Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: MrPink on April 09, 2024, 03:57:13 pm

Title: Anyone ever seen this? Replace with standard?
Post by: MrPink on April 09, 2024, 03:57:13 pm

Seems like

well i guess it is

Title: Re: Anyone ever seen this? Replace with standard?
Post by: acheld on April 09, 2024, 05:16:57 pm

Cool.  I have not seen and old one like that.   If it is red violet black gold, you'd replace it with a 27 ohm resistor + an appropriately sized fuse in series.

Title: Re: Anyone ever seen this? Replace with standard?
Post by: MrPink on April 09, 2024, 05:46:29 pm

they're in between power switch and PT
makes me wonder
and its red red black gold, so 22ohm, fuse beeing 1/8 A rated. found 20ohm replacement online so i'll go with that

Title: Re: Anyone ever seen this? Replace with standard?
Post by: Beezerboy on April 10, 2024, 06:37:32 pm

looks like rrb to me, so 22.  both yer fuses look to be blown... why?  you are going to drop the resistance 10%, also consider that your amp may have been designed to run on 110.... 115.... maybe 117 VAC. that may not end well. I would be more inclined to add a resistor to the fuse holder. maybe even one that will bring the voltage back to the original range

Title: Re: Anyone ever seen this? Replace with standard?
Post by: MrPink on April 11, 2024, 05:32:00 am

Quote from: Beezerboy on April 10, 2024, 06:37:32 pm

both yer fuses look to be blown... why?

It's two PT's in one, and one of them is broken/bulged. they're for 110 and 230v. tryin to get that thing running by getting the broken one out of circuit but maybe I'll leave it as well cause it's not worth the time... don't know yet
It's a crate TDP by the way

Title: Re: Anyone ever seen this? Replace with standard?
Post by: kagliostro on April 15, 2024, 02:46:29 pm

I asked in an Italian forum

A friend told me they were "extra slow blow"

They will blow in two different manners due to different problem

Manner one, a very large current over the spec, the wire will blow

Manner two, a small larger current only a bit over the spec, after some time the heat developed on the resistor will melt the alloy that joined the resistor to the spring, an alloy designed with a specific melting temperature, the function of the spring is to help the wire and the resistor to be separated from the other side of the fuse connection

Franco

Title: Re: Anyone ever seen this? Replace with standard?
Post by: MrPink on April 15, 2024, 05:31:34 pm

Thx!

in case anyone else searches this fuse type: 0313.150MXP Littelfuse is the closest/only replacement i could find, they have different impedances in that 0313 line but currently 17 weeks till delivery
guess someone switched that thing from 230v to 110 v while plugged in and running and blew the very small pt in it

it's a pitty i dont have a schematic or any information on what that pt output was supposed to be