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dbishopbliss
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« on: December 28, 2010, 12:03:28 PM » |
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I just picked up a ST-70 (like I need another project), but the price was right so I figured why not. It has the original driver circuit with 7199 tubes. There are a number of upgrade boards out there that vary considerably in price. Does anyone have any experience with upgrading a ST-70?
The deal also included a PAS-2 preamp and an EICO HFT-90.
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David B Bliss
Bottlehead: Foreplay I, Foreplay III, Paramour I w/Iron Upgrade, S.E.X. w/Iron Upgrade
Speakers: FE127E Metronomes, Jim Griffin Jordan/Aurum Cantus Monitors, ART Arrays
Other: Lightspeed Attenuator, "My Ref" Rev C Amps, Lampucera DAC
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ssssly
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« Reply #2 on: December 28, 2010, 01:03:46 PM » |
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Dynaco doctor also has some nice boards.
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JC
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« Reply #3 on: December 28, 2010, 01:26:12 PM » |
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I just paid the price for a couple of 7199s.
First item, for safety's sake, was to replace the Selenium rectifier in the negative bias supply circuit with a generic silicon one. You don't want to run the risk of breathing the results of a Selenium diode going "poof", I am told. I just mounted a little 3-terminal strip to the screw that holds the Selenium stack in place to mount the silicon diode. Since that bias supply is important, I replaced the caps and resistors in it while I was at it.
A new multi-section cap for the main supply was to be had at Antique Electronics Supply. They were actually manufacturing a drop-in replacement.
The plating on the input connectors is usually pretty grim, so I replaced those with a couple of cheap gold-plated ones from RS that fit into the same phenolic insulator that the old ones were in.
A three-wire power cord, again for safety's sake on an exposed steel chassis with lots of Voltage running around inside.
New film-and-foil coupling caps on the PC board. Some metal-film resistors where they were appropriate. New ceramic tubes sockets all around. Some new grounding.
I know this isn't what you asked for, but I wanted to hear what it sounded like in more-or-less its original configuration with a few updated parts.
I was not disappointed.
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Jim C.
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howardnair
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« Reply #5 on: December 28, 2010, 04:05:28 PM » |
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tubes for hifi also has a very nice psu board and input/ output rca board for the pas2-the input /output board only has 7 rca's instead of 9 much more room i liked that very much--i went with new stock boards for mine- instead of the upgraded boards--i kept the tone controls-i would get a new selector switch -i used prp resistors and a mix of soniccraft and jupiters on the phono and line stage--used soniccraft on the panel-i also used relcaps on the phono board --you will need to do the riaa eq phono board mod --just type that in your google and it will come up-if the faceplate of the pas2 is brass you can refinish that by sanding it down on the upper part with 600 and 1000 -and repaint the bottom strip and lightly sand the lettering then some spray lacqeur-will look brand new-- for the st-70--there is tubes for hifi--triode electronics--dynakitparts.com and of course the dynacodoctor--then the choice of upgraded driver board or stock-
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Grainger49
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« Reply #7 on: December 29, 2010, 06:58:48 AM » |
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Curcio Audio, The Dynaco Doctor, sells a replacement for the multi-cap that fits where the bias supply sits. It gets rid of the old bias supply and the Selenium rectifier. I would go with that for sure. Leave the old multi-cap there for stock looks.
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Grainger Morrison,
Mozzie quote: Sacred cows make the best hamburgers!
Remember, YOU are the only one who needs to be happy with the sound of your system.
Eros (Mods Have Begun!)/FP-2/Paramour 1/upgrades to all - PS Audio Regenerator, Triangle Zerius Speakers, BA Sub
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howardnair
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« Reply #8 on: December 29, 2010, 10:51:03 PM » |
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ward--that is simply excellent
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Listens2tubes
Newbie
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Posts: 5
Have you tweaked today?
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« Reply #9 on: January 03, 2011, 03:13:00 PM » |
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ward you are an artist. Most St-70 mods have simplistic additions to te original chassis that often look "add-on". Your design is original and sexy.
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Neal P.
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Paully
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« Reply #10 on: January 05, 2011, 05:11:28 AM » |
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Don't forget Triode Electronics. They have tons of stuff too. I used their Power Supply board this time around for my most recent Dynaco rebuild. http://store.triodestore.com/ |
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dbishopbliss
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« Reply #11 on: January 05, 2011, 06:15:08 AM » |
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I think I'm going to go with the Triode Electronics SDS power supply board and the EF86 Driver Board. Although, I really should finish the other projects I have on the bench before I start this one.
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David B Bliss
Bottlehead: Foreplay I, Foreplay III, Paramour I w/Iron Upgrade, S.E.X. w/Iron Upgrade
Speakers: FE127E Metronomes, Jim Griffin Jordan/Aurum Cantus Monitors, ART Arrays
Other: Lightspeed Attenuator, "My Ref" Rev C Amps, Lampucera DAC
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STURMJ
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« Reply #12 on: January 05, 2011, 08:25:26 AM » |
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Triode's transformers are great too! If you need them. Also, they are better than the originals.
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HF9
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« Reply #13 on: January 05, 2011, 09:37:20 AM » |
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Although, I really should finish the other projects I have on the bench before I start this one.
Sounds like you need a second bench  |
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Dyna Saur
Jr. Member
Offline
Posts: 69
Yippie-Ki-Yay....
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« Reply #14 on: January 05, 2011, 06:31:17 PM » |
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ed brown
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