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Hafler DH-200

avionic said:
What pn is printed on the old part.
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544252
After trolling through old threads it looks like it’s 25amp 200 volt.
Old threads had a suggested replacement that doesn’t appear to be available anymore, and mouser looks limited on equivalent bits. Do you have a suggestion for a better replacement?
And thank you for your help, it’s muchly appreciated.
 
Perfect, thank you. Both have been ordered and I’ll update this once they arrive and I swap them out.
 
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It lives!
Thanks for your help, avionic.
Popped in the new rectifier, started it up with L & R fuses pulled, didn’t blow the main fuse. Tossed fuses in one channel at a time, didn’t blow the main fuse.
Sounds pretty damn good running ads l810s.
Runs pretty hot, but from trolling old threads it seems that’s common?
Now that it’s up and running, what’s next? The input rca’s definitely need to be changed, they’re cheap junk. Do I need to worry about anything else being damaged when the bridge rectifier died (filter caps, etc)?
 
avionic said:
Most likely not..
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Awesome. Then, its inputs will be replaced, it’ll get a thorough cleaning, and then it will be brought inside and integrated into my main system. I’m quite satisfied with my $60 + $12 in parts purchase. :banana:
 
MKG said:
Runs pretty hot, but from trolling old threads it seems that’s common?
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Both channels or just one? If you cannot touch the heat sinks for very long then it is running hot. There's a bias adjustment but no DC offset adjustment on the '200s.

Cheers,

David
 
Regarding kit vs. assembled...

I don't know how it was with the power amps, but the preamps in kit forms were the finished circuit boards, and all the hardware bits and point to point wiring. So it wasn't the fun part (to me) of installing components on the circuit boards, but the tedious wiring and assembling. Gotta say I was a bit disappointed. But other than bad power supply capacitors over the years, no issues. I totally recapped it a few years ago and it still sounds fine. (I also recapped the power supply with higher voltage caps for reliability.)
 
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While in engineering school, I worked on a repair bench - excellent way to get practical experience! - and took in abandoned kit projects for some select customers. All of them had one thing in common: Poor soldering.

It is usually easy to spot a kit built Hafler by inspecting the solder joints. If they're all smooth and consistent in finish, it is likely a factory-built unit. If the joints have inconsistent amounts of solder, are not smooth and the wires are run helter-skelter then it is most likely a kit or has been extensively worked on by a hack.

I made a _lot_ of weekend girlfriend/date money finishing off kits simply by resoldering the joints and rerunning mis-prepared wires. By the time I got through with them, they could have bought the factory-built version!

Cheers,

David
 
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I’d be horribly disappointed. I also find populating boards and soldering all the bits to be the most enjoyable part of a build. I think that disappointment would have faded as soon as I turned it on though, it sounds pretty good.
 
The boards were preassembled so they could be tested, helping to eliminate the DIYers mistakes that Dave mentioned. If you wanted the opportunity to do some assembly work the PAT-4 was a much longer build than the amps. Not populating the boards but all those wires going to and from the selector switch and such were something my brother spent some time doing, decades ago.
 
Check/adjust the bias and check for voltage offset at the outputs before you go much farther. The bias output pots were the crappiest component on that amp. Also on the XL-280.
 
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Consider getting the Musical Concepts driver boards for the Hafler. I did for mine - what a transformation! Not cheap,.... but what you end up with will compete with most anything out there under $2500 (and many that sell for over that amount).
 
soundmig said:
Consider getting the Musical Concepts driver boards for the Hafler.
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I’ve been eyeballing them but they are pretty damn pricey. I’ve also considered getting the 220 pc-19 boards but haven’t done enough research to find out if they’d make any difference or what needs to be changed to put them in. For now, I’m gonna clean it up, check the bias, check the dc offset (but if that’s off I understand I need to replace stuff rather than just adjusting something), maybe install that current inrush limiter doohickey, and listen to it stock for a while.
I’m sure I’ll get an insatiable mod itch within a few months as I’m not capable of leaving things well enough alone.
 
I knew that my alligator clip jumpers were arriving today so I couldn’t wait to get home and check/set the bias on this thing. Hooked up leads, followed instructions and my multimeter started beeping angrily at me. Took another shot of Irish whiskey and then realized that both of my multimeters top out at 200ma and then jump to full amps (1-10).
Looks like I’m in the market for a new multimeter. There’s very little that frustrates me more in life than attempting to do something and not having the correct tool/s.
I did swap out the rca inputs at least. I was planning on also swapping out the speaker jacks but I went cheap and ordered something Chinese based without doing enough research on them- besides the bolts not being isolated from the chassis, the bolts aren’t long enough.
Failed twice.
I did manage to get in some extensive listening and a/b comparison to my sonance sonamp 260x3. I’ve realized that the sonamp (60wpc) is significantly cleaner/clearer and noticeably louder at similar volume settings. Something else is up with this heavy little bugger but I don’t know what.
 
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