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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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LANEY B1 (Tripath) audio Amp - Blown outputs
I am repairing this amp which is using the Tripath TA0104 preamp chip. The
output transistors are STW38NB20's (W38NB20) . I have found a supplier with the transistors in stock. At least one is shorted from what looks like a liquid spill near the heatsink where they mount onto. When powered up, and input signal applied, I can see the LED-VU levels bounce on both the input and output monitoring. There is a green LED near the tripath chip which is not lit, labeled 'run'. Does this mean the Tripath chip is not running and ought to be replaced? I have read about some replacements for this chip which are inconclusive. Ought I just replace it, or is the run light a sign its bad? Nothing else seems burnt, but there are 2 black color hi-watt resistors that dont seem to have any resistance at all, and may be open, but I need to remove them from the board to be sure. They are shown in the photo below each channels power transistors. No schematics - Thanks for any input. Image of amp's mainboard: http://www.imagechicken.com/uploads/...5039779400.jpg |
#2
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LANEY B1 (Tripath) audio Amp - Blown outputs
Circuit wrote in message
... I am repairing this amp which is using the Tripath TA0104 preamp chip. The output transistors are STW38NB20's (W38NB20) . I have found a supplier with the transistors in stock. At least one is shorted from what looks like a liquid spill near the heatsink where they mount onto. When powered up, and input signal applied, I can see the LED-VU levels bounce on both the input and output monitoring. There is a green LED near the tripath chip which is not lit, labeled 'run'. Does this mean the Tripath chip is not running and ought to be replaced? I have read about some replacements for this chip which are inconclusive. Ought I just replace it, or is the run light a sign its bad? Nothing else seems burnt, but there are 2 black color hi-watt resistors that dont seem to have any resistance at all, and may be open, but I need to remove them from the board to be sure. They are shown in the photo below each channels power transistors. No schematics - Thanks for any input. Image of amp's mainboard: http://www.imagechicken.com/uploads/...5039779400.jpg What are the 2 symetrically placed angular black lumps ? more epoxied hybrid specials ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#3
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LANEY B1 (Tripath) audio Amp - Blown outputs
N_Cook wrote in message
... Circuit wrote in message ... I am repairing this amp which is using the Tripath TA0104 preamp chip. The output transistors are STW38NB20's (W38NB20) . I have found a supplier with the transistors in stock. At least one is shorted from what looks like a liquid spill near the heatsink where they mount onto. When powered up, and input signal applied, I can see the LED-VU levels bounce on both the input and output monitoring. There is a green LED near the tripath chip which is not lit, labeled 'run'. Does this mean the Tripath chip is not running and ought to be replaced? I have read about some replacements for this chip which are inconclusive. Ought I just replace it, or is the run light a sign its bad? Nothing else seems burnt, but there are 2 black color hi-watt resistors that dont seem to have any resistance at all, and may be open, but I need to remove them from the board to be sure. They are shown in the photo below each channels power transistors. No schematics - Thanks for any input. Image of amp's mainboard: http://www.imagechicken.com/uploads/...5039779400.jpg What are the 2 symetrically placed angular black lumps ? more epoxied hybrid specials ? -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ Second viewing they are high current automotive type relays. The first thing to do is remove the obviously bad and then power up on much reduced voltage and check the prea is ok, if stable, and nothing else shows up as bad -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#4
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LANEY B1 (Tripath) audio Amp - Blown outputs
What is the year decade digit under the cable tie, ends 049 ?
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#5
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LANEY B1 (Tripath) audio Amp - Blown outputs
"Circuit" wrote in message ... I am repairing this amp which is using the Tripath TA0104 preamp chip. The output transistors are STW38NB20's (W38NB20) . I have found a supplier with the transistors in stock. At least one is shorted from what looks like a liquid spill near the heatsink where they mount onto. When powered up, and input signal applied, I can see the LED-VU levels bounce on both the input and output monitoring. There is a green LED near the tripath chip which is not lit, labeled 'run'. Does this mean the Tripath chip is not running and ought to be replaced? I have read about some replacements for this chip which are inconclusive. Ought I just replace it, or is the run light a sign its bad? Nothing else seems burnt, but there are 2 black color hi-watt resistors that dont seem to have any resistance at all, and may be open, but I need to remove them from the board to be sure. They are shown in the photo below each channels power transistors. No schematics - Thanks for any input. Image of amp's mainboard: http://www.imagechicken.com/uploads/...5039779400.jpg Download a copy of the service manual for the B1 from http://tremolo.elektroda.net/Firmowe...3%20Series.pdf. Then, download a copy of the datasheet for the TA0104 driver from http://www.datasheet4u.com/ and look at the signals. The Run LED gets turned on by the HMute output of the TA0104. If the Run LED is off, then the audio is muted (off). Since the TA0104 is DC coupled to the output FETs, then it's a good bet that it has been destroyed. If the black "hi-watt resistors" that you're talking about are the large devices on either side of the TA0104, then they're probably the protection relays, not resistors. You'll have to remove them from the board and energize them with a power supply in order to verify them. In searching for the schematic, I found a few forum posts that indicated that parts for the B1 and its siblings are nearly impossible to find. Hope this gets you started. Cheers! -- Dave M masondg44 at comcast dot net One good thing about Alzheimer's; you get to meet new people every day. |
#6
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LANEY B1 (Tripath) audio Amp - Blown outputs
Yes. Those resistors I forgot to mark them in the picture but they are below
the ceramic resistors and above the relays you pointed out - they check ok at 1K each. I have replaced the transistors hoping this is all it needs. Hopefully the tripath IC is ok and needs no replacing. Will power upo later and post an update. Second viewing they are high current automotive type relays. The first thing to do is remove the obviously bad and then power up on much reduced voltage and check the prea is ok, if stable, and nothing else shows up as bad |
#7
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LANEY B1 (Tripath) audio Amp - Blown outputs
N_Cook wrote: What are the 2 symetrically placed angular black lumps ? Output relays you MORON. Graham |
#8
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LANEY B1 (Tripath) audio Amp - Blown outputs
Circuit wrote: I am repairing this amp which is using the Tripath TA0104 preamp chip. The output transistors are STW38NB20's (W38NB20) . I have found a supplier with the transistors in stock. At least one is shorted from what looks like a liquid spill near the heatsink where they mount onto. When powered up, and input signal applied, I can see the LED-VU levels bounce on both the input and output monitoring. There is a green LED near the tripath chip which is not lit, labeled 'run'. Does this mean the Tripath chip is not running and ought to be replaced? Do they still have a website ? Get the app note. I suggest you replace blown devices before drawing any conclisions. Graham |
#9
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LANEY B1 (Tripath) audio Amp - Blown outputs
N_Cook wrote: Second viewing they are high current automotive type relays. No, they're not automotive, they're good for mains AC. I should know, I've used them. N_Cook is wrong as ever. What are you going to 'bodge' today btw ? Graham |
#10
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LANEY B1 (Tripath) audio Amp - Blown outputs
Dave M wrote in message
... "Circuit" wrote in message ... I am repairing this amp which is using the Tripath TA0104 preamp chip. The output transistors are STW38NB20's (W38NB20) . I have found a supplier with the transistors in stock. At least one is shorted from what looks like a liquid spill near the heatsink where they mount onto. When powered up, and input signal applied, I can see the LED-VU levels bounce on both the input and output monitoring. There is a green LED near the tripath chip which is not lit, labeled 'run'. Does this mean the Tripath chip is not running and ought to be replaced? I have read about some replacements for this chip which are inconclusive. Ought I just replace it, or is the run light a sign its bad? Nothing else seems burnt, but there are 2 black color hi-watt resistors that dont seem to have any resistance at all, and may be open, but I need to remove them from the board to be sure. They are shown in the photo below each channels power transistors. No schematics - Thanks for any input. Image of amp's mainboard: http://www.imagechicken.com/uploads/...5039779400.jpg Download a copy of the service manual for the B1 from http://tremolo.elektroda.net/Firmowe...3%20Series.pdf. Then, download a copy of the datasheet for the TA0104 driver from http://www.datasheet4u.com/ and look at the signals. The Run LED gets turned on by the HMute output of the TA0104. If the Run LED is off, then the audio is muted (off). Since the TA0104 is DC coupled to the output FETs, then it's a good bet that it has been destroyed. If the black "hi-watt resistors" that you're talking about are the large devices on either side of the TA0104, then they're probably the protection relays, not resistors. You'll have to remove them from the board and energize them with a power supply in order to verify them. In searching for the schematic, I found a few forum posts that indicated that parts for the B1 and its siblings are nearly impossible to find. Hope this gets you started. Cheers! -- Dave M masondg44 at comcast dot net One good thing about Alzheimer's; you get to meet new people every day. Yes, before spending out on power transistors its necessary to establish that that big lump proprietary is still functional. -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#11
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LANEY B1 (Tripath) audio Amp - Blown outputs
"Circuit" wrote in message ... I am repairing this amp which is using the Tripath TA0104 preamp chip. The output transistors are STW38NB20's (W38NB20) . I have found a supplier with the transistors in stock. At least one is shorted from what looks like a liquid spill near the heatsink where they mount onto. When powered up, and input signal applied, I can see the LED-VU levels bounce on both the input and output monitoring. There is a green LED near the tripath chip which is not lit, labeled 'run'. Does this mean the Tripath chip is not running and ought to be replaced? I have read about some replacements for this chip which are inconclusive. Ought I just replace it, or is the run light a sign its bad? Nothing else seems burnt, but there are 2 black color hi-watt resistors that dont seem to have any resistance at all, and may be open, but I need to remove them from the board to be sure. They are shown in the photo below each channels power transistors. No schematics - Thanks for any input. Image of amp's mainboard: http://www.imagechicken.com/uploads/...5039779400.jpg Without getting into a drawn-out ****ing contest about the definition of a 'digital' amplifier, be aware that Tripath devices are not analogue in the conventional sense that you might be used to working with on high power band equipment. They are a form of switch-mode or PWM driver or amplifier, which they as a company define as "digital". From my experiences with them, they are difficult to apply 'conventional' fault-finding techniques to, and are notoriously fickle on whether they decide to work or not, whether they decide to fail or not when the output switching FETs on the end of them go short, and whether or not they decide to re-**** the output FETs after you've replaced them (either immediately, or after just long enough a period to make you think you've fixed the thing ... !! ) You might be lucky. Sometimes it all works out just as you hope and expect, but other times it doesn't. I'll wish you good luck, 'coz you might just need it ... :-\ Arfa |
#12
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LANEY B1 (Tripath) audio Amp - Blown outputs
Arfa Daily wrote in message
... "Circuit" wrote in message ... I am repairing this amp which is using the Tripath TA0104 preamp chip. The output transistors are STW38NB20's (W38NB20) . I have found a supplier with the transistors in stock. At least one is shorted from what looks like a liquid spill near the heatsink where they mount onto. When powered up, and input signal applied, I can see the LED-VU levels bounce on both the input and output monitoring. There is a green LED near the tripath chip which is not lit, labeled 'run'. Does this mean the Tripath chip is not running and ought to be replaced? I have read about some replacements for this chip which are inconclusive. Ought I just replace it, or is the run light a sign its bad? Nothing else seems burnt, but there are 2 black color hi-watt resistors that dont seem to have any resistance at all, and may be open, but I need to remove them from the board to be sure. They are shown in the photo below each channels power transistors. No schematics - Thanks for any input. Image of amp's mainboard: http://www.imagechicken.com/uploads/...5039779400.jpg Without getting into a drawn-out ****ing contest about the definition of a 'digital' amplifier, be aware that Tripath devices are not analogue in the conventional sense that you might be used to working with on high power band equipment. They are a form of switch-mode or PWM driver or amplifier, which they as a company define as "digital". From my experiences with them, they are difficult to apply 'conventional' fault-finding techniques to, and are notoriously fickle on whether they decide to work or not, whether they decide to fail or not when the output switching FETs on the end of them go short, and whether or not they decide to re-**** the output FETs after you've replaced them (either immediately, or after just long enough a period to make you think you've fixed the thing ... !! ) You might be lucky. Sometimes it all works out just as you hope and expect, but other times it doesn't. I'll wish you good luck, 'coz you might just need it ... :-\ Arfa So are we talking about a class D driver stage , rather than preamp in the black lump ? I've only looked at the OP's pic -- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on http://home.graffiti.net/diverse:graffiti.net/ |
#13
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LANEY B1 (Tripath) audio Amp - Blown outputs
N_Cook wrote: So are we talking about a class D driver stage , rather than preamp in the black lump ? YES. Although Tripath called it 'class T' since it doesn't have a fixed switching frequency. I doubt you'll see this since you seem to ignore me despite the fact I know this stuff. Graham |
#14
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LANEY B1 (Tripath) audio Amp - Blown outputs
"Eeyore" wrote in message ... N_Cook wrote: So are we talking about a class D driver stage , rather than preamp in the black lump ? YES. Although Tripath called it 'class T' since it doesn't have a fixed switching frequency. I doubt you'll see this since you seem to ignore me despite the fact I know this stuff. Graham Careful Graham ... ! Me and thee are getting close to povoking another class D - class T - digital amp definition war on here :-) And yes, as Graham says, that is the 'digital' (term used loosely) class T bit in that Tripath lump. Arfa |
#15
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LANEY B1 (Tripath) audio Amp - Blown outputs
Arfa Daily wrote: "Eeyore" wrote N_Cook wrote: So are we talking about a class D driver stage , rather than preamp in the black lump ? YES. Although Tripath called it 'class T' since it doesn't have a fixed switching frequency. I doubt you'll see this since you seem to ignore me despite the fact I know this stuff. Graham Careful Graham ... ! Me and thee are getting close to povoking another class D - class T - digital amp definition war on here :-) And yes, as Graham says, that is the 'digital' (term used loosely) class T bit in that Tripath lump. Years and years back, I had a demo of a Tripath unit. The sales guy went ballistic when I tried to sinewave test it at full power. There were more than a few problems with it, one of which is inherent to any switching / Class D amp that results in the power rails being 'charge pumped' to a voltage beyond nominal dependent on the load being non-resitive. I heard of one 'PA' company that dropped Tripath totally for that or another reason. Graham |
#16
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LANEY B1 (Tripath) audio Amp - Blown outputs
Eeyore wrote:
N_Cook wrote: So are we talking about a class D driver stage , rather than preamp in the black lump ? YES. Although Tripath called it 'class T' since it doesn't have a fixed switching frequency. Class 'T"? - WTF are they trying to say? I would've thought that Class D would make things clear enough for anybody. I doubt you'll see this since you seem to ignore me despite the fact I know this stuff. Well, if he doesn't want to listen to anyone, he'll blow up a lot of silicon, which I think is punishment enough for anybody. ;^) -- W . | ,. w , "Some people are alive only because \|/ \|/ it is illegal to kill them." Perna condita delenda est ---^----^--------------------------------------------------------------- |
#17
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LANEY B1 (Tripath) audio Amp - Blown outputs
Bob Larter wrote: Eeyore wrote: N_Cook wrote: So are we talking about a class D driver stage , rather than preamp in the black lump ? YES. Although Tripath called it 'class T' since it doesn't have a fixed switching frequency. Class 'T"? - WTF are they trying to say? I would've thought that Class D would make things clear enough for anybody. Class D is generally taken to be at a fixed switching frequency. Tripath used spread spectrum and hence gave it another name. I doubt you'll see this since you seem to ignore me despite the fact I know this stuff. Well, if he doesn't want to listen to anyone, he'll blow up a lot of silicon, which I think is punishment enough for anybody. ;^) LOL ! Graham |
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