I've got a CS-800X that's used for a "stereo" in a shop for many years. Doesn't see a lot of high output use, just running ambient music. Yesterday it started buzzing loudly so it was switched off. I turned it in today to debug and it initially buzzed loudly alternating left and right channels so I turned it back off. When I powered it back up again now it's just flickering green on the power light, again alternating between channels. The relays are clicking intermittently. DDT lights are off, speakers are fine (running on another amp now), fuses are fine and have never been replaced (by us), no other indication of issues.
I took the lid off and immediately noticed R103 on the power board (20W 400ohm) is coooookkkked, it's heated the adjacent areas around the board but looking at the schematic it looks like it's related to the fan but not much else?
~75V on both capacitors
Going to start towards verifying +26V and +/-15V output. Any other suggestions on where to start/what to suspect? Seems like it should be on the power board given that it's effecting both channels but that could turn out to be a bad assumption 🙂
I took the lid off and immediately noticed R103 on the power board (20W 400ohm) is coooookkkked, it's heated the adjacent areas around the board but looking at the schematic it looks like it's related to the fan but not much else?
~75V on both capacitors
Going to start towards verifying +26V and +/-15V output. Any other suggestions on where to start/what to suspect? Seems like it should be on the power board given that it's effecting both channels but that could turn out to be a bad assumption 🙂
R103 runs the fan when heat sink is cool. I would look to see if dirt has got the fan stuck. Maybe replace the fan?
Buzzing and age indicates to me time to replace the mains caps. 30 years old maybe? I use ones rated >2000 hours service life to I do not have to ever do it again. Smaller ones in the 15 v circuits may be even more suspicious.
Do not use 2 hands to check voltages. Connect black lead of DVM with alligator clips to analog ground, make voltage checks with one hand, write numbers down and subtract. Wear no jewelry or metal on hands, wrists, or neck. 1 v at high current can burn your flesh to charcoal. Wear safety glasses, parts can explode and solder splashes, especially desoldering. 30 year old e-caps can be explosive if run too hard dry.
One can waste a lot of time determining exactly which e-cap could be causing a bozz. Change that one, put it together, you'll probably get to take the case off again in 2 to 6 months. More productive to do them all, but if you are working for a customer, hard to sell that practice. I've seen TV's with used caps spliced around the blown up ones. Mr. Bee shop (on the repair sticker) is now out of business. Most customers would rather buy something new that will give them a trouble free 6 years. A CS800x with new fan, all e-caps, pots, clean heat sink, could last another 30 years.
Buzzing and age indicates to me time to replace the mains caps. 30 years old maybe? I use ones rated >2000 hours service life to I do not have to ever do it again. Smaller ones in the 15 v circuits may be even more suspicious.
Do not use 2 hands to check voltages. Connect black lead of DVM with alligator clips to analog ground, make voltage checks with one hand, write numbers down and subtract. Wear no jewelry or metal on hands, wrists, or neck. 1 v at high current can burn your flesh to charcoal. Wear safety glasses, parts can explode and solder splashes, especially desoldering. 30 year old e-caps can be explosive if run too hard dry.
One can waste a lot of time determining exactly which e-cap could be causing a bozz. Change that one, put it together, you'll probably get to take the case off again in 2 to 6 months. More productive to do them all, but if you are working for a customer, hard to sell that practice. I've seen TV's with used caps spliced around the blown up ones. Mr. Bee shop (on the repair sticker) is now out of business. Most customers would rather buy something new that will give them a trouble free 6 years. A CS800x with new fan, all e-caps, pots, clean heat sink, could last another 30 years.
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