when tubes go bad... video and pic as promised!! (also DSL401 mod update)

[gusfinley]

as an update to this thread: https://homerecording.com/bbs/showthread.php?t=145982 and to follow through on a promise here they are!!

Pic:

http://cc.usu.edu/~davbradshaw/imghost/badel84.jpg

short video (maybe better to view fram by frame)

http://cc.usu.edu/~davbradshaw/imghost/badel84.avi


During the process of shooting the video the grid resistor burned up!! (as an effect the plate started flowing RED hot instantly) So I couldn't get anything better.... No problem I have a few of the proper value of resistors lyring around... I need to finish my other modification anyway...


Modification update:

After replacing the master volume pot, everything is sounding great, and there is no more hum.... After increasing the vaule of the coupling cap in the cathode follower bass response is MUCH improved, after removing the A/B ducking transistors the footswitch has a much better response time, and finally after removing the caps across the plate load resistors I can get feedback!!!

I was a good mod - kind scary at times, but it turned out alright....
Waiting for more parts for further modifications... still need to put in the bright switches and replace the newly fried resistor. (since I'm only using 2 of the four sockets, I just swapped to the inner sockets)

 

[gusfinley]

A good many years ago I had an amp that had a shorting failure of one its power supply filter caps that was directly after the 5Y3 rectifier tube. The amp wasn't fused. I wasn't playing at the time so I didn't notice anything until I caught the odor of something real hot. By the time I got to it the plates of the tube were cherry red and the glass was softening from the heat and starting to suck in from the vacuum inside the tube. Would have made an interesting video, 'cept consumer video cams and computers weren't even invented yet . Fortunately nothing else melted down and replacement of the tube and the cap fixed it.

YES!! I am beginning to love tube amps for thier ease of deciphering schematics and ease of modifications, and repairs. I have two projects ahead were I will be building tube amps now....