Need advice from tube experts

organ
organ Posts: 4,969
edited February 2004 in 2 Channel Audio
Well, I haven't used my Dyna for several months because once in a while it would try to blow a tube. The plates would glow red and amp start to hum.

I've been doing some reading around the net and a lot people say that this problem is usually due to bad tube sockets. The amp is still using the stock sockets, so it's 30+ years old. Anybody ever have this problem? Did the problem stop when you replaced the sockets?

Thanks

Maurice
Post edited by organ on
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited February 2004
    Sorry, no experience in this area...

    After several months idle though, I'd use a variac to reform the caps.
    More later,
    Tour...
    Vox Copuli
    Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb

    "Death doesn't come with a Uhaul." - Dennis Gardner
    "It's easy to get lost in price vs performance vs ego vs illusion." - doro
    "There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD
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  • organ
    organ Posts: 4,969
    edited February 2004
    No need for a variac because I replaced the quad cap and bias caps in the summer. Thanks for the suggestion though. I'm going to try to clean the sockets using pipe cleaners and fire her up again. Hope that's where the problem is.

    Maurice
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited February 2004
    Pipe cleaners with a little De-Oxit spritzer oughtta do it...
    More later,
    Tour...
    Vox Copuli
    Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb

    "Death doesn't come with a Uhaul." - Dennis Gardner
    "It's easy to get lost in price vs performance vs ego vs illusion." - doro
    "There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD
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  • organ
    organ Posts: 4,969
    edited February 2004
    Sockets seem to be clean. F#ck it, I'm just gonna save up and send it out. I don't trust those ancient parts anymore.

    Maurice
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  • madmax
    madmax Posts: 12,434
    edited February 2004
    www.partsexpress.com has the tube sockets. Why not just order them and install yourself? Have you found what causes them to glow red yet? I looked quickly but havn't found the cause.
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
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  • organ
    organ Posts: 4,969
    edited February 2004
    That's what I was planning to do but I don't want to keep waiting for problems arise as aging parts expire. The damage they cause is quite severe. I lost a total of 8 power tubes ($200CDN). One set is still functioning but the other have very low bias.

    Sending it out, be broke for a while and I should get a Dyna that's pretty much brand new with mods. I hear the mods sound way better. This way I should have troublefree operation for over 20 years. The only things staying are the transformers which is the amp's most valuable parts, and the chassis.

    Maurice
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  • bikezappa
    bikezappa Posts: 2,463
    edited February 2004
    Bad sockets may not be causing the red tubes. Red tubes means high filament voltage. You can check the filament voltage easy with a volt meter. The schematic shouyld tell you the tube terminals for the filament. Get the schematic. This is an easy unit to check voltages. The transmformer output supplies the filament power.

    Have fun. Point to point is fun to work on.
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  • disneyjoe7
    disneyjoe7 Posts: 11,435
    edited February 2004
    I think bias being off can cause this also.

    Cause ? I was thinking a cap but you said you replaced them, a bad diode maybe ? In the power supply maybe ?

    Speakers
    Carver Amazing Fronts
    CS400i Center
    RT800i's Rears
    Sub Paradigm Servo 15

    Electronics
    Conrad Johnson PV-5 pre-amp
    Parasound Halo A23
    Pioneer 84TXSi AVR
    Pioneer 79Avi DVD
    Sony CX400 CD changer
    Panasonic 42-PX60U Plasma
    WMC Win7 32bit HD DVR


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  • madmax
    madmax Posts: 12,434
    edited February 2004
    Originally posted by organ

    Sending it out, be broke for a while and I should get a Dyna that's pretty much brand new with mods. I hear the mods sound way better. This way I should have troublefree operation for over 20 years.

    Maurice

    Although I can kinda get behind that idea there is also the issue that you could go through the thing yourself, learn more than you ever thought you would and acquire the ability to go through future tube amps you may own. The ideas are common such as replacing old parts with premium parts, routing the wiring with power away from the signal leads, good quality solder, checking voltages to make sure they are correct, etc. You know the old saying about give a man a fish and feed him for a day or teach him how to fish and feed him for a lifetime. The only equipment needed is a decent soldering iron, a desoldering tool or wick, a cheap DVM and a desk to work at where you can leave things apart. Oh yea, and the knowledge of the internet!
    madmax
    Vinyl, the final frontier...

    Avantgarde horns, 300b tubes, thats the kinda crap I want... :D
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited February 2004
    maurice,

    You might try contacting the winner of this auction. I have a feeling he'll know how to fix your 70...

    http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=50593&item=3080024467&ssPageName=STRK:MEBWA:IT
    More later,
    Tour...
    Vox Copuli
    Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb

    "Death doesn't come with a Uhaul." - Dennis Gardner
    "It's easy to get lost in price vs performance vs ego vs illusion." - doro
    "There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD
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  • disneyjoe7
    disneyjoe7 Posts: 11,435
    edited February 2004
    Well heck,

    If I won that I would give it a shot on fixing it.

    But hard if you not in front it, nothing to go on:(

    Speakers
    Carver Amazing Fronts
    CS400i Center
    RT800i's Rears
    Sub Paradigm Servo 15

    Electronics
    Conrad Johnson PV-5 pre-amp
    Parasound Halo A23
    Pioneer 84TXSi AVR
    Pioneer 79Avi DVD
    Sony CX400 CD changer
    Panasonic 42-PX60U Plasma
    WMC Win7 32bit HD DVR


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  • organ
    organ Posts: 4,969
    edited February 2004
    Madmax,
    I'd like to do that but I just don't have the time. Changing the quad cap and bias supply was a major pain in the **** so I don't think I'm ready to do a rebuild alone. I'm not sure if the power tranny is healthy too. Replacements cost $100 but it's not hand wound like the original. However, I'd like to learn more and I plan on buying a foreplay kit this summer.

    Tour,
    Thanks for the link. I'll contact the seller as soon as I'm done my mid-terms at school this Friday. I don't want to think about tubes just yet. Too stressed out from studying. Have an exam on amplifiers, transistors, rectification, op-amps, BJT switching, etc tommorrow:(.

    Maurice
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited February 2004
    .. and you can't figure out your ST-70??? ;)

    Good luck on the mid-terms. I remember those sleepless cram sessions... vaguely.
    More later,
    Tour...
    Vox Copuli
    Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb

    "Death doesn't come with a Uhaul." - Dennis Gardner
    "It's easy to get lost in price vs performance vs ego vs illusion." - doro
    "There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD
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  • gatemplin
    gatemplin Posts: 1,595
    edited February 2004
    It looks like this book has specific info on the ST70

    http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=500-096&DID=7
    Graham
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