beautiful sound once again, you might check out the sites below for information...

Graz in Australia is manufacturing new ribbons... I know he is in the process of developing the bass ribbons for several models. You might check with him regarding availablity. He also can guide you on possibly repairing yours...

I also know another gentleman who has some new old stock from when ADS dumped the Apogee line... They are expensive ~$300 each bass panel if he happens to have them... If you are interested I'll forward you contact information...

The trick is properly tensioning the bass panels if you replace them... There are several folks who have been actively working the solution to this problem and would be glad share info with you. Search the following links for info...

Lots of good info here -

http://apogeespeakers.info/

http://audioworld.com/cgibin/sw/foru...=45&LastLogin=

The other source you might consider for a ribbon is Ebay. Every now and again damaged sets go through...

I wouldn't give up on the Apogee's... Newer technology can drive those speakers very well and with a few crossover mods there is very little on the market that can resolve (or sound) like they can...

Steve
  Reply With Quote
Old 22nd June 2002, 05:13 PM   #8
diyAudio Member
 
Join Date: May 2002
Location: Plano , TX
Send a message via AIM to jewilson
Default Apogee Speakers

Apogee,

I e-mail Graz in Australia about the bass ribbon he said he was thinking about doing one for the Scintillas. He said he would get
back in touch but he never did. So, if you have another contact that might do a panel please let me know. I watched a web video about replacing the panel, it looks like you really need to have done this several times, plus you need some special jigs- fixtures to set and hold the panel. I guess I could build the jigs.

As for another amp, I have a late model Krell KSA 150 which
I like very much. It drives the Scintilla's very well.

At one time I though about ripping the bass panels out and replacing them with a somthing like a fast 8" Scan-Speak woofer, but reality set in and I built a pair of three way speaker. Having said that I would like to listen to them again they were great while they lasted.

Regards





..
__________________
Jim W.
  Reply With Quote
Old 23rd June 2002, 12:17 AM   #9
Apogee is offline Apogee  United States
diyAudio Member
 
Apogee's Avatar
 
Join Date: Feb 2002
Location: Tacoma, WA
Jim,

The person that you need to contact is Bob Dragunas. He used to work for Apogee/ADS in their service department...

The ribbons that he has are new old stock from Apogee when they closed down...

Sometimes it takes a few messages before he replies back...

His email is:

apogeeribbons@yahoo.com

I also have his phone number but would rather not give it out without asking first... If you don't hear back from him within a couple of weeks, let me know. Again, it usually takes a while to hear back but he does usually answer... My impression is that this is not high priority for him and I think he just does it on the side when he has time/feels like it...

I hope he has the panels that you're looking for. It would be much better to replace the pair than try to switch to dynamic drivers IMHO...

Good luck,

Steve

PS - Let me know if you don't hear back and I'll call him and ask if it would be ok that I forward his phone number to you... Just do me a favor and try his email first as that's how he's always communicated regarding Apogee stuff... Thx!
  Reply With Quote
Old 23rd June 2002, 03:09 AM   #10
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
I see the MPS U10 and 60, what does everybody use for these?
  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
threshold SL10 - DC output pjmont Pass Labs 11 29th February 2012 07:26 AM
Threshold s300 Amp Power on Thud nellson Pass Labs 16 30th August 2010 05:57 PM
Matched transistors in Threshold SA/_e amplifiers? Danish Pass Labs 2 14th June 2005 01:11 AM
Long output lead or long output transistors leads? which one to pick? chris ma Everything Else 3 6th June 2003 12:06 PM
Output Transistors weinstro Parts 1 9th May 2003 11:51 AM


New To Site? Need Help?

All times are GMT. The time now is 05:45 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