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    Question for Bob

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    eickmewg

    Posts : 103
    Join date : 2014-08-29

    Question for Bob

    Post by eickmewg on Tue Jan 08, 2019 4:42 pm

    Over on the AudioKarma forum, an AK user named Destructor from MA posted he built up a VTA ST70 and "smoked" a choke. Said he was going to put it in a box in the closet. He is getting some useful advice to get the amp functional and I think he will pull it out of the closet. So, my question for Bob is "What is the success rate, or conversely the failure rate, with VTA kit builds?" Seems like this guy has been pretty quick to throw in the towel. I suggested he seek your excellent advice. I haven't seen him post here with the problem.
    ggnarley
    ggnarley

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    My Experience

    Post by ggnarley on Tue Jan 08, 2019 5:50 pm

    I can't speak of overall success rate, but I built same unit as a complete novice. Never soldered a board or seen a tube before building the kit. Took about 3 days, triple checking everything and emailing Bob a few times with questions.

    Amp fired up the first time and has been working fine ever since.

    Thanks
    Paul
    PeterCapo
    PeterCapo

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    Re: Question for Bob

    Post by PeterCapo on Tue Jan 08, 2019 6:48 pm

    How could that even be quantified?  I'm sure there are people of all skill levels who decide to build or work on tube amps.  My impression from reading through forums since around 2001 is that the vast majority of problems encountered are due to user/builder error. Getting discouraged is understandable, if you run into problems. But, yes, keep at it.
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    audiobill

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    Re: Question for Bob

    Post by audiobill on Tue Jan 08, 2019 6:54 pm

    I built over 100 of these amps, and if there was a very occasional problem it was my fault.
    Bob Latino
    Bob Latino
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    Re: Question for Bob

    Post by Bob Latino on Tue Jan 08, 2019 7:17 pm

    eickmewg wrote:Over on the AudioKarma forum, an AK user named Destructor from MA posted he built up a VTA ST70 and "smoked" a choke. Said he was going to put it in a box in the closet.  He is getting some useful advice to get the amp functional and I think he will pull it out of the closet.  So, my question for Bob is "What is the success rate, or conversely the failure rate, with VTA kit builds?"  Seems like this guy has been pretty quick to throw in the towel.  I suggested he seek your excellent advice.  I haven't seen him post here with the problem.

    Probably 80 % of all VTA amps go together and work and I never hear from the customer again. I assume they got it together fine because they have no questions and never again send me an Email? Maybe another 15 % run into minor "self inflicted" problems like bad solder joints, improper wiring, using a bad tube .. ("I don't need any tubes, I have the tubes I will use here already"). They send me a photo of the wiring and I can pick out the problem almost immediately and alert them where the issue is. The last 5% - send me a photo of the wiring and the symptoms of what the amp does and the problem is not easily fixed. After a number of Email and/or phone conversations we MAY get the issue resolved. Probably only 2 % of all kits require the customer to send the amp in to a VTA amp tech to get the issue resolved.

    Bob
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    eickmewg

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    Re: Question for Bob

    Post by eickmewg on Tue Jan 08, 2019 7:36 pm

    Bob, I am very pleased to hear that very low 2% value.  With your excellent instructions I would think total failures would be very rare.  I know that when I built my VTA ST 120, I mixed up some resistors on the power tube sockets and the triode switch, but I found the problem and a trip to Radio Shack (when it was open) fixed the problem and it worked fine on first fire.  I hope Destructor gets his amp working with help.
    sKiZo
    sKiZo

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    Re: Question for Bob

    Post by sKiZo on Wed Jan 09, 2019 12:39 am

    A little common sense and attention to detail during construct can work wonders. Here's my process on any build.

    I went thru the worksheets item by item and highlighted all the "solder later" connections, then worked my way thru the instructions one step at a time, checking them off as I went along.

    But wait. There's more!

    Once "done", I went thru the list one more time and checked off each step a second time to verify things were done correctly BEFORE first power up. Inspect all the socket and ground connections carefully for cold solder, and trim all the leads starting at one corner of the amp and working your way across. Make sure all the "solder later" joints are done too. Do the first power up per the suggested process and make sure you have proper voltages at all the test points.
    cci1492
    cci1492

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    Re: Question for Bob

    Post by cci1492 on Wed Jan 09, 2019 8:05 am

    If you're purchasing a kit for the sole purpose of saving a few bucks and the build process to you is going to be a hassle, my suggestion is don't do it, buy a WIRED one. The build should be something you 'll enjoy doing. Like others said, can solder and pay attention to details, not in a hurry are key points.
    tubes4hifi
    tubes4hifi
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    Re: Question for Bob

    Post by tubes4hifi on Wed Jan 09, 2019 3:47 pm

    I can concur (agree) with Bob's statistics completely, even concerning my preamp sales in which my page does proclaim that step-by-step instructions are NOT included with my preamp kits.
    About 80% of buyers build the preamp and I never hear from them, other than maybe to say, "wow, this sounds amazing" but no questions or concerns about the build process.
    So of course the other 20% do have some questions, usually the obvious stuff like wiring up the AC to the power transformers, wiring the selector switch, and wiring the volume controls.
    Only 2-3% have any real problems, or they have totally botched the job. Only about 1% return the product for me to rebuild.
    I would advise that if you aren't an experienced builder, buy it from me assembled/tested/warrantied! I would also say, the hard part is the chassis wiring.
    Ask me about having all that pre-done for you, and you can do the PCB assembly which is super easy anyway, and that will give you the pleasure of DIY for the most part!
    Rabindu
    Rabindu

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    Re: Question for Bob

    Post by Rabindu on Thu Jan 10, 2019 1:01 pm

    Three years ago I took the plunge and built an ST-120 with very limited soldering and electronics experience. I thoroughly enjoyed and savoured the building experience being in no rush, double checked everything methodically and in the end after a "drum roll please", all lit up without any magic smoke and nothing but sweet music followed. I used my Marantz PM8004 as a preamp to organize my various input sources.

    As time went by I was itching to make my system all tubes. After much contemplating whether I should tackle building one of Roy's preamps considering limited build instructions and therefore the need for the ability to follow wiring diagrams, again I took the plunge. Roy was kind enough to email the wiring diagrams, additional notes, etc. for me to pore over. These were not like Bob's step-by-step instructions which made it possible for a newbie like myself to understand.

    To sum it up, soon after the ST-120 build, I built an SP14 and a PH16 being methodical with limited instructions building on what I learned building the ST-120, thanks to Bob's super easy instructions. So far no magic smoke, all is working well. I have learned a lot lurking here on this forum each morning with my coffee, all you folks never cease to amaze me with your patience and the will to share knowledge and experience.
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    eickmewg

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    Re: Question for Bob

    Post by eickmewg on Wed Jan 16, 2019 10:22 am

    So Destructor has totally thrown in the towel with his VTA ST70. He now says anyone can come to Weymouth, MA and take it off his hands! Might be able to pick it up cheap or maybe even free if he is aggravated enough Very Happy He even complained that there wasn't enough room in the chassis! Check it out on the AK forum.
    bbqjoe
    bbqjoe

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    Re: Question for Bob

    Post by bbqjoe on Wed Jan 16, 2019 12:54 pm

    eickmewg wrote:So Destructor has totally thrown in the towel with his VTA ST70.  He now says anyone can come to Weymouth, MA and take it off his hands!  Might be able to pick it up cheap or maybe even free if he is aggravated enough Very Happy   He even complained that there wasn't enough room in the chassis!  Check it out on the AK forum.

    The whole thing seems rather lame to me.
    For starters, he decided to use some old tubes laying around.
    Next, and I'm no pro yet by any means, to burn up a choke would indicate a serious miswire somewhere, at least to me.
    The fact that he thinks there isn't enough room in the chassis means that he has left tons of extra length on his wires, or isn't routing at least close to the instructions.

    I believe he rushed through the build.

    To spend that kind of money, and just throw your hands up, says something that I will keep to myself.

    Go take it off his hands eickmewg!
    Please let us know what you find!
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    eickmewg

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    Re: Question for Bob

    Post by eickmewg on Wed Jan 16, 2019 2:05 pm

    Too far for me here in Nashville! If he offers free shipping, I'm all in.
    cci1492
    cci1492

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    Re: Question for Bob

    Post by cci1492 on Wed Jan 16, 2019 2:25 pm

    Bob is in Ma., maybe he can pay Bob to fix it.
    bbqjoe
    bbqjoe

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    Re: Question for Bob

    Post by bbqjoe on Wed Jan 16, 2019 2:33 pm

    cci1492 wrote:Bob is in Ma., maybe he can pay Bob to fix it.

    At this point, I don't think he cares.
    I'm afraid there's more damage than he knows, otherwise I might pay for shipping, fix it, and flip it.
    Peter W.
    Peter W.

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    Re: Question for Bob

    Post by Peter W. on Wed Jan 16, 2019 4:14 pm

    cci1492 wrote:Bob is in Ma., maybe he can pay Bob to fix it.

    If he blew up a choke - takes a dead-short for that - I fear for secondary windings on the power-transformer.
    bbqjoe
    bbqjoe

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    Re: Question for Bob

    Post by bbqjoe on Wed Jan 16, 2019 4:21 pm

    Peter W. wrote:
    cci1492 wrote:Bob is in Ma., maybe he can pay Bob to fix it.

    If he blew up a choke - takes a dead-short for that - I fear for secondary windings on the power-transformer.

    Indeed.

    It doesn't take a whole lot of not paying the proper attention to turn just about anything into a fuse.
    (don't ask)
    Ok you can, but I didn't, I just came really close.

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