Let's say an amp requires a 250ma B+ fuse which is located on one side of the HV secondary of the PT (before the rectifier). Would it then stand to reason that if you relocated the fuse to after the rectifier, a bridge in this case, then you would use a 500ma fuse?
Thanks in advance!
Inquiry about HT fuse location and size.
Moderators: pompeiisneaks, Colossal
Re: Inquiry about HT fuse location and size.
Anyone? 250ma fuses are a bitch to find.
Re: Inquiry about HT fuse location and size.
No bites? I'll take a stab.
You are asking about a full wave bridge with cap input? In this configuration, the CT on the PT isn't used. Normally, you'd fuse the CT to ground. I'm stating this to be sure the assumptions are correct.
Well, then, the negative side of the bridge is grounded. I think you are saying you want to put a fuse between the bridge and ground. Voltage is stepped up by the bridge (1.41x) and current goes down (.62x). By this logic, the 500mA fuse gets replaced with 300mA. eBait bargain of the day:
http://cgi.ebay.com/AGC-300mA-5-pcs-Fas ... 518fa77f33 I think you want fast blow for the B+.
How'd i do on this? I'm an amateur.
You are asking about a full wave bridge with cap input? In this configuration, the CT on the PT isn't used. Normally, you'd fuse the CT to ground. I'm stating this to be sure the assumptions are correct.
Well, then, the negative side of the bridge is grounded. I think you are saying you want to put a fuse between the bridge and ground. Voltage is stepped up by the bridge (1.41x) and current goes down (.62x). By this logic, the 500mA fuse gets replaced with 300mA. eBait bargain of the day:
http://cgi.ebay.com/AGC-300mA-5-pcs-Fas ... 518fa77f33 I think you want fast blow for the B+.
How'd i do on this? I'm an amateur.
Re: Inquiry about HT fuse location and size.
yep if its for 6L6 type amp then a 500mA Slo-Blo fuse is good
Re: Inquiry about HT fuse location and size.
Thanks for the reply. I should have said full wave bridge with cap input, but yes you are correct.
I was more thinking that instead of having the fuse on one side of the HV secondary of the PT, like in this drawing, that I could have it after the + side of the rectifier and before the cap. I figured that the current rating of the fuse may double, but that's where I'm not sure. From what you say it sounds like it goes down by .62x.
I'm considering just stocking up on 250ma fuses off the net and doing it like the drawing since it would protect the rectifier as well, but I'm still interested in the logic here.
I was more thinking that instead of having the fuse on one side of the HV secondary of the PT, like in this drawing, that I could have it after the + side of the rectifier and before the cap. I figured that the current rating of the fuse may double, but that's where I'm not sure. From what you say it sounds like it goes down by .62x.
I'm considering just stocking up on 250ma fuses off the net and doing it like the drawing since it would protect the rectifier as well, but I'm still interested in the logic here.
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Re: Inquiry about HT fuse location and size.
I could be wrong, but it seems to me that the current draw is going to be same with the fuse in either position. Nothing that draws current has been added or subtracted.
a'doc1
a'doc1
Re: Inquiry about HT fuse location and size.
Put the fuse in your B+ rail after your 1st (reservoir) filter cap and before the std-by switch (if you have one) and/or OT CT/supply