Debugging help: Brownface vibrolux edition

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matoni
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Debugging help: Brownface vibrolux edition

Post by matoni »

Hello guys,
I need some help debugging my latest build, which is a vintage brownface vibrolux. On the normal channel, when I plug something in, I get a loud humming noise. I think one of my tube sockets has something stuck in it, though, because the tube isn't sitting fully inside. I will grab another tube socket whenever I make my next order and let you guys know what the issue is there. My guess is it is most likely the socket.

Anyways, on the bright channel, if you turn up and down the volume knob (with or without anything plugged in) there is an increasingly loud buzz the more you turn up the volume. I have no idea what the problem is there. With the guitar plugged in, the channel works as normal, just it has this hum. Also, the "2" input isn't working on the bright channel. I believe I have it wired correctly, but when I plug something in, no guitar signal comes through.

When I DI into the effects return (which I added to this build), the hum goes away and it is quiet, and I can hear my guitar signal coming through the power tubes.

Let me know what you think the problem may be. I built my own PCB and designed my own chassis for this build (to make it a learning experience so my dad will keep funding these builds :) ), so it is possible that there is something wrong there, but I've been building PCBs for a few years now (for pedals), so I doubt that that's what the problem is, but I'm definitely no expert on this subject matter.

Let me know what you guys think the issue is. Thanks so much for taking the time to read this and for your willingness to help.

matoni
Stevem
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Re: Debugging help: Brownface vibrolux edition

Post by Stevem »

I think basically all your jacks are wired wrong.

I wound like you to post up some pictures, but with that said the jacks on your bright channel are not shorting closed like they should when nothing is plugged into them .

You can check this with your ohm meter by testing between the tip connection of the input jacks and the chassis.
With nothing plugged in you should read a short.
With a short taking place you will not have that gain hum when the volume is up with nothing plugged in.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
matoni
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Re: Debugging help: Brownface vibrolux edition

Post by matoni »

Here are some photos both of my (messy) build and the wiring of the input jacks. It is possible that I wired the jacks completely wrong. I will need to go back and check tomorrow.

Thanks for your help,
Matoni
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sluckey
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Re: Debugging help: Brownface vibrolux edition

Post by sluckey »

matoni wrote: Mon May 01, 2023 12:12 am It is possible that I wired the jacks completely wrong.
They are wired wrong. Look here...

https://el34world.com/Hoffman/files/CommonHookups.pdf
matoni
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Re: Debugging help: Brownface vibrolux edition

Post by matoni »

I just rewired the inputs, now its worse than it was earlier. There is no hum, rather, whenever i play a note, it buzzes really loudly. This is only when I hit a note super hard. When I hit a note softer, it will not play out. Nothing plays when I plug directly into the effects return, meaning that this could possibly be broken. I have no idea what happened, as all I did was change the wiring of the input jacks. Thanks so much for pointing this out, my jacks were wired backwards.

Let me know what you think could be the cause of this.
sluckey
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Re: Debugging help: Brownface vibrolux edition

Post by sluckey »

matoni wrote: Mon May 01, 2023 2:10 am Let me know what you think could be the cause of this.
More wiring errors.
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Re: Debugging help: Brownface vibrolux edition

Post by sluckey »

Took a quick look at your board. It seems that all four of those black bypass caps are installed backwards.
Cartman
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Re: Debugging help: Brownface vibrolux edition

Post by Cartman »

Looks like the fuse holder is not wired?

Edit: I see that the mains fuse is wired, sorry.
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pompeiisneaks
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Re: Debugging help: Brownface vibrolux edition

Post by pompeiisneaks »

sluckey wrote: Mon May 01, 2023 3:21 am Took a quick look at your board. It seems that all four of those black bypass caps are installed backwards.
This ^^

the dimple is the positive side, that's supposed to be connected to the tube side of the board, you've got the positive all connected to the ground.

~Phil
tUber Nerd!
matoni
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Re: Debugging help: Brownface vibrolux edition

Post by matoni »

pompeiisneaks wrote: Mon May 01, 2023 3:34 pm
sluckey wrote: Mon May 01, 2023 3:21 am Took a quick look at your board. It seems that all four of those black bypass caps are installed backwards.
This ^^

the dimple is the positive side, that's supposed to be connected to the tube side of the board, you've got the positive all connected to the ground.

~Phil
Thanks so much. I just switched all 4 of them and there is still the same problem, with there being no noise coming out of the amp unless i play a note very hard and then all that happens is that the note buzzes out.

did I mess something up in the flipping process? Is this characteristic of this?
sluckey
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Re: Debugging help: Brownface vibrolux edition

Post by sluckey »

matoni wrote: Mon May 01, 2023 7:20 pm Thanks so much. I just switched all 4 of them and there is still the same problem, with there being no noise coming out of the amp unless i play a note very hard and then all that happens is that the note buzzes out.

did I mess something up in the flipping process? Is this characteristic of this?
NO! You still have other building issues. Most likely wiring errors, messed up tube sockets, etc. With your track record so far, probably many more errors.
Stevem
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Re: Debugging help: Brownface vibrolux edition

Post by Stevem »

Where is that black wire that spans between the two preamp tubes going to and from pin wise on both of those sockets?

Also since you had your input jack wiring wrong you likely have the same thing taking place with your effects send and return jacks.


For now and just to get the amp up and running first I would remove that wiring to them and just bypass them.
Last edited by Stevem on Mon May 01, 2023 10:54 pm, edited 1 time in total.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!😊

Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
matoni
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Joined: Mon May 10, 2021 2:19 am
Location: northern VA

Re: Debugging help: Brownface vibrolux edition

Post by matoni »

Stevem wrote: Mon May 01, 2023 10:45 pm Where is that black wire that spans between the two preamp tubes going to and from pin wise on both of those sockets?
This is the cathode capacitor and resistor pair for the two preamp tubes. On the original fender schematic, it has them sharing one.
matoni
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Location: northern VA

Re: Debugging help: Brownface vibrolux edition

Post by matoni »

Hello All,

I have figured out that the amp is running hot, and I think this may be the cause of toe overdriven crackly problem. According to the Schematic, the C+ voltage should be at about 275vDC, but my C+ voltage is significantly higher, coming in at around 375vDC. This is signifigantly higher than it should be! How do I fix this? I traced the hotness of the voltage all the way back to the transformer secondaries, which are outputing 365VAC as opposed to 330VAC. This then makes the rectified voltage even higher, coming in at around 500vDC instead of 365vDC. DId i purchase the wrong type of rectifier tube, as I doubt that the voltage going into the choke should be that high. (I have a TAD GZ34 rectifier tube, which is what the layout calls for) The rectifier tube is getting extremely red and hot as well, so this may mean that it is being over worked. I'm not completely sure though, as I still am quite a novice amp builder. I will keep chugging away at trying to debug, you all need any more pictures or anything like that, I am happy to send it your way. Hope this information helped.

Matoni

*Edit: Changed VDC to VAC on the transformer secondaries.
Last edited by matoni on Tue May 02, 2023 7:34 pm, edited 1 time in total.
sluckey
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Re: Debugging help: Brownface vibrolux edition

Post by sluckey »

matoni wrote: Tue May 02, 2023 7:01 pm I traced the hotness of the voltage all the way back to the transformer secondaries, which are outputing 365VDC as opposed to 330VDC.
Transformer secondaries put out VAC, not VDC. You are using a wrong transformer.
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