Nooooooooo!

organ
organ Posts: 4,969
edited February 2006 in 2 Channel Audio
Looks like I won't be listening to the Dyna for a long time:(. For two nights in a row the amp tried to fry one of the power tubes.

At one time I was making cookies upstairs and heard a buzz coming from the speaker. I ran downstairs and looked at the amp and one of the power tube was glowing red. I shut down the amp, changed the Svet tubes to EH and it did the same thing again last night.

I will be sending it out for a complete rebuild if I can't find anybody here in Toronto. I'm more worried about the price for shipping than the rebuild. That thing weighs a ton!

A klipsch member recommended Craig from NOS Valves. He visits the Klipsch forum. He runs his own business on restoring, modifying and repairs on vintage equipments. Dynaco is one brand he works with. So far he looks like the right guy for the job. Anybody know another place for this kind of thing?

Here's another question. Do you think I should just buy another similar tube amp and get the Dyna fixed in the future? I know Jolida has a push-pull amp that use EL-34 tubes for $999US. That should be similar to the ST-70 but I don't know how it sounds. It doesn't use a tube rectifier though.I love the sound of my Dyna and I'd rather spend a lot on the rebuild than buy an amp and not liking it as much as the Dyna.

Maurice
Post edited by organ on

Comments

  • pjdami
    pjdami Posts: 1,894
    edited December 2003
    Maurice,

    Looks like you are going through some tough times with your amp. Your best bet especially if you like the way your amp sounds is to get it repaired. Word of mouth from another reputable member at the Klipsch forum is some good information. A repair should be cheaper than a new amp.

    If you are interested in Jolida, I would recommend talking to Walter Liedermann at Underwood Hi-fi in Roswell, GA. I purchased my Mod 1 Jolida tube cd player from him and it is spectacular. His number is 770-667-5633. Website is:

    http://www.underwoodhifi.com/retail.html

    Your best bet is to see what the price will be to repair the Dynaco since you enjoy it so much.

    I think Loud & Clear a Polk forum member here has a Jolida tube amp. You might want to ask him how he likes it.

    Good luck on you solution bro,
    Paul
  • organ
    organ Posts: 4,969
    edited December 2003
    Paul,
    Thanks for the help and link. You're right, I should try to get a parice for the repair first. I'm going to start calling around to see if anybody around here can repair and restore Dyna amps. If I can't find anybody, I'll probably ship it to Craig.

    I have my speakers hooked up to the ASL pre and NAD amp right now. It still sounds fu#king great with the Klipsch.

    Maurice
  • dcarlson
    dcarlson Posts: 1,740
    edited December 2003
    Sorry to hear your troubles.

    Baking cookies? :p Using canabutter I'm guessing. :D
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

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  • HBombToo
    HBombToo Posts: 5,256
    edited December 2003
    Its hard to diagnose the problem with the info so far but my assuption is you lost a diode in the power supply section or perhaps the cathode heater went nuts.

    if you have time please give us more info on what you see... meaning the bottom of the tube, top or just plain effed up if ya know what I mean.

    If it is the cathode heater the fix should not be that difficult.

    1/4 Twin or HBomb from a previous life;)
    ***WAREMTAE***
  • RuSsMaN
    RuSsMaN Posts: 17,987
    edited December 2003
    Good call Henry. I just wish he had a guru in his neck of the woods. Could just be a simple electrolytic or two bad, no?

    Are there any signs inside the amp? Anything look burnt, or anything starting to look 'funny'?

    Cheers,
    Rooster
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
  • HBombToo
    HBombToo Posts: 5,256
    edited December 2003
    Originally posted by RuSsMaN


    Are there any signs inside the amp? Anything look burnt, or anything starting to look 'funny'?

    Cheers,
    Rooster

    Great question bro. always look for the obvious first!

    1/4 Twin woken on 1/2:D
    ***WAREMTAE***
  • RuSsMaN
    RuSsMaN Posts: 17,987
    edited December 2003
    I'm just grasping at straws, maybe a resistor or 2 is on the way out, or another small electrolytic...

    Could it be an op-amp?

    Cheers,
    Rooster
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
  • HBombToo
    HBombToo Posts: 5,256
    edited December 2003
    Originally posted by RuSsMaN
    I'm

    Could it be an op-amp?

    Cheers,
    Rooster

    a chip in a tube pre or amp is most likely a timer. You can kill a tube fast if you apply voltage before the cathode is ready and a 555 is the switch to prevent this from happening. I only learned this recently after purchasing the manual for my Counterpoint SA12. When I saw the diagram I was most impressed.

    Twin
    ***WAREMTAE***
  • RuSsMaN
    RuSsMaN Posts: 17,987
    edited December 2003
    So what is regulating voltage to the 555 (timer) in a tube amp, like an sand amp would with an op-amp?

    Cheers,
    Rooster
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
  • HBombToo
    HBombToo Posts: 5,256
    edited December 2003
    Originally posted by RuSsMaN
    So what is regulating voltage to the 555 (timer) in a tube amp, like an sand amp would with an op-amp?

    Cheers,
    Rooster

    Excellent Question!

    In the case of my Counterpoint an additional 7v ac transformer with a full wave bridge is hanging off of the main transormer. There are 2 filter caps in parallel with the transformer and timer but they merely shunt transients.

    Twin needing another beer on this fine saturday night:D
    ***WAREMTAE***
  • RuSsMaN
    RuSsMaN Posts: 17,987
    edited December 2003
    We need a schematic for the Dyna. I've got a friend that has one I can go look at later this week.

    I need another shot.

    Cheers,
    Rooster
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
  • organ
    organ Posts: 4,969
    edited December 2003
    Derick,
    Actually, I made my special cookies a week before. I prefer to smoke the good stuff though:) It hits you hard and fast. Eating gives a very strong body buzz. I'm not saying it sucks. Eating pot will knock you off your **** :D LOL.

    Hbomb,
    The only diode in the amp is for the bias supply. I'm sure it's still good because I replaced it this summer along with the bias caps and resistor.
    The tube still looks normal and is still functioning properly but I haven't used it for a day now. I'm afraid something else might go bad. When I checked the tube socket, resistors, etc, everything was fine. Nothing visibly wrong inside the amp.

    Russ,
    Nothings looking funny inside the amp. The resistors are out of tolerance when I measured them but it's to be expected from 30+ years of use. They're not too far off.
    I've seen the guts of the amp too many times and I've never seen an op-amp. Not sure if op-amps were being used in tube amps at the time my Dyna was built. I hear this amp relies on the rectifier tube to "soft start" the signal and power tubes.

    The schematic can be found in www.dynaco-doctor.com You will see the original instruction book located on the left side of the screen. The parts list and schematic is in the instruction book.

    I will take more measurement of the resistors and see if I get any whacked readings. The amp is still working. I'm not using it because the problem could come back any time. The first time it happened was on the-front left tube and second time was on the back-right tube.

    I will contact Craig at NOS Valves to ask how much a total re-build will cost. If the price isn't too bad, this may be the best thing for me. The amp is very old and I'm sure there will be more problems coming. If I get a re-build, I wouldn't have to worry about a thing for long, long time.

    Thanks a lot for the help guys. I'll keep you posted.

    Maurice
  • F1nut
    F1nut Posts: 50,551
    edited December 2003
    Shot in the dark, but the rectifier is a known problem child. Look there first.
    Political Correctness'.........defined

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  • organ
    organ Posts: 4,969
    edited December 2003
    The rectifier haven't been used for too long. It is a NOS Mullard GZ34. It's the best GZ34 ever produced. They can take a lot of abuse and still test good. Some people have been using them for 30+ years. But I guess sometimes bad tubes can slip through QC.

    I also have a Sovtek GZ34. Next week when I have a lot of time I'll swap rectifer tubes and give the amp some long listening sessions. I really hope it's the rectifier:(.

    Thanks for the advice.

    Maurice
  • madmax
    madmax Posts: 12,434
    edited December 2003
    I have two of the 302A Jolida's and one of the 502A Jolida amps. Very nice amps!

    Sounds to me like step number one is to check all the speaker connections and make sure none are intermittant. Step two is to check the bias voltage. Standard stuff but either can take out your power tubes.
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
  • organ
    organ Posts: 4,969
    edited December 2003
    So far things are looking good. Last night I took a good look at every component in the amp to make sure there's nothing wrong. Everything looks okay after the visual inspection. Then I began to measure the resistors and everything looks okay there too. They're a little off because of age but still close. Ex. a 15.6 Ohms would measure 16 Ohms and a 1000 Ohms would measure 995 Ohms.

    I sat there looking at the amp and can't find anything wrong with it. So I decided to get it running again.

    I think I found the problem last night. I kept an eye on the bias voltage and it's not completely stable. It would reach its peak very late, around 2am. So if I set the bias early in the day, it might drift to far by 2am. So I set the bias to 1.5V during the peak hour and haven't had a problem. The amp was on for 5 hours last night and so far 3.5 hours today. So far so good.

    I feel so much better now. For two days I couldn't stop thinking about my baby. I hope the problem was with the bias.

    Thanks a lot for the help guys.

    Maurice
  • madmax
    madmax Posts: 12,434
    edited December 2003
    The bias should be stable after about an hour. If it continues to change it may be the line voltage. The bias moves right with the line voltage. In any case these changes are not enough to cause a problem unless you have it set at an extreme when line voltage is low and then it rises. You could have a resistor which changes resistance when it gets hot. The resistor values you are reading are well within tolerence ranges. If it were me I would hook up a voltmeter to the bias and keep an eye on it over time.
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
  • organ
    organ Posts: 4,969
    edited December 2003
    Thanks madmax. I will keep an eye on the bias. The only thing I'm worried about is the turn on/off. Now I'll be turning the amp off everytime I have to leave the room. Do you think this will harm the tubes? I usually leave it on until I have to go to sleep.

    How do you like the sound of your Jolida? Are there certain characteristics that really stand out? They use EL-34 power tubes right?

    Maurice
  • madmax
    madmax Posts: 12,434
    edited December 2003
    The Jolida's changed me within 5 minutes of listening. I cast out over 20K watts of SS power to use the tiny 50W per channel...
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
  • madmax
    madmax Posts: 12,434
    edited December 2003
    Originally posted by organ
    Now I'll be turning the amp off everytime I have to leave the room. Do you think this will harm the tubes? I usually leave it on until I have to go to sleep.


    Maurice

    It shouldn't hurt since you use a rectifier tube. If you were using a diode bridge you would shorten the life of the tubes.

    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
  • gkellerman
    gkellerman Posts: 8
    edited January 2004
    Heh, the red glow was probably the plate getting hot from the excess current. I don't have a schematic but I would guess that the bias voltage (Cathode to Grid) is from a resistor voltage divider network. Remember there isn't any law saying you can't do a Zener or other voltage regulator to stablize the voltage to a network and hence your (I'm guessing) Grid voltage. That should eliminate any drift.
    gkellerman@niche-soft.com
  • organ
    organ Posts: 4,969
    edited January 2004
    madmax,
    Thanks. It's going to be a while before I use it again though. I've exchanged several e-mails with Craig at NOSValves and it looks like I'll probably be getting it modded along with the re-build. What do you think? Keep it stock or get it modded? This is going to be tough.

    jkellerman,
    Thanks for the help. I'd like to work on the amp myself but it's just too much work and so little time. I'm sending it out in a few months for a rebuild and maybe a mod.

    Mauriced
  • F1nut
    F1nut Posts: 50,551
    edited January 2004
    Maurice,

    Do the mods and stop eating those special cookies.

    Jesse
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • organ
    organ Posts: 4,969
    edited January 2004
    Jesse,
    But the cookies are so good:cool:

    I was doing some reading on the mods but I think I'd rather let someone with more experience work with the amp. The rebuild is very hard to do also. I've done my part with the quad cap and bias supply replacement.

    Maurice
  • F1nut
    F1nut Posts: 50,551
    edited January 2004
    Maurice,

    Yeah, I'm sorry I meant, have the mods done by someone else.

    I use to like to roll my own (the best way IMHO), but I prefer reality these days and my Mom's chocolate chip cookies...lol.

    Jesse
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • audiobliss
    audiobliss Posts: 12,518
    edited February 2006
    I know I'm resurrecting threads from their graves here, but...

    Maurice - I was just wondering if you ended up sending your amp to Craig from NOS Valves and if so, how pleased you were with his work/price/etc.
    Jstas wrote: »
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  • fredv
    fredv Posts: 923
    edited February 2006
    Hey Maurice,

    I didn't see this thread until now. You can also give Jon Yaeger a call. He is really good guy and
    very competent. Take a look at:
    http://www.yaegeraudio.com/
    Click sale item on the left. He has a modified st-70 that looks really nice.
    IMHO, you won't go wrong with either Craig or Jon.

    Good luck!!

    -fredv-