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Stoopid question I know has been asked a zillion times before...

108.17.112.241

but I can't find the answer in the archives because I can't get the wording right...
I rebuilt my ST-70 circa 2006, Curcio rebuild kit with stock circuit driver board and quad cap PS replacement board, etc. Tubes good, NOS driver tubes, Winged "C" EL34s. Probably not more than 50 hours on the rebuild.
I haven't used the amp in three or four years, maybe five, but I want to try it again.
Can I just start this puppy up, or do I need a variac?
Sorry for asking this again...
___
The little old ladies wait in wild anticipation for the meetings of the Double-A-C-ASSN...

Follow Ups:

RE: Stoopid question I know has been asked a zillion times before... - petercapo 06:25:23 09/10/13 (18)
If you look around at some data sheets/specifications for even brand new electrolytic capacitors, you see specs for shelf life that indicate they need reforming after a while.
Although it may not be absolutely necessary, it probably is best to use the variac. When variac-ing the amp, start with a solid state replacement for the 5AR4 rectifier because it starts conducting much sooner than the 5AR4, BUT monitor the internal voltages in the amplifier so they don't get too high. I swap my SSR for the 5AR4 at about 70VAC line voltage or so, to finish variac-ing. (I would not use the SSR for normal operation)

Edits: 09/10/13 09/10/13 09/10/13 09/10/13 09/10/13 09/10/13 09/10/13 12/30/13
- How about Curcio's extended storage start up procedure? - olddude55 14:55:20 09/10/13 (17)
  The only issue I have is the quad cap bit, since I don't have the quad cap anymore (replaced with Joe's upgrade board).
  ___
  The little old ladies wait in wild anticipation for the meetings of the Double-A-C-ASSN...
  - RE: How about Curcio's extended storage start up procedure? - petercapo 15:32:26 09/10/13 (16)
    Not exactly sure what you are asking, but both the quad cap as well as the capacitors on your cap board are electrolytic and could need reforming. Again, it might not be absolutely necessary to bring the amp up slowly, but, if you don�t, and if anything goes wrong, it can be a headache to isolate problems and then do the rework. I figure it is better to be safe than sorry.
    
    I am not very familiar with Joe�s procedure for this, but I took a quick look and I think I saw that you need to desolder/solder things along with some other steps. Since the procedure is intended for the quad cap, you might want to look it over very carefully to make sure the instructions are portable to your cap board.
    - RE: How about Curcio's extended storage start up procedure? - xaudiomanx 16:28:57 09/10/13 (0)
      If the amp was running before he shouldn't have to de-solder anything. I think when the power supply board was installed originally is when all the de-soldering and re-soldering took place.
    - Right... - olddude55 15:36:46 09/10/13 (14)
      which wire gets desoldered from the replacement board...that's the question.
      Thanks for your help.
      ___
      The little old ladies wait in wild anticipation for the meetings of the Double-A-C-ASSN...
      - RE: Right... - xaudiomanx 16:25:00 09/10/13 (13)
        
        In Reply to: RE: Right... posted by olddude55 on September 10, 2013 at 15:36:46
        
        Why are you desoldering anything to bring the amp up on a variac. No need! Just plug the amp into a variac and the variac into the wall outlet, with the dial of the variac turned all the way down of course, and slowly come up until you see the rectifier tube filament start to glow a bit. Leave it there for about a half hour, then go a quarter turn more from where you are and repeat leaving it there. Keep doing it until you are totally powered up.
        
        The fact that you have four individual caps in place of the quad cap has nothing to do with powering up the amp. Each one of the caps on the board represents a section of the quad cap. The quad cap is four individual caps all sharing the one ground point within the can cap.
        
        Going with one of the power supply boards offered either by Joe Curcio or Sheldon Stokes is just another way of filtering the amplifier using more capacitance and for the most part, better quality caps(but that can be suggestive).
        
        The SS rectifier plug in is a good idea as you will get voltage to the caps sooner but I really don't think it is necessary. In fact, I would say you can just plug it in to a wall outlet and use it but as Peter said, better to be safe than sorry.
        
        It was down for an extended time once before after I rebuilt it. - olddude55 16:43:13 09/10/13 (11)
        
        In Reply to: RE: Right... posted by xaudiomanx on September 10, 2013 at 16:25:00
        
        I think it was out of service for over a year, and it powered up and sounded sweet.
        I don't have a variac yet. Parts Express has them with different current ratings. How much current handling will I need?
        ___
        The little old ladies wait in wild anticipation for the meetings of the Double-A-C-ASSN...
        
        A Variac is a great tool - 1973shovel 23:10:17 09/10/13 (8)
        
        In Reply to: RE: It was down for an extended time once before after I rebuilt it. posted by olddude55 on September 10, 2013 at 16:43:13
        
        And I would agree that you're better off buying a higher current model, so you can use it for other uses. But they can be pricy.
        
        However, if the only time you're going to use it is to warm up your hibernating ST-70, then you'll be able to get away cheaper building a dim bulb tester (link below).
        
        Good luck with your amp.
        dim bulb tester (Open in New Window)
        
        Great! - olddude55 14:24:50 09/11/13 (7)
        
        In Reply to: RE: A Variac is a great tool posted by 1973shovel on September 10, 2013 at 23:10:17
        
        Got everything I need except maybe the switch but that's OK; I have an idea for a really clean and safe tester.
        I'll need a 100w bulb, right?
        ___
        The little old ladies wait in wild anticipation for the meetings of the Double-A-C-ASSN...
        
        Another link - 1973shovel 14:49:25 09/11/13 (6)
        
        In Reply to: RE: Great! posted by olddude55 on September 11, 2013 at 14:24:50
        
        A stock ST-70 draws 190 watts, according to Dynaco literature. Using a bulb 1.5 times that would put you close to a 300-watt bulb. But, per the link below, you can start with a smaller bulb, say 15-watts, and work your way up. Just don't use a CFL or whatever they're called.
        I'd bet your amp would be OK to plug in as is, but since the DBT is easy to make, it's cheap insurance!
        Good luck with it.
        
        From the link below:
        Using the Tester
        "To use the tester, start with a 15-watt bulb. If it lights brightly, stop! You have a short circuit in the power supply, and should not plug the radio into the wall before investigating and repairing the fault.
        If the 15-watt bulb doesn't light, move on to larger wattages: 40, 60, and 100 in turn. Generally speaking, if the larger wattages don't glow, it's safe to plug your radio into the wall outlet."
        Passing the dim-bulb test doesn't mean your radio works perfectly, of course. There are many other faults that can't be detected by this device. But it does allow you a safe startup."
        Powering Up Your Radio Safely (Open in New Window)
        
        Edits: 09/11/13
        
        And to clarify again... - olddude55 15:22:28 09/11/13 (5)
        
        In Reply to: RE: Another link posted by 1973shovel on September 11, 2013 at 14:49:25
        
        Nearly everything in this amp was replaced when I rebuilt it. The only things left over are the output trannies, switches, speaker terminals, and the Mullard GZ34 rectifier tube.
        
        Thanks for your help.
        ___
        The little old ladies wait in wild anticipation for the meetings of the Double-A-C-ASSN...
        
        RE: "Mullard GZ34 rectifier tube" - 1973shovel 05:18:10 09/12/13 (4)
        
        In Reply to: RE: And to clarify again... posted by olddude55 on September 11, 2013 at 15:22:28
        
        Hang on to that tube. Baby it. You may want to consider doing the "diode mod" to the rectifier socket (see link at bottom). The mod is generally done to make Russian and Chinese 5AR4s last longer, but I don't know of any reason why you wouldn't want to use diodes with a Mullard.
        
        You're very welcome. You've given me plenty of good advice (sometimes while you're advising others) over on the Vinyl Asylum, so I'm just trying to return the favor.
        
        Keep us posted on your progress with your ST-70, Mr. Olddude!
        5AR4 diode mod (Open in New Window)
        
        Good news and bad news. - olddude55 14:38:30 09/14/13 (3)
        
        In Reply to: RE: "Mullard GZ34 rectifier tube" posted by 1973shovel on September 12, 2013 at 05:18:10
        
        The dim bulb tester didn't work. I tried it with a lamp connected to the top outlet, flipped the switch, got a soft "pop," and nothing else. No current through the outlet. Ran continuity tests, they confirmed something shorted in the outlet.
        So...I plugged in the ST 70, hooked an iPod and a pair of test speakers and there was nothing to worry about all along. It plays loud and sweet.
        Later on tonight or early tomorrow morning, I'll let it get good and hot on the work bench, set the bias, give 'er a try with my MMGs.
        And Stax SR-5s.
        Addendum: I did let it idle for about an hour and a half. Checked the bias, it was damned near perfect.
        ___
        The little old ladies wait in wild anticipation for the meetings of the Double-A-C-ASSN...
        
        Edits: 09/15/13
        
        Sounds like good news to me! - 1973shovel 13:10:28 09/15/13 (2)
        
        In Reply to: RE: Good news and bad news. posted by olddude55 on September 14, 2013 at 14:38:30
        
        I was hoping it wasn't your amp which went "pop".
        
        As I mentioned in one of my earlier posts, I felt it was probably OK to just turn your ST-70 on, but I didn't want to encourage "probably". It would have been different had it been in storage for the last ten or twenty years.
        
        I'm glad the came up strong. I hope you enjoy it driving your MMG's. Please keep us posted!
        
        It won't play loud, but damn, does it play good. - olddude55 16:49:24 09/15/13 (1)
        
        In Reply to: RE: Sounds like good news to me! posted by 1973shovel on September 15, 2013 at 13:10:28
        
        Quality over quantity.
        My "blow out the walls with sound" days are over anyway.
        ___
        The little old ladies wait in wild anticipation for the meetings of the Double-A-C-ASSN...
        
        RE: "Quality over quantity" - 1973shovel 17:51:09 09/16/13 (0)
        
        In Reply to: RE: It won't play loud, but damn, does it play good. posted by olddude55 on September 15, 2013 at 16:49:24
        
        Ain't that the truth?
        
        I remember trying a couple of tube amps (Marantz 8B and Dynaco ST-70) on my Dhalquist DQ-10s back in the late 1980s. Prior to that, I had been driving them with an SAE 100 WPC amp, using an Audio Research SP3-A-1 for many years.
        
        Dahlquist minimum recommended power was something like 50 or 60 watts, and their literature cautioned that clipping on lesser amps would burn out the tweeter.
        
        A guy in the audio club I belonged to lent me the Marantz, and I had one of those "jaw dropping" moments. I always thought the ARC preamp, along with an amp recommended by The Absolute Sound would have been just fine. But using a low wattage tube amp sounded SO much more like music.
        
        I've been a tube amp guy (other than my Pass First Watt F1J) ever since.
        
        I'm happy to hear the amp is working so well, and making you so happy!
        
        RE: It was down for an extended time once before after I rebuilt it. - petercapo 19:23:21 09/10/13 (0)
        
        In Reply to: RE: It was down for an extended time once before after I rebuilt it. posted by olddude55 on September 10, 2013 at 16:43:13
        
        I looked at Parts Express and I see three models: 3A, 5A and 10A. The Stereo 70 in its stock form takes a 3A fuse (don�t use a larger fuse in the Stereo 70 with the original power transformer). If you don�t ever have any problems with your Stereo 70 that causes its fuse to blow, and if it is all you might ever variac, then the 3A variac should be enough. However, if you ever do have any problems with the Stereo 70, then you might blow the fuse on the 3A variac, not that 3A fuses are expensive.
        
        If you think you might ever want to variac anything else that might draw more current, then the 5A or 10A models will give you more leeway.
        
        RE: It was down for an extended time once before after I rebuilt it. - xaudiomanx 18:44:54 09/10/13 (0)
        
        In Reply to: RE: It was down for an extended time once before after I rebuilt it. posted by olddude55 on September 10, 2013 at 16:43:13
        
        Mine is rated at 20A which is more than enough.
        
        RE: Right... - petercapo 16:35:13 09/10/13 (0)
        
        In Reply to: RE: Right... posted by xaudiomanx on September 10, 2013 at 16:25:00
        
        We were talking about Joe Curcio's procedure for bringing the amp up slowly without a variac. If you have a look at it, you will see that Joe's procedure requires that some things be desoldered/soldered, etc...

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