High plate voltages and screen voltages in my Express.

[M Fowler]

Yes it looks like 47R yellow violet black

[beasleybodyshop]

Yes it looks like 47R yellow violet black

I pulled it out and measured it - 466 ohms. I know, photos can be deceiving.

Well, good news is I cleaned my dress up, and now when I plug it in it sounds like an amp! i switched around the OT wires to the power tubes - did the trick

Now my issue is noise - this amp seems to have a lot more hiss with the volume turned down than I expected. Attached are my latest "as build" photos. Can anyone see anything that sticks out that could be causing the high amount of hum? Frequency of the hum appears to be an A note, especially the low A of the Low E string on my guitar - so that would make it approx 110hz? Any clues on the culprit for this?

[M Fowler]

Trainwreck Express and Liverpool have a lot of hiss nature of the gain structure.

Trainwreck grounding is not very good. All the pots are grounded to chassis and then have a buss bar soldered on back. In addition, the input jack is grounded to the chassis. All this makes a ground loop I think.

Could try isolate input jack from chassis and run a ground wire from the input jack to that first cathode resistor/cap ground.

[beasleybodyshop]

Trainwreck Express and Liverpool have a lot of hiss nature of the gain structure.

Trainwreck grounding is not very good. All the pots are grounded to chassis and then have a buss bar soldered on back. In addition, the input jack is grounded to the chassis. All this makes a ground loop I think.

Could try isolate input jack from chassis and run a ground wire from the input jack to that first cathode resistor/cap ground.

Isolating the input jack did bring a little of the hum down. Any other thoughts? I tried swapping in and out several known good preamp tubes and im not getting any appreciable hum difference.

[geetarpicker]

Though my original Trainwreck amps do hiss, when compared to a vintage Marshall they actually have a better signal to noise ratio when set to similar gain. That said you should have very little hum at all, and I'd say my old Marshalls (even with fresh power supply caps) actually hum more than my TWs.

[beasleybodyshop]

Though my original Trainwreck amps do hiss, when compared to a vintage Marshall they actually have a better signal to noise ratio when set to similar gain. That said you should have very little hum at all.

I really think my level of hiss is too high. And it's definitely hiss, not hum. I should have clarified that earlier.

[Bob S]

First - I'm the last person you should listen to about the Express.
I re-wired mine 3 times. Got worse every time.
So with that in mind, here's what I learned the hard way.
Chopsticking around V1 wiring / the Bright switch might tell you where it is coming from.
Pull V1 to see if you still get hum / hiss.
V1 in an Express has to be a very special tube...
If that doesn't help, try disconnecting the presence wire.
It runs all across the farm & sometimes gives probs.
If that helps, either re-route or I've even used screened wire.

[beasleybodyshop]

First - I'm the last person you should listen to about the Express.
I re-wired mine 3 times. Got worse every time.
So with that in mind, here's what I learned the hard way.
Chopsticking around V1 wiring / the Bright switch might tell you where it is coming from.
Pull V1 to see if you still get hum / hiss.
V1 in an Express has to be a very special tube...
If that doesn't help, try disconnecting the presence wire.
It runs all across the farm & sometimes gives probs.
If that helps, either re-route or I've even used screened wire.

I disconnected the NFB from the impedance switch. No difference.

Pulling V1 does remove the hissing. I have a tung sol ECC803S gold plated pins tube in V1 that I had purchased/tested for low noise/ micro phonics.

and wow, the volume comes on super early! this is one loud amp. lol.

[sepulchre]

. . . wow, the volume comes on super early! this is one loud amp. lol.

Now that sounds like a TW! I could barely crack mine open and it was too much for in the house (unless my wife was out ).

[beasleybodyshop]

. . . wow, the volume comes on super early! this is one loud amp. lol.

Now that sounds like a TW! I could barely crack mine open and it was too much for in the house (unless my wife was out ).

Yeeah buddy! Im going to install a PPIMV in this one instead of the VVR - it was causing too many problems. Going to rewire my controls and brite switch lead dress, and get back with yall.

[geetarpicker]

The quickness the volume responds on these amps is greatly dependent on potentiometer taper. Sadly most audio taper pots available these days ramp up much more quickly than the ones Ken used back in the day. For example on my '85 Express using a Strat the amp is still almost clean when on 1/2, and there is a ton more gain to be had when going from 1/2 to full up. With most new audio taper pots an Express will come on very quickly and after 1/2 there isn't much more left. Point is most clones come on much more quickly than original TWs and are trickier to dial in lower gain settings.

[redshark]

Glen do you have any idea what are the original pots used in trainwrecks? CTS? Alpha? what taper? 30%?

Thanks!!

[M Fowler]

Weren't the pots Clarostat brand?

[sepulchre]

Mine didn't get dirty right away, it was just Loud!

And I'd really be interested in what taper Ken used too.

[Mark]

If you want the amp to stay cleaner longer then you are looking for a 10% taper pot. A 30% taper pot will ensure instant distortion.

The CTS pots generally have 10% taper or less, the Alphas are around 15% taper, these are good for tone controls but not ideal for a Trainwreck volume control.

I've used sealed Clarostat pots in my Rocket, they have a 10% taper but these are not the same as the ones used by Ken Fischer.

Another option is to install the fast/slow switch from the Komet amp.