AIKIDO LV WON'T START - Page 2

M Gregg · 17th October 2010, 02:11 PM

Bill,
looks to me like he might have lost the heater return.

Any thoughts?

wushuliu · 17th October 2010, 05:44 PM

Quote:

Originally Posted by Bill Fuss

If you are measuring 48v from the PS to all the heater pins that means NO current is flowing. I would imagine that R17 is open.

I don't see a jumper at C1, it won't work without a jumper or switch there.

Thank guys! I swapped in a 2.2Ohm 10W Eagle resistor for R17 and now they're working. I'm reading 11.8v between heaters and 25,2v at the V3 junction... Is the 2.2 an okay value?

M Gregg · 17th October 2010, 05:46 PM

Sounds good to me!

Have fun

Regards
M. Gregg

M Gregg · 05:52 PM

What value is quoted for R17 in the circuit?

As long as you have 12.6V across each heater + or - 5% it should be OK.

Bill Fuss · 17th October 2010, 08:46 PM

I'm sure the turn on surge took it out, 1/4 watt was pretty iffy. A 3 watter would be plenty. The voltages across each tube wont match very well but anything close should work fine. Someone a few years ago did conductance tests on a few different tubes at different filament voltages and concluded that most will operate properly well below their rating. There is always a chance that one will not though, but you should be within 5% as M Gregg said.

wushuliu · 18th October 2010, 04:06 AM

Quote:

Originally Posted by Bill Fuss

I'm sure the turn on surge took it out, 1/4 watt was pretty iffy. A 3 watter would be plenty. The voltages across each tube wont match very well but anything close should work fine. Someone a few years ago did conductance tests on a few different tubes at different filament voltages and concluded that most will operate properly well below their rating. There is always a chance that one will not though, but you should be within 5% as M Gregg said.

Yes I think you're right. I'll continue to monitor the voltage.

wushuliu · 27th October 2010, 10:23 PM

I'm pretty good at building things, but math is not my strong suit. I'd like to figure out the output impedance of this 12BH7A LV Aikido but I'm stumped by 1) figuring out Rp. How do I get the value? And 2) Parallel lines - Er, what do they and 'in paralell with' mean?:

the formula in the pdf is this:

Zo = [rp/(mu +1) + R8] || R13 || [rp + (mu + 1)Rk]

halitun · 12th February 2013, 01:47 AM

Hey Guys, I know this thread was a year or so ago, but it helped me debug a problem with the LV. It was working on my bench system and then I brought it to a friend's house and hooked it up to his Adcom amp. It worked the first time and then the R17 resistor must have blown. Sure enough, it's open. I'll pick up a 3 watt 1 ohm resistor tomorrow. I've built several of Broskie's pre-amps and love them all. Next project is his SET amp with the Aikido pre in one box. Thanks!

17th October 2010, 05:50 PM	#14
M Gregg diyAudio Member Join Date: Jun 2010 Location: UK	What value is quoted for R17 in the circuit? As long as you have 12.6V across each heater + or - 5% it should be OK. Last edited by M Gregg; 17th October 2010 at 05:52 PM.

12th February 2013, 01:47 AM	#18
halitun diyAudio Member Join Date: May 2007	Aikido LV problem Hey Guys, I know this thread was a year or so ago, but it helped me debug a problem with the LV. It was working on my bench system and then I brought it to a friend's house and hooked it up to his Adcom amp. It worked the first time and then the R17 resistor must have blown. Sure enough, it's open. I'll pick up a 3 watt 1 ohm resistor tomorrow. I've built several of Broskie's pre-amps and love them all. Next project is his SET amp with the Aikido pre in one box. Thanks!

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17th October 2010, 02:11 PM	#11
M Gregg diyAudio Member Join Date: Jun 2010 Location: UK	Bill, looks to me like he might have lost the heater return. Any thoughts?

17th October 2010, 05:46 PM	#13
M Gregg diyAudio Member Join Date: Jun 2010 Location: UK	Sounds good to me! Have fun Regards M. Gregg

17th October 2010, 08:46 PM	#15
Bill Fuss RIP Join Date: Oct 2005 Location: Central Florida	I'm sure the turn on surge took it out, 1/4 watt was pretty iffy. A 3 watter would be plenty. The voltages across each tube wont match very well but anything close should work fine. Someone a few years ago did conductance tests on a few different tubes at different filament voltages and concluded that most will operate properly well below their rating. There is always a chance that one will not though, but you should be within 5% as M Gregg said.

27th October 2010, 10:23 PM	#17
wushuliu diyAudio Member Join Date: May 2008 Location: Los Angeles	I'm pretty good at building things, but math is not my strong suit. I'd like to figure out the output impedance of this 12BH7A LV Aikido but I'm stumped by 1) figuring out Rp. How do I get the value? And 2) Parallel lines - Er, what do they and 'in paralell with' mean?: the formula in the pdf is this: Zo = [rp/(mu +1) + R8] \|\| R13 \|\| [rp + (mu + 1)Rk]