TEAC A-BX10 MKii Service manuaL

jagdiy · 19th April 2011, 02:56 AM

Hi,I bought here in the Phils a used TEAC A-BX10 MKii amp.I didn't have much time to test from the seller, probably just a couple of minutes. The sound is good, all lights working, display, volume and input selector etc etc.At home while I was using it, trouble appears.1) The unit shuts down and turns on intermittently.2) When it ons again the bass and treble returns to flat settings and volume to 30. It seems rebooting, I suspect power supply issue but Im not sure.I turned it off and opened the cover and these what I noticed.1) There are 8 ICs (8pins), 4x on the LEFT, 4x on the LEFT rectifier. See pictures, only left side is shown.2) These 8x IC becomes very very hot in less than 10 seconds even at the back side of the PCB.3) Stranged! They are 8pins LM317 and LM337questions:1) Are these IC regulators? I read the datasheets of LM317 and LM337 and they are in fact regulator. Im confused, as per the datasheets I read, they should be 3 pins ONLY. But they are 8 pins. Is there something I dont know?2) Are they normal to heat like this, I dont think so, very hot really. If you touch it probably your finger will only last for 3 seconds.3) This is 100Volts AC, we are using 220volts here. In cases it was accidentlly plugged to 220volts, are there chances that those regulators were damaged? What other components that might be damaged?Im looking for a service manual of this model..... Please share your experiences with this beautifull amp, I want to fix it..I have a manual for A-BX10 but not for A-BX10 MKii, they have some similarities on the power and amp section.There are no burns, as Id said its working but shuts down later, then on again. I read that the LM regulators shuts down when hot. Something is making then really hot.The biggest question? Why are they 8pins??. I haven't taken a close look if the pins are all connected. They are in the middle of the power supply section and probably these are regulators.

BR/jag

jagdiy · 19th April 2011, 05:04 AM

I just read a datasheet.... in fact there are LM317 in SOIC 8pin package, some pins has NC. Now my problem is to find out why they are overheating.....

lineup · 19th April 2011, 08:03 AM

Just a guess.
There are 2 electrolytic capacitors at each place where LM317 is.
Maybe those capacitors are bad. Which is not good for the LM317.

Have you recapped the amplifier?
What is first suffering of age are the electrolytics.
If you have a multimeter with capacitance tester you can check those caps,

jagdiy · 19th April 2011, 08:17 AM

Thanks LIneup, I agree with you. This amp has never been serviced before, all parts are original.

In each LM317.337 there two types of capacitors, the smaller ones with pure alluminum casings marked with " 4.7 xxx" Im not sure if this are capacitors, any idea with these.. The other sets are the bigger ones, 100Uf 35V. I suspect these ones... Ill try to test them, they are hard to remove as the PCB is double sided.

The main caps 10000Uf has never been replaced

jagdiy · 27th June 2011, 06:58 AM

I had used it for a couple of months with blower on top, it didnt shut down.
Now its time to find the trouble.

FAULTY regulators???? I've searched the net about these LM317 and LM337 +/- voltage regulators. Most likely the regulators are WORKING, the outpin-adjustpin voltage is within its specs range 1.2v - 1.3v. below and above this means faulty as many claims.

I havent done any off board checking on those caps. I recorded all the voltage readings on all inputs and outputs including the OUT-ADJ pin voltage. see the next picture. TS means how long your finger tip will last on their surfaces, in seconds.

Heres what I observed further, the hottest ones are regulator for the PRE amp/DRIVER, really hot, as these have the highest voltage difference from input-output. This is theoretically correct, the cooler ones are the ones that has the lowest voltage difference.

What made them hot?

OSCILATION?? I measured the AC voltages on the input and output. The values are almost the same as the DC values. BUT if I reverse my test probes AC values are "zeros". Is this normal? BTW I used analog multitester in measuring the AC voltage, my digital multimeter seems dont work, the values are flactuating from 0 - 10v.

LOAD?? The sound is good, not distorted so I believed there are no problems on the predriver and tone sections. There are also caps connected on the input and output which acts a high load if they are faulty. But Im not suspecting them at the moment, why, did they become faulty at the same time? There are so many of them.

OVERVOLTAGE?? May be yes but I dont have service manual as basis for the correct voltages. The +/- out puts are balanced w/ only 1 or 2 voltage difference, some are just fractions of a volt. BUT BUT BUT, these regulators has a max input of +/- 40 volts. On the hottest ones i read more than 40volts. 41volts and sometimes flactuates to 40.xx. If I'm the designer of this amp I wouldnt supply these regulators with its max allowable voltage, right? Its seems I having overvoltage on the inputs. Where is it coming from? (faulty rectifiers? main line is okey).

Aside from what I mentioned, what else could be the problem...

jagdiy · 27th June 2011, 08:17 AM

I forgot to mention that all those caps around each regulator are rated 35volts. The hottest regulators inputs are 40v sometimes 41v. It has been exceeded. I really smell overvoltages here....where could they possibly be coming from hummmm..

In this section Im expecting apprx 35v supposedly.

Junm · 27th June 2011, 08:33 AM

Tryu this link for the manual.http://fileshare.eshop.bg/equipment_mfg/TEAC_5.html

This unit is 100vac, be sure to use exact voltage since if you are using AVR with 110vac standard here ...there might cause the voltage on your secondaries. I had experienced using stepdown or AVR 110v but they are not 110v they are higher up to 130v using a digital multimeter. Check those bro...

jagdiy · 27th June 2011, 08:41 AM

Salamat,

I had experiences with 110Vsupplies on 100v amps bad results, Im fully aware of that.. Im using 100volts transformer. Actual reading on the output is 106volts. Can this extra 6v on the primary can cause threat inside?

Junm · 27th June 2011, 08:48 AM

Quote:

Originally Posted by jagdiy

Salamat,

I had experiences with 110Vsupplies on 100v amps bad results, Im fully aware of that.. Im using 100volts transformer. Actual reading on the output is 106volts. Can this extra 6v on the primary can cause threat inside?

6V on primary has minimal effect on the secondary...did you measure the secondaries of your trafo? The secondaries multiplied by 1.414 should not exceed 35volts dc as per cap rating else theres something wrong...

jagdiy · 27th June 2011, 09:00 AM

There are four wire coming out as the secondary. There are no marking on the terminals. Colors are WHITE-BLUE-YELLOW-GREEN. See the 1st and 2nd pictures above.

I think there are marking on the transformer itself, I'll check tonight.

Where did you get this "1.414" multiplier? Is this the voltage increase caused by the filter caps?

19th April 2011, 02:56 AM	#1
jagdiy diyAudio Member Join Date: Apr 2011	TEAC A-BX10 MKii Service manuaL Hi,I bought here in the Phils a used TEAC A-BX10 MKii amp.I didn't have much time to test from the seller, probably just a couple of minutes. The sound is good, all lights working, display, volume and input selector etc etc.At home while I was using it, trouble appears.1) The unit shuts down and turns on intermittently.2) When it ons again the bass and treble returns to flat settings and volume to 30. It seems rebooting, I suspect power supply issue but Im not sure.I turned it off and opened the cover and these what I noticed.1) There are 8 ICs (8pins), 4x on the LEFT, 4x on the LEFT rectifier. See pictures, only left side is shown.2) These 8x IC becomes very very hot in less than 10 seconds even at the back side of the PCB.3) Stranged! They are 8pins LM317 and LM337questions:1) Are these IC regulators? I read the datasheets of LM317 and LM337 and they are in fact regulator. Im confused, as per the datasheets I read, they should be 3 pins ONLY. But they are 8 pins. Is there something I dont know?2) Are they normal to heat like this, I dont think so, very hot really. If you touch it probably your finger will only last for 3 seconds.3) This is 100Volts AC, we are using 220volts here. In cases it was accidentlly plugged to 220volts, are there chances that those regulators were damaged? What other components that might be damaged?Im looking for a service manual of this model..... Please share your experiences with this beautifull amp, I want to fix it..I have a manual for A-BX10 but not for A-BX10 MKii, they have some similarities on the power and amp section.There are no burns, as Id said its working but shuts down later, then on again. I read that the LM regulators shuts down when hot. Something is making then really hot.The biggest question? Why are they 8pins??. I haven't taken a close look if the pins are all connected. They are in the middle of the power supply section and probably these are regulators.BR/jag

19th April 2011, 08:03 AM	#3
lineup diyAudio Member Join Date: Dec 2005 Location: the north	Just a guess. There are 2 electrolytic capacitors at each place where LM317 is. Maybe those capacitors are bad. Which is not good for the LM317. Have you recapped the amplifier? What is first suffering of age are the electrolytics. If you have a multimeter with capacitance tester you can check those caps, __________________ lineup

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19th April 2011, 05:04 AM	#2
jagdiy diyAudio Member Join Date: Apr 2011	I just read a datasheet.... in fact there are LM317 in SOIC 8pin package, some pins has NC. Now my problem is to find out why they are overheating.....

19th April 2011, 08:17 AM	#4
jagdiy diyAudio Member Join Date: Apr 2011	Thanks LIneup, I agree with you. This amp has never been serviced before, all parts are original. In each LM317.337 there two types of capacitors, the smaller ones with pure alluminum casings marked with " 4.7 xxx" Im not sure if this are capacitors, any idea with these.. The other sets are the bigger ones, 100Uf 35V. I suspect these ones... Ill try to test them, they are hard to remove as the PCB is double sided. The main caps 10000Uf has never been replaced

27th June 2011, 06:58 AM	#5
jagdiy diyAudio Member Join Date: Apr 2011	I had used it for a couple of months with blower on top, it didnt shut down. Now its time to find the trouble. FAULTY regulators???? I've searched the net about these LM317 and LM337 +/- voltage regulators. Most likely the regulators are WORKING, the outpin-adjustpin voltage is within its specs range 1.2v - 1.3v. below and above this means faulty as many claims. I havent done any off board checking on those caps. I recorded all the voltage readings on all inputs and outputs including the OUT-ADJ pin voltage. see the next picture. TS means how long your finger tip will last on their surfaces, in seconds. Heres what I observed further, the hottest ones are regulator for the PRE amp/DRIVER, really hot, as these have the highest voltage difference from input-output. This is theoretically correct, the cooler ones are the ones that has the lowest voltage difference. What made them hot? OSCILATION?? I measured the AC voltages on the input and output. The values are almost the same as the DC values. BUT if I reverse my test probes AC values are "zeros". Is this normal? BTW I used analog multitester in measuring the AC voltage, my digital multimeter seems dont work, the values are flactuating from 0 - 10v. LOAD?? The sound is good, not distorted so I believed there are no problems on the predriver and tone sections. There are also caps connected on the input and output which acts a high load if they are faulty. But Im not suspecting them at the moment, why, did they become faulty at the same time? There are so many of them. OVERVOLTAGE?? May be yes but I dont have service manual as basis for the correct voltages. The +/- out puts are balanced w/ only 1 or 2 voltage difference, some are just fractions of a volt. BUT BUT BUT, these regulators has a max input of +/- 40 volts. On the hottest ones i read more than 40volts. 41volts and sometimes flactuates to 40.xx. If I'm the designer of this amp I wouldnt supply these regulators with its max allowable voltage, right? Its seems I having overvoltage on the inputs. Where is it coming from? (faulty rectifiers? main line is okey). Aside from what I mentioned, what else could be the problem...

27th June 2011, 08:17 AM	#6
jagdiy diyAudio Member Join Date: Apr 2011	I forgot to mention that all those caps around each regulator are rated 35volts. The hottest regulators inputs are 40v sometimes 41v. It has been exceeded. I really smell overvoltages here....where could they possibly be coming from hummmm.. In this section Im expecting apprx 35v supposedly.

27th June 2011, 08:33 AM	#7
Junm diyAudio Member Join Date: Dec 2008 Location: Mabalacat, Pampanga	Tryu this link for the manual.http://fileshare.eshop.bg/equipment_mfg/TEAC_5.html This unit is 100vac, be sure to use exact voltage since if you are using AVR with 110vac standard here ...there might cause the voltage on your secondaries. I had experienced using stepdown or AVR 110v but they are not 110v they are higher up to 130v using a digital multimeter. Check those bro...

27th June 2011, 08:41 AM	#8
jagdiy diyAudio Member Join Date: Apr 2011	Salamat, I had experiences with 110Vsupplies on 100v amps bad results, Im fully aware of that.. Im using 100volts transformer. Actual reading on the output is 106volts. Can this extra 6v on the primary can cause threat inside?

27th June 2011, 09:00 AM	#10
jagdiy diyAudio Member Join Date: Apr 2011	There are four wire coming out as the secondary. There are no marking on the terminals. Colors are WHITE-BLUE-YELLOW-GREEN. See the 1st and 2nd pictures above. I think there are marking on the transformer itself, I'll check tonight. Where did you get this "1.414" multiplier? Is this the voltage increase caused by the filter caps?

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