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JBL S650 Synthesis THX Amplifier (Marantz MA500 module)

Hello everyone.
I have just acquired a massive (75lb) JBL S650 Synthesis 5 channel power amp. Made in the USA, circa 1997, it's a 5 x 125 wpc with full monoblock design. I have since discovered that it's actually based on the Marantz PMA5310 module used in their acclaimed MA500. The Good: it's a beautiful piece, well crafted and appears to be a serviceable layout. The Bad: Only one channel works and there is little information available on the web. Nonetheless, I have found schematics (from acdconline.com in Australia) from which I deduced the link to the Marantz amp module topology. Will have detailed photos to share... The full complement of output power devices (20 total) are on order, but I am holding off on replacing the Elna 10,000 mF 71V caps for the moment. Now I just need patience, but will welcome any advice!
Cheers!
ChateauAudio



JBL S650 Synthesis THX Amplifier (Marantz MA500 module)

Thanks for the update and the great info.

JBL S650 Synthesis THX Amplifier (Marantz MA500 module)

Any update on this project.

Thanks

JBL S650 Synthesis THX Amplifier (Marantz MA500 module)

Three of the four bad channels had low/distorted output which was corrected by recapping. The principal bad actor I believe was the input coupling cap C701, a 4.7uF/50V electrolytic. I think this is the most common failure of these amps so I replaced with a high quality WIMA polyester film. In re-capping the rest, I skipped the 10,000uF/71V reservoir caps (which seemed OK) as 71V or 80V are nearly impossible to find in the required 30mm diameter (easy to find in 35mm). The fourth bad channel was completely dead, so in addition to the re-capping as above I replaced the four output devices, to no avail. I then replaced Q701, a uPC1342V driver IC, but also without success. I have since moved on to other repairs but eventually hope to get to the bottom of this so I can put this beast in service!

JBL S650 Synthesis THX Amplifier (Marantz MA500 module)

Thanks for the update and the great info