The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    Only a blown fuse? Anything else I should know?

    Share

    Tube Nube

    Posts : 641
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Only a blown fuse? Anything else I should know?

    Post by Tube Nube on Sat Jun 16, 2012 2:24 am

    Greetings to the group.

    Well, how long have I had my ST70 now, 3 years? No problems at all. But tonight I had an impulse to play an old Led Zeppelin record from my youth. 3 bars or so in I decide it's better left to the memory banks. Couldn't stand to listen to it.

    Down went the volume, off came the needle, but then a crackle, and the ST70 goes cold. I thought it was the rectifier, so replaced it with a spare Ruby, and nothing. The fuse. Must be the fuse.

    Sure enough, the glass is scorched, and the fine coil of wire that wraps around . . . something. A thick piece wire, it looks like. Well it's broken.

    So, I take it the fuse is burned out then.

    I have no idea why this happened. Lights didn't flicker like there was a power surge or anything. Shall I just replace it and see what happens?

    Any advice is appreciated.

    Thank you.

    Alan-14

    Posts : 46
    Join date : 2012-03-31
    Age : 56
    Location : Melbourne - Australia

    Re: Only a blown fuse? Anything else I should know?

    Post by Alan-14 on Sat Jun 16, 2012 7:00 am

    Hey Tube Nube,

    That's not good to hear....

    I would take the bottom cover off and visually check all the components and wiring for any signs of overheating or shorting (scorch marks on a resistor or cap) that might account for the extra current draw to blow the fuse.
    If all looks alright then replace the fuse and recheck the tube bias voltage and hope it's all good.

    No doubt Bob will chime in with a comprehensive check list.

    What Led Zeppelin album were you playing?
    Zeppelin were my favorite band when I was growing up ... Physical Graffiti was the 2nd record I ever bought back when I was 14 Smile

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Only a blown fuse? Anything else I should know?

    Post by Bob Latino on Sat Jun 16, 2012 8:37 am

    Probably what happened is that the rectifier just "bit the dust". Put in a new fuse and a new rectifier and you should be OK. It is sad to say that all the tubes made today are not as well made as those made in the 1950's and 1960's. Quality control isn't what it used to be and sometimes manufacturers skimp a little on the materials used. Shorter tube life span is the end result. This is especially true of rectifier tubes which look at 350+ volts on pins 2, 4, 6 and 8.

    On an ST-70 you can also use a 5U4 rectifier. There are plenty of American made 5U4's still in circulation and the prices for these are very reasonable. The only minor down side to using a 5U4 rectifier in an ST-70 is that the amp's high voltage will be lower and the amps overall power output will drop very slightly. The good thing is that unless you push your ST-70 really hard, you probably won't notice any loss of power.

    Bob

    Tube Nube

    Posts : 641
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: Only a blown fuse? Anything else I should know?

    Post by Tube Nube on Sat Jun 16, 2012 9:33 am

    Thanks guys for your immediate feedback. What a great group this is! I post a problem before bed time, and two helpful messages are here for me as soon as I awaken.

    Alan, it was the song Dyer Maker -- I forget which album. Old Robert Plant coulda been singing to my fuse there: "Oh, uh-oh ah oh-oh," {wait for it guys. . . } "you don't have to blow-oh".

    Sorry, I couldn't resist.

    Bob, thanks for recommending the rectifier along with the fuse. I was going to just change the fuse and try again. I have two spare rectifiers, the original Sov Tek and another Ruby.

    I'll get a hand full of fuses and report back this afternoon.

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Only a blown fuse? Anything else I should know?

    Post by Bob Latino on Sat Jun 16, 2012 9:43 am

    Make sure that you get 3 amp SLO-BLO fuses for the ST-70. There is an initial voltage surge at start up that will usually take out a normal fast-blo fuse. Any Radio Shack will have 3 amp slo-blo fuses.

    Bob


    Alan-14

    Posts : 46
    Join date : 2012-03-31
    Age : 56
    Location : Melbourne - Australia

    Re: Only a blown fuse? Anything else I should know?

    Post by Alan-14 on Sat Jun 16, 2012 10:03 am

    Ah ... D'yer Maker ... that's one of my favorite Zeppelin tracks. I don't think it sounds that bad ... LOL
    It's off the album Houses Of The Holy Smile

    And another bit of trivia ... my first ever record was Bachman Turner Overdrive's Not Fragile ... I do believe those guys were from your neck of the woods Smile

    Tube Nube

    Posts : 641
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: Only a blown fuse? Anything else I should know?

    Post by Tube Nube on Sat Jun 16, 2012 3:40 pm

    Hi Alan, you are right. Funny, they are from my neck of the woods, and I'm originally from your neck of the woods (born in Sydney).

    I had a client, once upon a time, who was a friend of Randy Bachman. He had some good stories.

    Tube Nube

    Posts : 641
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: Only a blown fuse? Anything else I should know?

    Post by Tube Nube on Sat Jun 16, 2012 3:43 pm

    Thanks Bob, I did get GDL3-AT fuses that claim to be 3A "time delay fuses".

    Think I'll save the fun for after I mow the lawn. Give me something to look forward to. To work for!

    Alan-14

    Posts : 46
    Join date : 2012-03-31
    Age : 56
    Location : Melbourne - Australia

    Re: Only a blown fuse? Anything else I should know?

    Post by Alan-14 on Sat Jun 16, 2012 5:58 pm

    So did your parents migrate over to Canada or did you move over yourself later in life?

    No doubt your client would have had some "interesting" stories about Randy Bachman Smile

    It's raing here this morning so no chance of mowing any grass ... damn ... might have to get out another CD and play it through some warm valve goodness Smile

    Tube Nube

    Posts : 641
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: Only a blown fuse? Anything else I should know?

    Post by Tube Nube on Sat Jun 16, 2012 8:12 pm

    Hi Alan,

    Yes, my parents moved us to Canada when I was 5. Some story about more opportunity in this country!

    Ok. So I replaced the fuse and rectifier. It came on, and about 30 seconds in, there was crackling and buzzing from the left channel, and a bit of a light show coming from the right rear KT 88.

    I presume this means that tube is probably done? I do have a pair of spares from the same brand . . . Do I go ahead and put in one or both right side tubes?

    Opinions? Ideas?

    Gentlemen, place your bets!

    Tube Nube

    Posts : 641
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: Only a blown fuse? Anything else I should know?

    Post by Tube Nube on Sat Jun 16, 2012 8:13 pm

    As to the lawn . . . well, I shouldn't have let the grass grow to 8". This is gonna be a two day job, at least! Al, I say go for it.

    Tube Nube

    Posts : 641
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: Only a blown fuse? Anything else I should know?

    Post by Tube Nube on Sat Jun 16, 2012 9:51 pm

    Ok, I risked it. I replaced the two right side KT 88 tubes with the spare pair, switched on, sat there waiting for trouble and nothing. After a couple minutes, I biased all tubes to 490 . . . millivolts I guess it is. Plus or minus. Amp's been warming up a few more minutes, and no snap crackle pop, so time for a listen to some actual music I say!

    Alan-14

    Posts : 46
    Join date : 2012-03-31
    Age : 56
    Location : Melbourne - Australia

    Re: Only a blown fuse? Anything else I should know?

    Post by Alan-14 on Sat Jun 16, 2012 10:30 pm

    Mowing long grass is a pain in the arse!

    Not good with that output tube flashing over like that ...
    I had one of my output tubes flashover as well not long after firing up my ST-120 for the first time as I cranked the volume up a bit.
    But 140 hrs later that tube is still running fine.

    Since you're replaced the rectifier tube I would re bias all the output tubes as the new rectifier might be out putting more than what the old one did and perhaps that caused the flashover.

    Follow Bob's bias setting process from the original start up procedure ... turn all the bias pots down to minimum before powering up the amp and start from there.

    I'm not sure if you would have to replace the pair of tubes because individual biasing removes the need of a "matched" pair.
    Maybe sonically it might be better to repace the tubes in pairs ...
    I'm sure others with more valve experience will let us know Smile


    Ah ... you beat me to it ... LOL

    Alan-14

    Posts : 46
    Join date : 2012-03-31
    Age : 56
    Location : Melbourne - Australia

    Re: Only a blown fuse? Anything else I should know?

    Post by Alan-14 on Sat Jun 16, 2012 10:38 pm

    All sounding good now Brenton?

    I've been listening to Joan Armatrading's Me, Myself I CD this morning ...
    In fact I had to listen to it twice I enjoyed it so much ...

    The combination of Bob's ST-120 and Roy's SP-14 is amazing ...
    The only downside now is ... I need better speakers ... Smile

    Tube Nube

    Posts : 641
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: Only a blown fuse? Anything else I should know?

    Post by Tube Nube on Sun Jun 17, 2012 11:44 am

    Hi Alan,

    I may just have to check out Joan Armatrading. I'm familiar with the name, but can't think of any of her tunes.

    You're right about the great sound. I've got the SP14, and it's a big improvement over the SP8, which I really loved! Still love. Just not as much.

    ;-)

    As to speakers, I wonder would you ever consider building them yourself? I was was in your dilemma, worried that worthy speakers would cost me a bundle when I tumbled to the idea of DIY, and I had no wood working skills, nor had I used anything bigger than a hand drill in 35 years.

    I've saved a bundle of money, and only spent . . . a smaller bundle.




    Tube Nube

    Posts : 641
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: Only a blown fuse? Anything else I should know?

    Post by Tube Nube on Sun Jun 17, 2012 11:50 am

    This ought to warm the collective hearts of you, Bob and Roy, as it does me.

    A friend of mine has a life long interest in hi fi. More at the speaker end of things -- a physicist by training, he designs and builds subwoofers and has written a number of articles published in audio magazines over the years on such things as subwoofers, room acoustics, etc.

    Well, he was over for a listen last week, and while he noted the lack of low end (below 100hz) from my speakers -- a common problem -- he otherwise was just thrilled with the sound of the stereo. He said it was the best he's ever heard in his life.

    I've always enjoyed wowing my friends, but I was quite nervous to have this guy hear my gear. What a thrill, I must say, to hear his enthusiastic praise.

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Only a blown fuse? Anything else I should know?

    Post by Bob Latino on Sun Jun 17, 2012 12:41 pm

    In regards to > "he otherwise was just thrilled with the sound of the stereo. He said it was the best he's ever heard in his life."

    I have these two scenarios below happen to me about 3 or 4 times over the past 6 + years. I am sure the same thing has happened to Roy and his preamps also ..

    Someone buys a VTA amp kit for his "second system" in his bedroom, family room etc. He puts the amp together and "trys it out" in his main system because his second system is missing the CD player, speakers etc. AND ... his main system sounds so much better now that the VTA amp never leaves the main system. It winds up replacing the amp that was in the main system. Some have bought another VTA amp for the second system ..

    I have also had people bring the amp over to a friends house with similar results. It sounds noticeably better than the amp that was there ... AND .. many times the friend buys a VTA amp to replace the amp that was there ..

    A lot of amp "quality" is pure hype that has been thrust upon the public by magazines like Stereophile (Stereophool?) and the brick and mortar "Hi-Fi Salons". Many Hi-Fi salons have closed down as customers become aware of the excessive hype being pumped out by these places. Internet sales have also been responsible for killing off the old Hi-Fi salon system.

    Near where I live in Worcester, MA there used to be four Hi-Fi salons. ALL are closed .. The nearest one to me now is in Framingham, MA (Natural Sound) about 40 miles away ..

    Bob

    Alan-14

    Posts : 46
    Join date : 2012-03-31
    Age : 56
    Location : Melbourne - Australia

    Re: Only a blown fuse? Anything else I should know?

    Post by Alan-14 on Mon Jun 18, 2012 7:20 am

    Tube Nube wrote:Hi Alan,

    I may just have to check out Joan Armatrading. I'm familiar with the name, but can't think of any of her tunes.

    You're right about the great sound. I've got the SP14, and it's a big improvement over the SP8, which I really loved! Still love. Just not as much.

    ;-)

    As to speakers, I wonder would you ever consider building them yourself? I was was in your dilemma, worried that worthy speakers would cost me a bundle when I tumbled to the idea of DIY, and I had no wood working skills, nor had I used anything bigger than a hand drill in 35 years.

    I've saved a bundle of money, and only spent . . . a smaller bundle.
    Hey Brenton,

    Yes you should look at buying Joan Armatrading's "Me, Myself, I"
    Once you start going through it you will recognise a few songs.
    And the best part is that it's really well recorded with lots of impact and dynamics and subtle nuances ...
    I have it in both vinyl and CD versions ... and the vinyl version just has that presence and warmth that the CD version can't match Smile


    As far as speakers go ... hell yeah I will be building my own!!!!!!!

    These are the speakers I'm going to build ... http://www.troelsgravesen.dk/JA8008_DTQWT.htm
    I have a friend of mine who is a cabinet maker and I asked him today if he would build the boxes for me as they are a bit complicated ... and I want them to look like a nice piece of furniture ... and with wood working I don't have the tools or the skill to get the quality I want.

    I'm hoping to order the components some time this week ... SmileSmile


    Last edited by Alan-14 on Mon Jun 18, 2012 7:45 am; edited 1 time in total

    Alan-14

    Posts : 46
    Join date : 2012-03-31
    Age : 56
    Location : Melbourne - Australia

    Re: Only a blown fuse? Anything else I should know?

    Post by Alan-14 on Mon Jun 18, 2012 7:40 am

    Tube Nube wrote:This ought to warm the collective hearts of you, Bob and Roy, as it does me.

    A friend of mine has a life long interest in hi fi. More at the speaker end of things -- a physicist by training, he designs and builds subwoofers and has written a number of articles published in audio magazines over the years on such things as subwoofers, room acoustics, etc.

    Well, he was over for a listen last week, and while he noted the lack of low end (below 100hz) from my speakers -- a common problem -- he otherwise was just thrilled with the sound of the stereo. He said it was the best he's ever heard in his life.

    I've always enjoyed wowing my friends, but I was quite nervous to have this guy hear my gear. What a thrill, I must say, to hear his enthusiastic praise.

    How cool is that ... I bet you had a smile from ear to ear Smile

    Thanks to Bob and Roy I now have the high end audio system that I have always dreamed of but could never afford Smile

    Tube Nube

    Posts : 641
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: Only a blown fuse? Anything else I should know?

    Post by Tube Nube on Mon Jun 18, 2012 11:01 am

    Alan,

    Those are stunning looking speaker. The cabinet construction doesn't look like it will be any problem for your friend to do a fantastic job with his cabinetry skills.

    I was perusing the site you linked to, but dont' have time to really explore it now, but I will do so later on, as that looks to be a very interesting speaker indeed.

    Regarding my friend's visit, yes. It was such a treat to have a guy so knowledgeable, listening with his discerning ear, telling me with such delight about what he's noticing in the sounds. His detailed comments about the imaging and sound stage, his ability to follow multiple things at once that different musicians were doing etc, compared to when he listens to the same recording (Graceland) at home.

    I encouraged him to let me have the bad and the good, and I think he was genuine. It's always nice to have someone say "oh, that sounds good", but to hear the praise from a guy who's so knowledgeable -- It did make me grin from ear to ear.

    Not that I should be surprised. Bob's experiences that he notes above are as amusing as they are satisfying, and he forewarned me a few years ago that these amps really punch above their financial weight class -- especially when compared against specialty boutique name brands.

    Encouraged by recent experiences, I'm really eager now to get the friend of a friend over here for a listen. He has a reputation as something of an audio phile. If not mistaken, Krell his brand. Even if his own stuff is stellar, I have no fear of being shamed.

    It's fun to share!

    Alan-14

    Posts : 46
    Join date : 2012-03-31
    Age : 56
    Location : Melbourne - Australia

    Re: Only a blown fuse? Anything else I should know?

    Post by Alan-14 on Tue Jun 19, 2012 11:03 am

    Brenton,

    Those speakers have been designed for high eficiancy to be suitable for valve amps.
    The designer Troels Gravesen is a die hard valve afficionado himself and these are his flagship speakers.

    The feedback on these speakers are that they are something special indeed.
    We have a HiFi forum here in AUS called StereoNET and on the weekend I stumbled apon a member that had built these speakers last year.
    He's had a couple of sessions where other forum members went to his place to audition his speakers and all came away very impressed ... and these guy's are like your friend ... hard core audiophiles who aren't easily impressed ... but they were in this case.

    Seems like we both have the same speaker issues ... a lack of low end bass.

    Do you have any pictures of the speakers you use?

    I have a feeling your audiophile friend will be suitably impressed with your system ... Smile

    Tube Nube

    Posts : 641
    Join date : 2008-12-06
    Age : 53
    Location : Calgary, AB

    Re: Only a blown fuse? Anything else I should know?

    Post by Tube Nube on Fri Jun 22, 2012 12:27 am

    Hi Alan,

    Having a hard time here figuring how to post a photo. Maybe I'll pm it to you.

    Sponsored content

    Re: Only a blown fuse? Anything else I should know?

    Post by Sponsored content Today at 7:28 pm


      Current date/time is Sun Dec 04, 2016 7:28 pm