Dynaco ST-70

dcarlson
dcarlson Posts: 1,740
edited April 2004 in 2 Channel Audio
I came across a classified ad for an ST-70 that seems like a decent deal, all depending on the condition. The ad says it's in immaculate and stock condition. No rust,shiney chrome,cloth-lead trannies, only mod is bananas.

What should I ask when contacting and how much is a reasonable price for one?
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  • gidrah
    gidrah Posts: 3,049
    edited April 2004
    When was it last used? What brand tubes are in it and how old are they? Does it have a hum? How good is the lettering?

    Prices range between $250 - $700, poor condition original - highly modded beaut. They usually are around $300-350 though.
    Make it Funky! :)
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  • dorokusai
    dorokusai Posts: 25,577
    edited April 2004
    DYNACO
    PWR, STEREO 70 SERIES IIc

    Description: CHROME CHASSIS

    Manufacture Years: 1991 - 1993

    Additional Information:
    Power: 35

    Retail
    MSRP: $1,100.00
    USED: $325.00
    Wholesale
    Mint: $190.00
    Average: $110.00
    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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  • F1nut
    F1nut Posts: 50,654
    edited April 2004
    Nah, it's either this,

    DYNACO
    PWR, STEREO 70 ASSEMBLED
    Description:
    Manufacture Years: 1972 - 1977
    Additional Information:
    Power: 35
    Retail
    MSRP: $180.00
    USED: $325.00
    Wholesale
    Mint: $180.00
    Average: $110.00

    or this,

    DYNACO
    PWR, STEREO 70 KIT
    Description:
    Manufacture Years: 1964 - 1969
    Additional Information:
    Power: 35
    Retail
    MSRP: $170.00
    USED: $250.00
    Wholesale
    Mint: $150.00
    Average: $85.00

    Keep in mind that the Bluebook isn't always on the money with what the prices are in the real world. Gidrah hit the mark with his prices and comments.
    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

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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    Here's some pics. What do you guys think of the condition?
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    Another
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    It seems to look pretty good but I've never owned any tube stuff, so I wouldn't really know any better. :D
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    One of the last two more than likely.

    gidrah listed several good questions. A couple more:
    Dynaco or Dynakit? The former are factory units. The kits are more sought after as components are not riveted to the chasis making tweaking easier.
    Are the cloth leads on the Output and Power transformers? Some sellers kind of ignore the PT and it's the one that changed to plastic.

    Things to look at
    Large or small PT - both are PA 060. The large is the more desirable, USA made one. The smaller is Japanese. The smaller one is more often found with plastic leads, but I've seen cloth coming from them.
    Big PT and Dynaco tubes:
    0aaee330.jpg

    Small PT:
    ef_1_s.JPG

    On the tubes... if it has the original Mullard - Dynaco EL34's (DYNACO in big, white lettering like in the first picture) with some life left in them, you can resell those for the better part of what the seller is asking.
    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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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    Here's another pic.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    So... Which is the PT?

    How can you tell if it's the big one or not?
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    PT (Power Transformer) is the one in the middle. OT (Output Trans) flank it. Height relative to the OT's is easiest way to tell.

    Well it's the big PT, anyway... Almost looks like the OT's have been painted which, if it's the case, would not be good.

    Looks original excepting the speaker posts and maybe the power cord (replacing neither is a bad thing). Even looks like the original electrolytic cap is in service. Looks like screws holding the board and tube sockets, so would be a Dynakit.

    Can't see the lettering. Any pic of the cage?

    The back right output tube looks like a mismatch for the other four, but could be the angle. Looks like front left is different as well. A new, matched tube set is not a huge expense, <$50 US, if buy new Svet's or other modern.
    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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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    Good eye. :D He said the tubes were mismatched but he could include a set of JJs whatever those are.

    Idiot me, the cage says Dynakit.
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    Nice cage... JJ's are a tube mfg, Tesla.
    http://www.thetubestore.com/teslael34l.html

    Ask the seller if the OT's have been rebuilt...
    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 April 2004
    Looks good Derick. Are those the pics the seller sent you? If it is, you should ask him to replace the selenium stack with a diode. From the internal pic, I can still see the selenium and no diode. If the selenium dies, the tubes are toast. Or you can buy a bias replacement kit for about $10 from several online stores.

    If it haven't been used in a long time you need to slowly bring it up on a variac.

    The biggest problem with the ST-70 is the age of the caps, resistors, etc. The trannies will last forever but it's the other parts you need to worry about. Mine gave up on me after about 5 months of daily use. I found a store that will do a complete restoration for about $1000CDN (worst case scenario). I'm getting it done in about a month.

    You can buy it and try it out. If you don't like it, sell it for the price you bought it for. If you like it, keep it. As a project, you can try to restore the unit yourself. You might fall in love with it's sound just like I did. That's why I'm getting it restored even though the price is a little high. I haven't found an amplifier I like more than the Dyna ST-70.

    If you decide to get it, make sure you have a multimeter to check the bias.

    Good luck

    Maurice
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  • organ
    organ Posts: 4,969
    edited April 2004
    "He said the tubes were mismatched but he could include a set of JJs whatever those are."

    JJ tubes: http://www.thetubestore.com/teslael34l.html Ask him if he has any other tubes. IMO, the JJ E34L are the worst tubes that ever went in my ST-70 along with the Sovtek 7199's. The Svetlana EL34 are the best IMO. http://www.thetubestore.com/el341.html

    Maurice
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    The pics are what the seller emailed me.
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    maurice,
    Do the output transformers look good to you? Especially the right one is bothering me as the four holes in the corners clearly show that the the caps are not aligned with the plates.

    dc,
    What is the seller asking for 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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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    He's asking $450CDN which works out to around $336US.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    I asked if it had a hum and he responded saying all inputs are dead silent except for the phono section. :confused:

    He also has Dynaco PAS-3 pre for sale and that may be where the confusion is coming from.

    It was last played friday or saturday.
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  • organ
    organ Posts: 4,969
    edited April 2004
    Tour,
    The output trannies look good to me. Not sure which four holes you're talking about but I hear ya on the caps. It looks like the original owner who built the amp didn't do a very good job there. It shouldn't be a problem though because the bias supply should be replaced anyway. Do they look like the stock caps to you? Mine were brown and labeled dynaco. I know there are different colors.

    Derick,
    That sounds like a good price. I'm sure the hum he was talking about was for the pre as the amp only have one input. If there's a hum from the amp, the quad cap is dead.

    Maurice
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    He mentions that it holds bias like a rock. Tho, high with new tubes. Does that mean anything to you guys?

    It sure doesn't to me. :D
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    If he's including the PAS 3 in that price I'd jump on it. If not...

    Caps look original to my eye as well. The resistors are defintiely original Black Cats...

    Here's photo enhancement of the left output transformer. Corner holes I was referring to are arrowed. Compare the way they look vs. the other OT in the original photo...

    EDIT: dc, the bias tends to drift in many of these. Has to do with the caps maurice and I have mentioned. If it's holding bias, the circuits are in good shape.
    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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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    What photo enhancement are you talking about?
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  • gidrah
    gidrah Posts: 3,049
    edited April 2004
    Originally posted by Tour2ma
    If he's including the PAS 3 in that price I'd jump on it.


    Run, don't walk. If not, walk quickly and listen. Is this a local seller? The lettering and chrome appear to be good. That's about what I (actually, the wife paid) for mine and I've been happy ever since.
    Make it Funky! :)
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    This one... :p
    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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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    BTW... nice PAS 3's fetch about $180 US on ebay.

    Nice ST-70's with the big PT are down a bit now and go in the mid-300's. A year ago they were about $100 higher.
    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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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    He's a couple hours drive away.

    One thing I did notice was the OT that Tour's talking about is the same side with the odd ball tube. Potential problem?
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  • organ
    organ Posts: 4,969
    edited April 2004
    Derick,
    So far it sounds like a healthy ST-70. The only thing you should replace is the selinium with a diode (5 mins with a soldering iron). How far away from you is the seller? If he's close, bring your pre and speakers to test with the amp. Do you still have your 1000i? Mine sounds awesome with my 800i.

    Maurice
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  • organ
    organ Posts: 4,969
    edited April 2004
    Tour,
    Ah I see. It could also be the angle of the pic. This is something Derick should look at if he could visit the seller.

    Maurice
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  • organ
    organ Posts: 4,969
    edited April 2004
    Still not sure about the mystery tube. Looks like it is covered by one of those things to reduce vibration in powered tubes. If you decide to get it, you should start looking for some NOS 7199's. The price is going up. The Philips 7199 are going for $30 each at thetubestore.com Don't even bother with the Sovtec 7199.

    Maurice
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    Looks to me like the mistery tube is the one with a cooper color top.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

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