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    IEC modification to ST-70 chassis

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    fmorelli

    Posts : 16
    Join date : 2013-08-27

    IEC modification to ST-70 chassis

    Post by fmorelli on Thu Aug 29, 2013 11:25 pm

    This is my first post. I've been quietly reading along and just placed my order with Bob.

    I've been doing a bit of looking around to see if there are good suggestions on how to put an IEC connector in for the power cable. I looks like a short (or right angle?) connector is needed, and the short may occur by making a standoff so the connector sits a bit more proud of the chassis (and gives room to the transformer in the back)?

    Has anyone done this and can either comment or point me to a thread, as my searches have run a bit dry.

    Thanks!

    Filippo

    kaner

    Posts : 88
    Join date : 2011-09-20

    Re: IEC modification to ST-70 chassis

    Post by kaner on Fri Aug 30, 2013 1:10 am

    I thought about putting an IEC in a different build (not an ST70) and ultimately concluded it wasn't worth the added effort for me. I had the socket and the room, but didn't have an easy way to cut the opening. I literally cut the end off of the chord and wired it as Bob suggests, other than connecting the ground to one of the power transformer mounting bolts.

    peterh

    Posts : 643
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: IEC modification to ST-70 chassis

    Post by peterh on Fri Aug 30, 2013 2:02 am

    fmorelli wrote:This is my first post. I've been quietly reading along and just placed my order with Bob.

    I've been doing a bit of looking around to see if there are good suggestions on how to put an IEC connector in for the power cable. I looks like a short (or right angle?) connector is needed, and the short may occur by making a standoff so the connector sits a bit more proud of the chassis (and gives room to the transformer in the back)?

    Has anyone done this and can either comment or point me to a thread, as my searches have run a bit dry.

    Thanks!

    Filippo
    Yes, i installed an IEC in a vta-70.

    It's located to the right of ( as seen from the back) the main transformer. The biggest problem was
    that since the vta is made by stainless, i had to have it milled away.
    The IEC choosen was one with a built-i fuse, thus making the supplied fuse unneded.

    I did send photos to bob, he might be able to dig them up and post it here...


    tomlang

    Posts : 34
    Join date : 2009-08-12

    Re: IEC modification to ST-70 chassis

    Post by tomlang on Fri Aug 30, 2013 8:54 am

    I've done it several times.  You have to be careful with clearance to the transformer bottom bell housing.




    arledgsc

    Posts : 330
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: IEC modification to ST-70 chassis

    Post by arledgsc on Fri Aug 30, 2013 8:59 am

    I installed an IEC inlet on the same chassis.  The chassis is strong and took me a couple of saw blades and drill bits to get the chassis opened up then a lot of filing to size the hole.  There are several types of inlet connectors and used one where the connector opening sits proud of the plastic mount (see pix below or post above).  This saves a couple of millimeters of clearance on the rear versus connector openings that are flush with the plastic housing.  After mounting the solder pins can bend over to ensure enough room to the power tranny.  

    IEC C14 Inlet Picture

    fmorelli

    Posts : 16
    Join date : 2013-08-27

    Re: IEC modification to ST-70 chassis

    Post by fmorelli on Fri Aug 30, 2013 9:28 am

    Thanks guys. I'm wondering if anyone has specific IEC part references - for example, with right angle connectors or particularly shallow plug body?

    The stainless is a bit of a headache, but I have a shop at the house so I'll work that out. Glad to post pictures and such when I get that far!

    Filippo

    tomlang

    Posts : 34
    Join date : 2009-08-12

    Re: IEC modification to ST-70 chassis

    Post by tomlang on Fri Aug 30, 2013 9:39 am

    fmorelli wrote:Thanks guys. I'm wondering if anyone has specific IEC part references - for example, with right angle connectors or particularly shallow plug body?

    The stainless is a bit of a headache, but I have a shop at the house so I'll work that out. Glad to post pictures and such when I get that far!

    Filippo
    Here is the one I used and in the photo above.

    http://www.mcmelectronics.com/product/28-12532

    PS, keep in mind I installed this in an original non-stainless chassis that is MUCH easier to file away than the newer stainless ones.

    fmorelli

    Posts : 16
    Join date : 2013-08-27

    Re: IEC modification to ST-70 chassis

    Post by fmorelli on Fri Aug 30, 2013 1:27 pm

    What would be great is to find a male receptacle with right angle soldering connections in the back. My other thought is to machine a "washer" for the IEC so that it sits more proud on the chassis face. Seems like a simple way to solve, maybe?

    Filippo

    sKiZo

    Posts : 1287
    Join date : 2013-04-01
    Location : Michigan USA

    Re: IEC modification to ST-70 chassis

    Post by sKiZo on Fri Aug 30, 2013 3:57 pm

    kaner wrote: other than connecting the ground to one of the power transformer mounting bolts.
    Hmmmmm ... no hummmmmm?


    ramon68

    Posts : 83
    Join date : 2009-04-12
    Age : 75
    Location : naples fl

    Re: IEC modification to ST-70 chassis

    Post by ramon68 on Fri Aug 30, 2013 6:27 pm

    Back in the '80s, when hi-fi manufacturers were starting to offer IEC receptacles on their gear for people who wanted
    to use high end a/c cords, at least one company, Audio Research, listened to its gear with power cords hard wired in, and
    with IEC receplacles. They found that the EIC junction degraded the power connection versus hard wiring. I guess that since then,
    they have come around to the view that if people insist on wasting, er- spending money on exotic a/c cords who are they to question
    it?

    fmorelli

    Posts : 16
    Join date : 2013-08-27

    Re: IEC modification to ST-70 chassis

    Post by fmorelli on Fri Aug 30, 2013 8:08 pm

    Interesting ...

    Filippo

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: IEC modification to ST-70 chassis

    Post by Bob Latino on Fri Aug 30, 2013 8:42 pm

    The hard wired power cord supplied with the VTA ST-70 and ST-120 amp kits is a quality 13 amp rated cord which has much more power transfer capability than either amp can ever use. The fuse blows at 3 amps on the ST-70 and 5 amps on the ST-120. I have swapped in some larger 2 and 3 wire cords in both the VTA ST-70 and ST-120 and have never heard ANY difference in the sound of either amp with a larger amp rated cord than what is normally supplied with both amps.

    Re: "Why not an IEC connector on the VTA ST-70 and ST-120 amps?" The design concept behind the VTA ST-70 and ST-120 was to make the amp look like an original Dynaco amp. Original Dynaco amps have two wire cords. To put an IEC connector on these amps would compromise the original look of the amp. Two other things > Installing an IEC connector in place of the power cord is more difficult to do than you might think. As was mentioned above, an IEC connector insets into the amp about 3/4 of an inch. If you do install one here, then the AC solder connections on the IEC connector inside the amp will come very close to the bottom cover of the power transformer. You will have live AC power about 1/16 of an inch from chassis ground - not a good thing. I have seen people bend the three solder connectors sideways inside the amp and/or grind off half of the solder terminal to gain more clearance to the power transformer's bottom cover.

    Having a 3 wire cord also runs the risk of a "ground loop" and increased hum level IF you have another audio component on the same line as your amp. Some audiophiles wind up floating the ground on one (or both) components with a 3 to 2 wire "cheater plug" to get rid of the ground loop.

    Bob

    peterh

    Posts : 643
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: IEC modification to ST-70 chassis

    Post by peterh on Sat Aug 31, 2013 8:42 am

    As shown in the pictures i sent to bob , mounting an IEC besides the main transformer is possible, thus a very long IEC well might be used.
    It will occupy the space used by the mains fuse, but since IEC wells with fuses are available that is
    no problem.

    ( Triode has IEC as standard on their ST-70 ... )


    fmorelli

    Posts : 16
    Join date : 2013-08-27

    Re: IEC modification to ST-70 chassis

    Post by fmorelli on Sat Aug 31, 2013 4:00 pm

    I'm certainly not criticizing the lack of an IEC, just was interested in possibly changing over to it. As for originality, that seems an arbitrary argument. I like the newer banana plugs and they certainly are not original, and in the same location as the power cord so ....

    Filippo

    kaner

    Posts : 88
    Join date : 2011-09-20

    Re: IEC modification to ST-70 chassis

    Post by kaner on Sat Aug 31, 2013 11:15 pm

    sKiZo wrote:
    kaner wrote: other than connecting the ground to one of the power transformer mounting bolts.
    Hmmmmm ... no hummmmmm?

    No hum whatsoever.  If your worried isolate your ground.

    peterh

    Posts : 643
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: IEC modification to ST-70 chassis

    Post by peterh on Mon Sep 16, 2013 11:01 am

    I have moved the photos of my VTA-70 with IEC connector.
    The IEC is a model that has a built-in fuses, thus i can skip the supplied fuse, in it's place is an isolated connector for controlling the added SSR ( the SSR is also visible on the photos)

    http://n.manet.nu/ST70-IEC.jpg and http://n.manet.nu/ST70-IEC2.jpg

    The worst was that i had to use a mill to create the IEC hole as stainless is difficult to cut.


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