jhaible

mounting an UTC transformer
« on: October 12, 2004, 09:04:42 AM »
I got this UTC A-19 transformer from ebay, read it needs "4-40" screws to mount it.

Living in Germany where 99,9999% is ISO / metric stuff, I'm not familiar with this description. I just guess it's an american / non-metric standard thread. Must be something between 3 and 4 mm from the looks of it.

Can anybody shed some light here, or even name a source in Europe where I can order such screws in small quantities? (Well, I just need 4 of them, plus a few spares ...)

Thanks in advance,

JH.



PS.: The mounting holes obviously are on the bottom (connector side). I saw there are 4 holes on the top as well. Are these threaded, too?


toby

mounting an UTC transformer
« Reply #1 on: October 12, 2004, 09:15:42 AM »
would that be four fourtieths of an inch? so thats one tenth of an inch so 2.5mm?

jhaible

mounting an UTC transformer
« Reply #2 on: October 12, 2004, 09:26:25 AM »
Quote from: "toby"
would that be four fourtieths of an inch? so thats one tenth of an inch so 2.5mm?


I have no idea. I won't try a 2.5mm screw before I'm sure I won't ruin the thread.

JH.

SSLtech

mounting an UTC transformer
« Reply #3 on: October 12, 2004, 09:26:40 AM »
No... the first number is the standard stock size. A number four is about 2.5mm (approx...) the second number is the number of threads per inch, so 40 threads per inch.

I have hundreds of 4/40 screws, if you can't find a local supplier (ask some specialty hardware stores and explain the thread measurement) then I'll happily mail you over a handful of them for free.

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

SSLtech

mounting an UTC transformer
« Reply #4 on: October 12, 2004, 09:27:33 AM »
Oh, and yes, an M2.5 will ruin the thread! :shock:

 Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

toby

mounting an UTC transformer
« Reply #5 on: October 12, 2004, 09:43:46 AM »
Quote from: "SSLtech"
Oh, and yes, an M2.5 will ruin the thread! :shock:

 Keith



wouldn't have stopped me trying :grin: you now realise why my house is full of broken stuff

jhaible

mounting an UTC transformer
« Reply #6 on: October 12, 2004, 10:05:45 AM »
Quote from: "SSLtech"
No... the first number is the standard stock size. A number four is about 2.5mm (approx...) the second number is the number of threads per inch, so 40 threads per inch.

I have hundreds of 4/40 screws, if you can't find a local supplier (ask some specialty hardware stores and explain the thread measurement) then I'll happily mail you over a handful of them for free.

Keith



Hi Keith,

thanks for the info and thanks for the offer.
I really appreciate this, and I'll gladly paypal you something to cover your expenses.

JH.

CJ

mounting an UTC transformer
« Reply #7 on: October 14, 2004, 06:06:50 PM »
yes those are #4 screws with 40 threads per inch.
There are 4 litle threaded pipes that get welded to the inside of the case, so the holes on the base are actually on the same piece of metal as the holes on the top.
If you want, you could just tap out the old threads with a slightly bigger metric tap, or just tie wrap the darn thing down with some heavy tie wraps.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

NewYorkDave

mounting an UTC transformer
« Reply #8 on: October 14, 2004, 06:27:37 PM »
Don't listen to him... He's totally gonzo. This is the same guy who solders directly to tube pins because he can't be bothered with sockets  :shock:

 :razz:

jhaible

mounting an UTC transformer
« Reply #9 on: October 14, 2004, 07:23:00 PM »
Quote from: "cjenrick"
yes those are #40 screws with 40 threads per inch.
There are 4 litle threaded pipes that get welded to the inside of the case, so the holes on the base are actually on the same piece of metal as the holes on the top.
If you want, you could just tap out the old threads with a slightly bigger metric tap, or just tie wrap the darn thing down with some heavy tie wraps.



Thanks CJ!

My first impulse was to just drill a plain 3mm hole thru the whole lenght and use long M3 screws that go thru it all.

I did the tie wrap method (with a velcro added on the bottom to avoid movement within the tie wrap) on that photo coupler in the opto compressor. Works great there, but it's a lot lighter than the transformer.

JH.


CJ

mounting an UTC transformer
« Reply #10 on: October 14, 2004, 09:05:27 PM »
There are some pop rivet like things that hold the base plate to the transformer, via the mounting screw holes, so don't use too big a drill or you will probably dislodge the fasteners or even crack the plate. I edited the 40 screw to r3ead #4 like it should. Sorry for anyconfusion.

Get out the welder. You can weld it down tight and de-gauss it at the same time, since it's probably been damaged beyond use by multimeter ohms checks. Watch for flaming drippng pbc potting compounds oozing from the open wounds!
 :razz:


here are links to A series and HA series templates, which can be very useful. One of the hardest things I have ever done is mount these two darn transformers, as the spacing is very very unforgiving.
Check the scale if you print these files. They may need tweaking as I don't know what printer you are using, etc.

http://vacuumbrain.com/The_Lab/TA/Templates/a10_template.pdf
http://vacuumbrain.com/The_Lab/TA/Templates/ha-100x_template.pdf
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

jhaible

mounting an UTC transformer
« Reply #11 on: October 15, 2004, 06:51:35 AM »
Quote from: "cjenrick"
There are some pop rivet like things that hold the base plate to the transformer, via the mounting screw holes, so don't use too big a drill or you will probably dislodge the fasteners or even crack the plate. I edited the 40 screw to r3ead #4 like it should. Sorry for anyconfusion.

Get out the welder. You can weld it down tight and de-gauss it at the same time, since it's probably been damaged beyond use by multimeter ohms checks. Watch for flaming drippng pbc potting compounds oozing from the open wounds!
 :razz:


here are links to A series and HA series templates, which can be very useful. One of the hardest things I have ever done is mount these two darn transformers, as the spacing is very very unforgiving.
Check the scale if you print these files. They may need tweaking as I don't know what printer you are using, etc.

http://vacuumbrain.com/The_Lab/TA/Templates/a10_template.pdf
http://vacuumbrain.com/The_Lab/TA/Templates/ha-100x_template.pdf



Thanks again for all the mounting tips!

Now you frightened me about the degaussing!

I'm quite sure I cannot do any harm with *my* multimeter
(the A-19 can stand several mA unbalanced DC), but who knows
what has been used to test it before.

But in general, how is the degaussing to be done?

I would expect something like this: Run a strong AC signal
thru the transformer (deliberately overdriving it), and then
slowly decrease the amplitude. Will this work ?

JH.

CJ

mounting an UTC transformer
« Reply #12 on: October 15, 2004, 05:38:16 PM »
just crank some Sabbath thru it at about 20 db and it will degauss itself.
give it about 24 hrs.
which tune? Iron Man, of course!
 :razz:
shameless rip.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

Kev

mounting an UTC transformer
« Reply #13 on: October 15, 2004, 06:35:52 PM »
:green:  :green:  :green:
Sabbath as an official piece of test/repair equipment.

Quote
He's totally gonzo.  

... is that the description I have been looking for, for the past year or so ?
Kev
DIY Factory


 

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