Vincent Pho 8 phono amp power supply

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CH46E
CH46E Posts: 3,549
edited September 2020 in Troubleshooting
After some help from a av repair guy, I know that the power transformer is bad.

There is no continuity or resistance on the input/primary winding. I removed the primary from the circuit also.

Now I'm trying to figure out why the primary might have failed.

Tom Ward of Pangea Audio /Audio Advisor said he has never seen one fail in the Pho 8.

The fuse in the iec connector is good.

I removed a small cap that was on the back of the iec. I appears to test good.

The only other part between the iec, the switch and transformer is a blue polyswitch. Thats the item I dont know how to test and or even if it was bad, would it cause the primary to fail?

You can see where this thread started here. https://forum.polkaudio.com/discussion/191754/van-alstine-vision-phono-preamp-vincent-pho-8-phone-preamp
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  • CH46E
    CH46E Posts: 3,549
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  • mhardy6647
    mhardy6647 Posts: 33,043
    edited September 2020
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    Does the PT have a fusible link in the primary?
    (over and above the mains fuse, that is)

    I mean, basically, an open winding - if not just a "QC" failure of a part - would indicate to me way too much current drawn by something downstream. Shorted capacitor or rectifier being the most obvious/likely culprit(s).

    Just musing, though, of course.
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  • CH46E
    CH46E Posts: 3,549
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    If there was a fusible link in the primary would it even be serviceable?
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  • mhardy6647
    mhardy6647 Posts: 33,043
    edited September 2020
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    CH46E wrote: »
    If there was a fusible link in the primary would it even be serviceable?

    nope.

    Well -- let me rephrase that :)
    It wouldn't have been intended to be serviceable.
    But, to some folks -- that's a challenge!
    Transformers -- sometimes -- can be dissected.
    I had to repair one on a Radio Shack SAF-40 once. Turns out that the output transformers on those had a weak spot, but it was very close to the outside world and could thus be repaired. Just have to lay off coffee for the morning before tackling ;)

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    You can probably see the discontinuity in the varnish-insulated copper wire in the photo above. :#

    ahem -- back on topic...
    My guess is that you'll need a new PT. But -- as they used to warn us in the days when stuff could be repaired -- it is folly to replace a PT prior to determining that no fault lies upstream of the transformer. Your interaction with the "Pangea Audio" person suggests that he thinks there's something goin' on upstream of the PT.

    That may be hard to troubleshoot -- although a "DBT" (dim bulb tester) might be helpful to suss it out after installing a suitable replacement PT.

    Given that the PT's specs (not current requirements, but output voltages) are given to you, it would (should!) be possible to rig up a power supply in the form of three cheap (e.g., surplus/junkbox) fixed voltage PTs and troubleshoot from the mains input without putting a 'bespoke' PT at risk. Should. ;)

    ... again, some folks take "impossible" as a challenge. :)

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  • CH46E
    CH46E Posts: 3,549
    edited October 2020
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    I found this photo of the inside of another Pho8 pre amp. It has what appears to be a part number but I can't find anything for a replacment.

    Does anyone else know where to search this part number??

    @ZLTFUL , I know you looked before but thought maybe this new number might help????

    ECTHF 0911.

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  • CH46E
    CH46E Posts: 3,549
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    I'm waiting to hear back from Pacific Transformer. They advertise "no job too small". So I asked for two of them. Not sure they will make them or not, worth a shot.
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  • ZLTFUL
    ZLTFUL Posts: 5,640
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    Let me shake a few trees and see what falls out. May not (read: most likely will not) be today as I have a very busy day between work and a house guest.

    But I will see if I can come up with anything...
    "Some people find it easier to be conceited rather than correct."

    "Unwad those panties and have a good time man. We're all here to help each other, no matter how it might appear." DSkip
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  • pitdogg2
    pitdogg2 Posts: 24,576
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    Tell Russ to go home....


    :p
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  • invalid
    invalid Posts: 1,277
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    Not to hijack this thread, but why does vincent solder the tubes into the circuit instead of using a tube socket?
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  • [Deleted User]
    [Deleted User] Posts: 7,658
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    They probably do it to eliminate a mechanical junction which because of different metals between the tube pin and the socket could cause a slight (possibly audible, who knows?) diode effect. Sure makes tube rolling a bit more challenging, eh?
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  • CH46E
    CH46E Posts: 3,549
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    I thought maybe it was cheaper to pay someone to solder then to buy the sockets??
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  • Clipdat
    Clipdat Posts: 12,602
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    At this point I'm just going to buy you a phono pre and have it drop shipped to you so you can start listening to vinyl. Life is too short lol.
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  • Clipdat
    Clipdat Posts: 12,602
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    PM me your address.
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  • CH46E
    CH46E Posts: 3,549
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    So check this out!
    This is a very well built unit. Can't wait to hook it up!

    Talk about a great Karma! Big thanks to Drew @Clipdat !

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  • Clipdat
    Clipdat Posts: 12,602
    edited November 2020
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    Nice dude! I like that all metal chassis! Enjoy! Looking forward to hearing about how it sounds.

    Also for the record I didn't choose to have it say a corny rhyme on the receipt.

    "A gift for you from Drew" really? REALLY? But Amazon wouldn't let me put anything less if I wanted to not have the price displayed lol :p
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  • CH46E
    CH46E Posts: 3,549
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    I will try to get this Pho 8 fixed and karma it off.
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  • BlueBirdMusic
    BlueBirdMusic Posts: 2,077
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    Drew, you are an exceptional person!!
    "Sometimes you have to look to the past to understand where you are going in the future"


    Harry / Marietta GA
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