I've had this system for 20 years with no problems. One day, all audio is missing and it turns out the ps mosfets are blown along with associated components including controller IC. Found a guy on YouTube with similar problem and replaced the parts he mentioned as well as 1 additional mosfet in the feedback circuit. The system worked great for 3 months, now back to original problem with blown mosfets, etc. There are 2 10uF 25V caps on secondary with ESR of 8.6-8.8 ohms, my replacement cap measures 1.2 ohms. Does the ESR on the secondary caps seem high enough to take out the mosfets or should I be looking elsewhere? Remember the repair lasted 3 months, it didn't blow right away.
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I picked up this used Bose Acoustimass 10 IV speaker system. Speakers seem to work fine, but the subwoofer does not make any noise. So I took apart the unit and found some obviously failed (burnt) components:
- 1x 3.14 A @ 250V main circuit fuse
- 1x bridge rectifier GBU601. there's actually two of these on the board, one is obviously burnt and the other does not seem to have any anomalies like shorts. However I figure may as well replace both.
- 2x diode. This is tricky because the only markings I see on it are: "617 402". No current rating or anything else.... -
Hi everyone,
I'm trying to fix this RF Bose remote (model nr. 420129) for a friend. After applying supply voltage the display shows the Bose logo, after a short period of time it goes dark and the MCU enters a sleep mode. It wakes up after a key is pressed, the display remains dark all the time after the start up sequence.
Sometimes it can still be paired with the main unit and you can control it for a short period of time, then the unit stops reacting again.
The pcb is clean, there are no signs of corrosion. The voltages look adequate.
I read... -
Howdy everyone!
I have a SUV with a Bose audio system and I'm considering either a system upgrade, or purchasing a complete replacement system while bypassing the integrated Bose system.
On the Bose side, I have not found any specifications yet. It's a decent system but I'm, at a minimum, replacing all the factory speakers, head unit and adding an amp and two 8" subs. The Bose is a 2ohm system and I'm not certain about this point. In order to use a 4ohm set of speakers (component/loud), I would need to install 2 sets of 4ohm speakers wired in parallel to match the... -
Hi everyone,
I'm working on a MacBook Air 2020 (A2337, board 820-02016) and running into a strange USB-C issue. I've gone through quite a bit of testing and part replacement, but I'm stuck — hoping someone here can shed some light.
🛠 Original Issue
The machine initially wouldn't negotiate 20V over USB-C — stuck at 5V.
Diagnosis showed PP1V5_UPC0_LDO_CORE shorted to ground.
I replaced U3100 (UF400) using a donor board (A2179), and the machine powers on fine now.
⚠️ New Problem: One USB-C Port Only Works in One Orientation... -
I have three identical-spec 820-01700 boards (2.6/32/512), and ALL THREE boards came to us with the same fault, from different sources: The boards don't wake from hibernation with the keyboard or lid, they ONLY wake when you press the power button. I understand this is a very minor issue, but the boards must be fixed!
We will of course begin with the obvious (checking lid signals), but I couldn't help but notice these three boards were all 32GB variants. Has anyone noticed an issue relating to these 32GB boards in particular? I of course don't think it's a RAM issue, but it's bizarre...
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