After 25 years in service, caps are what I woulda went for as well...great job! Interesting home made load....needs a project box and a bunch of do nothing switches and blinky lights! :) ~Jack, VEG
Nice. I have a late model D60 (mid 1970's) that I've owned for 20 years with what appears to be all original internal components and it still sounds solid (no pun intended) to these 48 year old ears. It has some minor transformer hum, which I think is inherent with the design (correct me if I'm wrong). I just checked the DC offset on my DVM and with both input channels shorted, it reads .5 mV on the Left and .20 on the Right set at 200 mV scale. Even new product from China does not measure that well. That is obviously not the be all / end all in bench testing but it is sonically dead quiet. I'd like to upgrade the op amp as I'm told that is the weak point, but I hear it is an unusual undertaking that is not worth the effort. I'm not a tech. I'm sure the caps should be replaced but I was told that when I bought it...yet here we are, 20 years later...and it's still working and sounding just as pleasing as it did then. I've had caps from China fail in 10 years or less, so what gives? If you have any recommendations, please share them.
I wouldn't do the opamp upgrade if you are OK with the way it sounds now. These things were a utility amp not aimed at the hifi crowd. They have a little bit of distortion but not so much that you can hear it when they are running below full volume. These were designed more as a PA amp.
Also, I have some vintage SS audio equipment from the 70's, 80's, and 90's that I inherited. However, they have sat unpowered for 30 years (mostly NAD and McIntosh brands, but also some Japanese receivers) and I'm wondering if I should use a VARIAC and dim bulb tester to power them up or just go for it and hope for the best. Is reforming caps possible? If so, what is the procedure that you recommend (specifically voltage increments and duration)? I'm reading a lot of mixed reviews regarding this. You sound like you know what you are doing and might have some sound advice (pun intended 😀). Thanks in advance. I will subscribe.
I do not believe in reforming capacitors. I just have not had any luck doing it but I would bring it up slowly to about 90 volts and let it sit turned on for several minutes before increasing it to 120. If all looks good on the dim bulb you should be good to go.
Ok. What size bulb do you recommend for a 225W/ch @ 8 ohms Class AB amp (NAD 218 THX)? How much larger does that bulb need to be for an amp that is twice a powerful (QSC 2450 RMX)? Also I have a couple of McIntosh MC250's 50W/ch. All of my equipment is SS, not tube. Everything I've read on this is regarding tube stuff. Thanks in advance. Appreciate the info. @@AERVBlog
Yeah. Don't turn it on anymore. Check all the transistors and the big filter caps. Bring it up on a light bulb limiter even after you fix what you think is bad.
