Bucking Transformer for an HF-81

[Eafnb]

Hello,

I am working on a bucking transformer for my HF-81. I got a CES 67-1124 (SS4-12C4A) a 12vct 4amp transformer from my local electronic store and it runs 24VA. Would this be enough to power my HF-81 in the long run? or should I get a higher wattage transformer?

 

[whoaru99]

I should think a 4A secondary would be more than enough bucking capacity for that amp.

 

[Eafnb]

I should think a 4A secondary would be more than enough bucking capacity for that amp.

Really? I would've thought you need the right wattage to run properly or you'd burn out the transformer? (apologies for the silly question, still learning)

 

[whoaru99]

I did not see a power consumption on the amp but for discussion say it is 200 watts. I'd think that is conservative (meaning actual is probably less).

Say your mains are ~122V and you want to supply ~115V to the amp. That means you need to buck ~7V.

If the amp consumed 200W at 115V, that is about 1.7A.

1.7A x 7 volts to buck means the transformer only need be ~12VA capacity, (1.7A secondary current capability at 7V).

 

[Eafnb]

Oh I see, so the amp is 140 watts (just found the power consumption) divide by 115V to get 1.2A.

Then multiply the 1.2A to the 7V to get 8.5VA (Watts?) and that's the average/maximum wattage, right?

 

[whoaru99]

The main thing is the current. If the amp draws 1.2A then the secondary of the bucking transformer needs to have that current rating, bare minimum, at the voltage you want to buck/drop.

If the transformer you are looking at is only rated in VA and voltage then you need to divide the VA by the voltage to get the rated current. Eg, 24VA @ 6V = ~ 4A.

 

[Eafnb]

The main thing is the current. If the amp draws 1.2A then the secondary of the bucking transformer needs to have that current rating, bare minimum, at the voltage you want to buck/drop.

If the transformer you are looking at is only rated in VA and voltage then you need to divide the VA by the voltage to get the rated current. Eg, 24VA @ 6V = ~ 4A.

Hello,
I greatly apologize for the extremely delayed response, but right after your reply, I got started putting everything together right away. I've ran it a week after assembling, and testing, and have continuously used it with my HF-81 since then and it has run very well with no problems. Here are some pictures for your troubles and a thank you for the help. It was greatly appreciated.