First-time power up of a new build

[richamor]

I've finally finished my Dynaco ST 70 build. I've installed a Classic Valve Dynamull driver board and Power Supply board, both build by Gregg van der Sluys himself. Beautiful work, and I see he is now offering the PS board as a completed unit on the website for a paltry 110 bucks.

So.....I want to power up. I've checked and re-checked the wiring and all seems OK. Gregg looked at it prior to my wiring the inputs and AC power cord
and deemed it good to go at that point. I have installed new 4 EL34 tubes, new rectifier tubes, and new EF184 tubes on the driver board.

I am unsure about how to turn it on for the first time. I will leave the rectifier tube out, as per instructions from CV on powering and setting bias with their PS board. I don't have a variac and don't have access to one. The amp sits in the cabinet waiting.

Do I need to have speakers connected? any sort of input?

 

[bktheking]

Yes you need speakers connected. Did Gregg tell you what to measure for bias after the fact. I know when I did my vta, bob latino supplied a power on and check procedure in which I followed. I have a dim bulb tester, you should build yourself one for the initial power on. Everything I repair and get that's dead or questionable always goes on the dim bulb prior to anything being powered on full wall power, even if it's just 1 cap or 1 resistor change it gets the dim bulb treatment.

http://www.tubes4hifi.com/VTA-Rebuild.PDF

Look at initial startup , besides the bias tests in which I'm not sure Greggs are setup it should give you an idea.

 

[dcgillespie]

You need speakers connected, and the input should either be shorted, or connected to the output of a preamp with no signal running through it. That way, you can hear if there are any inappropriate noises being made from the amp.

Preset the bias with the rectifier tube out according to instructions. With a new build, a variac is nice, but hardly necessary. Once all is good with the rectifier out, install it and proceed with any further biasing instructions. If you run into a problem in setting the bias at any point, stop, and do not proceed any further until the problem has been resolved -- this to save expensive components in case of a significant bias failure.

Good luck with your amp!

Dave

 

[richamor]

Gregg has supplied very good instructions for setting the bias and what values to look for, good and/or bad.

I will remove the rectifier tube, hook up some trash speakers, short the inputs, stand back, and fire it up as soon as I get home.

If it doesn't blow up or melt down, I'll go from there.