Biasing . . .

[i_got_a_mohawk]

Can i buy a voltmeter/ohmeter, whatever you want to call it (they are all one n the same multi function these days anyway ) , and check the biasing on my SVT II myself, it seems simple enough from looking at the back (where it tells you what to do and what reading it should be)


Or . . . should i shut up, go to bed and not even contemplate such an act of abject stupidity?

 

[James Hart]

it's not rocket science or brain surgery BUT IT CAN AND WILL KILL YOU IF GIVEN 1/2 A CHANCE!!!!!!


I'd get some books on how tube amps work... audiophile or instrument it's still tubes.

Maybe ask your local tech if you could "intern" (do some grunt work for free) after you know a little. Maybe some basic electronics coursing at the local Vocational/Technical school.

DON'T FORGET AN AMP THAT IF UNPLUGGED FOR DECADES CAN STILL HOLD CHARGE ENOUGH TO STOP YOU COLD.... AS IN DEAD!

 

[i_got_a_mohawk]

Ive done higher physics and actually passed it, have a decent knowledge of electronics, any books you can recommend ?

Looking at the back i dont see any easy way for me to kill myself

Its just a contol point and a ground point on the back of the case, i dont need to open any of the heart of it

 

[Tash]

Vacum tubes can act like capacitors and store a fairly decent charge. It only takes a few volts at the right amperage to stop a human heart.

 

[Kael]

Issues like this are why I'm biased towards SS.

 

[Tash]

I managed to shock myself pretty badly with a SS amp once or twice. Being dumb around electricity is always dangerous.

 

[i_got_a_mohawk]

Vacum tubes can act like capacitors and store a fairly decent charge. It only takes a few volts at the right amperage to stop a human heart.

Oh i know ( i actually learnt something at uni ! )

Any good websites with good information on biasing (im not gonna trust googling this time)

 

[paulie]

Make yourself up a dummy load that can dissipate 300w.

Anyone know if wirewounds ar ok for this (meant to be purely resistive, but is the inductance of these negligible or not?). Thick-films are pretty expensive here.

 

[i_got_a_mohawk]

i started a thread about dummie loads ages ago, apparently a 300watt resistor would do, but i wasnt actually thinking about that, would it not be ok to leave plugged into the cab paul ?

 

[paulie]

it might be a bit loud!

for calibrating the phase-splitter balance, 25v or so on the output is specified

 

[i_got_a_mohawk]

ah right, never considered that at all, probably wouldnt be too bright on the ol' speakers

have you ever biased your skunkworks yourself?

 

[tombowlus]

Any good websites with good information on biasing (im not gonna trust googling this time)

Here are some websites which were recommended to me after posing a similar question:

Invalid Link Removed

http://www.tone-lizard.com/

Link Removed

 

[tombowlus]

Make yourself up a dummy load that can dissipate 300w.

Does anyone know a source for 300 or 400w dummy loads? All I can find at Parts Express are 100w or 200w. Would a 200w load be adequate for testing a 300-400w tube amp? Can you use two 200w 8 ohm dummy loads for a total 400w 4 ohm load?

Tom.

 

[paulie]

Does anyone know a source for 300 or 400w dummy loads? All I can find at Parts Express are 100w or 200w. Would a 200w load be adequate for testing a 300-400w tube amp? Can you use two 200w 8 ohm dummy loads for a total 400w 4 ohm load?

Tom.

yeah. I was going to just wire up 4 x 100w 1R thick-film resistors in series on a heatsink. RS components in the UK .. whatever the equivalent in the States

 

[superfly]

I had an Ampeg v4bh last year that I biased by myself. Granted it was a single bias pot , but it was easy. I bought the bias kit online.http://www.amp-head.com/index.php?osCsid=ba36c191aa38e80a7dd84c9a4e7966c0
It included a multimeter and a tester lead for a 6L6 tube, cost about $40. It turns out I had "earballed" it almost dead on before I tested it.

 

[Tash]

I just tried to read one of those pages...now I know why I dropped EE...

 

[tombowlus]

I had an Ampeg v4bh last year that I biased by myself. Granted it was a single bias pot , but it was easy. I bought the bias kit online.http://www.amp-head.com/index.php?osCsid=ba36c191aa38e80a7dd84c9a4e7966c0
It included a multimeter and a tester lead for a 6L6 tube, cost about $40. It turns out I had "earballed" it almost dead on before I tested it.

Those are some interesting products, thanks!

Tom.

 

[superfly]

Yeah, the guy is very helpful, great instructions, fast emails and I recieved the product in about 3 days.

 

[steveksux]

Vacum tubes can act like capacitors and store a fairly decent charge

***???? That can't be right? I'm not a tube guy, but I thought the capacitors hold a charge, leaving parts of the circuit hot when power is disconnected, including higher voltages than the wall power. Some tube leads might be hot from voltages stored in the power supply capacitors, but the tubes are the victim, not the cause.

Not that it matters to you exactly WHY you're dead from touching the wrong thing.

And not that it matters what happens when the power is off anyway, don't you have to bias the amp while its on and running? So you'd better know your stuff if you try this at home. What you don't know CAN hurt you....

Randy

 

[i_got_a_mohawk]

***???? That can't be right? I'm not a tube guy, but I thought the capacitors hold a charge, leaving parts of the circuit hot when power is disconnected, including higher voltages than the wall power. Some tube leads might be hot from voltages stored in the power supply capacitors, but the tubes are the victim, not the cause.

Not that it matters to you exactly WHY you're dead from touching the wrong thing.

And not that it matters what happens when the power is off anyway, don't you have to bias the amp while its on and running? So you'd better know your stuff if you try this at home. What you don't know CAN hurt you....

Randy

Yeah, i thought it was the filter caps and other big hummy bas**ards that killed you