Hafler DH 220 Restoration - Part 1

[@CraigHollabaugh]

Excellent video. I built my DH500 in 1985, same design just double the output MOSFETs. I still have it and use it all the time. Thanks.

[@drwatson32bit]

I don't know how I missed that you put this out, but I'm psyched to watch. A DH-220 is my daily driver. It was a mystery gamble on ebay- I bought it because of tip of the iceburg details like upgraded terminals, nice feet, Allen head screws filling the holes in the heatsinks. When I opened it up, it turned out to have been recapped at some point and has worked seemingly perfectly for the last 3 years.

[@dell177]

I did the same thing with a used DH220 amp about 3 years back, mine also had one flakey channel and I decided it would be best to put in new boards.. I went with the Musical Fidelity driver boards and used 22,000 100v filter caps with a 35a bridge and a surgistor. The amp has been running just fine for the last 3 years.

[@kennethmccloskey6883]

This was a great video until you stopped diagnosing the problem and decided to get a complete upgrade kit. I was hoping to see you trouble shoot this so that I could learn something as I am having similar issue with a Soundcraftmens amp. Still love your videos and will keep watching, looks like you have a ton of good content here.

[@richardbrobeck2384]

JBL100s were great speakers I had a pair while I was in college !

[@robertyoung1777]

In the eighties I played my JBL100a speakers with a nice sounding David Hafler amp. The Hafler would frequently overheat and shut down. Maybe Haller and JBL don’t get along! I’m still enjoying the L100a speakers today.

[@hugobloemers4425]

Welcome back (not counting the summer update) nice little project to get going again.

[@tee-jaythestereo-bargainph2120]

I cant tell ya how much i appricate your videos ! Thanks

[@mosfet500]

I built a 220 and DH500 in the mid 80's. The output transistors failed and you just couldn't get them at the time mine failed (about 10 or 15 years ago). I have the DH110 preamp which was a decent preamp that I still have but the problem is I never really loved the DH500 sound and my 4 ohm Allison speakers at the time never worked well with it so I sold it. Now I'm running class D for high power which is much more efficient and a lot cheaper. The detail and sound is better than the Hafler was too although I imagine with the upgrade kit the 220 sounds better today especially since they got away from those original mosfets. Thanks for the video.

[@len9518]

Interesting. I built a DH-110 and a DH-500, to use with my Allison 4s. No issues...fabulous.

[@mosfet500]

@@len9518 The first week I had the 9's they blew a tweeter and I didn't push them. I talked to Roy Allison and he basically said to run lower power into those tweeters. I blew another tweeter a few years later and finally dumped the 500. My guess was as the transistors got worse there was ringing above the audio band that was cooking the tweeters. I never checked out the 500 on a scope to see if it was putting anything crazy out, it just wasn't that important to me. Don't get me wrong, I have a lot of respect for David Hafler. I still have the Dynakit Pass tube preamp and the FM3 but his first transistor amp the Stereo 120 was a horrible amp. You couldn't keep transistors from burning out in it. One of my friends built it and passed it on to me. I'm very experienced and went through it, he did everything right, it was the amp itself. The DH110 won a couple of awards, I used it for a few years after selling the 500. It was decent but there's just something about a tube preamp that pulls me in although Nelson Pass gets pretty close with his amps. I still have the 9's by the way, although they took a back seat to the Dynaudio Heritage Specials. If your Allison's' are in good shape you should try them with a Fisher 500c if you can find one restored or do it yourself, it has really sweet mids.

[@ja_bern4422]

@@mosfet500 'Dynaudio', right on. One of the purest speakers in the world. "Audio microscopes"....the one problem...they'll make badly produced LPs & CDs in your collection stand out like a sore thumb, the emperor's clothes...

[@wayneparris3439]

Nice to see a video! I will be moving to Georgia from Calif. DON'T WORRY, i i AM ONE OF THE GOOD ONES getting out while I can! it would be great to run into you at an east coast event!

[@richardbrobeck2384]

I bought A Hafler brand new I still use it mine is rated for like 300watts !

[@asland408]

Great Video!

[@johnsenchak1428]

You didn't menetion what the failed transistor did in the circuit ?

[@sirsuse]

Good stuff! Thanks for sharing.

[@bweabweabwea]

Great restoration video. I have a DH-110 preamp controlling a DH-220 with a bridging kit used to power a passive JBL B380 subwoofer with a DeCoursey Engineering Labs active crossover, and a DH-500 powering my JBL L100T's. However, I have an issue with my DH-220 and that is why I ended up on this restoration video. The 7-amp slo-blo main power fuse is blowing when I turn on the DH-220. Can anyone tell me a likely problem that may be causing this? A reply would be appreciated.

[@srtamplification]

He's back!!!

[@jaymagtulis5018]

How to know the primary supply of the transformer

[@tubeDude48]

What part number is on the MOSFETs ?

[@mguess]

Hey Mark, quick question. I just picked up a DH 220 at an estate sale. The amp works fine but runs warm. About 116 degrees on the right heat sync and 112 degrees on the left. Does that seem right to you. Ambient temp is 73 degrees.

[@JImmY1982MinG]

Thanks for the video!! Now I can go through my DH 220 with the dead left channel haha! One question though, do you recommend to replace the insulator sheet for transistors? Under what condition? Any preferred brands?

[@bobvines00]

What _is_ an "audio grade" cap? I'm not trying to stir up any arguments or 'holy wars," but _have_ heard of some outlandish claims on other "audio" components/parts/accessories. I honestly am curious about these audio grade caps though.

[@joaogonzaga6039]

What are the specs of the power transformer?

[@moodyga40]

you putting CL80 in

[@moodyga40]

good old amp

[@moodyga40]

i like the JBL L112 and my Altec model 18

[@harveyellis6758]

Interesting video. It may have been quicker to inject signal, refer to schematic, & locate where signal is degraded / lost.

[@ja_bern4422]

Dang!! That be 'signal tracing! - I was thinking the same thang...... 🙂

[@questioneverything1123]

May be that should actually be a CL series thermistor. The device shown [may] serve the opposite as a current limiter as it heats up... Not faulting you... the seller of the kit should be (made) aware of this ~unbelievable~ oversight. Check out that device. I use *CL-30 NTC thermistors* on my (many Hafler) amp builds... Check into this. Typically SL are PTC devices. Newarks own page on SL-32 is suspect... labeling as a NTC. Ametherm may be different.

[@ja_bern4422]

great comment!!

[@poormanselectronicsbench2021]

Depending on the brand / manufacturer, there are "CL" series, and "SL" series designations on different manufacturer's ICL ( Inrush Current Limiter) components. It is best to check the datasheets to insure that the components chosen are "Negative Temperature Coefficient" designs, as this designates them as going to a lower resistive value as they are energized. It is also best to consider the values you use, and what they are installed in as with that particular component, and what it's value @ 25C and at max sustained current is. That SL32 ICL only introduces 0,5 ohms when first turned on, but needs close to it's rated constant operating current of 36 amps in order to drop to its minimum rated resistive value of 0.008~0.010 ohms, so it will most likely not heat up much under normal use, but also not do a lot of inrush limiting at it's 0.5 ohm initial value. Something with a lower current rating, and a higher initial resistance would be a better choice to properly act as a ICL.

[@srtamplification]

Score!!!!

[@jdmccorful]

Good start! Enjoyed watching.