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ArcticBreaze 11th March 2012 03:06 AM

power supply? running off a generator
 
last night went to an outdoor gig we had 2 2kw generators supplying power my old jansen bassman 50 work a treat. but my 5e3 harmonica amp wouldnt go pluged into same supply valves got just a little warm nothing else. brought it home and pluged it into the power, way it went no probs at all. so why not off the generator? and is there anything i can mod so it will work next time.?

thanks in advance for any help

cyclecamper 11th March 2012 04:53 AM

What's a 5e3? Need details, as I've never heard of one.

Generators often don't make exactly correct correct voltage or hertz. And of course then you're running long extension cords, and they really need to be heavy-guage. Where is Oamaru? What's standard wall voltage there? In the US where we run off of 120v. we need really really hefty power cords because we need twice the current as 220v. countries for the same power. I've had really good luck with my smps, being regulated the amps still sound great regardless of house voltage. And my old Crown CE4000 power amps handled any supply from about 100 volts to 230 volts without any adjustment.

ArcticBreaze 11th March 2012 07:23 AM

wall voltage here is 240v, was thinking , the only real differance between the 2 amps is the bassman has solid stae rectifcation the 5e3 has a 5y3 how much differance does that make?

Trout 11th March 2012 02:40 PM

Quote:

Originally Posted by ArcticBreaze (Post 2941425)
wall voltage here is 240v, was thinking , the only real differance between the 2 amps is the bassman has solid stae rectifcation the 5e3 has a 5y3 how much differance does that make?

Should not have mattered, we do it up here in the USA all the time. I have a 5E3 that has seen over 1000 hours at outdoor gigs run off a generator.

I do however have an RCA NOS 5Y3 in the amp. When I used a Sovtek the voltage was already a tad to high so I switched it out (with no regrets).

You might want to carry an outlet tester to be certain the setup was wired properly though, sometimes we see bogus grounds at various stages.

Speedskater 11th March 2012 02:53 PM

Often the amplifiers that have problems operating with generator power are the modern design units. Some amps with SMPS supplies and many Carver amps don't do well on generators.

Pano 11th March 2012 03:03 PM

This is a really interesting problem. I have no idea what went wrong, but would love to know what y'all find. It seems most surprising that the tube PSU didn't like the generator.

FWIW, we have a 12KW backup generator here at the house. The waveform it puts out is UGLY. Never have tested a generator on a show.

cbdb 12th March 2012 09:43 PM

Yes, you need to test the voltage, with a scope. Its the peak voltage that matters. A meter will read 120v (230v) with a square wave output (inverter) but that will only give you 70% of the voltage needed at the amp power supply.

Nigel Goodwin 13th March 2012 09:24 AM

Quote:

Originally Posted by cbdb (Post 2943530)
Yes, you need to test the voltage, with a scope. Its the peak voltage that matters. A meter will read 120v (230v) with a square wave output (inverter) but that will only give you 70% of the voltage needed at the amp power supply.

Except we're talking GENERATOR not an INVERTER, and a generator uses an alternator with a sinewave output.

I'm with Pano, it'd be interesting to know exactly what the problem is? - it seems unlikely with a valve amp.

I've used generators a number of times over the years, never had a single problem - apart from running out of fuel, and no way to get more :eek:

cbdb 13th March 2012 06:56 PM

Quote:

Except we're talking GENERATOR not an INVERTER, and a generator uses an alternator with a sinewave output.
I know, the inverter was the extreme example. As Pano has mentioned the output of a generator is not a perfect sinewave (maybee at very little current draw), the only way to see the peak voltage is with a scope.


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