Using a Digital Multimeter + Amp Startup Procedure - AT THE BENCH!
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- Опубліковано 5 лип 2024
- A Mojotone 45 kit build has been dropped off for me to do final checks and startup. In this clip I show you how I go about using the DMM to verify some basic voltage readings and adjust the bias.
Stay tuned for an Oscilloscope clip to follow with this amp.
0:00 Case study - Mojotone 45 kit
1:20 Bench setup
2:22 First Power up
3:54 Check Heaters
5:13 Check Bias Voltage
9:03 Out of Standby!
10:55 Measuring Plate Voltage
13:30 Screen Voltage
14:19 Phase Inverter Node
15:29 Preamp Node
16:35 Using a Bias probe
18:13 Adjusting the Bias
19:04 Rechecking the Voltages
20:23 Checking preamp socket pin voltages
21:49 Final thoughts
headfirstamplification.com
Outstanding Video! You have wonderful way of explaining the technical aspects of why and what you are doing, that even a novice like myself can follow and easily understand, Bravo!!!!!
Thanks!
Haha I just built a Mojotone build using Alex's pcb and was wanting to find a vid on first power up and this is the first vid that popped up. I should know just go to your channel by now
Perfect timing! I’m nearly finished my amp and this is gold! Thanks Jason!
thank you so much for making this video. i have just started on amps and could not find a good video explaining first start up and checks . i have just finished my jcm 800 build and i was not going to turn it on before finding a video on voltage checks and yours was perfect. you explained everything so someone new could understand. you also explained why you had to do these check. I would recommend this video to anyone new to amp building. i cant wait to see more of your videos. thank you again
Welcome aboard!
very helpful video!
i had a bad (new) EL34 and it red plated. i wasnt paying attention and didnt notice until i saw smoke coming off the glowing resistor on the tube socket. thankfully the resistor did its job and didnt ruin anything
Great video. Looking forward to part 2.
Thanks Jason. This is very helpful (as always).
Great video, thanks Jason.
Great video. Very helpful!
Great vid! One other safety recommendation I would add: remove any watches/bracelets/rings on the hand you are using the probe with. 🤘🏻
Agree with that tip!
Great Video! You don't recommend using a variac to wind up mains on startup? I know some guys do that. Also, can you show how you connect the bias current meter? I don't think that was shown.
I don't own one, never have. Just flick the switch mate! I show a still picture of the probe setup in the video at 16:58
I can see how the meter itself is setup but you just say it’s connected to the power tubes but doesn’t show how. Thats what i was asking about.
Ah ok, gotcha. Its one of these,
www.amazon.com.au/dp/B07CR5DN1V/ref=cm_sw_r_cp_awdb_imm_E9CBNWAVFNKP1YFT7FP0
You plug the probe socket in between the tube and the chassis socket
Probably better to use a 10ohm load resistor instead of 8. Impedance and resistance are not 1:1
They are not the same thing at all.