1974x PT replacement

[foreverstrung]

Thx. I've emailed Marshall and Dagnell. We'll see what's what after they respond. This PT coming today I'll send back. Someone on the Marshall Forum mentioned a Hammond 290PAZ, At least to compare specs as to what to compare too, though this PT has 140mA

https://www.hammfg.com/files/parts/pdf/290PAZ.pdf

[geoff 1965]

That looks better at 140mA,is there any specs printed on the PT that failed?
Quote the serial number of the amp when asking Marshall so they know you are a genuine owner.if any of us tried the “reverse engineering” alarm would go off!
Good luck

[foreverstrung]

I added the amps serial number to marshall. No specs for the bad tranny. it's a a D4909 Dagnall electronics. TXMA 00115 Batch:1294800446

[geoff 1965]

Keep us posted with your progress on this,will be of interest to me and future reference.the amp is nearly 20 years old now so it might be worth renewing the electrolytics while you are in there.

[foreverstrung]

Marshall responded to my email. Sent a replacement tranny out today. I did not expect that.
I'd appreciate any info on installing a PT. Anything easily confused or that can get wired backwards.

[geoff 1965]

That’s good of Marshall,should be just a straight swap regarding wiring,take some pics of the old transformer wiring before you remove it or draw a diagram showing which wires go to which terminal.just ask if you are unsure and post some pics.

[foreverstrung]

OK, so I received a Hammond 290PAZ replacement PT. I'm enclosing some pics before I pulled The Dagnell 4909 PT and then sitting side beside the Hammond. I've got different color wire. I was pretty sure I would.....I'm hoping someones got a spec sheet for the dagnell. As I said, this is my 1st tranny replacement, would like to get it the first time.........Marshall still is sending me a free replacement, but IDK when that'll be here. I've got this one now, I'd like to put it in. Kinda OCD about it now. Any help laying this out would be appreciated.......also, I snipped the wires long from thew tranny

[foreverstrung]

not sure how to post these pics. Help!

[JMPGuitars]

not sure how to post these pics. Help!

Click the "Attachments" tab under message post box where I typed all this text into. You click "Add Files" and you can also click "Insert Inline" if you want after uploading them.

[foreverstrung]

dagnell1.jpg

danall2.jpg

danell3.jpg

These show the Dagnell 4909 PT before I pulled it

[foreverstrung]

hammond1.jpg

hammond 2.jpg

[geoff 1965]

Marshall-1974X-18W-Schematic.pdf

you're quite a bit off! here's the 2004 version of the 1974X schematic for you to study and see where your mistakes are i.e. you can't have both the 120V & 240V pirimary wires going to the switch,the red/yellow HT centre tap goes to ground via the HT fuse,the 2 red HT wires go to pins 1&7 of the ez81,the yellow/black wire is rectifier filament 5V and is not used etc,etc
note someone has been in there and changed the 91R bias resistor to 200R.
see if you can work out the wiring also do the mounting bolts of the 290 paz match your existing holes?
good luck

[JMPGuitars]

The unused wires get clipped and covered with heat shrink tubing.

Why are you using the Hammond if Marshall is sending you a replacement? I would use the Hammond for another build.

[foreverstrung]

Mounting bolts line up perfectly.
No telling when the Marshall replacement might be here. Maybe a couple weeks, IDK, but I've got this one here now

[foreverstrung]

Does anyone know where I might find a Dagnall 4909 PT drawing? I can't find one anywhere and Dagnall has not responded to emails.

[foreverstrung]

I might wait JPM, but I'd like to be able to install this one If I can. With the Marshall, I'll likely have the same color/location issues with the primary and secondary that I'm having now. A Dagnal 4909 drawing would take most all the mystery away, but I can't find one anywhere and Dagnall hasn't responded

[geoff 1965]

hammond 2.jpg

add a pic of the wiring from the mains in socket,remember to draw a layout of existing wiring colours for when the marshall transformer arrives,there looks to be 2 types "the pic i posted shows tags and yours has leads"
you won't get any response from dagnall,i've contacted them twice asking about their 18W transformers and had no reply!

[foreverstrung]

Thx for posting that geoff 1965. I. I've got this down now. 100%, but now that I do have my head wrapped around it, I'm thinking of waiting at least a few more days to see if the Marshall replacement shows up. I'm more of a purest than pushing this through. At first there, I couldn't leave it alone, because I didn't understand. Now that I do, I can wait a bit......Either way, the extra tranny I have I'll use to build a 18w clone....Love this stuff. Thanks everyone for the help and support........I'll post pics and updates as I move fwd

[geoff 1965]

Those hand wired marshall’s are a work of art! and I would wait and fit the Marshall PT for originality.check the bias resistor and capacitor and if you don’t have a tube tester I would monitor the bias voltage when you first power on.which brand of ez81 do you have?

[foreverstrung]

I've got a Tesla EZ81. Old original Tesla, not JJ. I did just order a NOS RCA EZ81. It'll arrive soon.
I don't have a tube tester, but 2 NOS Mullard EL84's.....They were NOS when I put them in after I purchased this amp. Maybe 25 hours of playtime on them.
When you say test the bias voltage, you mean, get the plate voltage and them mA of the EL84's and then do the math, right?