hi all,
i joined the forum because i need some assistance in repairing a r-300 yamaha amp+receiver (acquired of course on ebay).
short description:
- receiver part is ok (i checked the output from the receiver module with a speaker - because i don't have an oscilloscope - and i got signal)
- the amp module consists of an STK3042II and STK2030.
- relay works normally
- no sound in speakers
problem:
- with a voltmeter i checked the voltage in all indicated joints in the amp module. all values are as indicated on the board except two: on the STK3042II on pin 2 i get -9V instead of -15V and on pin 14 i get +29V instead of +15V
- around the second chip (STK2030) most voltages are about +(-)35V. the chip (and heat sink) become hot.
- on the speaker output on both channels and on both A and B i also get a voltage of +35V and -35V
any tips would be appreciated. if it helps i can also post the schematics
regards,
edgar
i joined the forum because i need some assistance in repairing a r-300 yamaha amp+receiver (acquired of course on ebay).
short description:
- receiver part is ok (i checked the output from the receiver module with a speaker - because i don't have an oscilloscope - and i got signal)
- the amp module consists of an STK3042II and STK2030.
- relay works normally
- no sound in speakers
problem:
- with a voltmeter i checked the voltage in all indicated joints in the amp module. all values are as indicated on the board except two: on the STK3042II on pin 2 i get -9V instead of -15V and on pin 14 i get +29V instead of +15V
- around the second chip (STK2030) most voltages are about +(-)35V. the chip (and heat sink) become hot.
- on the speaker output on both channels and on both A and B i also get a voltage of +35V and -35V
any tips would be appreciated. if it helps i can also post the schematics
regards,
edgar
If you have rail voltage at the speaker output, usually that means the output transistors are blown. You will have to replace the STK2030s. They are available at www.tversatzteile.de.
Pins 2 and 14 of the STK3042II are the non-inverting inputs and should get the feedback signal from the STK2030's outputs. No 15 V should be present there. Once you desoldered the STK2030s, check the voltages at pins 5, 6, 10 amd 11. They should be nearly 0. If they are around 35 V, replace the STK3042II as well. They are obsolete. You can use STK3062II or STK3082II as replacements with higher voltage rating, if you find them. Don't use STK3062III or STK3082III, they are power amplifiers. Or you can try to swap in STK350, which is the follow-up, but you might have to change some capacitors to different values for stability.
It may turn out less expensive to get another amplifier from ebay, however.
Pins 2 and 14 of the STK3042II are the non-inverting inputs and should get the feedback signal from the STK2030's outputs. No 15 V should be present there. Once you desoldered the STK2030s, check the voltages at pins 5, 6, 10 amd 11. They should be nearly 0. If they are around 35 V, replace the STK3042II as well. They are obsolete. You can use STK3062II or STK3082II as replacements with higher voltage rating, if you find them. Don't use STK3062III or STK3082III, they are power amplifiers. Or you can try to swap in STK350, which is the follow-up, but you might have to change some capacitors to different values for stability.
It may turn out less expensive to get another amplifier from ebay, however.
the particular amp
even in original condition dind say much soundwise anyway .
others that used similar topology ( Luxman i think ) had similar results ....
all amplifiers that are based on 30XX drive ic didnt sound ...perfect....
i know i am in the chip forum ..... but if it was my amp i would built a transistor amplifier to put inside there ( unless you are a person that likes things in original conditions )
there is a million of amps easy to bulit well documented arround the forum that will sound a gozillion times better
transistorian regards sakis
even in original condition dind say much soundwise anyway .
others that used similar topology ( Luxman i think ) had similar results ....
all amplifiers that are based on 30XX drive ic didnt sound ...perfect....
i know i am in the chip forum ..... but if it was my amp i would built a transistor amplifier to put inside there ( unless you are a person that likes things in original conditions )
there is a million of amps easy to bulit well documented arround the forum that will sound a gozillion times better
transistorian regards sakis
thank you for your quick replies!
as a remark: i bought this amplifier knowing it was broken. i just wanted to use it as a little exercise. my knowledge of electronics is not much above the basics, but still i enjoy opening cases, soldering and desoldering things (perhaps you know what i mean)
i followed pacificblue's advice and desoldered the STK2030 chip. after that i measured the voltages at pins 5, 6, 10, 11 on the STK3042II and unfortunately they are around 35V.. in the next days i'll try to order the two ics.
as a remark: i bought this amplifier knowing it was broken. i just wanted to use it as a little exercise. my knowledge of electronics is not much above the basics, but still i enjoy opening cases, soldering and desoldering things (perhaps you know what i mean)
i followed pacificblue's advice and desoldered the STK2030 chip. after that i measured the voltages at pins 5, 6, 10, 11 on the STK3042II and unfortunately they are around 35V.. in the next days i'll try to order the two ics.
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