Yamaha R-9 Receiver  - Page 1
Forum section: electronics / repair

author: logscool
author_rank: Contributor
timestamp: July 09, 2015, 06:01:28 am
content: I was working on fixing a Yamaha R-9 receiver which was having an issue where the protection relay wouldn't always close when powering it up. I was checking the power supply section of it and as I was trying to check the TR413 transistor I must have shorted something with my probe because I now get nothing powering up when I turn it on and none of the voltages are any good. I can't seem to figure out what I screwed up though. Any help or ideas would be great.A link to the service manual can be found here:http://elektrotanya.com/yamaha_r-9_receiver.pdf/download.html

author: divelectservices
author_rank: Contributor
timestamp: July 09, 2015, 03:34:21 pm
content: Obvious question: did you check the fuse(s)?

author: logscool
author_rank: Contributor
timestamp: July 10, 2015, 12:40:23 am
content: Yes I did check the only fuse I could find both before and after screwing stuff up and I even used some contact cleaner on the socket it seems to be just fine.

author: divelectservices
author_rank: Contributor
timestamp: July 10, 2015, 05:38:58 pm
content: Well then now the real fun begins...If you have the schematic this will not be too difficult.Start at the main power transformer and start working forward checking the voltages on the output of each stage of the power supply.Most audio receivers of this type have a 2 high voltage and current circuits (usually between 35 and 55 volts positive and negative) for the output transistors in the amplifier section.Be very careful probing around with the power on as one slip can cause a lot of damage as you have learned!The rest of the supply circuits are relatively low power. The only exception is the supply for the VFD on the front panel if it has one.I did not look at the schematic, but most receivers have a standby power circuit and a main drive circuit.Start with the standby section. It will either by powered by a separate, smaller transformer or possibly a tap off the main transformer. Very few receivers/audio equipment us a switching supply for this.Either way, you need to verify it is working. Then move to the main power circuits.You may want to desolder the legs of the output transistors or the amp module(s) if this unit uses that instead.You can do some quick cheat tests by finding the bridge rectifier(s) (or diode bridges if this uses them instead), disconnect the positive or negative terminal from the rest of the circuit and check the voltages there. That should isolate the power supply from the rest of the circuits and rule everything out from that point back to the plug.This may not work depending on the design.Sorry for the non-model-specific info, but I fix lots of consumer audio gear and I rarely use a schematic or service manual. When you break down the sections and think about how they work, they are relatively easy to repair.It's not like the good ol' days when you spent hours trying to restring a broken or missing dial-string without a diagram!

author: radhaz
author_rank: Regular Contributor
timestamp: July 10, 2015, 11:56:43 pm
content: Service manual:http://www.hifiengine.com/manual_library/yamaha/r-9.shtml

author: logscool
author_rank: Contributor
timestamp: July 13, 2015, 01:05:41 am
content: I have checked various voltages from the power supply section. The transformer taps measure 28.6 VAC and 93.9 VAC instead of the 32.7 and 61.7 that the service manual lists. Not sure if this is an issue or not. Coming off the diode bridge however I get very close to the 63.5 and -63.5 values in the service manual. The -18.5v rail however is at -15.5 and the 17v is at 19.2. I don't know if any of these voltages being off is anything to be concerned about or not.

author: mzacharias
author_rank: Frequent Contributor
timestamp: July 26, 2015, 02:09:57 am
content: The R-9's had issues with solder connections on some of the various driver / pre-driver transistors on the amp pcb. Been there.