Scored some NOS chokes today (in their boxes with the wax paper wrapping in tact). Each has 2 x 25 henry chokes (and instructions for series or parallel). Any guesses to how much current could be run thru them?
How do you actually measure current capability?
Southwestern Industrial Electronics Co, Huston TX. Model KC5005
dave
How do you actually measure current capability?
Southwestern Industrial Electronics Co, Huston TX. Model KC5005
dave
Attachments
A brace of choke!
Guestimate
200mA (sections in series)
As for testing, can only think of a contrived way to test (an actual circuit).
Someone must know an easier way....
You might also want to know whether they are suitable for choke-input use as well; eg whether they can stand some DC without loosing too much inductance and buzzing.
What is their DC resistance?
Time for a nice valve amp I think Dave....
Cheers,
Guestimate
200mA (sections in series)
As for testing, can only think of a contrived way to test (an actual circuit).
Someone must know an easier way....
You might also want to know whether they are suitable for choke-input use as well; eg whether they can stand some DC without loosing too much inductance and buzzing.
What is their DC resistance?
Time for a nice valve amp I think Dave....
Cheers,
Hello Take care i once destroyed some black Gate with a choke input with a surplus choke. If you will not use it for a choke input you can try to give it a try with a modest current and check the temperature from time to time. Maybe they are meant for aviation industry ( 800 cycles ) I would anymore go to a person with enough equipment to have them tested Succes, Ed
Re: A brace of choke!
I would like to use them in a PS, and i did get a pair so monoblocs are a possibility
the indings are 8.8 and 8.9 ohms
Yes... i have lots of candidtaes, the big missing ingredient is time.
dave
dhaen said:You might also want to know whether they are suitable for choke-input use as well; eg whether they can stand some DC without loosing too much inductance and buzzing.
I would like to use them in a PS, and i did get a pair so monoblocs are a possibility
What is their DC resistance?
the indings are 8.8 and 8.9 ohms
Time for a nice valve amp I think Dave....
Yes... i have lots of candidtaes, the big missing ingredient is time.
dave
Re: Re: A brace of choke!
man that a low DCR... given the size are you sure you didn;t miss a decimal on the 25hy... .25hy seems much more believable.
just for reference a 20hy 150ma choke about that size has a DCR of 300 ohms.... and remember the two 25 hy chokes in series is 100hy!!! a 100hy choke with an 18 ohm DCR seems very unlikely.
if they are indeed 2X25hy, i wouldn't expect them to handle much DC... or AC for that matter.
dave
dave
planet10 said:
the indings are 8.8 and 8.9 ohms
dave
man that a low DCR... given the size are you sure you didn;t miss a decimal on the 25hy... .25hy seems much more believable.
just for reference a 20hy 150ma choke about that size has a DCR of 300 ohms.... and remember the two 25 hy chokes in series is 100hy!!! a 100hy choke with an 18 ohm DCR seems very unlikely.
if they are indeed 2X25hy, i wouldn't expect them to handle much DC... or AC for that matter.
dave
dave
Re: Re: Re: A brace of choke!
The other one measures the same DCR wise.
I put 1st one on my inductance bridge and as close as i can figure each half is 10 Hy, but i was getting some weird results -- when i get a chance i'll take em both down and remeasure.
dave
dave slagle said:man that a low DCR... given the size are you sure you didn;t miss a decimal on the 25hy... .25hy seems much more believable.
The other one measures the same DCR wise.
I put 1st one on my inductance bridge and as close as i can figure each half is 10 Hy, but i was getting some weird results -- when i get a chance i'll take em both down and remeasure.
dave
9R is a very low DC resistance for a stated 25H inductance. The only way I can see of achieving two of those in a can that size is not to gap the core, making the DC current rating zero. I suspect that these chokes were made to be part of a signal filter, not a power supply - they have a telecomms look about them, particularly with the paint masked from the mounting surface.
EC8010 said:I suspect that these chokes were made to be part of a signal filter
As this thread developed, i wondered if that would turn out to be the case... do they have any use in an amp?
dave
EC8010 said:I rather suspect that you may have scored a pair of doorstops or bookends...
Well at least they are pretty....
dave
You might also want to know whether they are suitable for choke-input use as well; eg whether they can stand some DC without loosing too much inductance and buzzing.
What makes a choke buzz? My new amp buzzes, and I'm not sure which piece of iron in there is doing it. I haven't really bothered with fixing it because I can't hear it over the music, but it would be nice if it could be fixed.
I'm also wondering if I should bother about the hum. I can only hear it late at night with no music playing, and I'd need 3 new transformers to convert all my heaters to DC, I think. My RS DMM says 2mV, my scope is uncalibrated so I don't trust what it says.
Hi,
Crud from the mains is one source, badly implemented ground another amongst a dozen.
Oh, and if your mains xformers are toroids you can say hello to a lot of that aggrevating buzzing too.
That would bother me no end...your noisefloor becomes too high for comfort and it make soundstage depth colapse.
Does it happen with the input of the amp shorted?
Cheers,
What makes a choke buzz?
Crud from the mains is one source, badly implemented ground another amongst a dozen.
Oh, and if your mains xformers are toroids you can say hello to a lot of that aggrevating buzzing too.
I haven't really bothered with fixing it because I can't hear it over the music, but it would be nice if it could be fixed.
That would bother me no end...your noisefloor becomes too high for comfort and it make soundstage depth colapse.
Does it happen with the input of the amp shorted?
Cheers,
That would bother me no end...your noisefloor becomes too high for comfort and it make soundstage depth colapse.
I'm just starting to get over being dazzled by how much better this amp is than what I had before So I'll start fixing/changing things on it soon. I tried the caps from B+ to cathode using clip leads, and while they didn't lower the noise floor, the sound did improve. I also need to reduce the filament voltage on my 6SL7s a little (it's about 7.1V, IIRC), and change a few other things.
Crud from the mains is one source, badly implemented ground another amongst a dozen.
Well, it could certainly be the second. Any specific grounding issues that I should look at? And how would I test for mains noise? I have a small cap across the transformer primary. Also, I don't know if it's the choke that's buzzing or the power trasformer or the filament transformers.
Oh, and if your mains xformers are toroids you can say hello to a lot of that aggrevating buzzing too.
No toroids.
Does it happen with the input of the amp shorted?
Haven't tried that yet. I'll try it tonight.
Saurav said:
What makes a choke buzz? ..snip..
Apart from loose windings and laminations, it can be caused by using the wrong choke for an application.
Chokes used in choke-input filters should be 'specially designed. They have some DC across them. Ordinary chokes buzz in this application.
Cheers,
This is what the design called for (though I've modified the PSU from the original design):
This is what I used:
Increased current handling and lower DCR for a lower price, made sense to me. These are Hammond chokes, the prices are from the Angela website. Here's my PSU:
193G 10H, 150ma, 102 ohms, 800VDC. EACH $42.
This is what I used:
193J 10H, 200ma, 82 ohms, 800VDC. EACH $40.
Increased current handling and lower DCR for a lower price, made sense to me. These are Hammond chokes, the prices are from the Angela website. Here's my PSU:
An externally hosted image should be here but it was not working when we last tested it.
Choke spec:
http://www.hammondmfg.com/193.htm
Doesn't say it'll work on choke input. But your circuit has a small but reasonable first cap. I wouldn't expect a problem.
Cheers,
http://www.hammondmfg.com/193.htm
Doesn't say it'll work on choke input. But your circuit has a small but reasonable first cap. I wouldn't expect a problem.
Cheers,
Thanks. I could try temporarily increasing the cap to see if the buzzing goes away, but that will upset all the voltages. And I'd rather not use resistors to adjust the voltages - they'd have to be rated for pretty high power, and it seems to me that the more series resistance I have, the more the PS output will sag during high current transients.
Just making sure I understand this - in a choke input filter, the choke sees much higher current surges, because the first cap that's charging up comes after it. In a cap input filter, the current surges through the choke are smaller. Thus, even if the choke's current rating (200mA - that's DC, right?) fits the circuit, it might not work with a choke input filter. Is that correct?
Also, the 800VDC rating - voltage between what and what? The drop across the choke itself is fairly small. Is it the voltage between the windings and the enclosure (which may be grounded to teh chassis)?
Just making sure I understand this - in a choke input filter, the choke sees much higher current surges, because the first cap that's charging up comes after it. In a cap input filter, the current surges through the choke are smaller. Thus, even if the choke's current rating (200mA - that's DC, right?) fits the circuit, it might not work with a choke input filter. Is that correct?
Also, the 800VDC rating - voltage between what and what? The drop across the choke itself is fairly small. Is it the voltage between the windings and the enclosure (which may be grounded to teh chassis)?
Saurav said:Here's my PSU:
What's the point of the 3uF cap? It only makes for bad regulation, effectively increasing the critical inductance value.
Dave: do you have a mic or vernier to measure the wires coming out the bottom?
Tim
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