Dead RX-360

J

jhart

New Member
A friend dropped off a Yamaha RX-360 that he said was not working at all. It stopped working for him years ago and he's just been storing it in his attic since then. I hooked up some speakers and an FM antenna and turned it on. Sure enough, I could hear relays clicking but no lights, LEDs, sound, etc. It appears the unit is immediately activating the protection circuits. Pulled the cover off and checked the single fuse with a DMM and it tested good. Removed the bottom chassis and could not discern any cold solder joints on the PCBs. An inspection of the components on the top side of the PCBs found no evidence of burnt or defective components. I'm fairly new to electronics, so what is my next step? BTW, I searched the manual database on this website and didn't find one for this model, so I have uploaded the one I found on another website. AK has been an invaluable resource in my limited journey into receiver repair, so any help would be greatly appreciated. Thanks.
 
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An update - On closer inspection of the solder joints on the underside of the PCBs, I note that transistors Q25,26,29,30 and 40 have a hard, brown nasty looking residue sorrounding these joints. All of these transistors are heatsinked. As these are apparently the power transistors, could they have sustained too much heat at some point? Is my next step to desolder and test these components?
 
2d update - I talked to the owner and asked if the unit had been exposed to excessive heat. He indicated that just prior to the unit failing, he had mistakenly closed the doors to the cabinet it was housed in and left it on all night. There was very little ventilation in the cabinet. I'll pull those transistors and see if they are shot.
 
Whats your location? First thing that needs to be established is the functionality of the power supply.

Do you have a multimeter?
 
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I'm in CT and have a DMM, along with a scope, signal gen, and various other smaller electronic gadgets (opamp, tone generator, etc). I checked two of the power transistors with my DMM on diode mode and both checked out OK. Haven't checked the other ones, but I suspect they are OK as well.
 
Your hearing a relay clicking but no lights.There is at least two relays .One is the protect relay the other is a start up muting relay. So under normal operating conditions you should immediately here one relay click at power on and a second relay shortly after that.

.
 
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Definitely hearing two relay clicks as you describe. Took critical voltage readings as per schematic for the power supply. From the rectifier I read +39.8v and -40.27v. Should have been +42.3v and -42.9v, but that's fairly close. Reading on emitter on Q40 was +10.42, on emitter of Q42 was -8.87v, and on cathode of D18 was +11.07v - all within specs. Checked voltages at IC13 as follows:
All voltages positive
Pin1-.007
Pin2-.011
Pin3-.002
Pin4-1.731
Pin5-.002
Pin6-.756
Pin7-2.222
Pin8-3.432
Pins 1-3 and Pin5 should have been 0 volts according to the schematic. The other voltages were very close to spec. The power supply and protection circuits seem to be in order. I'll check the voltages in the Power Amp section tomorrow.
 
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IC13 is the protect circuit. It appears to be functioning as it should. If you are hearing a third click it would be the unit going into protect. Sounds to me like you have switching issues. ie. dirty switches or controls - improper switch settings. Is there a pre-out/main -in RCA connections on the rear panel? If so, are there little jumpers installed? Or a coupler switch un-coupled?
 
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I don't hear a third click from the relay and negative on pre-out/main-in connection on rear panel. Where do I look for a coupler switch uncoupled?
 
jhart said:
I don't hear a third click from the relay and negative on pre-out/main-in connection on rear panel. Where do I look for a coupler switch uncoupled?
Click to expand...

Never mind.No coupler switch on this unit.
OK . I just looked over the schematic. Need to verify voltages around a few more transistors and compare to the schematic.Power supply distribution to these transistors....
Q13,22,31,32,40,42 & 43

Your not getting any digital display whatsoever. Right?
 
No digital display whatsoever.

We'll have to wait a few days as I blew the Q42 transistor taking the reading and the replacement is in the mail. DOH!

In the meantime, I'm confused on a few points:

1. Looking at the schematic and pcb layouts from the manual I downloaded from the AK database, I note that Q22, 31 and 32 are on the RX-460 schematics as part of the "PHONO REMOTE CONTROL" circuit, but I have them on the pcb for the unit I'm working on, which is definitely a RX-360. And as far as I know, there isn't a remote control for this unit.

2. Related to the above, Q43 is not listed on any of the schematics, layouts or parts list.

Here are the readings I took before blowing Q42:

Q13: 10.41vdc at collector
Q40: 41.59vdc at collector

Thanks for your help with this.
 
jhart said:
No digital display whatsoever.

We'll have to wait a few days as I blew the Q42 transistor taking the reading and the replacement is in the mail. DOH!

In the meantime, I'm confused on a few points:

1. Looking at the schematic and pcb layouts from the manual I downloaded from the AK database, I note that Q22, 31 and 32 are on the RX-460 schematics as part of the "PHONO REMOTE CONTROL" circuit, but I have them on the pcb for the unit I'm working on, which is definitely a RX-360. And as far as I know, there isn't a remote control for this unit.

2. Related to the above, Q43 is not listed on any of the schematics, layouts or parts list.

Here are the readings I took before blowing Q42:

Q13: 10.41vdc at collector
Q40: 41.59vdc at collector

Thanks for your help with this.
Click to expand...
I'm probably working off the same shitty schematic that you have.

On the Display Driver regulator Q13
fill in the blanks....

E 5.6_____
B 6.2_____
C 10.5 _____

On Q10 the System Control regulator.
fill in the blanks...
E 5.4 _____
B 6.1 _____
C 11.3 ____
 
A correction to my last post. The manual I'm using is one I downloaded from another website. I sent it to the email address for inclusion in the AK manual database, but it hasn't appeared there yet. If you want a copy, I'll email it to you if you PM me and give me your email address. Here's the readings from Q10:
E 5.4 _5.408____
B 6.1 _6.067____
C 11.3 _11.0___

Q13 must be affected by the blown Q42 as I was previously able to measure the emitter voltage as per the service manual power checks and it measured out fine, but now all of the voltages are very low, between .067 and 1.20. I'll desolder it and test for funtionality later while I wait for the replacement for Q42 to arrive in the mail.
 
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Replaced Q42 today. Clearly, something else is blown as I'm still not getting anything near the -42.8 volts at the collector as per the schematic. I'm getting +.498vdc. Voltage reading at the recifier is -41.80vdc. Any ideas which component might be the culprit?
 
Hmm.Have to wait til I get off work. Bastards are forcing me to work all weekend from 3:00 - 11:30PM CST..
 
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Finally got around to testing R219 (too many unavoidable comittments over the weekend). It tested open, so I replaced it and got a good voltage reading on the collector of Q42. Unfortunately, the voltages as per the schematic for the base and emitter are way below what they should be. I'll test R215 and R216 as they may have blown as well.
 
jhart said:
Finally got around to testing R219 (too many unavoidable comittments over the weekend). It tested open, so I replaced it and got a good voltage reading on the collector of Q42. Unfortunately, the voltages as per the schematic for the base and emitter are way below what they should be. I'll test R215 and R216 as they may have blown as well.
Click to expand...


zener diode D26 might have taken a hit. MTZJ10A
http://www.mouser.com/ProductDetail...=sGAEpiMZZMsnCtsnHQqDlS6naFYfYC0oTFtDoUnLbOw=
 
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