upcoming 1969 SL build: PT orientation, wire dress?

[young flower]

Hi

As I´m a new builder planning my first build, I want to answer a few questions for myself before grabbing the soldering iron:

I bought the Metro spec Heyboer 1203-80-ML (laydown) PT:



This PT groups heaters, heater CT, high voltage terminals and PT CT together on one side. On the other side we have primaries (120V, 220V, 240V), PT common (orange) and BIAS taps.

I found that this configuration is different from what most builds with laydown mount PTs use: on most laydown PTs high voltage terminals are alone on one side, all other connections on the other side. This allows for short wire runs. Here is the tranny George uses on his 12xxx builds showing that configuration:



If I install my PT the "traditional" way, with heaters facing power tube sockets - this will cause extra long wire runs for high voltage terminals (to stdby switch) and primaries (to voltage selector I´ll use). Like in this picture of an amp using the exact same tranny I bought:


So - my question is: Could I install the tranny 180 degrees rotated (heater taps facing power switch instead of power tube socket side) which would allow for shorter wire runs (with exception of the heaters and heater CT)?

Would it be a good idea - or would it for some reason cause problems to flip the tranny?

Also - does anybody have a picture of my type of PT used in a 69 100W SL build with good wire dress?? Since I´ll use the Metro instructions - and these use the standup type PT, I´m very curious how I should best route the wires from my laydown tranny (actually all the wires) for maximum hum suppression and to avoid ghost notes etc.

Any suggestions would be very appreciated
Greetings
YF

[young flower]

Would it be possible to bundle high voltage terminals and primaries together to get a slightly cleaner look - or will that cause hum or other problems?
I mean something like that (just a sloppy sketch with paint):

[julkke]

You can bundle pt wires pretty freely as it is only AC in them. Just keep them away from dc and signal wires.

[jimmyride]

I see someone used photo of my amp as an example. Man I gotta do something with it, it looks really messy. But sounds awesome.

[young flower]

@julkke:

You can bundle pt wires pretty freely as it is only AC in them. Just keep them away from dc and signal wires.

Yes - I know you already told me that in my "fusing live or neutral" thread. But what I don´t understand is: why bother about twisting AC wires together if they won´t cause hum anyway as long as they´re kept separate from DC wires?? Also - there must be places where certain wires shouldn´t be routed to. F.e. I´m concerned that it could cause a lot of hum, if I bundle the wires as described above and route the primaries up to the voltage switch, directly between the power tube sockets.
So you don´t think bundling high voltage taps and primaries together would cause problems? I assume adding the 6,3V pilot light taps won´t make a difference either, right?
How about turning the tranny 180° (as described in my first post)?

@jimmyride:

I see someone used photo of my amp as an example. Man I gotta do something with it, it looks really messy. But sounds awesome.

Hey - yeah, I thought about asking you for permission to use it. But then I just reposted it, since there is really no connection to you in this thread. Hope you don´t mind .
I admit, it looks a bit messy - but if it sounds good, all is well . Do you get hum or ghosting with that amp?

[jimmyride]

Yeah, it hums and ghosts but it's nothing beyond normal. I used Larry grounding scheme which helps with both these issues. I'll try to do something about it but not before I build myself another amp because I need this one rocking right now because I have nothing to replace it with.

[julkke]

Twisting makes hum cancel more and looks neater. Neatest look would be to run pt wires on the sides of the chassis. Don't worry about hum too much here, its more about grounding and signal wire dress.

[young flower]

Don't worry about hum too much here, its more about grounding and signal wire dress.

Which wires exactly would be the "signal wires" and how should they be routed/dressed?
What about turning the transformer 180° (heaters facing power switch side)? That would of course mean that the heaters have a longer way to V7 pin2+7 but both high voltage terminals and primary taps would have a much shorter run.
Could that be a better solution - is there anything to be said against it?

[young flower]

I know there was an interruption since the site was down but it would be great if somebody could answer that last question - I´m just asking myself if turning the tranny could be a good idea concerning wire dress (except for the heaters - those would have a longer way then. Is it preferrable that the heaters have a longer way but high voltage taps and primaries don´t or the other way round?). And - which are the signal wires and how to route them/what to look out for? Thanks

[neikeel]

I would put the heaters at the front and then twist them and bundle up with the switch wires in a nice neat harness around the chassis edge with lacing cord (practice first). Keep the wires to the back of the chassis and avoid loops of heater wires around the first socket, just bring them down to the socket in the same way you see the black and red wires on the old Marshalls:http://amparchives.com/album/Marshall/1 ... es/14.html above is one of my early Superleads.

[young flower]

Hey - thanks for the advice Neil, as always.

Just to make sure I understood you correctly:

I would put the heaters at the front and then twist them and bundle up with the switch wires

"At the front" means - heater exits on tranny facing power switch side of the amp - i.e. tranny rotated 180° to usual mounting style, right? The "switch wires" would be just high voltage terminals (to Stdby switch) and PT common (to power switch)? In this case I don´t really understand why I should bundle the switch wires with the heaters since they´re going opposite directions (switch wires to switches, heaters around the chassis edge to front)?
Again, my power tranny has a sort of special wire configuration if you didn´t see it.

Thanks again
Karim

[neikeel]

Hi Karim

Yes I saw your pics.

Did you look at the link?

That amp has the wires in the same layout as your tranny. I would bundle the lamp wires in with that harness too.

It is neater and keeps the ac heaters out wide and your ac HT to the standby switch short.

Just my opinion................

ps look at all the pics of that amp and you will see the position of the grey feet in relation to the gold string etc

[young flower]

Of course I looked at the link .

Oke - I will do it in that fashion then. Is it generally preferrable to have the HT taps as short as possible? And leaving the heaters long is not that much of a problem concerning hum and oscillation (the heaters have high current on them, the HT taps high voltage)?
When you use lacing cord - do you twist+lace the wires or do you only bundle them but not twist them in addition to that inside the bundle?

Thanks for the hint with the feet in relation to the golden piping - seems pretty much lined up. That´s a good point to start with.

[neikeel]

http://forum.metroamp.com/viewtopic.php?f=7&t=25733

[young flower]

Oke - thanks for the lacing tutorial.
I noticed that the heater wires on my tranny are not quite long enough to go that long way along the edge of the chassis. I could of course extend them with some wire of the same rating. But would it also be oke to bring the heaters directly down to the V7 tube - I mean twist them and route them down between the tranny and mains and screens filter caps directly to V7?
If I extend the heaters, does anybody know the wire rating - these seem to be made of aluminum and pretty thick compared to the other wires from the tranny.