|
MX 3000a early clip? |
Post Reply 
|
Page <12 |
| Author | |
Randy Bohannon 
Registered User 
Joined: 29 May 2022 Location: London Status: Offline Points: 107 |
 Post Options
 Thanks(0)
 Quote Reply
 Posted: 30 November 2022 at 12:39pm |
|
Closest I have any experience of and is possible to get would be:https://www.mouser.com/datasheet/2/408/toshiba_2SC4793-587292.pdf
But I see that the original stands a collector current of 1.5A vs 1A and a base current of 150mA vs 100mA of the 2sc4793. Hmmm, perhaps not then...  Edited by Randy Bohannon - 30 November 2022 at 1:28pm |
|
 |
|
|
Greg32
Registered User
Joined: 14 December 2004 Location: Australia Status: Offline Points: 116 |
Post Options
Thanks(0)
Quote Reply
Posted: 30 November 2022 at 8:01pm |
|
Thanks Randy, they might just work. collector current should be around 240ma.
|
|
|
|
|
Greg32
Registered User
Joined: 14 December 2004 Location: Australia Status: Offline Points: 116 |
Post Options
Thanks(0)
Quote Reply
Posted: 16 December 2022 at 10:53am |
|
Update i have replaced the output devices with mjl1302 and mjl3281 and the pre drivers with MJE15032/33 the service manual suggests to set the bias at 100-110mv accross the driver transistors emitter resistors, this value only just turns on the output transistors with 1mv across the output transistors emitter resistors, that is about 4.5ma per device which seems a bit low. all other voltages seem to be good. more testing tomorrow...
Edited by Greg32 - 16 December 2022 at 10:54am |
|
|
|
|
Greg32
Registered User
Joined: 14 December 2004 Location: Australia Status: Offline Points: 116 |
Post Options
Thanks(0)
Quote Reply
Posted: 19 December 2022 at 1:50am |
|
I never tried changing out the step driver boards on the -ve side, the high rail step driver board has 2 leds that are illuminating as signal level is increased, I only saw 1 led on my other mx3000a. what is the correct sequence of led illumination? or what do they indicate?
Thanks Greg
|
|
|
|
|
Greg32
Registered User
Joined: 14 December 2004 Location: Australia Status: Offline Points: 116 |
Post Options
Thanks(0)
Quote Reply
Posted: 26 December 2022 at 7:07am |
|
Ok finally got time to try swapping out the negative step driver board, success it works.
now i need to find a replacement board. qsc # ic-000090-00 
|
|
|
|
|
Randy Bohannon
Registered User
Joined: 29 May 2022 Location: London Status: Offline Points: 107 |
Post Options
Thanks(0)
Quote Reply
Posted: 26 December 2022 at 4:23pm |
|
Well done on diagnosing it at last Greg!
Edited by Randy Bohannon - 26 December 2022 at 4:23pm |
|
|
|
|
Greg32
Registered User
Joined: 14 December 2004 Location: Australia Status: Offline Points: 116 |
Post Options
Thanks(0)
Quote Reply
Posted: 27 December 2022 at 7:14am |
|
Thanks Randy, Me being impatient I had a go at repairing the step driver board, i couldn't get the sot-23 devices(quickly at this time of year) so i used the to-92 version 2n3904 and 2n3906. looks rough but functions as it should.
 |
|
|
|
|
Randy Bohannon
Registered User
Joined: 29 May 2022 Location: London Status: Offline Points: 107 |
Post Options
Thanks(0)
Quote Reply
Posted: 27 December 2022 at 2:39pm |
|
Should be fine unless it's going gigging again. :)
|
|
|
|
|
Post Reply
|
Page <12 |
| Tweet |
| Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |
Topic Options