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Forum Index : Electronics : I need a replacement STK459 amplifier module...
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9303 |
Anyone know where I can find a GENUINE one of these? I have an older National brand stereo system, whose power-amp module has died. There is audio on the headphones jack, and I can trace audio right up to the pins on the amplifier module, but nothing comes out of the speakers. The amplifier module is most likely cooked or otherwise has failed, so I plan to replace it. There are a plethora of them all over ebay and AliExpress, but I really don't want to buy from there, as 95% of the time, components are just outright fakes from those sites. I've looked at element-14, RS, Mouser and DigiKey, but none of those suppliers stock it - probably simply cos it will be obsolete these days. Anyone else got any pointers, or if I HAVE to use ebay etc, do any members here have any sellers they can recommend as having sold them good stuff before? Smoke makes things work. When the smoke gets out, it stops! |
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phil99 Guru  Joined: 11/02/2018 Location: AustraliaPosts: 2129 |
Wagner Electronics, Sydney shows STK460 as a substitute and in stock. |
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Marcel27 Regular Member  Joined: 13/08/2024 Location: NetherlandsPosts: 53 |
What type receiver/amplifier is it? I thought it might have burned in contacts of the loudspeaker relay if it has one. Has it fuses in the loudspeaker line? Speaker A, B contact switch burned in. Edited 2024-10-29 19:40 by Marcel27 If you use AI, you lose your mind. |
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| Ziki_the Newbie  Joined: 13/04/2023 Location: YugoslaviaPosts: 39 |
Stk 457/459/460/461/463/465 Pin to pin compatible. Find what you can. Pozdrav iz Srbije |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9303 |
@ phil99: Thanks!  @ Marcel27: I'll get the make/model number and post it later. No fuses in speaker lines, no speaker relay that I can remember. Does have an A/B switch, but it feels OK. @ Ziki_the: Good to know, thanks.  Smoke makes things work. When the smoke gets out, it stops! |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9303 |
Photos:   No relay, no speaker fuses. Very nicely assembled.  Back from the days when things were DESIGNED to be easily accessible for service. Those days are gone, unfortunately.  Smoke makes things work. When the smoke gets out, it stops! |
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| Marcel27 Regular Member Joined: 13/08/2024 Location: NetherlandsPosts: 53 |
Nice old lady. How do the solder joints look on the solder side, all clean and no round star cracks? Last year I bought an old Pioneer amplifier/receiver and I thought I could repair it. It had -21V at the output terminals. No, way. This had 2 of these hybrid amp modules. I disassembled the device and used only the remaining good parts. Now, I first get at the service manual (if present) and check if these "things" are inside and when it does I skip them. There are some repair man in the world who repair these devices with bjt devices soldered on them. Edit: btj > bjt  Edited 2024-10-30 17:48 by Marcel27 If you use AI, you lose your mind. |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9303 |
I've never seen inside one of those STK modules - thanks for the photo - quite fascinating! Yeah, on my one on the bench, the wooden side panels simply unscrew, revealing the chassis. Rear wooden panel is the same - remove some screws, it just lifts off. But the stellar design point I thought, was that you just take out a few screws on the bottom, and remove a sheild plate that covers the bottom of the PCB, so then access to the PCB is dead easy with the unit sitting on it's front on the workbench. If only new designs would have access panels like this now.... Yes, examined the PCB solder joints carefully with a monicle thing, and the A/B speaker switch solder connections are all perfect - no dry joints. The soldering on the amp module is also good, BUT it does show signs that things were getting hot there. The amp module is just bolted to a bit of flat aluminium plate/chassis, and with no fins etc, I expect it probably overheated or developed a hot-spot(cos there are no fins and the plate is only about 2mm thick), and this has most likely cooked it. That's my working theory at this point anyway. The replacement modules are very affordable, so I plan to order and fit one and am reasonably confident that this will fix it and bring it back to life.  Smoke makes things work. When the smoke gets out, it stops! |
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