Yamaha RX-1100 Receiver: BOOM went the output stage!
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- Опубликовано: 12 сен 2024
- A no power condition is traced to a blown fuse caused by a seriously damaged output stage. The magic smoke has definitely been released on this one and extensive repairs are required.
Since it's a top of the line unit, I'm going to proceed with repairs anyway.
It's good for 125W/ch into 8 ohms from 20-20kHz with no more than 0.0015% THD. S/N ratio is 103dB for line in, 92dB for MM phono. In short, it's a beast that deserves to be saved.
New output transistors will be 2SC5242 and 2SA1962 which are the TO3P package variants of 2SC5200 and 2SA1943 respectively. They are the same transistor in a smaller package.
Power dissipation ratings are lower with the TO3P than the TO264 but the 130W C5242/A1962 is still superior to the originals which are only good for 100W dissipation. Maximum collector current is also much higher, 17A on the new devices vs. 10A on the old ones.
I think that this was available in '88.
I bought a Yamaha AX-500, KX-500 & CDX-810 in '88, which all are in the same range as this.
It went all smooth-styled after this lot, which doesn't look so good IMO.
I like this RX.
you could have used On Semi njw3281/1302 here in place of the originals, they are in to-3p package and have superior SOA. generally emitter follower output stages are forgiving if you change output devices to a different type, provided you take care of the driver section and preceding stages.
I ended up using 2SC5200/2SA1943 in a TO-3P variant. I forgot the actual number off the top of my head; Fairchild gives these a different part number while Toshiba uses a different suffix instead (O for TO-3P, N for TO-264). These, though not as large as the transistors you suggested also provided a very large increase in SOA and will probably last for decades. The drivers do not normally fail provided the output stage remains intact.
they are 2SC5242/FJA4313. still much better than the originals. good work mate.
Did you ever found those "hooks" for the bracket? Or print them? I have the same problem, both broken off. I don't even know how these "hooks" should look like.
what caused the output stage to blow up ..shorted speaker wires or listening at high volume to long or using to low ohm speakers
Peak Atlas DCA 75 Pro is not for in circuit test.
I wasn't testing in circuit. A device still mounted to the heatsink via a thermal pad and a device with leads still soldered to the PCB are two entirely different things. Watch the video more closely and you'll see that the leads are indeed lifted from the pads.
Using the DCA 75 in circuit usually results in a "No Component Detected" error, not a short circuit error. To say I'm familiar with this little device is an understatement.
I have a question for the tester. Does it matter where the tester leads are connected or can they be put onto any leg of the transistor and still receive valid results?
Dudefoxlive It does not matter; the Atlas DCA Pro automatically identifies leads.
have you tested them after desoldering? i doubt the all blew up....
+ᅚ They were desoldered. You never replace just failed units when one unit in a pair fails. The other one may have been stressed beyond limits and poised to fail. Also, it's easier to gain match with all new transistors, especially when the original part number is discontinued and a substitution must be made. This unit blew out most of its output devices so the "savings" would have only been a few dollars. The potential costs, should it fail again, are much higher. Andrew's Electronics does it the right way or not at all.
@@MadScientistsLair Yep, ordered all the outputs for my Sansui G-8700DB receiver. All 8 outputs at $7 each is cheap insurance. T03 devices made by ON semiconductor, from Mouser. Looking for the driver devices, or rather the replacement equivalents. They are not showing as shorted, but they have had a lot of current running through them due to several resistors on the driver board open, or unsoldered themselves because they got hot enough to melt the through hole solder joints.
Still wonder what causes common output/driver failure this model working on one now r ch failed twice
Check the bias current! This one was WAY high after the repair and it needed a very significant adjustment.
Also, check the output snubbing circuit if you have oscillation issues. Bad solder joints are also an issue on these.
I cleaned and reset bias 10mv, resoldered all drive board new filters etc, been running 2 days so far.... 1st time I used some china outputs from ebay now using orig japan running on 8 ohm load box crossing fingers...so far so good!
4 days still holding pushed to 50w so far so good
MrMotownjoe Those Chinese transistors were your problem. You're lucky the originals you found weren't counterfeit. At my shop, I almost always use a modern device for replacement purchased from an authorized distributor. Counterfeit obsolete Japanese parts are just too common.
I used original Japanese 2sc3281 2sa1302 160v 15a I had back in the day when I had my repair shop, still test running good thanks for your help Andrew.
I wonder what happened. Almost like someone blew the shit out of it, cranking the worlds worst music through it in the process. Maybe even DC'd their speakers too!