NAD 7175PE Repair

[@ctrlzyx2]

I have both 7250pe and its bigger brother, the 7175pe. Both use those 200 ohm trimmers with 5 mm pin spacing for the distortion adjustment. It is not uncommon to see these read in the kiloohm or megaohm range when they fail. On my 7250 both failed. On the 7175 they were both within spec. I believe the failure is due to surface oxidation. If you probe around you will find the entire surface where the wiper sweeps has sky high resistance on the failed units. Probably has to to do with where these units were stored over the years. Some just choose to replace the trimmers with 100 ohm resistors, because the optimal adjustment seems to always be close to that value. Other common failure for these is the supercap for the preset memory. Should hold memory for 2 weeks with a good supercap.

[@raygianelli3612]

Wow, that's good information. Thanks for posting! I was skeptical about those trimmers being stock.

[@AnthonyFrancisJones]

Great video. I still have a 19" rack with the Nad hifi (CD, amp, tuner and cassette player) I bought in the 1990s as a kid and it still looks modern and works really well!

[@raygianelli3612]

Thanks! NAD had solid designs but often used cheap parts. Some models/lines didn't suffer from this, and it sounds like you got lucky with yours. When working properly it's nice sounding gear. I got an NAD 1300 preamp in which almost every electrolytic capacitor measured horribly bad or completely failed. It worked that way, but sounded noticeably better after a complete recap.

[@abelabner]

I like your organization method!!

[@raygianelli3612]

Like a lot of things, I came by it the hard way. Losing parts, mixing up parts, you name it. Finally hit upon bags in bags.

[@Trucam2020]

Dear Ray, as usual, excellent repair video. Thanks

[@raygianelli3612]

Thanks Url. Do you fix electronics?

[@raygianelli3612]

Predictive text strikes again. I typed "Uri".

[@Trucam2020]

@@raygianelli3612 Yes. Only for as hobie.

[@raygianelli3612]

@@Trucam2020 Same here. I'd probably starve if I did it for a living. 😁

[@LaserGuy64]

How timely. I just picked up one of these with the same problem. Total preamp section works and I am just starting to look at it. Thanks for sharing the expertise and sharing the content!

[@raygianelli3612]

Fortuitous indeed; I've never seen one before! It sounded pretty good, even on my small bench speakers. The bass was overloading my lapel mic in the video.

[@RectifiedMetals]

Mention a Sansui being touchy and I just get chills. Working on a 3000a that is just nuts with its design. The SCR protection is a bear.

[@raygianelli3612]

Yeah, it seems like all the Sansui's I've worked on have touchy adjustments, usually the offset. I get why people use multi-turn trimmers for these. I've yet to work on a 3000A, but it sounds like a bear. In the finest Sansui tradition!

[@knifeswitch5973]

LOVE my 3000! Took a long time to get it safe and stable but, worth every effort. Ray, I have to thank you for not editing the booboos. As a boo-boo expert, it’s nice to be reminded that we’re all human. Peace

[@raygianelli3612]

@@knifeswitch5973 😁

[@andymouse]

Great fix Ray !....cheers.

[@raygianelli3612]

Thanks Andy!

[@gillanland]

It would've been nice if you could analize how did -78V get all around that Q609 transistor as a result of potentiometer failure.Thank you.

[@raygianelli3612]

While that would have been interesting , it was more productive to compare left to right channel voltages to help pinpoint the area causing the trouble.

[@electronicsanta8149]

Awesome…

[@tjules7]

Great video. I have a NAD receiver 7400. The outpout from the right speaker is not coming out right. I have to play the the volume knob to get to a normal level, and the bass and treble are not reaching their peak. Would you be able to take a look at it for me? Where are you located?

[@raygianelli3612]

Tony, I'm not taking in anything for others right now. I'm located in South Florida.

[@SebastianTechArchive]

Hi Ray I'm in the middle of a re-cap on a Marantz 2015 receiver aka baby. And I have a question about this tiny Caps on the amplifier bored C605 and C606 at 1μ 25v what would be the best equivalent replacement? I already re-cap the power supply and everything seems to be working now (it was only a big hammmmm.. before) bios DC etc.. okay. But can you explain with Caps I can get in there? sorry for my bad English and great video's

[@raygianelli3612]

Sebastian, it's always desirable to replace small values of electrolytic capacitors with film capacitors. Film capacitors are superior in every way, and this goes double for capacitors like the ones you're replacing, which are in the signal path. I would use these for your Marantz: www.mouser.com/ProductDetail/WIMA/MKS2B041001C00MF00?qs=sJjjjplDs9s75Jp9u8FMdQ%3D%3D

[@raygianelli3612]

And your English is fine, my friend!

[@marnav9205]

Your cam was out of focus Ray.

[@raygianelli3612]

It can happen when I go to manual focus when showing a schematic, sot the autofocus doesn't go in and out, which I find distracting. And then I forget to put it in autofocus. Apologies.

[@Gjb3504442]

I have the same NAD unit and it keeps blowing the main fuse. I have read that it is a bad output transistor. Where can I aquire one of these transistors, or where can I send it to have it repaired? Thanks

[@raygianelli3612]

Just replacing transistors can result in more blown transistors. It really needs to be evaluated to find all defective components. Not sure where you can send it.