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akai AM-52 gives no sound at all
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estate



Joined: 08 Mar 2010
Posts: 11

PostPosted: Thu Mar 11, 2010 9:57 pm    Post subject: Reply with quote

okay here are the readings from the power print, does not look good.

incoming power is 50 V AC on both 1-2 as 2-3 thats okay.
W101 reads +64,3 V on 1-2 and -67,8 V on 2-3
W102 reads +68,2 V on 1-2 and -64,5 V on 2-3
W103 reads +16,7 V on 1-2 and -16,6 V on 2-3
W104 reads +33,38 V on 1-3 and +16 V on 2-3 and -40 V on 3-4
W105 reads -16,6 V on 1-2 and +16,75 on 2-3
W106 reads 57,5 V on 1-2
W115 reads 16,5 V on 1-2 and -16,5 on 2-3

so far the measurement on the power print, I find the voltages very high, which explains why the R105 gets very hot (170 degrees Celcius)

I hope you can help me find the problem, if I read the measurements right there is one of the transistors who has a defect after all ?
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Fri Mar 12, 2010 3:44 am    Post subject: Reply with quote

Jan,
I see your readings may be on the high side but your measurements can not be all correct; as an example connectors W103,(part of W104),W105 and W115 are all tied to the same voltage lines yet you posted different readings!! Is it possible you are not making good connection or something wrong with the probe? -- 33.8V on W104 (1&2)?? while 16.7V on W103 and W115 and all three tied to the same line??

Either way, instead of going from point 123etc, pick out any one of the identical GND (same as metal chassis) as a reference point & leave it connected. Then measure each voltage in respect to it. Looks like the 24V may be a definite problem and if in fact you are reading something like 56V, there is a problem with TR103 regulation.
Tr103 is a simple series pass regulator, it is regulated by means of zener diode D106 which sets the output to be around 25Volts
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estate



Joined: 08 Mar 2010
Posts: 11

PostPosted: Sun Mar 14, 2010 7:11 pm    Post subject: Reply with quote

Sorry to say that today during measurements the transformer gave his last sigh, looks like that was the next thing to die on me.

I'll look to see if I can buy me a working one and use this only for the casing and front panel with buttons and pots.

Thanks for helping out.
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PostPosted: Fri Apr 10, 2015 2:10 am    Post subject: AKAI AM-52 Reply with quote

I'm having the same problem.,Try reflowing tr109 and110(i found them loose) and do a good visual inspection of the main board. I have ALL of my voltages +/ - 5v or so. You just might have bad solder connection
I actually ran out of solder so i'll have to try it later.....
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