BEC Posted December 31, 2002 Share Posted December 31, 2002 Well for some reason this Ebay purchase arrived today by UPS second day air which is the only kind of USP service available on New Years Eve. My second recent old tube integrated amp purchase. The first is a Scott 222B which is awaiting arrival of caps I have on order. I decided to just throw caution to the wind on this one and "hook er up". I did look inside to make sure nothing looked burned or broken. It seems all original except for the tubes. It has a quad of Sovtek 6BQ5s for outputs, a pair of Sylvania 12AX7's and one Sylvania and one Dyna 7199s. I haven't tested them yet. As far as its function, pretty good. I hooked it up to a set of Cornwalls, let it warm up then turned the volume all the way up with no signal. A bit of hum (60 Hz.) present. Might need a filter cap. Hit it with some Manheim Steamroller (Classical Gas) and it sounds nice. I was barely able to get it to my normal listening level (about 92 db per Rat Shack Meter) before running out of volume control pot. The Scott 222B will reach this level at about 1 o'clock on its volume control pot and has a bit left before clipping. The Dyna should be able to do about the same but like I said I haven't even tested the tubes yet. The Dyna gave no hint of clipping even at full volume but like I said full volume was nothing like the Scott. I plan to start reworking both of these amps when the caps arrive. Nice work for cold rainy winter days in Arkansas. The Dyna looks way simpler to work on than the scott. I think it has fewer than half the components in it compared to the Scott. I also have a Scott LK 48B on the way so the three of these should keep me out of mischief for awhile. Quote Link to comment Share on other sites More sharing options...
lynnm Posted December 31, 2002 Share Posted December 31, 2002 I think you will like that amp. I built one years ago and it was one sweet little unit. Keep us posted. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted December 31, 2002 Share Posted December 31, 2002 You should easily be able to achieve zero clipping at near 100% volume out of the Scott once you get it rebuilt every unit I've done has no problem putting out rated wattage with near zero distrortion through the ears or a scope. The Dyna looks simpler because of its circuit board design rather than point to point. When you start replacing parts on those circuit boards you will wish it was point to point they are very delicate. Have fun and happy New Year Craig Quote Link to comment Share on other sites More sharing options...
BEC Posted December 31, 2002 Author Share Posted December 31, 2002 Craig, Yeah the stuff on the old circuit boards will be a challenge to replace without doing major damage to the boards. Back in the 70's right after I graduated from Air Force High Value and Micro-Miniature Soldering School would have been a better time for me to do that sort of stuff. A Pace Soldering Station like I used in the Air Force would be nice also. By the way, any ideas on how I can get a manual or at least a schematic for the Dyna SCA 35. Bob Quote Link to comment Share on other sites More sharing options...
NOSValves Posted December 31, 2002 Share Posted December 31, 2002 http://www.geocities.com/vintageaudio/ there you go Quote Link to comment Share on other sites More sharing options...
DRBILL Posted January 1, 2003 Share Posted January 1, 2003 I do a lot of DYNAKIT rebuilding. Everything that has been said about how fragile the board is is true. It doesn't look as nice, but I clip the old leads off near the component and solder the new stuff on to these. Go ahead and replace the filter caps. As long as you have the iron hot and the unit unwrapped, it makes sense. That's a sweet little amp. You will like it with highly efficient speakers. Don't worry if the volume control doesn't go up to "11"! That has much to do about the "slope" of the control and how it is wired. Apples and oranges. Yes, you need to test the tubes! I don't know everything, but I'll be happy to be stumped if you run into trouble. You have probably looked at all the links for DYNACO advice and parts. If not, let me know, and I'll mention my favorites. Good luck! DR BILL Quote Link to comment Share on other sites More sharing options...
DRBILL Posted January 1, 2003 Share Posted January 1, 2003 BOB Get the manual and schematic free on-line at www.triodeel.com/schindex.htm DR BILL+ Quote Link to comment Share on other sites More sharing options...
BEC Posted January 1, 2003 Author Share Posted January 1, 2003 Dr Bill Thanks for the link. I only saw the schematic there for the SCA-35. Did I miss the manual. Also thanks for the advise and offer of help on the Dynaco. Actually I was already thinking about the lead-cutting shortcut you mentioned. That would sure simplify things. Bob Quote Link to comment Share on other sites More sharing options...
BEC Posted January 3, 2003 Author Share Posted January 3, 2003 Thought I might bump this topic back up to let you know that the third of my old tube integrated purchases has arrived. This is the Scott LK-48B. As I stated before, I planned to rebuild all three (Scott 222B, Dyna SCA35 and this Scott LK-48B) once caps I have ordered get here, but wait! I can't find anything wrong with the LK-48B. I hooked it up to the Cornwalls and musical delight was immediately present. This old amp is dead silent at full volume with no input. It will get loud and stay clear in this big room (24 X 30) and I don't think my cornwalls have ever sounded better. Whoever built this kit (or perhaps rebuilt it) knew his wiring and soldering. I say "perhaps rebuilt" because it has a lot of Sprague Orange Drops underneath. I think orange drops may have been around when this kit was built but sort of doubt that they would have been supplied with a kit. Anyway, Craig told me the LK-48 would blow the other two amps out of the water and I have to agree. This thing has some real serious looking output transformers looks to be a real quality piece of gear all the way. Right now I am just enjoying listening to it. Bob Quote Link to comment Share on other sites More sharing options...
DRBILL Posted January 4, 2003 Share Posted January 4, 2003 Bob, I'm afriad I misspoke. I was unable to find the booklet, either. The schematic is really all you will need. Sorry. DR BILL Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 4, 2003 Share Posted January 4, 2003 Bec, If the coupling caps have been replaced then the only other part you really need to check is the Selenium rectifier . I believe this amp has it hid in the tone control area right next to the volume pot. Make sure this peice has been updated to a new Silicon Bridge rectifier. If this has been replaced and the amp is dead silent at 100% volume you should be all set. They are indeed nice amps when all is well. Shoot me some pics of the under chassis and right near the volume pot and I can tell you if the part in question has been replaced. You should also check the Neg. Voltage headed in series to the 12AX7 heater (pin 5) it goes in pin 5 and out pin 4 and then on to the next 12AX7 pin 5 and so on. This voltage should start out at about - 46 VDC . and drop by 25% for each tube. You also should learn to Bias this amp it has all the pots and test points available and should be set to 46 ma per pair of tubes and then balanced. Craig Quote Link to comment Share on other sites More sharing options...
BEC Posted January 4, 2003 Author Share Posted January 4, 2003 Craig, Not sure about the selenium. I don't know if I would recognise it. Looks like a square block with 4 wires attached in the assembly manual that came with this LK-48B but I don't see anything that looks like that so far in the area where the assembly manual shows it (behind the front panel near the input selector switch). I will fire you a few pics of the underside by email. There are still some cerecaps in the unit along with some orange drops. The assembly manual that came with the unit does not have a schematic in it. Bummer! I was hoping for a big fold out schematic. Also, the bias procedure in the assembly manual flat doesn't work. It involves running an audio cable from Bias test point L to Channel L and adjusting one bias pot while operating the bias switch for minimum "clicking" sound in the speaker. That procedure does nothing. I wonder if someone has set the bias up as "fixed". Anyway, the unit sounds great and I will have to research the bias issue more. Bob Quote Link to comment Share on other sites More sharing options...
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