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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:

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Reply to
Circuit
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with

Tripath

it,

are

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

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Reply to
N_Cook

The

near

sure.

hybrid

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

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Reply to
N_Cook

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

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Reply to
N_Cook

Download a copy of the service manual for the B1 from

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Then, download a copy of the datasheet for the TA0104 driver from
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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.
Reply to
Dave M

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.

Reply to
Circuit

Output relays you MORON.

Graham

Reply to
Eeyore

Do they still have a website ? Get the app note.

I suggest you replace blown devices before drawing any conclisions.

Graham

Reply to
Eeyore

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

Reply to
Eeyore

The

with

near

burnt,

turned

audio

that

remove

verify

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

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Reply to
N_Cook

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

Reply to
Eeyore

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

Reply to
Arfa Daily

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

Reply to
Eeyore

Class 'T"? - WTF are they trying to say? I would've thought that Class D would make things clear enough for anybody.

this

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
---^----^---------------------------------------------------------------
Reply to
Bob Larter

Class D is generally taken to be at a fixed switching frequency. Tripath used spread spectrum and hence gave it another name.

this

LOL !

Graham

Reply to
Eeyore

spread

this

My all digital Waller guitar amp has a tripath output inside. 100 watts from a postage stamp sized device. Nice sound and has been reliable except for the intermixing of digital and analog grounds in the DSP which Waller allowed me to repair under warranty 5 years ago. All the repair involved was cutting a trace and adding a chassis ground to the circuit.

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Reply to
Meat Plow

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