Home » VintageKustom.com » Replacement Part Suggestions » Help (I need a replacement Transformer for a K100 8)
Help [message #17681] Fri, 16 November 2012 14:03 Go to next message
Cowboy is currently offline  Cowboy
Messages: 6
Registered: November 2012
Junior Member
Does anyone have any idea for a replacement transformer for a K100. The primary voltage was measured at 118v and 59 to 61v on the secondaries.
That is all I know other then it got really hot due to the external recterfier bridge failure. I replace the bridge and the amp worked for a short time, but then the Transformer finally gave up.
Re: Help [message #17691 is a reply to message #17681] Fri, 16 November 2012 22:34 Go to previous messageGo to next message
chicagobill
Messages: 1932
Registered: April 2003
Senior Member
The obvious answer is a dead donor amp. There is seller on eBay that is selling nos power transformers from a Musicman bass amp that would probably work, but you will need to find a way to mount it.

Maybe one of the guys here has a donor head that still has a good transformer.
Re: Help [message #17692 is a reply to message #17691] Sat, 17 November 2012 07:38 Go to previous messageGo to next message
pleat is currently offline  pleat
Messages: 1408
Registered: June 2004
Location: Belding, Mi
Senior Member
Which K100 amp do you have? K100-5 PA head? K100-1 or K100-2 Piggyback head or the one of the self contained amp/speaker in one box?
I had a self contained K150 with a blown transformer and I used a transformer from one of rack mount Kustom lll monitor amp and it took some drilling for mounting it, but it fit and works great.
pleat
Re: Help [message #17695 is a reply to message #17692] Sat, 17 November 2012 11:17 Go to previous messageGo to next message
Cowboy is currently offline  Cowboy
Messages: 6
Registered: November 2012
Junior Member
The Amp is a K100-8, it is a self contained combo style (no Piggy Back) with 4 speakers. (everything is in one cabinet)

Remounting of a different style would be no problem if I can find one with compatible electrical specifications
Re: Help [message #17705 is a reply to message #17681] Sat, 17 November 2012 16:03 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4198
Registered: June 2004
Location: NY
Senior Member
If you want to up grade and only have one mounting hole to deal with than Antec toriod tyoe model AN-3440 comes with a 36 dollor price tage.
Re: Help [message #17706 is a reply to message #17705] Sat, 17 November 2012 16:34 Go to previous messageGo to next message
Cowboy is currently offline  Cowboy
Messages: 6
Registered: November 2012
Junior Member
When you say upgrade...do you mean that it will work with the current circuit or do I need to replace other components?
Thanks for the info!
Re: Help [message #17710 is a reply to message #17706] Sun, 18 November 2012 00:20 Go to previous messageGo to next message
chicagobill
Messages: 1932
Registered: April 2003
Senior Member
I think that he's talking about the fact that this is a toroid transformer.
Re: Help [message #17711 is a reply to message #17710] Sun, 18 November 2012 05:30 Go to previous messageGo to next message
pleat is currently offline  pleat
Messages: 1408
Registered: June 2004
Location: Belding, Mi
Senior Member
I'm not a tech, but you mentioned in your original post that your transformer measured 59 to 61 volts on the secondary before it went bad. My schematic shows the secondary voltage of 39.5 volts. Just wondering why the difference?
pleat
Re: Help [message #17712 is a reply to message #17711] Sun, 18 November 2012 10:07 Go to previous messageGo to next message
Cowboy is currently offline  Cowboy
Messages: 6
Registered: November 2012
Junior Member
I am not a Tech either so I really can't answer why the difference other then the 59 to 61 volts was measured with the secondaries lifted from the rectifier bridge (AC voltage). However, with the secondaries laid back down, the DC voltage measured to the caps was 37v +/- respectively.

Does anyone have a Transformer that works that they would be willing to part with?
Re: Help [message #17715 is a reply to message #17681] Sun, 18 November 2012 14:48 Go to previous messageGo to next message
chicagobill
Messages: 1932
Registered: April 2003
Senior Member
Pleat, I think the 40 volts that you are referring to is the plus and minus dc voltage after the rectifier, that is used to power the main power amp.

The 60 volts is the ac output directly from the power transformer which is center tapped, creating two 30 volt taps that are then rectified to get the 40 volts dc.

The basic theory is that the ac voltage times 1.4 gives you the dc voltage for the power supply. So 30vac X 1.4 = 42vdc.

Cowboy, if you can't find one check the eBay listing for the Musicman power transformer that I mentioned before, it's something like $30 shipped and should work fine with no mods to the amp, as long as you can find a way to get it mounted.
Re: Help [message #17718 is a reply to message #17715] Sun, 18 November 2012 18:53 Go to previous messageGo to next message
pleat is currently offline  pleat
Messages: 1408
Registered: June 2004
Location: Belding, Mi
Senior Member
Chicago Bill, now you know why I'm not a tech. I do have an extra power supply out of a non T&R Kustom Mixer PA that a quick check reading the voltage on the secondary side before any filter caps was about 60 volts.
pleat
Re: Help [message #17719 is a reply to message #17718] Sun, 18 November 2012 21:32 Go to previous messageGo to next message
Cowboy is currently offline  Cowboy
Messages: 6
Registered: November 2012
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Hi pleat, do you want to sell the extra one?
Re: Help [message #17720 is a reply to message #17719] Mon, 19 November 2012 07:30 Go to previous messageGo to next message
pleat is currently offline  pleat
Messages: 1408
Registered: June 2004
Location: Belding, Mi
Senior Member
My email address is don@tremorbender.com Shoot me an email and I will send you a photo of the tranny and complete power supply.
pleat
Re: Help [message #17732 is a reply to message #17681] Wed, 21 November 2012 06:51 Go to previous message
stevem is currently offline  stevem
Messages: 4198
Registered: June 2004
Location: NY
Senior Member
The 39.5 volts that most kustoms run on is the voltage output from the PT with the amp at idle a drawing current, unloaded it will be higher, with the amp running at full max wattage the 39.5 volts will dip to around 32 to 34 volts.
The Torid PT I posted about is step up due to it being a torid, also it has more current output so the amp will output more power and give more clean head room, also being a Torid type it will put out less 60 hz hum into the reverb pan/output.
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