750 replacing a dead JSD 60

[Steve Guttag]

Since Dolby doesn't do manufacturing in-house anymore, I don't think that they are really set up for that sort of RXO. Remember, Dolby yore made schematics available and talking component level stuff with them was definitely done. I'm surprised, honestly, that more wasn't done for the CP750, given its popularity...a Dolby Field Bulletin discussing its wear components. The closest they got was some parts on the internal power supply.

I think there could be a market for CP750 motherboard repair. Swapping motherboards is going to be faster/cheaper (even if an RX board is knocking on the $1,000 range) than changing units. Knowing that heat is the main driver of the problem...as I noted, move the power supply out of the box.

[Ryan Gallagher]

Well, even the IC's can be replaced as long as it's a generically available chip. SMT is pretty easy to do. I just repaired an old Parasound Zone Preamp for a friend. In his unit the micro controller failed. I know a retired HP Engineer that can download the stored program, then write it to a file he saves, then rewrite that file to new chips. I met him on another forum a long.time ago, because I used to have an HP Digital scope that sometimes refused to boot, or sometimes would not fully boot. The type of chips in that old scope were the kind that whats written on them fades over time. So I sent him the chips and he cleared them and rewrote the program, which he already had back on to them.
On the Patasound I sent the controller out of another working unit plus a NOS chip. And so he returned the NOS and the factory original. Both units work fine. So if the 750 is havimg micro controler chip issues, it still may be able to be fixed. Other non programmed chips if obsolete are always still available, just not in production quantities, and often from places that specialize in obsolete semiconductors.

Off topic, but hah, I still have and use all my parasound component gear I bought not long after highschool. Had a analog pre-amp go out on me, they fixed it at no charge not that long ago (some 20 years after manufacture), I didn't even have to pay the return ship. Good folks! I think they also sent me a new belt for my CD transport free at some point. Still in business, and these stories are kinda why I would imagine.

[Mark Gulbrandsen]

Since Dolby doesn't do manufacturing in-house anymore, I don't think that they are really set up for that sort of RXO. Remember, Dolby yore made schematics available and talking component level stuff with them was definitely done. I'm surprised, honestly, that more wasn't done for the CP750, given its popularity...a Dolby Field Bulletin discussing its wear components. The closest they got was some parts on the internal power supply.

I think there could be a market for CP750 motherboard repair. Swapping motherboards is going to be faster/cheaper (even if an RX board is knocking on the $1,000 range) than changing units. Knowing that heat is the main driver of the problem...as I noted, move the power supply out of the box.

All that is quite easy to do... Especially moving the power so it's external. It may be possible to come up with a kit do do that. Seems to me the CP65 and CP500 had the longest lived supplies of all their products. Have had to rebild CP100, CP50, and 55 quite a few times. But those were more likely due to age. The 650 had power supplies for a couple years that had capacitor plague stuff in the power supply, easy fix there. Most 650's were fine. Never got to work with a 750 because customers rejected the idea of using them and they bought USL instead.

[Mark Gulbrandsen]

Off topic, but hah, I still have and use all my parasound component gear I bought not long after highschool. Had a analog pre-amp go out on me, they fixed it at no charge not that long ago (some 20 years after manufacture), I didn't even have to pay the return ship. Good folks! I think they also sent me a new belt for my CD transport free at some point. Still in business, and these stories are kinda why I would imagine.

The down side of Parasound is they will not let schematics out. But a lot of the stuff is pretty easy to decrypt if you look up the chips used. Usually just recap them entirely and all is well. I have a zone system at my desk because the components are so small. The whole system is made up of components I bought on Ebay that were as-is non functional, for parts only. Preamp, tuner, and two amps run as monoblocks. Still looking for the matching Z CD player... Parasound was recently sold... The owner retired.

[Leo Enticknap]

I think there could be a market for CP750 motherboard repair. Swapping motherboards is going to be faster/cheaper (even if an RX board is knocking on the $1,000 range) than changing units.

If an aftermarket vendor could figure out how to fix them, agreed. That having been said, CP750s are now dying and being replaced with something else so quickly (out of necessity) that the size of that potential market is now diminishing rapidly.

[Dave Macaulay]

We have had some CP750 boards repaired. I haven't followed up on the testing here, don't know were they OK?
I was told by someone at Dolby that level loss the issue is with certain capacitors, and there are a LOT of them in the list. I looked into replacement but we're not set up to do board repair and some of them weren't too easy to get particularly if I didn't want 1,000.