DR #45 - NAD 1155 Audio Preamplifier Repair, Service, and Testing
ฝัง
- เผยแพร่เมื่อ 20 ส.ค. 2024
- - Resolved intermittent output issue
- Replaced both power supply transistors
- Replaced all electrolytic capacitors
- Verified power supply and preamp functionality
I remember these. It was NAD when we all could afford it. I was an NAD dealer, and sure they had their quality issues, but when they worked, they sounded pretty nice.
When they worked... I bought an AV-716 receiver and a 5000 CD player back in the 90s. I absolutely loved NAD's industrial design and the components sounded great, but reliability wasn't their strong point. The AV-716 kept blowing its output transistors despite me never listening at high power levels. I finally got fed up with taking it to be repaired, so I replaced it with a Yamaha that has been going strong for nearly 20 years. The CD player developed a skipping problem that lens cleaning didn't fix. After my experience throwing money at the receiver, I just cut my losses.
@@FlyingShotsman Ironically I have a Yamaha 5.1 AV receiver amp here that started frying its impedance compensation circuit. It had been operating with 6 Ohm speakers while minimum impedance is 8 for each channel.
What a great way to document your work. It's one of the best videos on this type of repairs that I've seen. Very clean, efficient and informative work.
So helpful. Thank you
I have one of these in storage in the garage. It was a great preamp. I like the dual pre outs I think one was standard 1v and the other 2v peak to peak. It feed into my Sigma SE400 power amp (A New Zealand design and built amp) which is now connected to the sub out on my Onkyo A/V receiver. I blew up the Sigma amp so many times I had to replicated the amp circuit board and had heaps made. I met up with the guy that made them (I think he may have made the Roberts amps as well) and he gave me all his original hand drawn circuits and notes. Nice video, I would have put some better modern heatsinks on those transistors.
I have a couple NAD 1155s and the sound from the higher outputs is stunningly good. Their biggest problem is you have to physically change the volume in a world of remotes.
Awesome thanks 😊
Like youre methodic calm and steady approach.
One thing though, why not get a desoldering iron (with vacuum). Makes the most of your desoldering a breeze, and is a big time saver..
Ahh yes someday. Maybe. For some reason I somewhat enjoy the very manual, slow process of using braid. But, I’ve heard once you go desoldering iron you don’t go back. Probably true.
I had an NAD 3020e integrated amp when I was a student in the early 90s. Our student house was burgled and it was stolen. I'd tried a small mod to turn off the power LED via a toggle switch I mounted on the rear (I liked listening in total darkness), but the LED was apparently part of the audio circuitry and affected the sound (or maybe the long wires to the back just caused EMI hum). So I disconnected the switch internally, but left it in place on the back because lazy 18-year-old.
After the burglary, I always hoped that whoever ended up with my stolen amp got _really_ confused about that little switch on the back that apparently did nothing.
Nice tutorial. I have seen already number of services of NAD and CAudio. Conclusion is in general capacitors quality in both are rubbish. And rated 85C deg instead of 105Cdeg specially for those located close to heat sinks.
I OWN the same unit and i modified it ...if you replace ALL electrolitics capacitors with Elna cerafine o similar you make a great preamp cause the stock caps are junk.
I don't use phono section...Can i skip the caps on the phono section?
6:32 Realized after looking around, that the two transistor part numbers you mention are for the same transistor. Got my parts and doing that swap. Already did the caps, with higher-voltage ratings. Thanks for the great video?
Nice work sir!
Thanks Brian.
Watching you work is an absolute joy. I have a 24 year old Rotel RC03 Pre Amp has been a real work horse along with 4 x Rotel power amps. I have a channel selector switch jumping channels issue that will need investigation. With its age, is it really worth fixing as other components are likely to be at the end of their life span. Or should I just buy another Pre Amp that's compatible?
It's not just the greasy grunge on the switch rails and moveable contacts thats causing the channel dropout and noise; there's a thin yellowish layer of oxidation on all the metal parts. Clean the rails with a pencil eraser after you degrease them. The little metal clips used as sliding jumpers can also be oxidized where you can't really see it, and these are very problematic to clean without bending or damaging them, in which case you are totally screwed because you will never be able to reform them into the correct shape. There really isn't sufficient contact pressure from those clips sliding across the rails to wipe the oxidation off as you activate the switch. I clean them with a slip of ultra fine, very thin, plastic backed sandpaper known as lapping paper or polishing cloth, the type of stuff that is used for polishing fiber optic connectors. This is not a job for the faint of heart or anyone with shaky hands (ease up on the caffiene), and you only get one chance to do it right. If you bend or deform one of those clips even slightly, or you lose one, you're screwed!
Nice work....cheers.
Thank you
Great preamp.
good job mate..
Well thank you.
I really like the way you detail your work. I have a NAD receiver 7400. Where are you located? maybe I can have you take a look at it?
Nice
Silly question maybe but did you create your list of electrolytics simply by going through the circuit diagram/board ? Or is it in the service manual?
Not silly. I typically go through each cap in a unit, 1 by 1, and write down the capacitance & voltage ratings, along with marking the top of the cap with a sharpie so I don’t double-count the same cap. If something looks out of place, I’ll reference the service manual if it’s available.
Do you have any suggestions for long lasting thermal compounds? I mean like 10 years plus?
Sometimes these types of switches are secured to the board prior to soldering by bending a couple of the terminals over, flat against the foil, and they tend to snap off when straightened back up for switch removal. Luckily not an issue on this particular unit! PS, poke a series of holes in the desoldering braid, about a half inch apart, with a dental pick or jeweler's screwdriver, prior to desoldering, and then you can position the braid right on the tip of each terminal where it protrudes from the cone of solder.
What are you using to isolate your scope from mains ground. When service the amps you repair?
Nothing. I’m just extremely careful. So far so good. Eventually I’ll get an isolation transformer and / or a differential scope probe.
Hey ive got a question for ya. My preamp has no output until the volume knob is turned way up, then it can be turned back down to appropriate listening levels. Is this due to falty/leaking transistors? I noticed my rectifier cap is also much darker. I will be copying you and replacing all the elctrolytics, but wanted to know the culprit anyway. Ive already cleaned the potentiometer so it cant be that. Thoughts?
Good question. It could be the transistors. It could be the relay/s as well. It’s difficult to say without testing with an oscilloscope.
@@dualityrepair4770 I found a full electrolytic kit for 35 dollars online. Is this a rip off? Would I be better off ordering each cap from a supply website, and if so, what do you recommend?
@@dualityrepair4770 would a full electrolytic repair kit for 35 dollars be reasonable for this job or would it make sense to special order all of them from an online supplier. If so which do you recommend?
That depends on the quality. Does the kit list the brand of caps?
@@dualityrepair4770 I just inquired, you were right about the relays in the power amp. I swapped them today and both channels are coming through just great. I am getting the same static when adjusting the volume knob as you, but other than that even without a recap it's going strong. What are the odds of producing a sonic difference with the new electrolytics? Or is it just future proofing? Appreciate your replies!
What user clenar with hisopos?
I have threshold CAS-1 amp in need of repair. Would you be up to the challenge?
Potentially. Send me an email with details. My email is in the about tab.
👏 "Promo sm"
use ultra sonic machine to clean those switches