JMI Vox AC30 Repair Pt.7 - [Electrolytic Tetris]
Рет қаралды 475
Күн бұрынJMI Vox AC30 Playlist: • Vintage JMI Vox AC30
00:00 - Start
00:06 - 30uF ground connection
00:52 - Sporadic grounding
03:16 - Soldering the lead
05:11 - Quick way to test which tag is ground
06:07 - Closeup of work done
07:49 - Reviewing the remaining (known) work needed
09:44 - Removing the last of the old caps
12:33 - Cap game plan
14:40 - Mounting dilemma
17:43 - Prep and silicone
20:13 - Cleaning up and Top Boost
21:26 - Understanding the top boost install more
24:16 - Cleaning up the preamp ground
28:00 - Back to the electrolytics
29:03 - Cap ground connections
30:45 - Cap positive connections
36:03 - Recap
36:53 - It's quite late...
37:24 - Thank you to the few that watch
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@YeatzeeGuitar 10 ай бұрын
Oof, we're struggling to even hit 100 views now. Thinking this amp content might have run its course.
@lionscircle4700 10 ай бұрын
I'm getting allot out of this because there isnt allot of JMI vox amp content out there. I wouldnt be surprised if this playlist continues to get views as the algorithm directs more searches this way.
@christophersambuco9414 10 ай бұрын
I've been missing out because its been busy at work lately and I haven't been checking out any guitar related things. I've got to say that I'm very impressed with the attention to detail that you had going on the Vibrolux project from a few months ago.
@brandonferrar5398 10 ай бұрын
Love watching these videos. I have always wanted to understand amps more so I can start working on mine. Thank you for being so thorough!
@YeatzeeGuitar 10 ай бұрын
🙏🙏
@almightyguitarnerd 2 ай бұрын
I'm glad that the layout I created years ago was helpful to you. I enjoyed watching this, so thank you. I'm fairly sure I did the "treble" layout too...
@YeatzeeGuitar 2 ай бұрын
You're a legend, so helpful here! If you've got that treble version it'd be great to have handy, I can share a link in the description.
@almightyguitarnerd 2 ай бұрын
Cheers 😊 I'll message you on IG
@MichaelSmith-rn1qw 10 ай бұрын
Personally, for the negative ends of those 2 caps, I would have installed a terminal strip using that transformer bolt that you removed the terminal from. It would have made it look a lot neater than the double J-hook connection floating in the air. The positive ends look fine with the heat shrink applied. More of a cosmetic thing than anything, but your work was certainly better than what was there before. Enjoying this series. I found out about it from your post on the tdpri forum!
@YeatzeeGuitar 10 ай бұрын
Thanks! Yeah I opted not to do that because I wanted all of the preamp filtering grounds to be with the preamp ground found by V1. You're right it's not as pretty, but it's sold and because it's solid core wire it's not going anywhere without forcing it.
@MichaelSmith-rn1qw 10 ай бұрын
@@YeatzeeGuitar I didn't mean using that transformer bolt as a ground for the caps, but just used to anchor a terminal strip for the connections you made. It would also provide some stability for those 2 caps in the event the silicone ever broke loose.
@YeatzeeGuitar 10 ай бұрын
Ah sorry I misunderstood. Gotcha yeah not a bad idea.
@MichaelSmith-rn1qw 10 ай бұрын
@@YeatzeeGuitar As I suspect you are not done with the inside of the amp, it is something you could do in the future. About as daring as I have gotten with an amp is to add a bias adjustment pot to the bias trim pot to my '69 Bandmaster Reverb.
@matthewf1979 10 ай бұрын
I still don’t understand the reasoning behind grounding one half of the heater circuit in these amps. Manufacturers used to do that to save money on wire and assembly time by using the chassis as one side of the heater circuit. Vox has always used a twisted pair from what I can tell.
@YeatzeeGuitar 10 ай бұрын
No clue why! We'll see how bad the hum is when live and then if it's bad try before and after to see the change.
@goodun2974 10 ай бұрын
@@YeatzeeGuitar, As you do the other work, plan it out in such a way as to have easy access for installing twisted-pair heater wiring. Both my gut and my prior experiences tell me that you won't be happy with the noise level until you do rewire, plus you can put in a pair of balancing resistors on the heater supply, which will give you some additional fusing of sorts in case an output tube short circuits: the resistors will fry open and protect the transformer. The 2 part nature of the chassie and these amplifiers probably makes for a port ground plane with lots of ground loops anyway; isn't one half steel and the other half aluminum? Use of dissimilar metals is a recipe foreground loops.
@YeatzeeGuitar 10 ай бұрын
@@goodun2974 Yup top part here is aluminum, the bottom part is steel. I intend on adding 100ohm resistors for the heaters but I think I want to record before and after to see what the difference that it makes is.
@goodun2974 10 ай бұрын
@@YeatzeeGuitar, Assuming that you do end up adding a pair of balancing resistors to the heater supply, you could also take the DC voltage from the cathodes of the output tubes and feed it to the balancing resistors instead of connecting them to ground. This will elevate or "float" the preamp tube cathodes above ground and should greatly lower hum (and would also tend to prolong the life of any tube(s) used as a cathode follower; some Russian tubes are known for having a short lifespan when used as cathode followers).
@YeatzeeGuitar 10 ай бұрын
That's exactly what I intend on doing!
The Guitar Amp Tech
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