Hughes and Kettner Switch Blade 100 guitar head

[bsco]

Good Morning everybody....I have in my possession a H&K switchblade 100 guitar head that has the very unusual problem of producing a loud feedback type squeal after it has been on for awhile. This squeal can be turned up and down with the master volume control.All other controls are turned completely down. Took out the boards and soldered up some bad connections.....soldered all the connections to the tubes and it takes pretty much all bloody day for the problem to occur.....Has anybody here on the forum had any experience with this unit and possibly with this type of weird problem...any help and suggestions greatly appreciated......
Cheers,
Bernie

[mozwell]

i hope this helps

[bsco]

Hey Mozwell!!!!! Thanks a bunch!!
Cheers,
Bernie

[bsco]

Hi Mozell..Getting back at that Switch Blade 100....Looking over the schematic...there is a Pre-Tube Send and a pre-tube return...among other sends and returns for external effects...Is this pre-tube send and return going to external jacks?? Can't seem to find any indication of that...maybe I am not looking in the right place...Advice??
Cheers,
Bernie

[mozwell]

not overly familiar with these
send_pre_tube, sheet 2 location D7
return_pre_tube, sheet 2 location B1
both go to sheet 4, header W1 location C1
follow the signals from W1, they end up at Q2 and the cathode resistor of T1B

hope this helps

[bsco]

Hi Mozwell...Thanks for the reply...I seen that on the schematic....I couldn't see what was between the pre-tube send and return.. I will take a closer look this week....
Thanks,
Bernie