i've just been troubleshooting my bass amp build and have been looking at the signal as it passes through on a scope while the amp is on a dummy load.
when there is some signal passing through output of the amp you can hear the signal. i was running a 1 khz signal most of the time, but i tried some other frequencies which also came through. at first i thought it must be the valve holder (one of the spring mounted ones to hold the valves in place) as there were 2 near the output transformer that didnt have a tube in them. i then got a bit frustrated with the amp and decided to test the power of another amp (5e3 styled) to make sure i am measuring the power right. to my surprise the frequency on the test signal was able to be heard again.
also the signal didnt seem to transfer to the signal going into the dummy load very well (seemed like an on off thing this time when viewing on the scope).
is this normal? could it be that the resistors i bought to make a dummy load have alot of inductance and the load at 1khz is much higher than the dc resistance causing a similar condition to having an open load? (6x 24ohm 50w resistors in parrallel for 4 ohms, in parrallel/series for 16 and half of them for 8ohms (150w only) here are the resistors. WELWYN|WH50 24R JI|RESISTOR, 50W 5% 24R | Farnell Australia
i was pretty happy to be able to get these resistors for a dummy load as they seemed more reasonable than most, but a dummy load needs to work correctly.
edit: i measured the resistance of the dummy load, and the the dummyload and lead connecting to it measured 9.3ohms when i was aiming for a 8ohm load, so its not a missed connection or similar.
when there is some signal passing through output of the amp you can hear the signal. i was running a 1 khz signal most of the time, but i tried some other frequencies which also came through. at first i thought it must be the valve holder (one of the spring mounted ones to hold the valves in place) as there were 2 near the output transformer that didnt have a tube in them. i then got a bit frustrated with the amp and decided to test the power of another amp (5e3 styled) to make sure i am measuring the power right. to my surprise the frequency on the test signal was able to be heard again.
also the signal didnt seem to transfer to the signal going into the dummy load very well (seemed like an on off thing this time when viewing on the scope).
is this normal? could it be that the resistors i bought to make a dummy load have alot of inductance and the load at 1khz is much higher than the dc resistance causing a similar condition to having an open load? (6x 24ohm 50w resistors in parrallel for 4 ohms, in parrallel/series for 16 and half of them for 8ohms (150w only) here are the resistors. WELWYN|WH50 24R JI|RESISTOR, 50W 5% 24R | Farnell Australia
i was pretty happy to be able to get these resistors for a dummy load as they seemed more reasonable than most, but a dummy load needs to work correctly.
edit: i measured the resistance of the dummy load, and the the dummyload and lead connecting to it measured 9.3ohms when i was aiming for a 8ohm load, so its not a missed connection or similar.
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