stereo psu diagnosis from schematic - Page 1
Forum section: electronics / beginners

author: algorithm
author_rank: Regular Contributor
timestamp: February 15, 2022, 04:39:00 am
content: so I have a yamaha natural htr5150, Ive had this receiver fully disassembled multiple times. its quite a chore. after exhausting my best ability and still unable to get it after a year on and off.when I got it the diode feeding the first power board relay was blown it seemed. was seeing 18v on - of diode. which service manual says should be 0.I replaced that diode when I first got it, and the transistor on the same first main power input board. then, it showed 0 like it should. but still had auto protect poweroff happen. found a lot of broken traces on main amp board, repaired all the breaks. but still get protect poweroff. and that diode is back to showing 18v on -. the diode is across the traces leading to both sides of the coil in relay, which is supposed to be energized, but isnt the diode supposed to block it?If you could look at the schematic and give me an idea on what might be causing the problem? because I feel like I tested everything on the board out of circuit and everything passed. but yeah any ideas would be much appreciated. I do have to say I think c806 a 0.1uf ceramic tubular type (looks like a resistor) did have like 2ohm esr. Could a little ceramic cause such a powerful machine to buckle? arent ceramics not supposed to have esr? or like 0.1ohm max?theres a chance bridge rectifiers were put in backwards on the secondary transformer mounted board. because I also had to depopulate most of that board to clean it. and I think I put the 2 smaller bridges in backwards. but I noticed somehow, probably with tricky photos and turned them around. tested them before turning and got good diode junctions. hmm.I figure my problem is on 1st board because it wont even power on if using the self calibration startup. it actually locks that feature out after initial powering. lights a ac short bulb briefly but I think it would do that working too. anyway. any advice would mean a lot. thanks.https://elektrotanya.com/yamaha_htr-5150_rx-v595a_rds.pdf/download.htmlpower is on page 54 I think.

author: Renate
author_rank: Super Contributor
timestamp: February 15, 2022, 05:30:51 pm
content: You'll get more help if you post a PNG of the applicable section and mention actual parts designators (like D7).

author: strawberry
author_rank: Super Contributor
timestamp: February 15, 2022, 07:47:22 pm
content: override protectiontest CB505 : PRV1 1.9V , PRD 0.3V , PRI 0.0V

author: algorithm
author_rank: Regular Contributor
timestamp: February 15, 2022, 09:18:37 pm
content: thanks renate, I like your name. yeah I wanted to but Im usually pretty discombobulated. I cant open pdfs on the device that gets online so hard to take a png without leapfrogging from devices. still not sure how to do so because any online view is pixelated. I miss having a computer.actually was so discombobulated I referenced the wrong model #.I meant htr5250.https://elektrotanya.com/yamaha_rx-v596_htr-5250_sch.pdf/download.htmlsub power supplyrelay RY801 sdts-112LMA+diode D801 hss104also should be 12v going into but I got 16 last night.but I bet htr5150 is almost identical.so, is that diode supposed to get voltage across it to signal shutdown across relay from protection ic? while I would like to fix this Im most interested in learning how and why this is failing.repairing this is just an attempt at learning but I need help lol.any chance that tubular ceramic caps esr is a problem?strawberry thank you. I will test the relevant ic. its on the front panel ironically. working on these receivers is quite a duty. maybe should say dooty instead. lol so do you think the protect ic is blown? or something near it? thanks again.

author: strawberry
author_rank: Super Contributor
timestamp: February 15, 2022, 11:48:14 pm
content: powersupply problem then16V is way off from 12V