Tonic Trainwreck Express Clone hum issue

[Bryan Cox]

Hey all,

Been lurking in the forum for a few years but haven't posted much. Always wanted to build an Express and Liverpool but the military had different ideas about what to do with my free time. I spotted an Express clone on Reverb and scooped it up as a retirement gift for myself.

I've read many forums and watched videos so I know what I expected in the tone and this NAILS it. To be fair, I've never played a real Wreck and don't expect to, but I'm hearing all the things in this amp that I've read about and I like it. That's all that matters to me. However, I have an issue and I need a little help.

The amp is dead silent in standby but has a nasty hum out of standby. The hum volume increases as the volume is turned up so I haven't been able to get the amp up to war volume. I bought this used online from the Chicago Music Exchange. It originally belonged to some LA guitarist. I heard several clips of it and the hum was not there so I suspect it is not a design issue. Here's what I know:

1. The amp was originally built with NOS Siemens EL34 and Amperex/Philips 12AX7. The store I bought it from yanked the NOS glass and put in JJ KT77, a Sovtek 12AX7 and two JJ 12AX7.

2. I tried every preamp tube in V1 with no noticeable change.

3. The amp hums badly beginning at 9 o'clock on the volume and just increases.

4. It does not hum with the standby in the off position.

5. The hum does not change with instrument cable plugged or unplugged, guitar swaps, room/outlet changes, and only varies in tone when I manipulate the EQ.

I purchased some NOS Siemens EL34 and Amperex/Philips 12AX7 to see if that solves the issue. If not, I wanted NOS glass anyway. I have a few basic tools here with me but the rest has been packed and sent to my new home ahead of me. I may be able to get gut shots if you need. See video link below.

I retire from the military next Friday and am moving back to Missouri so I can't do any real in depth probing for awhile. Just thought I'd see what you guys think so I can form a plan. Thanks!

https://youtu.be/MKK0N0Hg73c

Bryan

[xtian]

Hi, Bryan, welcome. Do you have experience working with HIGH VOLTAGE circuits? These can kill you.

There are three preamp tubes in your Express, and the one closest to the power tubes is the PI (phase inverter). Remove the PI tube and power up--is there still hum? This will give us a helpful clue. (The Volume control will make no change in hum when the PI is removed).

[Colossal]

The gentleman that built that amp is named Darin Ellingson and was a regular frequenter of this site back when Trainwreck amps were really happening. You might try PM'ing him. Do you have any service records or history? If the amp has never been serviced, it is likely needing (at least) the electrolytic capacitors in the power supply replaced. Likely, one or more is starting to fail. And/or, it could have a power tube starting to go. I believe that amp has an Express preamp, a pseudo-PI driver stage, and dual single-ended output section. Loud and proud.

EDIT: The Tonic Absinthe is dual single-ended, not the Vapour. The Vapour is push-pull.

[Bryan Cox]

Hi, Bryan, welcome. Do you have experience working with HIGH VOLTAGE circuits? These can kill you.

There are three preamp tubes in your Express, and the one closest to the power tubes is the PI (phase inverter). Remove the PI tube and power up--is there still hum? This will give us a helpful clue. (The Volume control will make no change in hum when the PI is removed).

Thank you for the reply. I do have experience working with high voltage circuits. I will try your suggestion and let you know what I find.

[Bryan Cox]

The gentleman that built that amp is named Darin Ellingson and was a regular frequenter of this site back when Trainwreck amps were really happening. You might try PM'ing him. Do you have any service records or history? If the amp has never been serviced, it is likely needing (at least) the electrolytic capacitors in the power supply replaced. Likely, one or more is starting to fail. And/or, it could have a power tube starting to go. I believe that amp has an Express preamp, a pseudo-PI driver stage, and dual single-ended output section. Loud and proud.

Colossal,

I've been writing Darin pretty frequently for the last two weeks or so. Nice guy! I have no records on the amp. Darin said it changed hands many times so I'm sure those are lost.

Loud and proud is right! Haha! I'm hoping once I get it in top shape I can get those nice drive tones. So far I love it but I've heard no clean to mean yet.

I sent the same info to Darin that I posted here; burning the candle at both ends. I've yet to hear from him but he's usually pretty responsive. Thanks for the reply!

Bryan

[Bryan Cox]

Hi, Bryan, welcome. Do you have experience working with HIGH VOLTAGE circuits? These can kill you.

There are three preamp tubes in your Express, and the one closest to the power tubes is the PI (phase inverter). Remove the PI tube and power up--is there still hum? This will give us a helpful clue. (The Volume control will make no change in hum when the PI is removed).

Thank you for the reply. I do have experience working with high voltage circuits. I will try your suggestion and let you know what I find.

I removed the PI 12AX7 and the hum wasn't near as loud as before. There was still a low hum but it sounded like the hum from fluorescent lights.

[Bryan Cox]

I heard back from Darin. He's thinking possibly filter caps (like Colossal) and/or tubes. There's a bias knob right behind the power tubes, near the PT. Darin suggested I manipulate that a little to see if it has any effect, and it did! When I biased it colder the hum got noticeably quieter. Not quiet enough to want to play, but it was substantial. When I set the bias at the suggested (sharpie) mark, the hum was at its loudest. When I biased it hotter the hum's volume did not increase further.

I leave Minot ND next week Friday following my retirement. Once I get to my house I'll throw the NOS tubes in and see if that makes a difference. Alao, Darin offered to repair it for me. So I'll probably send it off to him regardless.

[M Fowler]

If your still in North Dakota stop and see me, I will fix your amp.

Mark

[Bryan Cox]

If your still in North Dakota stop and see me, I will fix your amp.

Mark

Oh, man! I wish I'd posted this stuff sooner. I'd have taken a weekend to come down to Walcott. At this point though, I won't be able to squeeze it in. It's about a 5 hour drive and the AF has me busy as hell up until I leave.

But that's an amazing gesture I didn't expect. Thank you!

[M Fowler]

Happy to help. Minot AF not the end of the world but you can see it from there! Chuck Yeager quote.

Take care enjoy being a civilian again.

Mark

[Bryan Cox]

I have a question that I expect is a bit subjective. But if I'm lucky, I'll get some good info.

When I got my amp it had all Sovtek tubes in it. It hummed like a MFer but all the tone (typically expected from an Express) was there. Aside from the hum, it was breaktaking.

It bought some NOS Siemens EL-34s and Amperex 12AX7s. Those greatly reduced the hum but all that harmonic content is reduced. It still sounds great but it's more boxy, and the crystal highs and harmonics are not as present. To my ears it sounds like a slightly more touch-sensitive Marshall.

Could this be because the new tubes aren't yet broken in? I only have an hour or two on them so that could be the case. I still have to send it off to Darin to have the caps replaced so I'm holding my judgement. All opinions welcome.

[gktamps]

First, did replacing the power tubes cut the hum, or was it the preamp tubes?
Did you re-bias the output tubes?
NOS tubes aren't all good or have consistent gain or performance, and so new tubes can sound better.
I have many TW style amps with a wide range of new or old tubes, whatever sounds best.
Roll 'em and see what the amp sounds best with, but only after biasing the amp.

[Bryan Cox]

I don't know if it was the power or preamp tubes that cut the hum. I'll have to roll between them to be sure.

I did not bias the amp after swapping tubes. I know that's a must, but I didn't want to mess with it since it's going back for maintenance.

Thanks for the info!