Couple questions about undocumented express...

[redshark]

I've been checking the pics of both Francesca and the "undocumented express". I don't know if this has been commented before but...

Undocumented express has the heater wires in correct phase, Francesca has inverted phase V1 to V2 and then invert the heaters again from V4 to V5....why is that? any special mojo there?

In the Undocumented express there's a resistor in pin 2? the white wire that goes to the volume control, Francesca don't have one and neither mine...that seems to be like a grid stopper resistor...what value? and why is it used? wouldn't it be more convenient on pin 7 coming from the input jack?

I see Francesca's bright switch is wired diferent than the undocumented express...which one is brighter?

thanks for the answers!! just curious

[Cliff Schecht]

I'm curious as to why the undocumented Express is missing a name too. Are we sure it isn't a clone (albeit a good one)?

[hairyandy]

I'm curious as to why the undocumented Express is missing a name too. Are we sure it isn't a clone (albeit a good one)?

I'm absolutely, 100% positive it is not a clone. I took the pictures, I know the guy who still owns it and I know for a fact it is not a clone, it is a real TW...

Andy

[Noel Grassy]

This may have been among the later amps Dave Funk was assembling for Kenny.

redshark, There's a pretty long thread going back a year or so re:
the bright switch wiring. It was determined IIRC that this method
(the undocumented) had a much better ability to keep spurious
noise out of the signal.
OTOH I don't remember any threads discussing that resistor you
mentioned. Good eye lad.

NG.

[funkmeblue]

isn't her name reject?

[paulster]

That's the one. 'Reject' from 1990.

[redshark]

Ok it was a reject, then what? is that resistor a way to make it work? why was it a reject to begin with?
then...if Francesca's wiring of the bright switch was noticeably putting more noise in the signal..was that double change in phase wiring the heaters a way to decrease the noise?

I would like the more experienced builders to write about this..this "little details" explained is one of the reasons to come to this forum...to learn!

[paulster]

Ken probably made no attempt to maintain any phase relationship on the heaters in the preamps because it makes no appreciable difference. You've got dual triodes in each of the three preamp tubes so each pair of triodes is humbucking to a certain degree anyway, and the spiral wound filaments are also quiet in isolation.

As regards the bright switch, it seems that nearly every Express and Liverpool encountered (and there have been quite a number that have been studied but not photographed for public consumption) has been wired the 'proper' way and Francesca was the exception to the rule.

It may have been that Francesca was just a mistake one day, or that Ken later realised that there was less noise when the bright switch was wired the other way.

I can't remember the whole story on Reject at the moment. I'll try to dig it out, unless Andy can remember and describe it in the meantime. There have been a couple of amps with grid stoppers on the second or third stage which were seemingly only added to stop oscillation on problematic builds.

It's not something I'd get hung up on unless you have any problems since this is definitely the exception rather than the norm.

[Richie]

820 ohm and 1k , and sometimes seen a snubber used. As any amp builder will tell you, along the way you may find new things that work better,and you revise the circuit. Thats probably all that was done about the wiring of the bright cap. It will work either way. The heater wiring, same thing, some other amps are wired like that, or been used before.
maybe after trying it, he changed back to the normal way. Hard to say exactly, only Ken could answer as why.all we can do is make a guess or opinion. But, seems he changed it for a reason.

[mac0611]

Hi everyone! Question, Is the Ron Worley Layout with regards to the bright switch wiring the "correct way" or the fransesca way? thanks

[paulster]

Ron's is the 'correct' way, as mentioned in the notes!

Basically, you don't want the wiper of the volume pot connected to the caps, as they can act as nice antennas when there's nothing connected at the other end and the volume pot is in the middle of its electrical travel so there's high impedance at both ends.

[mac0611]

sorry pulled for being a thread crapper

[hairyandy]

Ok it was a reject, then what? is that resistor a way to make it work? why was it a reject to begin with?

Here's what I posted in an earlier thread about the pics that I took regarding the "Undocumented 1990 Express":

Evidently it was sold by Ken to a friend who was on the waiting list for an Express at that time. The story I was told was that the amp suffered from parasitic oscillation when Ken first fired it up and that he was going to scrap it and start over. His friend, supposedly a respected amp technician as well---NOT Dave Funk, persuaded Ken to let him have it and solve the issue himself rather than keep waiting on his rapidly lengthening list. Supposedly an out-of-spec resistor was the culprit and that was the only change made which fixed it. This is all that I was told about this amp by the owner who had made contact with Ken who had confirmed this supposedly. Regardless of it's history, we've got another great example of Ken's genius to learn from.

My friend that owns it said that Ken had told him that he stamped the chassis "Reject" since he sold it to his friend in an "un-Trainwreck-approved" state, meaning that it wasn't working quite up to snuff. Funny enough, it wasn't named either so it has been referred to as Reject.

Andy

[paulster]

Andy

Thanks for posting that. I knew the history had been discussed before.

The grid stopper may well have been left in there from an attempt to suppress the PO rather than actually being necessary in the end, since it was another part that was the cause of the problem, so it still remains a bit of an enigma since it wasn't officially Trainwreck-endorsed!

[Wayne]

You never know - "Reject" could have been named after somebody's wife. Or more likely ex-wife.