Express in single ended format?

[geoffrod]

I'm assuming you followed the Jones Derailment schematic? No way you should have high voltage on pin 5 of the 6v6,or is that a typo? Check your wiring.

A bad ground at the cathode will give you a high cathode voltage.

You should have different voltages at pin 1 & 6 because the cathode resistors are different values. You'll even get a 10 volt or so different reading if they both had the same value cathode resistors. This is due to tube manufacturing tolerances .

Here's another clip of what it will sound like after you fix it

crap i hope it is a typo
how the hell didn't i take notice of that unbelievable

i will check that out when i get home

the schematic is more like the SExpress in this thread before the derailment ones, barring a couple of differences, pot sizes are different in the tone stack i have 1M for treb, bass and volume, and 25k for mid.
at the moment i dont have a presence pot in there so r24 is gong straight to ground.
it is cathode biased.i did have a 47uf in there but changed it for a 1000uf.

that clip sound good bigbeck

i will see what i come up with when i get home this arvo.

thanks for responding

cheers
Geoff

[geoffrod]

I'm assuming you followed the Jones Derailment schematic? No way you should have high voltage on pin 5 of the 6v6,or is that a typo? Check your wiring.

A bad ground at the cathode will give you a high cathode voltage.

You should have different voltages at pin 1 & 6 because the cathode resistors are different values. You'll even get a 10 volt or so different reading if they both had the same value cathode resistors. This is due to tube manufacturing tolerances .

Here's another clip of what it will sound like after you fix it

crap i hope it is a typo
how the hell didn't i take notice of that unbelievable

i will check that out when i get home

the schematic is more like the SExpress in this thread before the derailment ones, barring a couple of differences, pot sizes are different in the tone stack i have 1M for treb, bass and volume, and 25k for mid.
at the moment i dont have a presence pot in there so r24 is gong straight to ground.
it is cathode biased.i did have a 47uf in there but changed it for a 1000uf.

that clip sound good bigbeck

i will see what i come up with when i get home this arvo.

thanks for responding

cheers
Geoff

ok it was a typo, most definitely, should have read pin 6 not 5.

i have found issues with the wire running from the wiper of the volume to pin2 on V1a, i changed it too shielded wire.
Also i have found issues with the bright switch, if i touch the caps on it i get lots of wierd noises.
any how i have changed a few wires and now i have a microphonic chassis again, and it is now picking up my phone recieving signal as well as the local radio station, bit late here so i couldn't dig in on the guitar, but clean sounds bright and clear.
i still have that high cathode voltage of 56V, i have reflowed all the joints accociated with the cathode but still remains the same.

it will have to wait till wednesday arvo now, got band practice tomorrow night.

[bigbeck]

Geoff, Have you heard a clip of that SExpress? It looks to me like it wouldn't sound too wreckish. Maybe you'll get flubby bass with that .02 coupling after the second stage? Only one way to find out.

That clip I posted was my 15 year old playing guitar .I'm on drums. It was recorded on a little Zoom portable recorder sitting in the middle of the room.

[bigbeck]

duplicate

[geoffrod]

Geoff, Have you heard a clip of that SExpress? It looks to me like it wouldn't sound too wreckish. Maybe you'll get flubby bass with that .02 coupling after the second stage? Only one way to find out.

That clip I posted was my 15 year old playing guitar .I'm on drums. It was recorded on a little Zoom portable recorder sitting in the middle of the room.

hey bigbeck,
no i haven't heard it before, so yep time will tell,
thats why i put the 1000uf cathode cap in to maybe tighten up any flabbyness.

that cap should be .002

hey thats cool.
playing with your son great stuff,
he plays nice slide

those zooms are great aren't they
our bass player got one and recorded our practice one night, it was supprisingly good quality for playing in a big tin shed

[bigbeck]

those zooms are great aren't they
our bass player got one and recorded our practice one night, it was supprisingly good quality for playing in a big tin shed

Yes,I was very impressed by the high quality. Mine is the cheap H2 model. I converted that clip to an mp3 before I posted it and it lost a lot of detail.Or maybe it's my 30.00 computer speakers. It sounds much much better on my home stereo. The recording quality even beats the pants of remastered CD's. Although I guess that's not saying much.

Did you get the 6V6 voltages sorted?

[geoffrod]

those zooms are great aren't they
our bass player got one and recorded our practice one night, it was supprisingly good quality for playing in a big tin shed

Yes,I was very impressed by the high quality. Mine is the cheap H2 model. I converted that clip to an mp3 before I posted it and it lost a lot of detail.Or maybe it's my 30.00 computer speakers. It sounds much much better on my home stereo. The recording quality even beats the pants of remastered CD's. Although I guess that's not saying much.

Did you get the 6V6 voltages sorted?

our bass player has the zoom h4n,
nice bit of gear i reakon, i told him to tell his wife the band thanks her very much for kyles birthday present!!! lol

the clip still sounded good without the detail, a bit jon butler trioish
i like it.

as for the voltages, no nothing is sorted yet, i must have some bad solder joints, because when i probe the high voltage pins on the tubes i get big cracks then silents, and if i then probe the cathode on the 6v6 you can see the voltage rise from about 19volts back up to 57v, as it rises you hear the buzzing noise coming back.
i think i will de-solder and re-solder all the connections on the power tube as well.

quick question,- the buzz bar on the pots, it isn't suppose to be connected anywhere other than the back of the pots? is it??

my lead dress is terrible at the moment,but i wanted to address the voltage issues first then tackle the noise.

cheers
Geoff

[geoffrod]

The B+ voltages are 365 - 360 - 350 - 322 - 320. The dropping resistor on the first filter node is 100R 2 watt. That's pretty much the only changes I made.

in my power supply i more or less coppied the trainwreck express,

i have a dropping resistor of 150 ohm before the B+ node, then it goes to the series of 3 10k resistors.

i have a 470ohm cathode resistor as well.

on the derailment it doesn't have the dropping resistor before B+

are these values going to make any difference other than lowering the voltages

cheers
Geoff

EDIT:
also my heater voltage is at 57v dc and 7v ac

[bigbeck]

Well,you don't need a buss bar soldered to the back of your pots. But if you have one and you're soldering the ground wires from components on it then it has to be connected to chassis ground. Don't rely on continuity between the pot and chassis. That's just looking for trouble.

The preamp B+ on an Express goes something like 300V - 285V - 275V. Not that you need to change it-yet. Just so you know, high preamp voltages tend to make the amp sound cleaner. You may need it as you have 4 gain stages.

The power tube B+ is ok.

[geoffrod]

Well,you don't need a buss bar soldered to the back of your pots. But if you have one and you're soldering the ground wires from components on it then it has to be connected to chassis ground. Don't rely on continuity between the pot and chassis. That's just looking for trouble.

The preamp B+ on an Express goes something like 300V - 285V - 275V. Not that you need to change it-yet. Just so you know, high preamp voltages tend to make the amp sound cleaner. You may need it as you have 4 gain stages.

The power tube B+ is ok.

well yeah i was relying on the pots to be grounded to the chassis, so i guess i will add a grounding wire to the bussbar.
so i may need to tweak those 10k resistors down a bit.

i was measuring some dc voltage on the "other " side of the coupling cap after the 4th gain stage going to the power tube, i was measuring 1.5v up to 2.5v, i changed the cap out and it is now down to like .5v, i thought there would be no dc voltage on that side of the cap???

[KellyBass]

Geoff, I'm glad to hear your amp is coming along! I've got a few of those pot grounding lugs if you need them. I guess I could send them to Australia... Let me know, I'll be happy to try.

My PT is arriving from edcor today or tomorrow...so I will be (finally) firing my SE express up very soon. I'm going to try and give fixed bias a shot based on dartanion's results and recommendations.

[Zippy]

well yeah i was relying on the pots to be grounded to the chassis, so i guess i will add a grounding wire to the bussbar.

Have you measured the resistance from the pots to ground? If you choose not to have a grounding wire, it is a good practice to verify ground rather than assume.

[geoffrod]

Geoff, I'm glad to hear your amp is coming along! I've got a few of those pot grounding lugs if you need them. I guess I could send them to Australia... Let me know, I'll be happy to try.

My PT is arriving from edcor today or tomorrow...so I will be (finally) firing my SE express up very soon. I'm going to try and give fixed bias a shot based on dartanion's results and recommendations.

i reflowed the solder joints on the back of the pots and added a ground wire to the buss bar, its all good now, but i thanksyou very much for the offer of the solder lugs.

still having a few issues with the power valve cathode voltage, still at 57v

[Firestorm]

57 volts across a 470R implies 120mA of current (!!!) and at least a 7W resistor not to burn up. Could your cathode resistor be a 4K7 by mistake?

[bigbeck]

I was thinking the same thing. A 4K7 or a bad cathode ground or a bad resistor. How about a bad tube?

Also,if the amp does not have an MV, the grid leak resistor could have a shaky ground.

I once removed an MV from a build and forgot to put a grid leak in When I fired it up, the cathode voltage started at 18V and went all the way up to 60V. It rose by about 1 volt per second. The resistor started smoking. A poor ground could mimic this.

edit: Do you have one end of R25 going to ground? I know the schemo shows one end as bias - but that's wrong. Is that why there's 300V on pin 5?