Soundcraftsmen troubles - Page 4 - 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 2005, 04:14 AM   #31
diyAudio Member
 
still4given's Avatar
 
Join Date: Oct 2004
Location: Victorville, CA
Hi Zc,

I have been hoping you would show up. I have read many of your posts about the Soundcraftsmen amps.

I bought new parts and replaced all of the 2N3440's and MM4003's. I think those are the drive transistors you refer to no?

They all had missing legs. Two of them were just laying in the chassis. Most of them only had one lead still attached. Not sure if they corroded away or burned. Looked like corrosion though. There are rust spots on the cases of the MOSFETs. This thing has had some moisture in it.

The PSU measures good. I'm thinking it is probably the MOSFETs. I pulled every componant except for the MOSFETs that looked like it lead to the output and still there was voltage on it. I will post back when I get it apart again. Should be jsut a couple of days.

Blessings, Terry
__________________
X-BoSoZ, B1 Mezmerize, ESP P101, Symasym, KSA 50 X 2 Aleph-X, Leach Low TIM, Leach Superamp, Dx MKIII, DX Super A, Honey Badger, JLH 1969, Gainclone. FetZilla, Peeceebee X2, VSSA PMI, VSSA jkuetemann, SKA GB150, Ovation nx, Slewmonster with; CFA-XH, Wolverine, Spooky, Symasui, Low TIM hybrid
  Reply With Quote
Old 23rd March 2005, 12:02 PM   #32
diyAudio Member
 
chris ma's Avatar
 
Join Date: Sep 2001
Location: Pickering, Canada
Quote:
Originally posted by djk
Go ahead and ignore 30 years worth of experience.

Many amps will not work when brought up slowly on a variac.

I agreed with one building experience that the Variac brought up slowly the amp did not work. The amp was the BrianGT first GC group buy version. As to why I do not have any clues.

The Butcher
  Reply With Quote
Old 23rd March 2005, 01:15 PM   #33
diyAudio Member
 
still4given's Avatar
 
Join Date: Oct 2004
Location: Victorville, CA
Quote:
Originally posted by djk



Go ahead and ignore 30 years worth of experience.

Many amps will not work when brought up slowly on a variac.



Quote:
Originally posted by chris ma



I agreed with one building experience that the Variac brought up slowly the amp did not work. The amp was the BrianGT first GC group buy version. As to why I do not have any clues.

The Butcher


First off, I said I would build the light bulb gadget. I'm not trying to ignore anything. I bought and started using the variac due to several suggestions by many experienced folks on this very forum.

Secondly, I am not trying to get the amp to "work" on the variac. I'm not connecting speakers to this thing until I get that high voltage off of the output. I have been using the variac so that when I see 7 or 8 volts on the output, I know I still haven't fixed the problem and yet I feel safe that I haven't burned up any more parts. If this logic is flawed then I will stop doing it. In my mind, it seems as though even with the light bulb in the loop I would still get 120V to my transformer. Is this not true? Would I actually see less than 8VDC on the rails by using the light bulb trick? Are you guys saying that with the light bulb in the loop that there is no way that any of the components can get too much voltage? I'm trying to wrap my mind around this but for some reason Iím not seeing something here. Maybe it's just too far over my head to understand. I'm just trying to keep from damaging stuff while I search for the problem. Is there chance that using both the variac and the light bulb device would allow me to work with the lower voltages and have the added safety of bulb in the circuit? I feel like the chances of me getting shocked are much less with 8VDC than with 65VDC or so.

Please, help me understand this better.

Thanks, Terry
__________________
X-BoSoZ, B1 Mezmerize, ESP P101, Symasym, KSA 50 X 2 Aleph-X, Leach Low TIM, Leach Superamp, Dx MKIII, DX Super A, Honey Badger, JLH 1969, Gainclone. FetZilla, Peeceebee X2, VSSA PMI, VSSA jkuetemann, SKA GB150, Ovation nx, Slewmonster with; CFA-XH, Wolverine, Spooky, Symasui, Low TIM hybrid
  Reply With Quote
Old 23rd March 2005, 01:25 PM   #34
K-amps is offline K-amps  United States
diyAudio Member
 
K-amps's Avatar
 
Join Date: Nov 2003
Location: Indiana
Terry,

It's the current that will kill components not necessarily voltage.

The bulb limits current, the variac limits voltage.

Go ahead use both if it makes your mind as ease, as Zerocool said, he has repaired the PCR's and used a variac with little or no ill effects.

The bulb will let your amp get a max of 80 volts ac ONLY if everything is working ok, otherwise it will drop the current (and hence voltage) to much lower levels. With a Variac, you get a relatively constant current with no auto failsafe like the bulb.

As I said earlier, use a 4 or 8 ohm dummy load at the outputs, that will decrease the power delivered to the amp if there's a fault and in such a scenario you will not see over 70-80 volts on the amp unless it is working fine, or you have removed all semiconductors.
  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 900X2 screamersusa Solid State 36 8th July 2012 08:57 AM
Soundcraftsmen RA6501 Troubles squall_line_79 Solid State 6 29th January 2011 02:49 AM
Soundcraftsmen Pre-amp enzedone Solid State 2 27th March 2007 01:07 AM
FS: Soundcraftsmen PM-840 410 watt amp $150.00 Zero Cool Swap Meet 0 27th May 2005 01:45 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 04:07 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