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Old 19th September 2003, 02:38 PM   #1
G is offline G  United States
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Default Quality of Hammond 300 series power transformers compared to 200 series?

Hi All,

I've ordered a 300 series power transformer from Hammond for a ongoing project and I was wondering. Do the 300 series have the same mechanical hum problem that the 200 series have? Thanks.

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Old 19th September 2003, 02:54 PM   #2
Colt45 is offline Colt45  Serbia
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mechanical hum problem?


you sure you had it attached to your chassis properly?
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Old 19th September 2003, 03:03 PM   #3
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I don't have it yet. I've heard about people having problems with mechanical hum from the 200 series. I was wondering if anyone had heard of or experienced a problem with the 300 series?

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Old 19th September 2003, 10:21 PM   #4
Fuling is offline Fuling  Sweden
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My 6B4G SE amp has a Hammond 372-something in the PSU, and it does hum.
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Old 20th September 2003, 12:11 AM   #5
Elkaid is offline Elkaid  Canada
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I'm experiencing quite the same with the 182 toroidal series... But only when one of my halogen lamp is turned on at about 50%. If it's fully on, the transformer won't hum a bit.

Maybe adding some kind of line filter would help but I haven't tried it yet.

I hope this helps !
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Old 20th September 2003, 07:14 AM   #6
EC8010 is offline EC8010  United Kingdom
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Default Oh no, not the dreaded diode!

There's a long list of, "transformers don't like," and DC is top of the list. A lamp dimmer undoubtedly involves a switching triac, which shouldn't impose DC on the mains, but will certainly impose some nasty current pulses, and as these dimmers are always made for extreme cheapness, I wouldn't like to guarantee it can't impose DC. I've just had a horrible thought. That halogen lamp doesn't have a switch to set 50% does it? Because if it does, it achieves 50% by half-wave rectifying the mains, which is absolutely the worst imposition of DC!

Another point is that in terms of DC sensitivity, toroids are most sensitive, followed by C and R core, and lastly, EI.
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Old 20th September 2003, 01:26 PM   #7
Elkaid is offline Elkaid  Canada
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Quote:
I've just had a horrible thought. That halogen lamp doesn't have a switch to set 50% does it?
You're right, no dimmer. Only a 3 positions switch. 100%, 50% and OFF.

It took me some time to find out that my toroidal transformer didn't like my lamp.

Do you think that somekind of line filter would do the job ?

Thanks for your comments !
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Old 20th September 2003, 01:50 PM   #8
EC8010 is offline EC8010  United Kingdom
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Default A two-tone response

Quote:
Originally posted by Elkaid
Do you think that some kind of line filter would do the job?
I'm afraid not.

On parallel lines, I've recently been thinking about dimmers and decided that they are downright unpleasant things. Not only do they squirt RF everywhere, but they drastically reduce efficiency, so they waste energy. If you want to control the amount of light, it's far better to control the number of lights switched on. When I was little, prior to our house being rewired, one room had a central light fitting with three bulbs. Two bulbs were wired in parallel, and two circuits came back to the twin mains switch, giving three levels of brightness, all at the same colour temperature, and all at optimum efficiency. The next time the floors are up, those dimmers are going, and the superior 1930s technology of a trio of bulbs is going in...

Power control using a diode is an abomination and should be outlawed.
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Old 21st September 2003, 02:27 PM   #9
mcs is offline mcs  Denmark
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I have used two Hammond 300 series transformers and none of them hum. I use them with tube rectifiers and choke input filters though - they may hum with cap input supplies.

I have no experience with the 200 series for obvious reasons.

Best regards,

Mikkel C. Simonsen
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Old 3rd August 2012, 07:31 AM   #10
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Dear all,
I've experienced some hum problems when rectifying with center-tapped transformer and only 2 diodes (full wave rectification) instead of a bridge: I assume that's because each winding draws half-wave current which is not correct mechanically. Also, you may think that's more interesting for efficiency because you only have one diode voltage drop but copper losses are doubled as compared to the case you put windings in parallel with a bridge which is more significant than diode loss. Sometimes you need to open insulator of center tapped transformer to wire it in parallel.
Another thing that happen when you need very high voltages (around 1kV like for my SE GM70), if you have quite slow diodes (like those that are used in microwave oven, not very easy to find 1500V or more power diodes), during the long recovery time your secondary is quite shorted making vibrations and heat !
In case you need such high voltage I recommend to use RGP1520 diodes (fast, 1A5, 2000V) that are cheap and effcient. You can bypass them with 3kv 4.7nF ceramic capacitor to have soft recovery diodes.
Finally, in this case, because you'll never have low resistance winding (around 100 Ohms if you do not use enormous transformer) you need small value (less than 100F) of head smoothing capacitor to have time constant below 10 ms (8.33 ms for 60 Hz, sorry colleagues from US!). Electrolytics are not desired in this place because small capacitance values do not allow high ripple current, so I suggest to use polypropylene capacitors (20F head cap is enough for 125mA if you use several pi filters). Personnally I only use polypropylene in this way (3 x 60F MKP 550V in series with 1 MOhms equilibrating resistor then choke then I double capacitors then choke and then 3 x 3 x 170F 550V MKP (series & parrallel combination to obtain 170 F 1650V) + 3 x 60 F series with 6 220 kOhms equilibrating resistors for this 190F equivalent cap. MKP capacitors have lower leakage current.

Kind regards,

Christian.
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