Rowe jukebox with low sound output

[oz]

Hello everyone, this is my first post on jukebox addicts. A friend of mine has a Rowe AMI CD II Phonograph jukebox. He said when he bought it ( a used one ), it played o.k. and the volume was adequate. Since then, the sound level has decreased, so much that at full volume the sound output was really low. He asked if i could have a look at the jukebox for him. I have to explain, i am NOT an electronics expert, i came to have an interest in audio equipment rather late in life ( i am now 72 years old ), but have now got a basic understanding of how circuits work. I removed the amplifier chassis from the jukebox and the label on the chassis says it is an R-3812A stereo amplifier 50 watts. The preamp and the 2 driver boards are all solid state, not valves. I was given a memory stick with the owners manual on it. Although the manual has a circuit diagram of the stereo preamplifier ( model R-3758A ) it doesn't have a diagram of the driver boards ( L-5771B ) or of the power supply. On inspection of the driver boards, R80, a 1000 ohm 2 watt resistor looks discoloured as if it got hot. This is the same on both boards, but the resistors measure o.k.There is a 1500mf 75volt electrolytic capacitor that reads wrong on my lcr meter ( i think this is causing the hum when i listened to the jukebox ). I think this is a smoothing capacitor in the power supply. I have replaced the two 1000 ohm resistors in the driver boards, but still have low sound output from both channels. I am writing to ask if anyone has come across this problem previously. Any help is greatly appreciated. Apologies for the long thread. I live in Devon, England. Best regards, Oz.

[sedouglas]

I’m having this exact problem right now myself. I’m almost certain the preamp is bad. I’m able to plug a line level audio source into the phono input and the aux input and get normal volume. I have already replaced all of the electrolytic capacitors (and double checked they are in right) so it isn’t those. I suspect some of the chips are bad. I had a couple cold solder joints which have also been repaired. I’m going to have to send it to Jeremy to take a look, is my guess.

[oz]

Hi sedouglas, the amp i am having a look at is the stereo 50 watt one. I would have thought if the preamp was faulty, one channel might be faulty, but not likely both, unless it is something that is common to both channels, like the power supply. Unfortunately, apart from a circuit diagram for the preamp, i have no circuit diagram for the power supply or the driver boards.I hope you have better luck with your amp. Best regards, Oz.