Hafler DH 220 Restoration - Part 2

[@randallscott4094]

This brings back memories for me when I built a multimeter, an oscilloscope, and a 25" TV made by Heathkit. It was very fun and educational. I wish these kind of project kits were available today for home study courses.

[@tcell7192]

Love watching other people stuff circuit boards! I love the detail in your videos. A modded DH-220 was my main amp until I started building Bottlehead tube kits.

[@Mark-rw3kw]

I built one these in about 1982. The main left and right circuit boards came fully assembled, tested, and biased. Only the power supply components and other connections had to be wired. Later on, I did replace the 2 large capacitators with some Japanese ones, and replaced the RCA connectors and speaker connectors with gold platted ones. I am sorry I sold it.

[@jimc5423]

I miss mine too. friend gave me his NAD 2200 power amp and associated preamp. My wife liked the way the NAD looked so the Hafler went into a closet for 10 years.

[@mcgjohn22]

The Halfer 200 and 220 were among three amps that really changed solid state amps in the late 70s and early 80s. The other two were the Amber Stereo 70 and the Apt Holman Apt 1. Nice work at doing the upgrade.

[@robertyoung1777]

Great video!! My college roommate had a Hafler (factory) built. It sounded good. Nice detailed sound. The only negative I recall is that the Hafler would shut down if run hard (probably a circuit protection device to prevent amplifier damage).

[@TheReal1953]

I've never had that happen and even used the amp to power double Advents at a youth dance with their 'house music'......that will task any amp. Probably depend on your speakers ohm/sensitivity rating and how hard you're driving them, music dynamics etc. That electronic 'house music' is more taxing than rock I think. In college you tend to max out everything.

[@TheReal1953]

Wow....I have the kit to do my preamp and this has given me the courage(and a source) to do my amp. Probably this winter. I put all new RCA jacks already in the preamp. Hafler's originals were pure junk....even when new....horrible design. I got the jack kit from the guy that offers rebuild kits for Dynaco gear. Heathkit was always adamant about taking breaks and walking away from your work. When you start to get eye fatigue, getting up and away from your project really helps. Not trying to be a 'Karen', but not taking breaks will cause small mistakes or reversals of parts etc. I've done that a bunch....made simple mistakes. Thank you so much for this. I will use it as my guide when I do the rebuld!!

[@compass504]

Just like the Old Heathkits.. Wow that's nice. Great Job!

[@FreakishPreacher]

Super great sounding amps.

[@bobvines00]

Thank you for posting these videos. I learn something from every one, like the Audio Analyzer Suite (& Analog Discovery unit) that look awful useful for audio work!

[@srtamplification]

I have one of those Fluke 8060a meters. Love that thing.

[@EJP286CRSKW]

Wow. Do you really stuff one resistor, then turn the PCB over and solder it, then stuff another resistor ..? It's several times as quick to stuff all the resistors, then solder them all, clip them, then proceed to the diodes, then the taller components in increasing order of height.

[@seanobrien7169]

You put the rack mount back on? Thanks for that walkthrough, I am impressed with the upgrade kit, they sure offer a great package. I am glad you took the time to record that for us.

[@seanobrien7169]

Hahaha, just started watching the preamp video, I see now...Too bad, I think it looks better without the rack mount stuff too.

[@marka1986]

Best to keep rack hardware on the Amp. If some day you need it by then could get misplaced lol

[@bweabweabwea]

In the final section concerning BIAS adjustment, you mentioned dummy load at the speaker outputs. Is a dummy load necessary? What is the best way to build one? Sorry for a not so informed question, but am an interested hobbyist and just trying to learn!

[@ABC-rh7zc]

Drinking game - slam a shot every time Blueglow says "whatnot". I dare ya!

[@sabelli33]

Please, I would like to ask a question: would it be worth repairing a Hafler DH200 and pairing it with an AMC CTV 1030 preamplifier with a pair of Dynaudio 52 speakers and an Arcam cd73 CD player?

[@Bakafish]

Seems like you ended up using the rack mount plate. I think it looked better without. I sold those amps new, was nice to see one again.

[@roberthurley4424]

Thank you for posting your videos. On this restoration, you showed the kit included 0 Ohm 'resistors'. What is the value/importance/advantage of using these instead of a jumper wire?

[@MrDoneboy]

Go back in the video, and listen to what Mark said!

[@EJP286CRSKW]

He didn't really answer the question. A zero-ohm resistor is just as much of a crossover as a piece of wire, surely?

[@johnsweda2999]

How is that make any difference of 0 ohm resistor crossing the Signal Path? are you saying they are shielded if not making a difference

[@albundy1956]

Nice one, Mark.

[@AndrewTa530]

those tiny solder holes are ridiculous

[@scinpdx3981]

I'm looking at doing the same restoration but am curious if you think it is better to spend the money on this kit or to apply that money to another modern amp. Thanks for your vids.

[@TheReal1953]

Tough call. But for the money you probably paid for the Hafler(used) and the price of the rebuild kit(forget about your time), you'd have to spend thousands to beat the Hafler. So for value, you can't beat the Hafler. If you're going for purity of sound and trying to emulate today's best solid state amps, you'll not get there with this Hafler. However, everyone I know that ditched the Hafler to upgrade, regretted it(lol, look at Mark's comment below). It has a unique, endearing sound for a solid state amp. I would completely ignore the phono preamp though and go with something external. I used to think their phono stage was good, but not after I went separate.

[@andydelle4509]

That small circuit on the switch pilot light blinks it if the fuse blows.

[@thxepsilon8292]

So...what went wrong with the amp in the first place?

[@TheReal1953]

Bad channel.

[@EJP286CRSKW]

@TheReal1953 That's hardly an answer.

[@MrElectrowhiz]

The Instructions are very similar to Heathkit

[@ssks1979]

Yes, I was going to comment the same. I've recently cleaned up three Heathkit units and their manuals have ample layout drawings with individual steps for the builder to follow and check off.

[@leohobbleohobb3781]

Those brown bipolar caps need,s to be tested witch way they block noise the best from be introduced in to the circuit.Tape a mono jack to the work bench that is connected to a amlifier(small gitar combo) or one that is connected to a speaker.Hold the brown cap between you thumb and 1 finger let one lead touch the negative on the mono jack(lots of noise from the surroundings as you holding the cap act like a antenna.then press the second lead down so both leads touch negative and positive and listen is the noise went away.Then try it the other way around.Mark the end that touch the positive when you got the least amount off noise.If they are marked with a black stripe,dont trust it.often wrong marked.This is very audible if a cap like those brown is in signal path.

[@TheReal1953]

Has to be an easier way, especially if you don't own a guitar amp. Some sort of tester etc, where you can run some nominal current through the caps.

[@johnsenchak1428]

You should mount the amp and a preamp in a small 6U rack cabinet

[@karimdailyjazz]

Very good job

[@kozkoz7776]

are you aware that david hafler bought acoustat from dr james strickland who was making ESL speakers and couldnt find an amp high current at that to drive his esl speakers so he designed his own amp and preamp if you study his amp design theirs alot of his magic in david haflers tripology l own the acoustat tnt 200 pwr / pre and l would put it up against a macintosh or mark levinson its an incredible sounding amp of its time l also own hafler class A pre amp 915 and its fantastic sounding pre JUST A FOOTNOTE l love your tutorials and your passion for audio

[@len9518]

Problem with your distortion readings. Spec is 0.02%, and most tested units, were way lower than that.

[@TheReal1953]

Maybe he was reading the scale wrong? So instead of .1% it was really .01%. They are fully capable of that distortion range. Maybe he'll see this and weigh-in.

[@Wizardofgosz]

I was more interested in seeing you fix the original boards. This is basically just a new amp.

[@TheReal1953]

And that is a positive in my book if the new boards are designed correctly. One of the guys selling rebuild kits used to work for Hafler....not sure if it was this seller. I got into all that yrs ago including the 'famous' guy;where you send your amp/preamp to him and for thousands of dollars he updates and or tubes your equipment. I contacted him and told him what my price limit was per piece and he never responded. You don't want to play his money game, you're nothing but a gnat. I see this as a positive kit with great instructions....that's worth a lot unless you're an EE.

[@johnohara7590]

I bought a Hafler P225 couple years ago and what I did was replace the 10,000 main caps with 27,000 caps and finally opened my wallet for a good used B&K MC 101 pre amp. This arrangement along with my "76" AR 11 speakers is the closest I'll get to a warm and tube like sound just begging to be opened up with no unpleasant harshness. High quality pre amp is the answer and game changer in my book

[@harveyellis6758]

Should have been titled as kit building video, rather than restoration.

[@seanobrien7169]

Is there a difference? You solder in caps...

[@harveyellis6758]

@@seanobrien7169 A restoration would have been replacement of old caps & other out of tolerance components. Just about anyone can solder a kit together from PCBs, components, & follow step by step directions.

[@seanobrien7169]

@@harveyellis6758 So instead of replacing some components he replaced all the components. I still don't get your problem. He didn't trouble shoot the initial problem granted, but the course he chose he didn't need to. With what was available I would have taken the same road. He has lots of troubleshooting videos i that is what you are after. Or maybe it is just a question of semantics?