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
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.....
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,
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,
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
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
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...
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...
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.
In this section Im expecting apprx 35v supposedly.
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...
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...
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?
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...
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?
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?
problems with Teac ABX-10 MkII
I also had problems with this amplifier, made for Teac by Thule Audio from Denmark.(it seems the Thule brand is no more active by now?)
This amplifier is O.K. for sound quality, but I think it has a major design fault.
Indeed, those four little SMD voltage regulators are becoming way too hot and this leads to various problems (no power on, strong his etc...)
I replaced all four of them, and the electrolytic capacitors in their neighbourhood. Then I made small and rather high U shaped cooling fins out of red copper. I have fixed these copper fins on the small regulators with heath resistant, heath conducting glue.
The regulators stay reasonable cool now, and since then the amplifier is working O.K.
Regulators and glue were from Farnell.
Best regards, 968driver.
I also had problems with this amplifier, made for Teac by Thule Audio from Denmark.(it seems the Thule brand is no more active by now?)
This amplifier is O.K. for sound quality, but I think it has a major design fault.
Indeed, those four little SMD voltage regulators are becoming way too hot and this leads to various problems (no power on, strong his etc...)
I replaced all four of them, and the electrolytic capacitors in their neighbourhood. Then I made small and rather high U shaped cooling fins out of red copper. I have fixed these copper fins on the small regulators with heath resistant, heath conducting glue.
The regulators stay reasonable cool now, and since then the amplifier is working O.K.
Regulators and glue were from Farnell.
Best regards, 968driver.
good pictures.
read post #30 and #51 about
http://www.diyaudio.com/forums/solid-state/126352-what-happen-thule-audio.html
so as post #5 about
http://www.diyaudio.com/forums/solid-state/180929-thule-audio-components-overview.html
schematic you will find by post #7 about
http://www.audiokarma.org/forums/showthread.php?t=333004
concerning Anders Thule's "virtual Class A", also realized in this TEAC model, go to
http://www.diyaudio.com/forums/soli...ss-b-thule-audio-topology-also-used-teac.html
The reason for the unwanted high temperature of the 317/337 regulators for the 5Vdig-rail is the too great amount of VA (and thus thermal power loss) between the input and output, darkly independend of the displayed numbers for "VOLUME" in the display (number "68" = highest current flow and lowest voltage loss; number "1" lowest current but highest voltage loss between in/out).
The resistors between the main voltage rails and the input pin of 317/337 are not a good solution therefore.
Only replacing of the SMD caps thus helps only a short time. Pre-regulators or additional transformers are absolutely neseccary.
Arround the voltage enhancer for the power amp front end there is also to observe thermal stress - both by the associated voltage regulators various smd chip resistors.
The main issue by all Thule amp PCB's.
read post #30 and #51 about
http://www.diyaudio.com/forums/solid-state/126352-what-happen-thule-audio.html
so as post #5 about
http://www.diyaudio.com/forums/solid-state/180929-thule-audio-components-overview.html
schematic you will find by post #7 about
http://www.audiokarma.org/forums/showthread.php?t=333004
concerning Anders Thule's "virtual Class A", also realized in this TEAC model, go to
http://www.diyaudio.com/forums/soli...ss-b-thule-audio-topology-also-used-teac.html
The reason for the unwanted high temperature of the 317/337 regulators for the 5Vdig-rail is the too great amount of VA (and thus thermal power loss) between the input and output, darkly independend of the displayed numbers for "VOLUME" in the display (number "68" = highest current flow and lowest voltage loss; number "1" lowest current but highest voltage loss between in/out).
The resistors between the main voltage rails and the input pin of 317/337 are not a good solution therefore.
Only replacing of the SMD caps thus helps only a short time. Pre-regulators or additional transformers are absolutely neseccary.
Arround the voltage enhancer for the power amp front end there is also to observe thermal stress - both by the associated voltage regulators various smd chip resistors.
The main issue by all Thule amp PCB's.
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Teac ABX-10 MkII / Thule Audio problems
There is something I do not understand.
These people design a very good high-end amplifier to be sold on the international markets, and they fail to see that these voltage regulators run way too hot.
Was the prototype never fully tested? Touching a voltage regulator with your finger is a clear indication that it runs hot and will fail early. Surrounding capacitors will be baked and also will fail.
And still no cooling fins?
Someone explain please!
There is something I do not understand.
These people design a very good high-end amplifier to be sold on the international markets, and they fail to see that these voltage regulators run way too hot.
Was the prototype never fully tested? Touching a voltage regulator with your finger is a clear indication that it runs hot and will fail early. Surrounding capacitors will be baked and also will fail.
And still no cooling fins?
Someone explain please!
Such things I don't understand, too. Even by certainly models of Mark Levinson and Krell you will observe the same burned aeras by their PCB's (VAS aera by the main board of ML-23 power amp and power supply of KBL line preamp as I recall right).
There are severral other brands, where is the same effects.
Nobody was able to explain, why such things happens.
A contrary example is to observe by Linn (Kairn, Karik) and Bryston. No "hot spots" (and thus no burned PCB aeras) occurs. The condition of PCB and components like resistors and caps is even by very old and excessive used devices often like new. By Linn the enclosure (envelope) is the heat sink at the same time (have a look to the jpg-image; three voltage regulators 317/337 left of the three black caps).
read in this case post #20 about
http://www.diyaudio.com/forums/solid-state/145793-do-you-measure-component-temperatures-2.html
Attachments
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Sqrt of 2 is 1.414 . Your supply voltage will be (Vac x 1.414) less diode drop of 0.7v = Vdc supply. If your spply is 35vdc your trafo secondary voltage will be approximately 24.7vac or 25Vac. This will drop when loaded.
Im nearly coming to conclusion that the trafo was replaced with higher secondary out put.... PRI:100V SEC:37. I adjusted my regulator so the secondary is exactly 37VAC, the results are still not ok. Im reading about 35vDC on those small caps. Again I lower it further to 34VAC and on those small caps its apprx 32vDC close to its max rating and they get warm a bit. . Im still not yet convinced this is the right voltage. my guess is apprx 30VAC secondary or even less.
On the service manual of its older sister A-BX10 the secondary was not specified. Its probably almost the same as this A-BX10 MKII.
Anybody there who has this MKII, I would like to know the secondary output of its trafo..kindly measure the AC on WHITE-BLUE or YELLOW-GREEN wires. There should also be markings on the trafo itself about its primary and seconday...
On the service manual of its older sister A-BX10 the secondary was not specified. Its probably almost the same as this A-BX10 MKII.
Anybody there who has this MKII, I would like to know the secondary output of its trafo..kindly measure the AC on WHITE-BLUE or YELLOW-GREEN wires. There should also be markings on the trafo itself about its primary and seconday...
Hi 968DRIVER,
Can you measure the secondary output of your trafo sir? White-Blue or Yellow-Green. I just want to confirm this before I do modifications. Im afraid that If I lower the voltages, the supply on the amp side might be affected..
So.. Im not the only one having problems with this AMp.. I talked to my friend and he also has this amp also with the same voltage regulator heating issues.. He just lost his right channel with visible burnt SMD transistor....
I can see a grill opening on the forward section not covered by the heat sink, a good place for a small fan..
I don't have the amplifier in my possesion anymore.
As I posted earlier, I replaced the SMD electrolytic capacitors around the tiny voltage regulators and glued small but high mounted heatsinks/fins on the regulators.
This decreased the temperature a whole lot!
As I posted earlier, I replaced the SMD electrolytic capacitors around the tiny voltage regulators and glued small but high mounted heatsinks/fins on the regulators.
This decreased the temperature a whole lot!
Good idea... but those regulators are not the only ones becomes hot, even the other ICs, touch them (but not too much hot). Our attention was taken but those really hot regulators... this is a thermal design flaw. Those components could not dissipate properly due to lack of ventilation.
But If the inside is exposed to too much air, humid may also be a threat specially if "off". The solders are thin and done precisely, if corrosion happens it may cause extensive damages.
Im planning to install small fans on top or to the sides. I like this amp, good looking, good sound, sturdy and compact design, sadly with design problem.
Theres another problem, it is remote controlled. The bass and treble adjustments can only be done in the remote controller,,, If the main power is off, everything is flat. hard to find..
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