In 1982, I bought an M-500. To this day, I'm impressed by the smooth and effortless way it does its job, with never a hint of strain. I had a chassis refresh accomplished by Rolland Barr at Hi-Tech Audio (Stevenson, WA) on the M-500 in 2014. Things were fine until in mid-2016 I noted a low-level buzzy hum in both channels. I did the usual troubleshooting, and determined it was indeed the M-500, not from an upstream source, nor was it any kind of RFI. Rats. At this point, inertia took over, and I used two Dynaco Mk IVs I had just refurbished as backup power amplifiers in place of the M-500. A couple of weeks ago, I finally got the bug to fix the M-500, so I emailed Rolland, and described the symptoms to him. I expected him to give me an RA number so I could ship it off to him. Instead, he advised me of the possibility for a grounding contact tab on one of the three circuit boards having partially or completely lost chassis ground contact, adding that was probably the only way the amp could possibly be displaying the symptoms I described. He further described the location of the tabs, each secured to chassis ground by a small Phillips head machine screw. Armed with that information, I checked all three screws, and all appeared to be secure. To double check, I ohm'd tab to ground resistance. Two were zero, but one showed a resistance of about 20 ohms. Ah-ha! Screw tightened a bit more, and resistance was now zero. Plugged in amp, and dead silence from both speakers. I removed the screw, cleaned it and tab contact area (no signs of any corrosion or anything which might cause resistance), everything back together, and what a difference. The Mk IVs are good, but the Carver is breathtaking by comparison.
It would have been easy for Rolland to have simply ask me to send the amp in (for me, across country), but he made it incredibly easy for me to deal with the issue, saving me most likely $300(+). If you have a Carver product, and want top-notch quality service, with wonderful customer support, I can't recommend Rolland and Hi-Tech highly enough! And, if you have symptoms with your M-500 as I had, one of those three grounding points is almost certainly the culprit.
It would have been easy for Rolland to have simply ask me to send the amp in (for me, across country), but he made it incredibly easy for me to deal with the issue, saving me most likely $300(+). If you have a Carver product, and want top-notch quality service, with wonderful customer support, I can't recommend Rolland and Hi-Tech highly enough! And, if you have symptoms with your M-500 as I had, one of those three grounding points is almost certainly the culprit.
