trinityamps.com

Trinity Amps Guitar Amp Forum
It is currently Tue Sep 29, 2020 9:31 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 5 posts ] 
Author Message
 Post subject: bypass vrm
PostPosted: Mon Jan 04, 2016 4:43 pm 
Offline
Friend
Friend

Joined: Sat Feb 23, 2008 6:20 pm
Posts: 19
Location: Nashville TN
hi all,
i built my trinity amp in 2008/09 or somewhere around then and haven't really messed around inside it since (and have forgotten pretty much all the things). i've got a plexi voiced v6 with the boost switch and VRM module. i played it for years with the VRM turned down to about 50% and had no issues. this year i moved out to the country and my neighbors aren't 5 feet away from my house, so i have been turning the vrm up to full blast. a few days ago, i was trying to play quietly and noticed and awful random humming/hissing, but it only happens if the vrm is turned down anything below 100%. it sounds similar to a guitar cable that has a ground issue, so with that in mind, i immediately changed guitar cables. the issue persisted. i changed guitars and the issue persisted. i even changed the cable from the amp head to the speaker box and the issue persisted. at this point, i don't know if it's an issue with the vrm specifically or a component inside it (maybe the mosfet?). i'd like to temporarily or maybe even permanently bypass the vrm. i opened up the amp to look and can't find my vrm manual to tell me how exactly it's hooked up. from looking at where the wires go........

green from the vrm pot goes to the standby switch
green from the vrm board goes to chassis ground
red from the vrm board goes to B+ on the filter cap

i don't remember if any resistors had to be changed when i installed this. it seems that just from looking, i should be able to just remove the green from the standby switch and the red from the B+ and then connect the green from the standby switch to the B+.


does this sound accurate?


i've attached 3 pictures. one shows the vrm board and pot on the back of the amp. the pot is in the 2nd output hole. in that pic, the green wire coming off the pot goes all the way around to the standby switch (you can see it in the other pic). the green and red that are "braided" together go toward the B+ with the red connected to the B+ and the green connected to that ground bolt for the chassis.


Attachments:
IMG_20160104_143847.jpg
IMG_20160104_143847.jpg [ 232.51 KiB | Viewed 5224 times ]
IMG_20160104_143922.jpg
IMG_20160104_143922.jpg [ 205.62 KiB | Viewed 5224 times ]
IMG_20160104_143936.jpg
IMG_20160104_143936.jpg [ 272.7 KiB | Viewed 5223 times ]

_________________
---
stephen
-----------
If you need to find me, just go to the end of the longest line.
Top
 Profile  
 
 Post subject: Re: bypass vrm
PostPosted: Mon Jan 04, 2016 5:57 pm 
Offline
Friend
Friend

Joined: Sat Feb 23, 2008 6:20 pm
Posts: 19
Location: Nashville TN
didn't wait for advice.. went ahead and did it anyway. nothing blew up and i didn't get shocked. =D

the amp is much less noisy now and that sound has completely gone away. even when the vrm was turned all the way up, there was a weird crackling that you could hear if you had a guitar turned up but weren't playing...sounded kinda like a tube arcing.

_________________
---
stephen
-----------
If you need to find me, just go to the end of the longest line.


Top
 Profile  
 
 Post subject: Re: bypass vrm
PostPosted: Tue Jul 19, 2016 10:08 am 
Offline
Holy Ghost
Holy Ghost
User avatar

Joined: Sun Mar 13, 2005 4:10 pm
Posts: 7430
Location: Brighton, Canada
not sure why it was making noise. but was most likely a soldering joint in the VRM somewhere. you could touch them up and see. could also be the control pot. having said that, haven't seen this behaviour in any we did.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps


Top
 Profile  
 
 Post subject: Re: bypass vrm
PostPosted: Sat Oct 20, 2018 12:37 am 
Offline
Friend
Friend

Joined: Sat Feb 23, 2008 6:20 pm
Posts: 19
Location: Nashville TN
So the noise came back even with the vrm out of the circuit. I 100% have it nailed down to something in the normal channel (tone and vol). Even with no guitar plugged into that side and the volume all the way down on the tmb channel, I get a crackling sound when I turn the normal channel up. I experimented with different volume settings on both channels. It always comes back to the normal channel. The amp is silent if normal has the volume all the way down even with the tmb channel's gain and vol set to 11. I recorded a video of the sound. I took the amp out of the head can and tapped around inside the amp with a chopstick to see if I could affect the sound. Nothing. I didn't find anything loose. I'm not sure what else to check.

_________________
---
stephen
-----------
If you need to find me, just go to the end of the longest line.


Top
 Profile  
 
 Post subject: Re: bypass vrm
PostPosted: Sat Oct 20, 2018 12:57 pm 
Offline
Friend
Friend

Joined: Sat Feb 23, 2008 6:20 pm
Posts: 19
Location: Nashville TN
i think it's a tube issue. i swapped around the preamp tubes to see if i could figure out which one it was. swapping v1 with v3 and the noise stopped.

for reference, here's the tubes i'm using starting at v1

12at7 mesa
12ax7 electro harmonix
12at7 mesa
el84 eh
el84 eh
6v6 jj
6v6 jj
6ca4 eh

_________________
---
stephen
-----------
If you need to find me, just go to the end of the longest line.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 5 posts ] 

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group