Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Tube DIY Asylum ]

---

[ Alert Moderator ]

---

Transfomer Testing?

Posted by jk (A) on November 28, 2016 at 11:41:54

Hi all, Wondering if I could bounce something off you.

Background: VTL MB150 amp, intermittent distortion

Progress: Found someone had replaced high voltage fuse holder's spring with non stock spring, which over the years has corroded extensively. Replaced fuse and bias current restored.

At the request of Mr Manely (VTL) I replaced a few sand resistors with proper wire would resistors of same value.

Finding: Distortion noise gone but now just a hum. No music until I power off, then when I listen closely music comes through speaker as capacitors discharge.

Well as you can imagine I am hunting high and low for the cause of this issue. I did come across this burned transformer, as seen in the photo. Wow, the new WW resistor fits awfully nicely into the burn mark.

The truth is I think I have proof that the burn was there before. Gosh the high resistance fuse connection couldn't have caused the resistor to heat up right?

Well since I've looked everywhere else, I bought 2 of these transformer (thank God they are still available). Unfortunately the soldering job is HUGE to get access to the pins.

Today I had a thought. If the transformer was damaged by heat, it would affect conductivity right? I measured resistance pin by pin, and compared it with the brand new transformer. All matches perfectly.

Is this in your opinion enough for me to say the transformer is good and look elsewhere?

If not, has anyone ever disassembled a VTL amp? This is worse than a rubics cube.

Well I can't wait to get back to tube amps, but I've got to sort this one out first. Thank you for any input you can provide. I sure do appreciate it.

John

This post is made possible by the generous support of people like you and our sponsors:

Signature Sound

[ Signature Sound Lounge ]

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---