What to build with this PT?

[dartanion]

Is there any good way to measure the VA that it will actually handle?

I understand that VA is sort of irrelevant unless you know the resistance of the winding right? Larger wire, less resistance, and a larger core influence the actual VA rating correct? All those things sounds like a Mil-Spec unit to me. So, how do I measure this or is it a shot in the dark?

[skyboltone]

I mis read you David. You said VA not MA, so that's correct.

Dart, the test needs to be done at DC I was just reading in the Radiotron Handbook the other night. Makes sense too because of counter EMF and all that. Make up a breadboard power supply with a couple of 4007s in each leg and ground the center tap. Put some sort of cap on there then load the thing. I've made up years ago a bank of 1K 15 watt resistors on a perf board that I can clip onto with allegator leads. I'd like to do something similar with a couple of hundred watt adjustable resistors. Say 5K each. It's really useful. When I get home I'll give you a 450V 220uf can cap. I've got several still I think. Anyway, I'm shooting from the hip here but load it with about 1K in combinations of series and parallel resistors so that you have 110 watts of disapation. Continue to load it until you get somewhere around 10% voltage drop. I'd say that's pretty much the capacity.

Like I said, I have no reference for this, just a gut feeling that that's the way we'd do it in power distribution. I do know that it's routine to load transformers to 125% of nameplate capacity in any kind of commercial use.

I haven't seen PRR around in a long time. If I'm wrong I'm sure he'll plumb me up.

Oh, and you've got a DMM right? Measure the winding resistance and then plug the value into Duncan's Power Supply software.

[dartanion]

Of course I have a DMM...silly you

I'm one of those anal types that measures every resistor and cap that my DMM can handle before it makes into one of my builds. I'm not an EE, so I end up over-thinking everything.

Your description of the test rig sounds very intriguing, however a bit too ambitious for me at this point. I think a ballpark figure is in order.

I am thinking of an 6EZ5 PP PA, LTP, and a high gain octal preamp. I've got some fun ideas for this one.

[tubetek]

In Hammond's catalog, the CCS rated power transformers are 50% uprated for ICAS service... 200mA CCS = 300mA ICAS. This should be a safe rule of thumb. Also, When using a voltage-doubler setup the current is halved. Have fun with this one, dart!
(Best idea so far: 6AQ5/6005W PP; Dart, these sound GREAT!)
tubetek

[dartanion]

So by the 50% uprating in mA, that would put it at:

0.330 + 0.165 = 0.495 A

VA = 0.495 A x 270 V = 133.65 VA

That opens things a bit on what I could use for power tubes right? This should easily handle some larger power tubes than a 6AQ5. I know this tube sounds great and is the flavor of the day, however I have a nice stash of NOS 6EZ5s that I want to try out in some circuits. Anyway, a low power brown sound with some of these tubes should be interesting to say the least.

Anyway, this one will be on the back burner for a while. I have a 5 other amps in various stages of being built, and have a few speaker cabs to knock out.

I'll have to fire up the PSU designer app when I get closer to using this little beast.

[klingo]

Hi Dart!

I will try to post some (poor PC recorded) clips of my 6AQ5 10watter and even a 18wlite in a blues jr cab clip this afternoon (France)...they may help you...

Olivier

[skyboltone]

I'm reorganizing my "stuff" and found a big transformer today.

300-0-300 @ 500ma
5 volts at 5 amps
6.3 volts at 3 amps
6.3 center tapped at 7 amps

No mystery what you could build with that baby. But who needs a 100watt trainwreck?