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    My progress on my VTA ST 120

    Tom Pickett
    Tom Pickett

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    Post by Tom Pickett Mon May 03, 2021 1:29 pm

    Good afternoon everyone. I hope all of you are having a good day and that all of you are safe.

    So far as you can see in the photos this is about as far as I can go with my assembly. I still have a lot of work to do on the chassis before I can start installing components. I also have a 3/8" x 2 1/2" x 18" aluminum flat bar stock on its way for the faceplate I’m going to install of the front of the chassis. I also have some copper RCA inputs to install on the back of the chassis.

    I need to get a machinist to cut the hole for the AC power entry module that I am going to install on the back of the chassis where the original power switch was to be installed.

    I also need to drill two holes in the back on both sides of the new power switch location for the left and right RCA imputes. Then I plan on painting the chassis and the transformers.

    I'm also going to install two 1v analog power meters in the front so I can visually see where the bias is set on the amplifier.

    Also as most of you already know I am going to install the driver board on the outside of the amplifier up on some standoffs with a see-through Dynaco style cage where you can see the components but you can't touch them with your fingers. Plus I will have outlet holes for the driver tubes to stick out of the top of the driver cage.

    All  of you have a good day and clear skies and stay safe.

    Tom

    My progress on my VTA ST 120 18242310
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    My progress on my VTA ST 120 18248610
    My progress on my VTA ST 120 S-l16029
    My progress on my VTA ST 120 S-l16030

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    Dale Stevens

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    Post by Dale Stevens Mon May 03, 2021 2:08 pm

    Tom, Nice. Also like your soldering skills. Dale

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    Tom Pickett
    Tom Pickett

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    Post by Tom Pickett Mon May 03, 2021 2:52 pm

    Dale Stevens wrote:Tom, Nice.  Also like your soldering skills.  Dale

    Thanks Dale..... My progress on my VTA ST 120 1f600

    Tom
    Bob Latino
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    Post by Bob Latino Mon May 03, 2021 4:09 pm

    Tom,

    It looks to me that your SCM is wired wrong unless you are doing something that I am not aware of. The SCM should be set up with positive (Lug 5) to negative (lug 4) to positive (lug 2) to negative (lug 1) with a jumper wire between lugs 4 and 2. It appears that you have the two negative sides of the two caps together so that you have positive to negative to negative to positive. Unless you are doing something "different", your SCM is wired wrong ?

    SCM instructions below ..

    7. Assemble and mount the Supplementary Cap Module (SCM)

    A. Obtain the five lug terminal strip from the SCM kit plastic bag
    B. Hold the strip with the grounded lug that attaches to the chassis towards your RIGHT - The lug closest to you is lug 1 and the next four lugs are lugs 2, 3, 4 and 5.
    C. Connect one 330K 1 watt resistor (found in SCM bag) between lugs 1 and 2 - have the resistor straight in line with the terminal strip and not on the side of the lug.
    D. Connect a jumper wire between lugs 2 and 4 - have the jumper straight in line with the terminal strip and not on the side of the lug. Arch the jumper over the top of lug 3.
    E. Connect one 330K 1 watt resistor between lugs 4 and 5 - have the resistor straight in line with the terminal strip and not on the side of the lug.
    F. Connect a 6 inch wire to lug 1 on the side of lug 1 which faces the strip's chassis attachment hole.
    G. Connect a 3 inch wire to lug 5 on the side of lug 5 which faces the strip's chassis attachment hole.
    H. Obtain one of the two supplementary caps and connect the NEGATIVE terminal of this cap (the terminal with the GRAY STRIPE next to it) to lug 1 of the terminal strip. Connect it on the side OPPOSITE the chassis attachment hole. (S) Fit the other lug of this cap into lug 2 of the terminal strip (S)
    I. Fit the OTHER supplementary cap with the NEGATIVE terminal (the terminal with the GRAY STRIPE next to it) in lug 4 (S) and the POSITIVE terminal in lug 5 (S). Connect it like the other cap on the side OPPOSITE the chassis attachment hole.


    Bob

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    Tom Pickett
    Tom Pickett

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    Post by Tom Pickett Mon May 03, 2021 5:17 pm

    Bob Latino wrote:Tom,

    It looks to me that your SCM is wired wrong unless you are doing something that I am not aware of. The SCM should be set up with positive (Lug 5) to negative (lug 4) to positive (lug 2) to negative (lug 1) with a jumper wire between lugs 4 and 2. It appears that you have the two negative sides of the two caps together so that you have positive to negative to negative to positive. Unless you are doing something "different", your SCM is wired wrong ?

    SCM instructions below ..

    7. Assemble and mount the Supplementary Cap Module (SCM)

    A. Obtain the five lug terminal strip from the SCM kit plastic bag
    B. Hold the strip with the grounded lug that attaches to the chassis towards your RIGHT - The lug closest to you is lug 1 and the next four lugs are lugs 2, 3, 4 and 5.
    C. Connect one 330K 1 watt resistor (found in SCM bag) between lugs 1 and 2 - have the resistor straight in line with the terminal strip and not on the side of the lug.
    D. Connect a jumper wire between lugs 2 and 4 - have the jumper straight in line with the terminal strip and not on the side of the lug. Arch the jumper over the top of lug 3.
    E. Connect one 330K 1 watt resistor between lugs 4 and 5 - have the resistor straight in line with the terminal strip and not on the side of the lug.
    F. Connect a 6 inch wire to lug 1 on the side of lug 1 which faces the strip's chassis attachment hole.
    G. Connect a 3 inch wire to lug 5 on the side of lug 5 which faces the strip's chassis attachment hole.
    H. Obtain one of the two supplementary caps and connect the NEGATIVE terminal of this cap (the terminal with the GRAY STRIPE next to it) to lug 1 of the terminal strip. Connect it on the side OPPOSITE the chassis attachment hole. (S) Fit the other lug of this cap into lug 2 of the terminal strip (S)
    I. Fit the OTHER supplementary cap with the NEGATIVE terminal (the terminal with the GRAY STRIPE next to it) in lug 4 (S) and the POSITIVE terminal in lug 5 (S). Connect it like the other cap on the side OPPOSITE the chassis attachment hole.


    Bob

    No Bob... I'm not doing anything any different. I just "goofed" lol and put one of the capacitors in the wrong direction.

    How does it look now ? I labeled it the way that I see it here.

    Thanks, Bob for the heads up. :-)

    My progress on my VTA ST 120 18121410
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    Bob Latino
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    Post by Bob Latino Mon May 03, 2021 5:37 pm

    It looks good now !

    Tom .. You are building a custom version of the ST-120 .. When you go off the beaten path from a normal build, I can't be responsible if what you do causes a problem. If you had started the amp up with the SCM incorrectly wired, not only would the SCM parts have gone up in smoke but other parts of the high voltage system may also have been taken out. I know that you will be mounting the driver board differently also. Just be careful. Sometimes a "mod" can cause a problem if you are not careful about how you do the mod ?

    Bob

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    Tom Pickett
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    Post by Tom Pickett Mon May 03, 2021 5:48 pm

    Bob Latino wrote:It looks good now !

    Tom .. You are building a custom version of the ST-120 .. When you go off the beaten path from a normal build, I can't be responsible if what you do causes a problem. If you had started the amp up with the SCM incorrectly wired, not only would the SCM parts have gone up in smoke but other parts of the high voltage system may also have been taken out. I know that you will be mounting the driver board differently also. Just be careful. Sometimes a "mod" can cause a problem if you are not careful about how you do the mod ?

    Bob

    Yes, Bob... my eyes are getting really bad and my brother keeps telling me I need to go down and get some glasses and have my eyes checked because I'm getting to where I can't see.

    That's part of the problem.

    But anyway thanks for catching that Bob.... that was definitely a bad mistake on my part.
    penguinpages
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    Post by penguinpages Fri May 14, 2021 1:10 pm

    Tom,

    If I can clarify. I am new to building an amp etc.. so was trying to collect details and suggestions and collect into what was my build of my ST-120. I think their was a separate posting where you spoke about Yellow Page mod.. and I must have read it wrong / documented wrong that the mode used "10A10 10 Amp 1000V 10A 1KV Axial Rectifier Diode" but.. I think it was my mistake. I later found the sticky posting for the official steps to do the mode for AC input voltage protection. these diodes I think .. per this post.. were to go on the four post standoff that is next (see picture) can you clarify if that is correct. And WHY you did not use the "green ones" that came in the kit for the "10A10 10 Amp 1000V 10A 1KV Axial Rectifier Diode". Thanks

    My progress on my VTA ST 120 Diodes10
    corndog71
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    Post by corndog71 Fri May 14, 2021 1:30 pm

    Those little green parts are capacitors for the heater center taps.

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    DavidR
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    Post by DavidR Fri May 14, 2021 5:27 pm

    Tom, I have had vision issues for years (including legally blind in one eye) and have corrective glasses BUT when I work on gear I always put on a mag-visor. It has several different lenses with different magnification.
    My progress on my VTA ST 120 XPD0bL5n4eWWPzVFwIozjXjyJsYyMx7DC-lyvbd5NirO6x-G57jz3ah3BGChXnP2Itqt1imz02qKDO3wFxDmRBxmF-Bk3z0UR5fJdpNyXnE

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    zuheyr

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    Post by zuheyr Sun May 16, 2021 3:21 am

    Dear Gentlemen! I admire your work... Please tell me where and how can I purchase a kit... I am from belgium though :-(

    Kindest regards,
    Zuheyr
    Bob Latino
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    Post by Bob Latino Sun May 16, 2021 4:48 am

    zuheyr wrote:Dear Gentlemen! I admire your work... Please tell me where and how can I purchase a kit... I am from belgium though :-(

    Kindest regards,
    Zuheyr

    Right now I am not shipping the VTA ST-120 amp kits outside the USA/Canada. I also do not have at this time any 240 volt power transformers for the VTA ST-120.

    Note - You can also a 220/240 volt to 120 volt step down converter which is actually less expensive that the $70 USD upcharge for the 240 volt power transformer on the amp. See link below ..

    750 watt drop down voltage converter

    Bob

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    zuheyr

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    Post by zuheyr Sun May 16, 2021 5:05 am

    Dear Bob,


    Thank you... Can I inquire about the details, or we better wait till things get a bit sorted out...

    Kindest greetings, Zuheyr
    Bob Latino
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    Post by Bob Latino Sun May 16, 2021 5:14 am

    zuheyr wrote:Dear Bob,


    Thank you... Can I inquire about the details,  or we better wait till things get a bit sorted out...

    Kindest greetings, Zuheyr

    I have had problems shipping outside the USA last year and this year. Very slow shipping times. I also had a package returned to me that I shipped to France. Maybe in a month or two we can resume shipping to places outside of USA/Canada.

    Bob

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    Dale Stevens

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    Post by Dale Stevens Sun May 16, 2021 2:01 pm

    Zuheyr, contact member Peterh here; he is in Sweden and has contacts on the Dyna. Dale

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    peterh
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    Post by peterh Sun May 16, 2021 10:52 pm

    Dale Stevens wrote:Zuheyr, contact member Peterh here; he is in Sweden and has contacts on the Dyna.  Dale

    Sorry but i have no shipping magic, i can only recommend that parcels have correct shipping address, checked by both parties before shipping.
    I have good experience with the US post, less positive with UPS

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    Tom Pickett
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    Post by Tom Pickett Mon May 17, 2021 8:11 pm

    penguinpages wrote:Tom,

    If I can clarify.   I am new to building an amp etc.. so was trying to collect details and suggestions and collect into what was my build of my ST-120.   I think their was a separate posting where you spoke about Yellow Page mod.. and I must have read it wrong / documented wrong that the mode used "10A10 10 Amp 1000V 10A 1KV Axial Rectifier Diode" but.. I think it was my mistake.  I later found the sticky posting for the official steps to do the mode for AC input voltage protection. these diodes I think .. per this post..  were to go on the four post standoff that is next (see picture) can you clarify if that is correct.  And WHY you did not use the "green ones" that came in the kit for the "10A10 10 Amp 1000V 10A 1KV Axial Rectifier Diode".   Thanks
    My progress on my VTA ST 120 Diodes10

    Yes... those are two green capacitors and not diodes for which I'm not going to need soldered on the three lug terminal strip because the same two capacitors are mounted on the time delay relay board (TDR) instead of the terminal strip.

    penguinpages.... The only difference between the yellow sheet mod and my setup is that I'm using bigger diode's's that handle 10A per my own preference.
    The yellow sheet mod uses smaller 1A diode's that handle less amperage. The rated voltage on the other hand is the same for both diodes but the amperage is less for the yellow sheet mod.

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