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 Post subject: Hafler Amp Repair
PostPosted: 18 May 2010, 22:28 
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Joined: 07 Jan 2009, 00:42
Posts: 20
Hey guys. So I have a Hafler Trans-Nova P3000 that was going to be used to repair another P3000, but was unneeded as the problem turned out to be a cold solder joint on one of the outputs.

The 'parts' unit is damaged. Some would consider it scrap, but taking a scan over the PCBs it looks intact. Only one channel has made it through the trials and tribulations of years of abuse, and UPS-handling. The other channel had its final power rectifier bridge sheared off from the transformer which was floating freely in the case, not sure why it wasn't mounted.

I haven't pulled the finals yet to test if they even switch on, but I am going to redo some parts mainly any electrolytics, final bypass caps, volume pot., regulators, and transformer (seeing as the stock one is damaged). Most of those parts I can compile from the basic selection of vendors, but the transformer is the only part that I'm not to sure about. Would it be worth it to attempt rewinding the damaged side, or could I replace it with 2 toroidal transformers (one for the +/-17V Drive and +/-67V Finals)?

Unit as it came:
Image

Damaged Transformer (Probably from slamming into the rectifier):
Image


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 Post subject: Re: Hafler Amp Repair
PostPosted: 19 May 2010, 12:28 
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Joined: 28 May 2008, 21:53
Posts: 4586
Location: Winnipeg, CANADA
The worth it is really up to you and dependent on repair or replacement costs.

The limited space could cause a problem if you go to two toroidal transformers. You may be able to find a single torroid as 100V and 24V are not uncommon values. Repairing the transformer has the advantage in that you know it will fit nicely.
Cheers

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 Post subject: Re: Hafler Amp Repair
PostPosted: 19 May 2010, 13:56 
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Joined: 07 Jan 2009, 00:42
Posts: 20
We got the unit for free, I'm bored, and I have almost all the parts on hand. What would the best way of going and repairing the transformer? The E-I laminations look fine, just need to be unglued. I just need to get the secondary voltages and figure out how to go about rewinding.


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 Post subject: Re: Hafler Amp Repair
PostPosted: 20 May 2010, 23:05 
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Joined: 07 Jan 2009, 00:42
Posts: 20
So after I looked at the transformer again, it is actually a C-Core. Not sure how I managed to call it a E-I with the thing sitting in front of me.

After looking at the manual and schematic, I came down to conclude that the transformer has 2x 30VCT @ 2A, 2x 50VCT @ 4A for secondaries. Now I have to find a transformer that at least can give me two one one voltage. Off to the electronics vendors!

I don't mind spinning a board, so I may do 2 PCB mount toroids for the 15-0-15 (PN# L01-6383) or free mount with 2 Antek (AN-0515). Still working on the 50VCT transformers.


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 Post subject: Re: Hafler Amp Repair
PostPosted: 21 May 2010, 19:01 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
Those values should be easy to find. Let us know how you make out.
Cheers

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[ DIY Mains AC Power Cable Cord ] - [ Gobo LM1875 Amp Kit ] - [ Tang Band D4-1 Horn Speaker Kit ] - [ Monoblock Push-Pull KT88 Tube Amp Kit ]


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 Post subject: Re: Hafler Amp Repair
PostPosted: 21 May 2010, 20:08 
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Joined: 07 Jan 2009, 00:42
Posts: 20
I got the transformer apart. I got it soaking for a bit so I can unwind the one good bobbin and get the length, turn count, wire gauge, and layout.


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 Post subject: Re: Hafler Amp Repair
PostPosted: 22 May 2010, 14:53 
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Joined: 07 Jan 2009, 00:42
Posts: 20
Almost through the whole transformer. :mrgreen: I've got wire gauge for all three windings and the total turn count for the low-voltage winding. I already measured the resistance of the windings before I took it apart and did some really rough math with what I figured the voltage should approximately be, and was with in about 4 feet. At least my guesses are close enough to start looking for new magnet wire.

Now to somehow build a winder. To google!


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