Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: BobbySkidz on July 05, 2013, 07:29:15 am

Title: Must find replacement power transformer!
Post by: BobbySkidz on July 05, 2013, 07:29:15 am

I am trying to find a replacement power transformer for Kustom "The Defender" 50w 1x12 amp.

I can get one from the manufacturer for $80 but would prefer to find a more readily available replacement if at all possible.

Made by a chinese manufacturer named NRE, the transformer is 120v, has 4 primary leads and 7 secondary leads.

A picture of the power transformer label can be found here (http://i61.photobucket.com/albums/h61/Skoked/My%20Pictures/NRE%20Transformer/Transformer-NRE_zpsffdbdf09.jpg)

Any suggestions would be appreciated. :BangHead:

Title: Re: Must find replacement power transformer!
Post by: SILVERGUN on July 05, 2013, 08:18:33 am

It might be pretty hard to find an exact replacement that fits in that hole....
If it were any of us, we'd probably enlarge the hole and go with a more common PT
Only problem with that would be finding one that's got the 12-0-12 winding.......looks like that 24vac (converted to -28vdc) is your op amp supply and also provides a DC filament supply for your preamp tubes...
http://www.el34world.com/charts/Schematics/files/Misc/kustom_defender112.pdf (http://www.el34world.com/charts/Schematics/files/Misc/kustom_defender112.pdf)

So it might be in your best interest to go with the original replacement you mentioned..............

This is gonna get asked, so I might as well ask it:
How do you know the PT is bad?

Title: Re: Must find replacement power transformer!
Post by: eleventeen on July 05, 2013, 09:54:43 am

One of those amps was for sale around here, (100 watt model) in perfect shape for $330, with new replacement Celestion speakers worth about $100 ea and it was all I could do not to total up the parts costs and buy the thing on that basis.

IMHO, trying for a non-OEM replacement transformer, you are going to save an absolute maximum of $25 and spend hours searching for it and hours either enlarging the hole or changing something or other....and in the end, you will pay for the savings you envision by working for $3 an hour.

That is my one-sentence comment on your situation.

Title: Re: Must find replacement power transformer!
Post by: stratele52 on July 05, 2013, 02:15:59 pm

Better to buy original , no trouble .

You are sure PT do not work ?

Title: Re: Must find replacement power transformer!
Post by: jarmoke on April 17, 2015, 01:59:22 am

Does anyone know, where to find original transformer?
I have for sure broken one in my friends amp. One of the
120v coils is blown...

Title: Re: Must find replacement power transformer!
Post by: octal on April 17, 2015, 07:34:24 am

Looks like that transformer has thermal fuses in it. If one or both the primaries are open, you might be able to peel back the wrap around the winding and just replace the thermal fuse(s), taking care to insulate everything carefully after reassembly.

Title: Re: Must find replacement power transformer!
Post by: mresistor on April 17, 2015, 10:59:54 am

I read also that if you could reach the fuse and it's bad, you could jumper around it (bypass) and the PT might work many more years.

Title: Re: Must find replacement power transformer!
Post by: eleventeen on April 17, 2015, 01:35:11 pm

Maybe I'm going out on a limb here, but IMO placing fuses under the wrapping of a power transformer is goofy.

Title: Re: Must find replacement power transformer!
Post by: mresistor on April 17, 2015, 04:41:24 pm

Here's an interesting thread about internal PT fusing (http://music-electronics-forum.com/t25580/)

makes me wonder when mfg's started doing this and how many of mine are internally thermally fused. ?