just came across a Knight KP-40 32 watt amp that was assembled as a kit...tubes are 4 ea 7189,,,5 ea 12ax7,,,1 7025 and 1 GZ34 all MULLARD from the 50's...I think the tubes alone were a score...The amp plays fine but for a mystery HUM my other Knight a KG 250 is dead quite.Oh yea i also have an ST-120 and a SP 9 Preamp you know ware them tubes are going..That being saidi love those little Knight amps..can anyone help me figure the mystrey of the hum...
2 posters
Tube amp hummmmmm
rfbro- Posts : 27
Join date : 2014-12-28
Age : 69
Location : Vancouver WA
peterh- Posts : 1869
Join date : 2012-12-25
Location : gothenburg, sweden
rfbro wrote:just came across a Knight KP-40 32 watt amp that was assembled as a kit...tubes are 4 ea 7189,,,5 ea 12ax7,,,1 7025 and 1 GZ34 all MULLARD from the 50's...I think the tubes alone were a score...The amp plays fine but for a mystery HUM my other Knight a KG 250 is dead quite.Oh yea i also have an ST-120 and a SP 9 Preamp you know ware them tubes are going..That being saidi love those little Knight amps..can anyone help me figure the mystrey of the hum...
120hz hum ( in US , 100 in europe) means bad electrolytic caps.
60hz hum could be tubes ending their life and AC from filaments flods across cathode ends
Similar topics
» Another problem with my ST-70 build.......Rectifier tube flashed and now dead Right Rear Tube......any ideas?
» Bent / Splayed Power Tube Pins KT88 - Octal Tube Pin Straightener
» Glass piece inside output tube and tube placement
» Tube store tube number
» VTA 120 output tube red plated -- what do you check if you're using the AB board?
» Bent / Splayed Power Tube Pins KT88 - Octal Tube Pin Straightener
» Glass piece inside output tube and tube placement
» Tube store tube number
» VTA 120 output tube red plated -- what do you check if you're using the AB board?