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Friday Night Hafler XL280 Brain Surgery....

gaspipe

gaspipe

Just a dude.....
Six pack of Fat Tire. Check.

One bone-stock Hafler XL280. Check.

One ebay cap upgrade kit. Check.

Soldering iron plugged in, new batteries in the multi meter. Off we go.

Off comes the lid, and in we go. I've never opened this one up before. It's cleaner in there than I expected.

xl280-003-XL.jpg


The stuff going in...

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[more coming]
 
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I was expecting some crumbly wire insulation, maybe some mice, etc. But it looks pretty good. This was a later edition of the XL280, having factory installed gold (colored?) RCA jacks and such. Output binding posts are banana :banana: plug capable, so that'll be good enough.

The first stage of this kit is modifying the power supply board.

xl280-004-L.jpg


Hafler put a piece of foam rubber on top of the board which has some really nasty, sticky glue schmootz (an industry term). Wreaks havoc on soldering, so needs to be cleaned up.

Done with step one. New caps in, board reinstalled, ground wire resoldered

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On to the PC40 boards next.

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Cheers. :smoke:
 
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The PC40's are the driver boards. These Haflers are made to be worked on. Lots of wiggle room. Good for old palsied hands and degrading eyesight. Oh yeah, and the beer.

Before....

xl280-050-M.jpg


Two polarized caps and one bi-polar cap swap later.....

xl280-007-L.jpg


And then deletion of three other caps....

xl280-008-L.jpg


And that's all there is to the modification of the driver board. Time to bang out the other channel with the identical steps.
 
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The last step in this kit is modifying the mosfet support circuit.

This is simple too, deletion of one cap, and swapping in a film cap. That yellow cap in the void between the PC40 board and the heat sink is the new guy to the party.

xl280-009-L.jpg


xl280-012-L.jpg


Just about ready to button it up.
 
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The dead soldiers.....

xl280-011-L.jpg


I thank them for their valued and dedicated service, and give them a proper burial.

Check the last solder joints and it's power up time! Offsets look good. On goes the cover, and the XL280 gets reinstalled.

xl280-013-L.jpg


Got three beers left, so what to test the sound with?

stuff-009-L.jpg
 
I had expected to have to spend a bit of time cleaning up the chassis and doing some rewiring, but it wasn't (yet) necessary.

My impression: Super easy installation, noticeably cleaner and richer sound. For an hour of time and $30 worth of caps, I am happy.

Two thumbs up. :thmbsp: :thmbsp:

I have two more XL280's, so I'm gonna do the same thing to those also. I hope they are in as nice shape as this one was when I open them up. If not, more upgrades! :yes:
 
What do you think of the 740C?. Should sound real good with the MOSFET's.
 
I really have been wrestling with getting some PC boards from Musical Concepts, but it grates against the Scot in me to part with that many greenbacks. But I'm trying to talk myself into it.
 
gaspipe said:
I like the 740C enough that I moved the NAD to the "B" pile this evening.
Click to expand...

I just picked up a new one myself about a month ago.:thmbsp: Also got one of those Mod Kits for a DH200.Haven't got around to mess'n with it much.Gots to get a few other pieces out the door first.
 
Great work. Do you notice an improvement in sound? I'm slowly putting in PC-19C boards (used in the DH-220, DH-500, P-225, P-230, and other Hafler models) into my DH-200 that used the old PC-6 boards. PC-6 boards don't have a DC Offset adjustment, and the PC-19C boards do.
 
Thank you, sir.

Yes, there is a bit of a difference in sound. Bear in mind this particular Hafler was bone stock, and about 20 years old +/-. I didn't take the time to audition the amp at each step. I guess I am lazy.

I did run 'em today, the modified one I did last night bridged mono, and a second bone stock, unmolested cousin on the other channel. My ear is pretty used to these amps, so slight changes were noticeable. IMVHO, the XL280 as it comes from Hafler is a decent amp. The modded amp was a bit warmer, a little less grainy, a little more transparent. Subtle, but it's there. I liked it well enough that I modded #2 XL280 tonight, and both modded amps are running mono, doing a nice rendition of Pink Floyd's Meddle right now. I tested both in stereo mode too, sounds equally nice.

I am not sure exactly what component(s) warmed up the old gals, but for $30 a throw, the kit(s) were certainly worth it to me. I've recapped some stuff before from parts I sourced from Digikey/Mouser/etc., and ended up with something slightly worse, sometimes better. But this time, Mo Betta! The man did his homework here picking the caps and architecting the mods to the circuits.

I'm liking it. :music:

I also used a kit from the same individual on a DH200 a while back, and the improvements were even a little more noticeable than this kit on the XL280. I sold that amp, should have kept it.

HTH.
 
One last thing I was going to mention....I have three XL280's, and each one is slightly different internally. I bought them all at the same time, too.

Evidently there are some 'running changes' as they built these things. I've seen two different PC40 boards, two different PC41's, and slight changes to the mosfet support circuits.

Oddly enough, each one sounded damned near identical.
 
Nice job on the recap. could you advise what type of caps were selected for the positions that you replaced? There's quite a thread on recaps and electrolytic cap selection going on so wonder if your experience could add something to that?

In the past, what did you try that did or did not result in positive improvement?

Thanks for the reply. You are up late!
 
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