Hafler DH110 Preamplifier - NFF (Ep. 200 )

[@mdzacharias]

At around 18:00 to 19:00 you show a volume control tracking issue, enough to account for the customer's problem. I had a defective volume control in one of these that acted the same, maybe worse. I confirmed it by removing the control and feeding DC to it externally and viewing the DC output on a scope as the control was rotated. I could easily see the shifting balance characteristic. Replaced the control with one from a parts unit, problem solved. Also, the DH-110 is quite notorious for dirty controls. Don't be too surprised if this one comes back for a re-do. By the way I have extensive experience with these.

[@SergZak2023]

Congrats on 200, Trevor! Thanks for your continued awesome content.👍

[@scrappy7571]

I built my Hafler amp kit in 1982. The boards came soldered, so it was basically assembly of the chassis and power supply. Also built a few Heathkits as a kid. Sure miss the kits. Guess that's why I got into restoring/tinkering with old audio. Congrats on 200 episodes! Hope you can do many more, always enjoyable to watch, and I learn alot of good info!

[@Poppinwheeeeellllllieeeeez]

200 Episodes. I have watched them all. I was sort of expecting a special episode... but anticlimactic was sort of a troll. Congrats Trevor. 👏

[@CharlieParkour]

Happy 200 Trevor. Congrats!!

[@mistermac56]

David Hafler was the original owner of Dynaco. After he sold Dynaco, he started The David Hafler Company. Hafler's MOSFET amps and the DH-100 and DH-110 preamps were excellent and you could purchase either kits or fully assembled units. All of the PC boards for the kits were preassembled and tested at the factory. The David Hafler Company was eventually sold to Fosgate.

[@Amplified208]

Definitely agree on the conclusion of that video. Something is going wrong in his setup at home. Congratulations on 200 videos.

[@FMonick-ez6zk]

Nice video. I built one of these in back in 1981. Still have it. I had the same balance issue a couple of years ago with it and it turned out to be dirty output RCA to the amp (Hafler DH230). Cleaned all the input and output RCA jacks and it has been fine ever since. I have three other preamps, all of them cost 2-3 times what the Hafler kit did. To me, it is still the best sounding of them by a small margin all but actually all sound very similar and the differences are minute. BTW "ELP" is External Processor Loop. I use for an equalizer if .

[@chrishoffman6537]

Trev Your videos are my favorite on electronics. I’m on my way to viewing them all. Your method is great so please never quit providing this content!

[@alexismethenitis]

Thank you so much for explaining the schematic in the begining.

[@rlgrlg-oh6cc]

EPL is External Processing Loop Just a way to add something like an equalizer or some other processor (Dolby decoder, etc) in series with the signal path.

[@sirsuse]

CONGRATS ON 200 EPISODES!! 🎉

[@zx8401ztv]

That's a neat amplifier kit, i love simple designs. Very little to go wrong. Ok the panel pots and switches always get noisy, but a spray of servisol or similar shuts it up :-D

[@steveoszman8746]

Thanks!

[@ThomasSteves]

Pehaps he's losing his hearing in one ear? I feel like I have the same issue... Congrats on #200, I always look forward to your videos!

[@ian-c.01]

There's nothing more frustrating than intermittent faults ! I was surprised you didn't test it before you took the cover off, that ribbon cable appeared to be slightly loose, it's possible that may have been enough to add a tiny bit of resistance to the output, we'll probably never know.

[@PeterMilanovski]

That's exactly my thoughts too! It didn't look it took much force to remove the ribbon cable, the pin header and cable socket could have tarnished over time? See this same issue with vacuum tubes, some contact cleaner and it's good for another 20 years.... The only other thing that I could suggest is broken solder joints... A reflow with some flux will take care of that problem... Especially when RCA connectors are involved, connecting and disconnecting RCA cables can break solder joints...

[@geirendre]

You didn't check the Phono inputs did you? The issue might be there. If not, then I guess you'll have the main amplifier coming in soon for repair.

[@Timothycan]

I guess the owner could try reversing the left and right channel connections on the feed to his power amp, and if the disparity between the channels does not swap over, then the problem is with the power amp. If it does swap over, then it could be the leads.

[@ermennda]

Don´t forget to tell him to check his ears.

[@JosevaldoSilva-p8c]

Muito bom👍👍👍👍👍🇧🇷🇧🇷🇧🇷

[@stefanegger]

Sadly you could not repair this one 😢

[@exenx2995]

It was an easy repair he just doesn't know a whole lot about amplifiers and such we all learn with time .

[@tubeDude48]

EPL (external proccessor loop) is usually for an EQ, surround proc., etc This was created by Polk Audio. --- Without watching the video past 10:55, I suspect that replaced transistor. To much gain, to little gain, etc. But I'll wait for your finding!

[@johnsenchak1428]

CAN'T READ THE SCHEMATIC YOU ARE WASTING VIEWERS TIME

[@exenx2995]

What else is new?

[@kelleyhagan960]

You can't read so it shouldn't concern you.

[@exenx2995]

I don't understand why every video you have to name EVERY little part in every unit before you work on them "here's the capacitors, here's the power supply, here's the power switch, here's the bass, here's the treble, here's the power cord, ect, ect, ect...." It's like you are constantly just trying to impress your viewers to MAKE them think that you are so intelligent or something. Of all the repair channels on here no else gives a rats arse about trying to look smart. Just do repairs everything will still work out just fine.. geezzzz...

[@zx8401ztv]

Trevor is making it obvious for people learning what is what. It takes a while to sink in.

[@scrappy7571]

Glad he does this, in this vid he explained the muting circuit. Never knew how that worked, good info. Also never knew the bass/treble circuit are in the feedback, more good info. So yea, it's good... if you don't need it fast forward.

[@TurntableGuy]

If you don't like it, don't watch. What he doesn't need is asshole-like comments.