Need Hammond pt transformer hook up Help

[martin manning]

The correct connection is as shown in the Weber layout- Mains live goes directly to the fuse (so if the fuse blows there is no voltage beyond that point), and one PT primary lead (doesn't matter which one) goes to the mains neutral (US terminology). I assume that you have a redundant safety ground there too?

[showbander]

I will post some pics up later with IEC socket and fuse installed...Off to work now...oh & Yes i have a dedicated safety ground from the IEC to chassis .
Thanks

[showbander]

Yep , i meant one of the black mains, straight to fuse then onto the live of IEC


Am i right in hooking the neutral of The IEC to the other lug on the power on switch ? (like photo (blue) )

Thankyou

[martin manning]

Yes, and just to be clear... Also, it's best to run the mains live to the center terminal of the fuse holder to minimize danger of shock when inserting a fuse.

[showbander]

Thanks Martin, I got there in the end ...So now i nearly have the Pt hooked up , i'm gonna tackle OT tomo.

If ya dont mind could ya explain a couple things ....pweeeease!! i cant decipher the hammond OT data/pic

Should i assume the 3 primary wire colours on the hammond OT match up with the Weber diagram ?(are these standad colours for the OT's Primary wires)

Also unsure of hooking up the secondary wires...i will be using the 4&8 ohm taps ( not sure which is which )but there are 4 leads....

Many thanks

[ampgeek]

On the OT Primary side: The red wire is the center tap and goes to the appropriate B+ supply for the power tube plates. The blue goes to one tube plate and the brown goes to the other tube plate.

On the OT Secondary side: The black wire is the common, white is 2 ohm, green/yellow is 4 ohm and green is 8 ohm.

Take a close look at the label on the OT. It lists the secondary wire color and, right below it, is the impedance for that color. The label matches the wiring diagram.

Good luck,
Dave O.

[showbander]

Nice one , i have that now i reckon ,makes sense after being told
Concerning the black common wire is that grounded to the earth of output jacks?

And can the 2 ohm tap just be unused /heatshrinked and tucked away neatly just incase it ever needs using in the future...

Anyway chaps ,thats all my questioning for tonight ,you have been a great help ...Special thanks to Martin.

cheers

[ampgeek]

Give a man a fish...and he only eats for a day. But...teach him to fish and....you know the rest!

Yes. The unused wire should be wound up (in case you find the need to use it later on), heat shrinked off and tucked away somewhere out of the way.

Yes. The common goes to that location. However, the location where it gets brought to earth might depend on your configuration and type of output jacks.

Download and have a look at the document here for some insight.

http://www.valvewizard.co.uk/Grounding.html

Cheers,
Dave O.

[showbander]

Cheers Dave 0, i have downloaded that link & will study it more tomo !...I personally have only heard "Teach a man to fish, and you can sell him a ton of accessories" .

Right my final Q for anyone is ...wait for it ! Where should the first cap be grounded too?

Should this 1st cap have a dedicated ground to chassis?

On the weber layout the 40uf cap is directly connected to the PT's 0v red/yell.
At present this wire is grounded at chassis....

Thanks.

[martin manning]

I would either run the PT's HT CT (red/yellow) directly to the negative end of the 40uF reservoir cap and then run another wire from there to the place where the power tube cathodes are grounded, or, ground the cap and the PT CT to the chassis at the same point, near or with the power tube cathodes. That keeps all of the heavy ripple current within that loop, and not flowing through the chassis.

[showbander]

I currently have a 3 star ground point on the chassis. one for the PT, ht/ct wire , one from a lead running from negative of the 1st cap. and lastly the grounding of the power tube cathodes....all at one point ! this ok then ?

Apologies to break it own to real basic but its a steep learning curve , i am learning lots as i trundle on

Thankyou

[martin manning]

If I understand you correctly, PT CT, reservoir cap, and power tube cathode resistor are all grounded to the same point, near the PT. That should be fine.

[showbander]

Yep thats it Martin...Thankyou! I think i'm nearly there with the build now .
Gotta small amount of tidying up at the input jacks as solder isnt taking too well there for some reason...and triple check continuity throughout .

[ampgeek]

LOL!

The end of that quip goes......."and he can feed himself forever"!

Rock on,
Dave O.

[showbander]

Right guys ...after going through the amp many many times i ,powered up and all fine! very slight bit of hum without a guitar plugged in but i think thats possibly normal ,as i checked a couple other valve amps i have and its no louder than them....The hum tends to disappear as i crank the volume!

Not yet banged it through a decent cab but it sounded pretty sweet to me and lovely cleans.
I have the ay7 in V1 and that sounds so much better than the ax7.

Could i just confirm again my power on switch is correct ...i have one black primary 240v to the fuse the onto the live of the IEC ....

The other black 240 v primary is going straight to the power on switch (is this correct) !

From neutral of IEC goes to the other lug of the power on switch !

And i have securely earthed the IEC to the chassis .

Anyway no funny smells ,no burning valves! cant wait to bang this through my cab !

Thanks all ,and thankyou martin ,you were a great help indeed.