Author Topic: Akai AC 3750L Restoration - Repair  (Read 3085 times)

Offline AC3750L

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Akai AC 3750L Restoration - Repair
« on: September 06, 2020, 04:38:17 AM »
Hi all,

I am new to this forum, just really desperate for some help :)

I have this hifi, i had one given to me when i was 4 years old, my first hifi, i was so amazed with it, i kept it until i was about 10 years old and it got ruined in a flood

I am now 30 years old and a few years ago i bought another one luckily as they are extremely rare

It was working, other than the tape deck and turntable belt, which i replaced, Unfortunatly a year or so ago i plugged it in and switched it on, not realising i had also connected the speakers to another stereo (Cambridge Azure) without disconnecting the other speaker wires from it, it blew 2 5a fuses and a 3.15a fuse, i have replaced the fuses and when i turn the machine on it buzz's through the speaker for a second and blows the 2 5a fuses again.

I have it apart, i have teken photo's and videos for people to help me diagnose this problem, but without knowing exactly what im looking for its really hard to diagnose, especially since just to remove the board completely i have to remove 20+ wires which are wrapped around metal poles.

I have re capped boards before, screens and washing machine power boards so im capable in that department, but this being 1977 with no wiring diagram i can find, im at a loss, im desperate to hear this play music through the speakers again

Side note, sound works perfectly through the tape play output auxiliry wires if i put that into an input on my Aiwa stack system, as the line output doesent need to be amplified, so im certain its just that one board, with sometihng with a direct short on it, like a diode/transistor?

http://www.youtube.com/watch?v=CDmm7xSCCyM
http://www.youtube.com/watch?v=nShcUxoLVIM

here are the pictures :)

https://photos.app.goo.gl/8kZZ5ZcWdyDfR78u9

Thanks all :)

Offline AC3750L

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Re: Akai AC 3750L Restoration - Repair
« Reply #1 on: September 06, 2020, 04:47:15 AM »
Why is there a huge gap where the youtube video links are?

http://www.youtube.com/watch?v=CDmm7xSCCyM

http://www.youtube.com/watch?v=nShcUxoLVIM

Offline Sir Thrift-a-Lot

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Re: Akai AC 3750L Restoration - Repair
« Reply #2 on: September 06, 2020, 09:49:19 AM »
Welcome to our broken board.   I hope vpgh can help you out with getting the videos to us.

Offline AC3750L

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Re: Akai AC 3750L Restoration - Repair
« Reply #3 on: September 06, 2020, 05:30:46 PM »
Yeah, no matter hahaha, good news is, ive fixed it, with a little help from someone on a forum, i managed to fix it (temporarily) by cutting the left channel transistors out completely, and just running it off a right hand speaker, all for testing purposes only obviously, when i was testing the transistors, the right hand chanel was showing some values on the meter, close to the values for those transistors, both left hand chanel ones were just causing continuity, due to direct short circuit inside!!

Problem solved i believe, 2 new transistors on the way, solder in, test! should be great

Offline Sir Thrift-a-Lot

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Re: Akai AC 3750L Restoration - Repair
« Reply #4 on: September 06, 2020, 09:30:59 PM »
Congrats!   Stick around.   Tell us a bit about yourself on the new members thread.