Hello all it's been awhile since i posted anything, my Tubelab SSE has been working for years now with no issues. Last year i purchased a set of KT88's and have been running them since. After a move i hooked up the amp and puff, smoke arose.
Has anyone had an issue with R14 blowing up? Anything else i should replace along with R14?
Any help would be greatly appreciated.
Has anyone had an issue with R14 blowing up? Anything else i should replace along with R14?
Any help would be greatly appreciated.
The most likely cause of R14 destroying itself is a short ciruit to ground on point A of U10.
If the valve was A-C short circuit R10 would also have suffered, so I don't think that is an issue.
Probably something conductive touched between point A and the chassis momentarily.
If the valve was A-C short circuit R10 would also have suffered, so I don't think that is an issue.
Probably something conductive touched between point A and the chassis momentarily.
Thanks for the reply, it is very possible something fell into the amp though i did not find anything when i took it apart. Do you think u10 could have been damaged? I have replacement 10m45s that i could use.
It would appear that something shorted the Anode of U10 to ground. R14 looks like it fried quickly as opposed to a slow cook which usually discolors the ends of the resistor and the surrounding PCB. U10 is configured as a CCS set at about 10mA. A totally shorted tube would only pull 10 mA through R14 making it eat 1 watt. This will make it get hot but should not burn it up. A shorted tube would also only pull 10 mA through the cathode resistor, R10 which would not burn it up. It is possible that a shorted tube could make U10 get hot enough to fail, which could have let the tube overheat possibly shorting out and blowing R14.
It is also possible that U10 failed to a short which fried the resistor and possibly overheated the 12AT7. This would have reduced the volume in one channel and caused some distortion.
Safe bet likely to fix it on the first try, Replace the tube, U10 and R14. Make sure that the tab on U10, the heat sink and the screw cannot touch the chassis or anything else that is grounded.
Want to troubleshoot it, replace R14. Connect a voltmeter across R14 set on a range higher than 500 volts. Fire the amp up while watching the meter. There should be zero voltage with cold tubes which should rise to about 100 volts as the tubes heat up. If the voltage goes past 150 and / or the 12AT7 starts to red plate cut power and replace U10 and the 12AT7. U10 is likely shorted and the 12AT7 has been cooked.
It is possible that the tube is still good if the amp was not left on for more than a few minutes in the inoperative condition.
It is also possible that U10 failed to a short which fried the resistor and possibly overheated the 12AT7. This would have reduced the volume in one channel and caused some distortion.
Safe bet likely to fix it on the first try, Replace the tube, U10 and R14. Make sure that the tab on U10, the heat sink and the screw cannot touch the chassis or anything else that is grounded.
Want to troubleshoot it, replace R14. Connect a voltmeter across R14 set on a range higher than 500 volts. Fire the amp up while watching the meter. There should be zero voltage with cold tubes which should rise to about 100 volts as the tubes heat up. If the voltage goes past 150 and / or the 12AT7 starts to red plate cut power and replace U10 and the 12AT7. U10 is likely shorted and the 12AT7 has been cooked.
It is possible that the tube is still good if the amp was not left on for more than a few minutes in the inoperative condition.
Thanks that is really helpful, since I have the parts on hand I'm going to replace r14 and u10, I have a bunch of 12at7's so no problem. Makes me feel better that it's a relatively easy fix. I will have to get better stand offs to support the board, the way it was mounted allowed some movement which could have let u10's heat sink to touch the chassis.
For anyone interested the 12AT7 was cooked also it tested bad on my Jackson 648. So i replaced r14, u10 and the tube.
I'll let everyone know how it goes when i put it back together.
I'll let everyone know how it goes when i put it back together.
Update: after replacing R14, U10, and the 12at7 the amp works great again! Thanks for all the replies.