Power fault in Yamaha RX-A730 a/v receiver - Page 1
Forum section: electronics / repair

author: Natebcx
author_rank: Newbie
timestamp: September 28, 2019, 06:33:05 pm
content: My receiver shuts down immediately after i turn it on and when i go into diagnostics mode i get the code telling me PS2 value was 77 and that seems to be the same issue in this threadhttps://www.eevblog.com/forum/repair/yamaha-rx-v667-ps2-fault/at the very bottom. They replaced their IC104 (KIA7812) with a 1.5 amp regulator but my RX-A730 seems to have a (KIA7912).I have not been able to test the regulator yet but was wondering what could i replace it with? I found thishttps://www.digikey.com/product-detail/en/texas-instruments/LM7912CT-NOPB/LM7912CT-NOPB-ND/6355and other than it being 1.5 amp output compared to the 1 amp of the original it seems very similar. Would i have an issues with TI replacement part?

author: keymaster
author_rank: Regular Contributor
timestamp: September 28, 2019, 07:04:55 pm
content: No but i thing the replacement is uninsulated , so you will need to put a mica or a pad between the heatsing and the regulator .

author: Natebcx
author_rank: Newbie
timestamp: September 28, 2019, 08:17:08 pm
content: Thank you are you talking about something like this?

author: mariush
author_rank: Super Contributor
timestamp: September 28, 2019, 08:28:52 pm
content: KIA7812 is a +12v linear regulator.7912 is a-12v linear regulator.So make sure it is indeed 7912 or you may damage your device.If you want to avoid using insulators, you can use to-220fp packaged regulators which are full plastic.Here's a couple examples of 7912 regulators that would work for youL7912CP :https://www.digikey.com/product-detail/en/stmicroelectronics/L7912CP/497-7294-5-ND/1165903NJM7912FA :https://www.digikey.com/product-detail/en/njr-corporation-njrc/NJM7912FA/NJM7912FA-ND/805806Double check the pinout to make sure it's same as the one on the regulator you have (should be)Any of the ones in this link should work for a 7912 replacement:https://www.digikey.com/short/p2w2n5Some are 4 or 5 pin, you can just leave the extra pins unused (typically enable pin, on by default) and/or adjust voltage pins (defaults to -12)

author: drussell
author_rank: Super Contributor
timestamp: September 28, 2019, 09:08:08 pm
content: Quote from: Natebcx on September 28, 2019, 06:33:05 pmThere is probably both a 7812 (positive) and 7912 (negative) regulator in there somewhere since most things in audio are going to require both positive and negative voltages.Be sure to verify which one (or both) are causing you problems before randomly replacing components.

author: Natebcx
author_rank: Newbie
timestamp: September 28, 2019, 09:22:34 pm
content: Quote from: mariush on September 28, 2019, 08:28:52 pmThank you for the better recommendation for replacement, i searched the schematic and found there are NJM7812FA regulators (IC103) and KIA7912 regulators (IC104) they are right next to each other so i will test both when i get a chance.

author: Natebcx
author_rank: Newbie
timestamp: December 17, 2019, 11:44:22 pm
content: So i pulled out and tested the two voltage regulators in question and they both tested fine. I re soldered them in and got audio for about 2 seconds in pure direct mode but then it cut out. I am running through the service manual right now going through the diagnostics and found that, Communication and bus line connection between microprocessor (IC83) and DSP (IC921). it gave me a DSP BUS error telling me the communication between those two items is failing. Does this seem like a case where i would need a new logic board?