hogwylde09 Posted March 26, 2017 Share Posted March 26, 2017 Anybody know what the miniature sockets are? Bias points? 1/8 input jacks? I know nothing about Dynaco stuff. Other than the tubes in this thing alone are probably worth what I gave for the whole amp. Sent from my SM-N900V using Tapatalk Quote Link to comment Share on other sites More sharing options...
USNRET Posted March 26, 2017 Share Posted March 26, 2017 I know jack about them as well but with the two blue pots in the back the red points bias points makes sense with common ground in the middle; black would have made it more intuitive if that is the case. Quote Link to comment Share on other sites More sharing options...
hogwylde09 Posted March 26, 2017 Author Share Posted March 26, 2017 Don't think l'll plug my headphones in it! Sent from my SM-N900V using Tapatalk Quote Link to comment Share on other sites More sharing options...
waxburger Posted March 27, 2017 Share Posted March 27, 2017 I think they are the bias points, but you could try a post at the Dynaco forum to find out for sure, those guys know their Dynaco. http://dynacotubeaudio.forumotion.com Quote Link to comment Share on other sites More sharing options...
hogwylde09 Posted March 27, 2017 Author Share Posted March 27, 2017 Probably should. Really want all electrons hitting the plates. At the speed of sound. Front & back. Narrowed down to the Belle's and CF4'S. I'll let the kg5.5 and JBL L200T rest comfortably numb. While I'm the same.Sent from my SM-N900V using Tapatalk Quote Link to comment Share on other sites More sharing options...
hogwylde09 Posted March 27, 2017 Author Share Posted March 27, 2017 Catch ya'll at the Gathering Sent from my SM-N900V using Tapatalk Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted March 27, 2017 Share Posted March 27, 2017 A clear close-up of the underside of the chassis may help to answer the question of what those jacks are connected to. Maynard Quote Link to comment Share on other sites More sharing options...
Marvel Posted March 27, 2017 Share Posted March 27, 2017 That's not a Dynaco driver board. The ST-70 used two 7199 tubes, but yes, the pots with the blue shafts on the original ST-70 would be to set the bias for the output tubes. The red jacks on the front were added to make it easier to use your meter probes. The must have added those when the took out the octal sockets that were on the front. They were used to power the Dynaco preamp. Also used one of the socket pins and ground to measure for stting the bias. Bruce Quote Link to comment Share on other sites More sharing options...
hogwylde09 Posted March 27, 2017 Author Share Posted March 27, 2017 Bruce could you enlighten me on the updated driver board? I am assuming the two mesh plate preamp tubes have been converted to something other than what wa originally in it. Is it 7199? I know I have a lot of research to do on mods. But maybe you could tell me what the factory used in those 2 positions, and what their recommendations were for it? Sent from my SM-N900V using Tapatalk Quote Link to comment Share on other sites More sharing options...
Marvel Posted March 27, 2017 Share Posted March 27, 2017 The 7199 contained a pentode and triode in one tube. The pentode was the input stage and the triode used as a phase splitter/inverter. There are various all triode boards available as upgrades. Craig (nosvalves) used a modified version one on an early version of his VRD amps (although I believe he used point to point wiring). The 7199 is no longer in production, and hasn't been for quite some time, and remaing ones are getting costly. The upgrade boards usually provide more features, such as individual bias settings for each output tube, etc. Bruce Quote Link to comment Share on other sites More sharing options...
avguytx Posted March 27, 2017 Share Posted March 27, 2017 That's definitely not a tubes4hifi VTA driver board as it has no bias adjustments on the board itself. That one of the other brands that slips my mind at the moment. I'll see if I can find it. I believe it goes with those front bias adjustments in place of the original sockets where the probes would normally go. Looks like a single adjustment per pair versus separate for each tube. Quote Link to comment Share on other sites More sharing options...
avguytx Posted March 27, 2017 Share Posted March 27, 2017 It kind of looks like the Triode, USA board. Just sell that board and get the VTA board with separate bias adjustments. It's a great sounding board. Quote Link to comment Share on other sites More sharing options...
tube fanatic Posted March 27, 2017 Share Posted March 27, 2017 It's never good to assume that circuit changes are what you think they should be based on what you would have done! Direct examination of the circuit is the only way to proceed when dealing with an unknown of any type. Trust me on this. I have encountered some really nasty things in home built/modified equipment over the years. Maynard Quote Link to comment Share on other sites More sharing options...
Srinath Posted March 27, 2017 Share Posted March 27, 2017 7 hours ago, Marvel said: That's not a Dynaco driver board. The ST-70 used two 7199 tubes, but yes, the pots with the blue shafts on the original ST-70 would be to set the bias for the output tubes. The red jacks on the front were added to make it easier to use your meter probes. The must have added those when the took out the octal sockets that were on the front. They were used to power the Dynaco preamp. Also used one of the socket pins and ground to measure for stting the bias. Bruce +1. That's the ever popular dynaco mod kit in there. Populrly installed by every hamfisted clown with delusions of "ability" and "knowledge". I know, cos I got one too. Thankfully, it does work, however some things in it are bypasses. By design ... yea right, the manufacturer intende to not be able to do 1/2 the functions they install. Yea sure. Cool. Srinath. Quote Link to comment Share on other sites More sharing options...
hogwylde09 Posted March 27, 2017 Author Share Posted March 27, 2017 Bruce, do you know who manufactured the board, part#, etc?Sent from my SM-N900V using Tapatalk Quote Link to comment Share on other sites More sharing options...
derrickdj1 Posted March 27, 2017 Share Posted March 27, 2017 17 hours ago, hogwylde09 said: Really want all electrons hitting the plates. At the speed of sound I have a hunch those electrons are moving faster than the speed of sound. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted March 27, 2017 Share Posted March 27, 2017 1 hour ago, tube fanatic said: Direct examination of the circuit is the only way to proceed when dealing with an unknown of any type. Trust me on this. I have encountered some really nasty things in home built/modified equipment over the years. Here's a good example. I bought this for 25 bucks from the retired EE friend. Masco "Audiosphere 100" 6550 PP PA amplifier. A guy would think no problem, check over the circuit, replace what is necessary and power it up. But unfortunately, some slob hacked on the amplifier and the wiring is a mess. Which makes things really difficult to trace through the circuit and figure out. A guy figures okay, it's hacked so maybe there is a online schematic or a Sams...nope... I dunno if this unit is a one off, or they were manufactured in really low numbers. It's like it doesn't exist. One of these days, I'll sit back down and try to trace through it again. It uses a 6V6 or some such for a voltage regulator...not really the most simple of circuits to chase through. Searched online for Masco "Audiosphere 100" to no avail. The older and lower power Masco PA amplifiers are popular with Blues Harp players, and there is a lower power smaller sized Masco PA amp which looks the same with the grey cover, brushed aluminum faceplate, and white knobs. The Audiosphere 100 must be a misfit. While it's not really an amp for fidelity audio, it would make a rather nice guitar head. Mike Quote Link to comment Share on other sites More sharing options...
Marvel Posted March 27, 2017 Share Posted March 27, 2017 There are many ST-70 driver board options: Curcio Audio (I have one of these but am replacing with another) http://www.curcioaudio.com/dynadr_3.htm#DYNACO STEREO 70 POWER AMPLIFIER Tubes4hifi board (what I'm wiring up now) http://www.tubes4hifi.com/ST70.htm And on and on... http://www.kta-hifi.net/projects/amp_page/st70amp/st70.html http://triodeelectronics.com/st70buildkit.html Take your pick 1 Quote Link to comment Share on other sites More sharing options...
davesans Posted March 28, 2017 Share Posted March 28, 2017 53 minutes ago, Marvel said: There are many ST-70 driver board options: Curcio Audio (I have one of these but am replacing with another) http://www.curcioaudio.com/dynadr_3.htm#DYNACO STEREO 70 POWER AMPLIFIER Tubes4hifi board (what I'm wiring up now) http://www.tubes4hifi.com/ST70.htm And on and on... http://www.kta-hifi.net/projects/amp_page/st70amp/st70.html http://triodeelectronics.com/st70buildkit.html Take your pick I have an ST70 with a Curcio Audio mod and thought about changing it as well. I am not real impressed with it. What are you going to replace yours with? Quote Link to comment Share on other sites More sharing options...
hogwylde09 Posted March 28, 2017 Author Share Posted March 28, 2017 Well, since it has Valvo EF86 pentode mod, I am going to have to give it a try. They sound incredible in our guitar amp builds. I don't plan on changing anything if it sounds half decent.Sent from my SM-N900V using Tapatalk Quote Link to comment Share on other sites More sharing options...
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