Search results

Hi All, Just wanted to provide a quick update on status of this project, as it is now complete! The issue was caused by a couple of burned out resistors in the bias circuitry of the power amplifiers. The same resistors were actually failed on both boards. All of the failed components were...

Ok, here is a pic of the board in question. It's mounted to a heatsink as large as the board for the power transistors. The four large blue resistors on the left are the ones that dissipate a lot of heat. I did find a few more things wrong with it today. First, I noticed that the +80V and...

I usually use rubbing alcohol and a brush to clean off the cap juice, followed by compressed air to make sure everything gets blown off well. Let it dry for an hour or two before plugging it in, but if your working on it that's probably not an issue anyways haha. Replacing the caps is not a...

Thanks everyone, I'll take another look at it tomorrow and let you know what I find. Powertech - The driver transistors do have heatsinks, and there are a couple of resistors that seem to be kicking out some serious heat. Conveniently, there are couple of small transistors (TO-92 size) without...

+1 Also a good thing to check

Hi D-Owen, I would start by checking the capacitors in that area. Are any of them bulged or leaking?

Ill try and listen immediately upon turning it on and let you know what happens as far as distortion. I did try cooling the board off with some compressed air to see if there was any affect, and i did notice some "blips" where it started reading a value. My test speaker also started to...

Hi pillofight, Also ask the seller about the impedance of their speakers, and have them double check that there aren't any errant strands of speaker wire that could be causing a short. Dan

Thanks Binkman, TP1 and TP2 are labelled on the actual amp boards, so I am pretty sure that I am measuring the correct points. I just spent some time working on it, focusing on the right channel for now. I noticed that when I start up the amp, the voltage slowly increases to the correct 6.6mV...

Hi All, Has anyone here ever adjusted the idle current on a NAD C 275BEE? I have repaired a few other unrelated circuit issues in this unit, and once I got it up and running, noticed a small amount of distortion on the right channel. It only occured during low volume passages, which led to...

Found the issue... By sheer coincidence, one of the power supply wires that the previous owner "repaired" shorted out and caused the issue. All repaired now and sounding good! :music:

Well I did it now... Replaced the bias pots and was careful to pre-set them to the values of the originals. 310 ohms in this case. I turned on the amp and blew both power supply fuses. Is there a "safe" value I should adjust them to before replacing the fuses and trying again?

I would start with Deoxit and clean all the potentiometers and switches on the front panel. They can make a huge difference in the sound and be the root of many issues. Good luck!

Thanks for the feedback! I will definitely be re-flowing the joints. Also found some cut and spliced signal wires that must have been messed with by the previous owner, so I'll be sorting that out as well.

I just got done fixing one of these, albeit it was experiencing the "buzz" of bad capacitors. There is a soldered in fuse on the circuit board behind the transformer, have you checked to see if it is completely intact (low ohm)?

Hi Guys, Been working on a new to me Harman Kardon 730 receiver. Upon receipt the left channel was completely shorted, there was 38V at the speaker output:yikes:! Luckily I had the sense to measure it before hooking any speakers up, so no speakers were harmed in the making of this post...

Dave, Gadget, You guys both pointed me in the right direction. The problem was with one of the 6CW4 Nuvistors. Replaced it and it started working great! Thanks! -Dan

Will do. Is there a test point that I can use my oscope with to view the frequency of the oscillator?

Dave, I followed your suggestion and removed the three tubes from the RF section. When I turned it on, the tuning meter stayed at zero and it produced static with no fading. I guess this means the problem is in the RF section? -Dan

Hi All, I have a very late production 500c that I am attempting to get the tuner working on. The amp sat for many years before I got it, but with a replaced selenium rectifier in the bias supply, I was able to get the amplifier up for some basic testing. A full restoration is in the works for...

I have been having the same problem for the last couple of months with RoadRunner Lightning. Theres a really long lag time, then the page will load quickly; everything is fast if I use the LTE connection on my phone... Here is a traceroute:

Thats a good idea! Also, this project does not need to be too complicated as I am currently working on my senior design project, which is a low cost PC Based Oscilloscope. I actually just finished designing the circuit and PCB, and have to start working on the communications software. Maybe...

I'm really open to either at this point. SS may be easier to get approved, but I've always wanted to build a tube amp as well. If I was to build a tube amp, it wouldn't need to be class A. -Dan-

Hey Guys! I'm looking to build an amplifier as an independent study project for my final semester as an electrical engineering student. Im looking to go all out and make something fairly substantial that I'll keep for a long time. I've looked around and found a couple of neat looking Class A...

I will look into that too, if their tube amps sound as good as the SS ones I have heard, then I'm sure I would like the sound! -Dan-