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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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Strangely marked BUZ Mosfet
Hi,
I have a Trace Elliot 300W bass amp here that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. I've repaired a few of these in my time but never come across this marking. Is it a Trace internal number, or have these been substituted in from elsewhere? Are they actually BUZ906? (One BUZ901 is blown, the other 3 check out OK on a PEAK component tester). Cheers, Gareth. |
#2
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Strangely marked BUZ Mosfet
"Gareth Magennis is a ****ING MORON " I have a Trace Elliot 300W bass amp here ** I suppose you whole life is over if you tell us the ****ing model number ? that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. ** The device is labelled " STUPID " ??? April 1st has gone you know. One BUZ901 is blown, ** I suppose your whole life depends of not telling us what YOU mean by the word "blown" ?? Lateral MOSFETS fail ( if they fail) in a unique way - not like any other power devices. WHAT IS IT ??? ..... Phil |
#3
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Strangely marked BUZ Mosfet
Gareth Magennis wrote in message
news Hi, I have a Trace Elliot 300W bass amp here that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. I've repaired a few of these in my time but never come across this marking. Is it a Trace internal number, or have these been substituted in from elsewhere? Are they actually BUZ906? (One BUZ901 is blown, the other 3 check out OK on a PEAK component tester). Cheers, Gareth. While at it toroidal mains Tx ? any inrush limitation ? no ken those markings. Trace Elliot GP12 SMX, 1998 300W bass amp last week PA was marked "Bipolar Bear" on overlay and devices under spring clips, not seen , but checked out as BCE npn & pnp devices |
#4
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Strangely marked BUZ Mosfet
"Phil Allison" wrote in message ... "Gareth Magennis is a ****ING MORON " I have a Trace Elliot 300W bass amp here ** I suppose you whole life is over if you tell us the ****ing model number ? that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. ** The device is labelled " STUPID " ??? April 1st has gone you know. One BUZ901 is blown, ** I suppose your whole life depends of not telling us what YOU mean by the word "blown" ?? Lateral MOSFETS fail ( if they fail) in a unique way - not like any other power devices. WHAT IS IT ??? .... Phil You do make me laugh, Phil. If it matters, it is a 7215 combo, i.e. a GP7 300 Watt SM series, but I believe all Trace Amps share the same 2 amplifier modules. There's a Bi-polar Bear which is Bi-polar (you might like that one), or the 150/300W Mosfet board which is Mosfet. I guess the 150W one uses just 2 Mosfets and smaller PSU caps. But the question is only about the markings on the output devices, and whether this STUD1P device is the original Trace part or some numpty repairman has retrofitted a dodgy part he manufactured himself in his kitchen of took it out of a Studiomaster or summat. Sigh. |
#5
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Strangely marked BUZ Mosfet
p.s. it has been repaired at a place I know about that is well known for dodgy repairs, and the soldering is absolutely shocking. |
#6
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Strangely marked BUZ Mosfet
On Wed, 06 Apr 2011 15:45:02 +0100, Gareth Magennis wrote:
p.s. it has been repaired at a place I know about that is well known for dodgy repairs, and the soldering is absolutely shocking. Why not just replace all 4 with known pairs? TT manufactures a bunch of different audio mosfet devices http://www.semelab.com/magnatec/alfet.shtml -- Live Fast Die Young, Leave A Pretty Corpse |
#7
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Strangely marked BUZ Mosfet
"N_Cook" wrote in message ... Gareth Magennis wrote in message news Hi, I have a Trace Elliot 300W bass amp here that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. I've repaired a few of these in my time but never come across this marking. Is it a Trace internal number, or have these been substituted in from elsewhere? Are they actually BUZ906? (One BUZ901 is blown, the other 3 check out OK on a PEAK component tester). Cheers, Gareth. While at it toroidal mains Tx ? any inrush limitation ? no ken those markings. Trace Elliot GP12 SMX, 1998 300W bass amp last week PA was marked "Bipolar Bear" on overlay and devices under spring clips, not seen , but checked out as BCE npn & pnp devices Toroid, will get back to you tomorrow with the rest. Gareth. |
#8
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Strangely marked BUZ Mosfet
"Meat Plow" wrote in message news On Wed, 06 Apr 2011 15:45:02 +0100, Gareth Magennis wrote: p.s. it has been repaired at a place I know about that is well known for dodgy repairs, and the soldering is absolutely shocking. Why not just replace all 4 with known pairs? TT manufactures a bunch of different audio mosfet devices http://www.semelab.com/magnatec/alfet.shtml -- Live Fast Die Young, Leave A Pretty Corpse Yes, that is my preferred option, and I could get them from Farnell tomorrow. However, that would cost me about £50 for the four, so perhaps £60 to the customer, which is getting on for $100. If there is any doubt what these oddly marked devices actually are I will do just that. Cheers, Gareth. |
#9
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Strangely marked BUZ Mosfet
Ah, I see now you meant alternatives.
Not really my policy I'm afraid. If it blew up again I wouldn't have a leg to stand on. Cheers, Gareth. |
#10
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Strangely marked BUZ Mosfet
On Wed, 06 Apr 2011 20:25:57 +0100, Gareth Magennis wrote:
"Meat Plow" wrote in message news On Wed, 06 Apr 2011 15:45:02 +0100, Gareth Magennis wrote: p.s. it has been repaired at a place I know about that is well known for dodgy repairs, and the soldering is absolutely shocking. Why not just replace all 4 with known pairs? TT manufactures a bunch of different audio mosfet devices http://www.semelab.com/magnatec/alfet.shtml -- Live Fast Die Young, Leave A Pretty Corpse Yes, that is my preferred option, and I could get them from Farnell tomorrow. However, that would cost me about £50 for the four, so perhaps £60 to the customer, which is getting on for $100. If there is any doubt what these oddly marked devices actually are I will do just that. Cheers, Gareth. $100 isn't bad for a slayed output stage. Especially on previously bodged repairs. For that combo and most others including vintage my minimum fee is $100 before parts. I do more work on vintage than anything. People drag in these Silvertone, Airline, Ampeg, Gibson etc.. from the late 1950's/60's all the time. If it's a small combo like a GA series Discovery,Maestro,Explorer etc...I'll slide the $100 minimum fee unless it needs a restoration. Last Silvertone 50 watt head I restored I charged $200 labor and the customer never batted an eyelid. I'd replace all 4 of those devices and take a hard look at the whole thing probably before I ordered parts. -- Live Fast Die Young, Leave A Pretty Corpse |
#11
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Strangely marked BUZ Mosfet
"Gareth Magennis" If there is any doubt what these oddly marked devices actually are I will do just that. ** What does your PEAK say about the pin out and the Gate threshold voltage ? Should be Source on the case and about 0.5 to 1.0 volts. ..... Phil |
#12
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Strangely marked BUZ Mosfet
"Phil Allison" wrote in message ... "Gareth Magennis" If there is any doubt what these oddly marked devices actually are I will do just that. ** What does your PEAK say about the pin out and the Gate threshold voltage ? Should be Source on the case and about 0.5 to 1.0 volts. .... Phil Doesn't display voltage information, it either says its a "* channel mosfet" and identifies the pins, or "no valid part found". Its a PIC based device I believe. I bought it purely to check Mosfets go or no go, and it works well. Gareth. |
#13
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Strangely marked BUZ Mosfet
Gareth Magennis wrote in message
news Hi, I have a Trace Elliot 300W bass amp here that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. I've repaired a few of these in my time but never come across this marking. Is it a Trace internal number, or have these been substituted in from elsewhere? Are they actually BUZ906? (One BUZ901 is blown, the other 3 check out OK on a PEAK component tester). Cheers, Gareth. perhaps obtained from these people http://www.autogarduk.com/stock%20list%2027.htm 41 P and 274 N What are the test parameters of a Peak? |
#14
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Strangely marked BUZ Mosfet
"N_Cook" wrote in message ... Gareth Magennis wrote in message news Hi, I have a Trace Elliot 300W bass amp here that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. I've repaired a few of these in my time but never come across this marking. Is it a Trace internal number, or have these been substituted in from elsewhere? Are they actually BUZ906? (One BUZ901 is blown, the other 3 check out OK on a PEAK component tester). Cheers, Gareth. While at it toroidal mains Tx ? any inrush limitation ? no ken those markings. Trace Elliot GP12 SMX, 1998 300W bass amp last week PA was marked "Bipolar Bear" on overlay and devices under spring clips, not seen , but checked out as BCE npn & pnp devices Toroid and no inrush limit device. The Bipolar Bear uses 2SA1695 and 2SC4468 devices. Gareth. |
#15
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Strangely marked BUZ Mosfet
"Gareth Magennis" Doesn't display voltage information, it either says its a "* channel mosfet" and identifies the pins, ** IS THE *SOURCE* ON THE ****ING CASE OR NOT !!! You ****ING MORON !! ......Phil |
#16
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Strangely marked BUZ Mosfet
"Phil Allison" wrote in message ... "Gareth Magennis" Doesn't display voltage information, it either says its a "* channel mosfet" and identifies the pins, ** IS THE *SOURCE* ON THE ****ING CASE OR NOT !!! You ****ING MORON !! .....Phil Bye bye. |
#17
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Strangely marked BUZ Mosfet
"N_Cook" wrote in message ... Gareth Magennis wrote in message news Hi, I have a Trace Elliot 300W bass amp here that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. I've repaired a few of these in my time but never come across this marking. Is it a Trace internal number, or have these been substituted in from elsewhere? Are they actually BUZ906? (One BUZ901 is blown, the other 3 check out OK on a PEAK component tester). Cheers, Gareth. perhaps obtained from these people http://www.autogarduk.com/stock%20list%2027.htm 41 P and 274 N What are the test parameters of a Peak? Don't have a clue. It runs on a 9v battery. It does claim to measure hfe, but again I don't know with which parameters. I don't think its meant to be a precision instrument but I find it very useful, mostly for finding dead mosfets and possible good ones, and identifying pinouts of bipolars. I once had terrible problems with a C-audio amp that I just couldn't get working. They had loads of BC184 (I think) doing the bias and stuff. I replaced the lot with BC184L, not realising that the "L" meant the pinout was different. Took me a looong time to suss that one out. Now I always double check with the Peak when replacing any signal transistor, just in case. Likewise Farnell once sold me some resistors that were a decade lower than marked on the packaging. Again took me a while to suss out the problem, and I now always meter EVERY resistor before soldering it in. Cheers, Gareth. |
#18
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Strangely marked BUZ Mosfet
Gareth Magennis wrote in message
... "N_Cook" wrote in message ... Gareth Magennis wrote in message news Hi, I have a Trace Elliot 300W bass amp here that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. I've repaired a few of these in my time but never come across this marking. Is it a Trace internal number, or have these been substituted in from elsewhere? Are they actually BUZ906? (One BUZ901 is blown, the other 3 check out OK on a PEAK component tester). Cheers, Gareth. perhaps obtained from these people http://www.autogarduk.com/stock%20list%2027.htm 41 P and 274 N What are the test parameters of a Peak? Don't have a clue. It runs on a 9v battery. It does claim to measure hfe, but again I don't know with which parameters. I don't think its meant to be a precision instrument but I find it very useful, mostly for finding dead mosfets and possible good ones, and identifying pinouts of bipolars. I once had terrible problems with a C-audio amp that I just couldn't get working. They had loads of BC184 (I think) doing the bias and stuff. I replaced the lot with BC184L, not realising that the "L" meant the pinout was different. Took me a looong time to suss that one out. Now I always double check with the Peak when replacing any signal transistor, just in case. Likewise Farnell once sold me some resistors that were a decade lower than marked on the packaging. Again took me a while to suss out the problem, and I now always meter EVERY resistor before soldering it in. Cheers, Gareth. If mains fuse is designated T3.15 amp, it wil probably need an inrush fitting sometime in the near future , see thread here last week T-E GP12 SMX and Studiomaster comparison Dealt with a heap of C-audio Pulse 2 1100 last year. Stored outdoors (open sided barn) with the thinking that plastic tarpaulin over the rack with a pack of silica gel (as found, not activated) inside it in the autumn would keep them ok over a GB winter. Except for a few colateral damage burnt out 1/3W R , all the problems were those TO92 , gone slightly ohmic presumably from damp ingress. Throws out the bias and then amp always goes into protect. |
#19
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Strangely marked BUZ Mosfet
"N_Cook" wrote in message ... Gareth Magennis wrote in message news Hi, I have a Trace Elliot 300W bass amp here that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. I've repaired a few of these in my time but never come across this marking. Is it a Trace internal number, or have these been substituted in from elsewhere? Are they actually BUZ906? (One BUZ901 is blown, the other 3 check out OK on a PEAK component tester). Cheers, Gareth. perhaps obtained from these people http://www.autogarduk.com/stock%20list%2027.htm 41 P and 274 N What are the test parameters of a Peak? Just realised I've got the old version of the Peak. The new one does more things than mine, like gate threshold voltage. http://www.rapidonline.com/Tools-Fas...ource=googleps Gareth. |
#20
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Strangely marked BUZ Mosfet
"N_Cook" wrote in message ... Gareth Magennis wrote in message ... "N_Cook" wrote in message ... Gareth Magennis wrote in message news Hi, I have a Trace Elliot 300W bass amp here that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. I've repaired a few of these in my time but never come across this marking. Is it a Trace internal number, or have these been substituted in from elsewhere? Are they actually BUZ906? (One BUZ901 is blown, the other 3 check out OK on a PEAK component tester). Cheers, Gareth. perhaps obtained from these people http://www.autogarduk.com/stock%20list%2027.htm 41 P and 274 N What are the test parameters of a Peak? Don't have a clue. It runs on a 9v battery. It does claim to measure hfe, but again I don't know with which parameters. I don't think its meant to be a precision instrument but I find it very useful, mostly for finding dead mosfets and possible good ones, and identifying pinouts of bipolars. I once had terrible problems with a C-audio amp that I just couldn't get working. They had loads of BC184 (I think) doing the bias and stuff. I replaced the lot with BC184L, not realising that the "L" meant the pinout was different. Took me a looong time to suss that one out. Now I always double check with the Peak when replacing any signal transistor, just in case. Likewise Farnell once sold me some resistors that were a decade lower than marked on the packaging. Again took me a while to suss out the problem, and I now always meter EVERY resistor before soldering it in. Cheers, Gareth. If mains fuse is designated T3.15 amp, it wil probably need an inrush fitting sometime in the near future , see thread here last week T-E GP12 SMX and Studiomaster comparison I contributed to that thread. I'll be sticking a T4 in it instead. ;-) 4 new Mosfets and labour is almost an uneconomical repair as it is. Dealt with a heap of C-audio Pulse 2 1100 last year. Stored outdoors (open sided barn) with the thinking that plastic tarpaulin over the rack with a pack of silica gel (as found, not activated) inside it in the autumn would keep them ok over a GB winter. Except for a few colateral damage burnt out 1/3W R , all the problems were those TO92 , gone slightly ohmic presumably from damp ingress. Throws out the bias and then amp always goes into protect. I looked inside 2 of these C audio pulse (nothing to do with C audio really) and quickly put them back together again and gave them straight back. Fist time I'd ever done anything like that. Gareth. |
#21
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Strangely marked BUZ Mosfet
On Thu, 07 Apr 2011 14:03:34 +0100, Gareth Magennis wrote:
"N_Cook" wrote in message ... Gareth Magennis wrote in message news Hi, I have a Trace Elliot 300W bass amp here that uses 2 pairs of BUZ901/906 mosfets. All output devices have been resoldered or replaced at some point, and the amp now contains 2 x BUZ901 (SML) and 2 marked STUD1P. I've repaired a few of these in my time but never come across this marking. Is it a Trace internal number, or have these been substituted in from elsewhere? Are they actually BUZ906? (One BUZ901 is blown, the other 3 check out OK on a PEAK component tester). Cheers, Gareth. perhaps obtained from these people http://www.autogarduk.com/stock%20list%2027.htm 41 P and 274 N What are the test parameters of a Peak? Just realised I've got the old version of the Peak. The new one does more things than mine, like gate threshold voltage. http://www.rapidonline.com/Tools-Fas...quipment/Test- Equipment/Analysers-Testers-Counter/Atlas-DCA-Semiconductor-component- analyser/36637/kw/85-2514?source=googleps&utm_source=googleps Gareth. I own a really old Sencore Cricket transitor/fet checker. You don't have to identify BCE correctly because it has 6 pushbuttons on it. It's still a useful tool to check leakage and gain. -- Live Fast Die Young, Leave A Pretty Corpse |
#22
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Gareth Magennis is xxxxxxxxxxxx
On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote:
Interestingly the customer said that the amp went DC and fried his speaker - the amp has no relay or DC protection. My little bit or research so far indicates that dv/dt failure in industrial motor applications can be down to pulling the power cable off a stalled motor, zapping the gate/substrate connection in a nanosecond. Might this also apply to a faulty speaker in this kind of audio amp which burns short then eventually self disconnects? I also understand extremely electrically noisy environments can also induce this failure mode. The customer is daisy chaining this amp with another one via the FX send, I'm wondering if this has any chance of being the cause of the failure. Slaving another amp via the send isn't likely but a failing speaker or poorly wired/connected load might be the reason. -- Live Fast Die Young, Leave A Pretty Corpse |
#23
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Gareth Magennis is xxxxxxxxxxxx
"Meat Plow" wrote in message news On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote: Interestingly the customer said that the amp went DC and fried his speaker - the amp has no relay or DC protection. My little bit or research so far indicates that dv/dt failure in industrial motor applications can be down to pulling the power cable off a stalled motor, zapping the gate/substrate connection in a nanosecond. Might this also apply to a faulty speaker in this kind of audio amp which burns short then eventually self disconnects? I also understand extremely electrically noisy environments can also induce this failure mode. The customer is daisy chaining this amp with another one via the FX send, I'm wondering if this has any chance of being the cause of the failure. Slaving another amp via the send isn't likely but a failing speaker or poorly wired/connected load might be the reason. Check this out, if just for educational purposes. Quite interesting. http://www.4qd.co.uk/serv/MOSFETfail.html Gareth. |
#24
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Gareth Magennis is xxxxxxxxxxxx
On Sat, 09 Apr 2011 00:12:23 +0100, Gareth Magennis wrote:
"Meat Plow" wrote in message news On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote: Interestingly the customer said that the amp went DC and fried his speaker - the amp has no relay or DC protection. My little bit or research so far indicates that dv/dt failure in industrial motor applications can be down to pulling the power cable off a stalled motor, zapping the gate/substrate connection in a nanosecond. Might this also apply to a faulty speaker in this kind of audio amp which burns short then eventually self disconnects? I also understand extremely electrically noisy environments can also induce this failure mode. The customer is daisy chaining this amp with another one via the FX send, I'm wondering if this has any chance of being the cause of the failure. Slaving another amp via the send isn't likely but a failing speaker or poorly wired/connected load might be the reason. Check this out, if just for educational purposes. Quite interesting. http://www.4qd.co.uk/serv/MOSFETfail.html Gareth. Mostly pertaining to motor control applications. My experience is limited to audio applications. Some similarities exist thought. Still a good read for failure modes. -- Live Fast Die Young, Leave A Pretty Corpse |
#25
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Gareth Magennis is xxxxxxxxxxxx
"Gareth Magennis" Check this out, if just for educational purposes. Quite interesting. http://www.4qd.co.uk/serv/MOSFETfail.html ** Got nothing WHATSOEVER to do with LATERAL mosfets !!! These are completely different animals to switching mosfets. Originally invented by Hitachi and sold in TO3 packs as 2SK ( N ch) and 2SJ ( P ch) numbers as the perfect output devices for audio amplifiers. Power amp makers in the UK, Australia and NZ pounced on them and for a while in the mid 1980s, MOSFET amps were the industry standard. Later, Hitachi supplied plastic pack ( TO3P) versions too - then stopped making the TO3 devices completely in the late 1980s. There was shock, horror and nashing of teeth until it was discovered that an obscure semiconductor maker in Scotland ( of all places) was making very similar lateral devices to Hitachi ( under licence?) - this was Semelab. Initially, all Semelab devices had SML part numbers on them, but later this changed to BUZ part numbers. The exact same devices are also sold under the Exicon brand and Magnatec. Magnatec also supply dual chip versions of the same devices - this simply doubles the max current and max power dissipation ratings. Hitachi lateral mosfets in plastic packs are now sold under the brand " Renesas " . A lateral mosfet will always have the source connected to the case or heatsink tab, have a threshold voltage of about 0.7 volts, come in P and N channel versions and be found in audio amplifiers and very little else. OTOH - switching mosfets have the drain connected to the heatsink tab, are almost all N channel types ( no genuine P ch compliments exist) have threshold voltages of 2 to 5 volts and are found mostly in switching PSUs, motor drives and class D amplifiers. ..... Phil |
#26
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Gareth Magennis is xxxxxxxxxxxx
"Meat Plow" wrote in message news On Sat, 09 Apr 2011 00:12:23 +0100, Gareth Magennis wrote: "Meat Plow" wrote in message news On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote: Interestingly the customer said that the amp went DC and fried his speaker - the amp has no relay or DC protection. My little bit or research so far indicates that dv/dt failure in industrial motor applications can be down to pulling the power cable off a stalled motor, zapping the gate/substrate connection in a nanosecond. Might this also apply to a faulty speaker in this kind of audio amp which burns short then eventually self disconnects? I also understand extremely electrically noisy environments can also induce this failure mode. The customer is daisy chaining this amp with another one via the FX send, I'm wondering if this has any chance of being the cause of the failure. Slaving another amp via the send isn't likely but a failing speaker or poorly wired/connected load might be the reason. Check this out, if just for educational purposes. Quite interesting. http://www.4qd.co.uk/serv/MOSFETfail.html Gareth. Mostly pertaining to motor control applications. My experience is limited to audio applications. Some similarities exist thought. Still a good read for failure modes. Isn't a speaker a motor? Gareth. |
#27
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Gareth Magennis is xxxxxxxxxxxx
"Gareth Magennis" Isn't a speaker a motor? ** And chaulk an cheese are the same too. ****wit. .... Phil |
#28
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Gareth Magennis is xxxxxxxxxxxx
"Gareth Magennis" wrote in message ... "Meat Plow" wrote in message news On Sat, 09 Apr 2011 00:12:23 +0100, Gareth Magennis wrote: "Meat Plow" wrote in message news On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote: Interestingly the customer said that the amp went DC and fried his speaker - the amp has no relay or DC protection. My little bit or research so far indicates that dv/dt failure in industrial motor applications can be down to pulling the power cable off a stalled motor, zapping the gate/substrate connection in a nanosecond. Might this also apply to a faulty speaker in this kind of audio amp which burns short then eventually self disconnects? I also understand extremely electrically noisy environments can also induce this failure mode. The customer is daisy chaining this amp with another one via the FX send, I'm wondering if this has any chance of being the cause of the failure. Slaving another amp via the send isn't likely but a failing speaker or poorly wired/connected load might be the reason. Check this out, if just for educational purposes. Quite interesting. http://www.4qd.co.uk/serv/MOSFETfail.html Gareth. Mostly pertaining to motor control applications. My experience is limited to audio applications. Some similarities exist thought. Still a good read for failure modes. Isn't a speaker a motor? Maybe the "speech coil" head actuators in old 5&1/4 FH HDDs blur the distinction a bit. |
#29
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Gareth Magennis is xxxxxxxxxxxx
On Sat, 09 Apr 2011 00:43:51 +0100, Gareth Magennis wrote:
"Meat Plow" wrote in message news On Sat, 09 Apr 2011 00:12:23 +0100, Gareth Magennis wrote: "Meat Plow" wrote in message news On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote: Interestingly the customer said that the amp went DC and fried his speaker - the amp has no relay or DC protection. My little bit or research so far indicates that dv/dt failure in industrial motor applications can be down to pulling the power cable off a stalled motor, zapping the gate/substrate connection in a nanosecond. Might this also apply to a faulty speaker in this kind of audio amp which burns short then eventually self disconnects? I also understand extremely electrically noisy environments can also induce this failure mode. The customer is daisy chaining this amp with another one via the FX send, I'm wondering if this has any chance of being the cause of the failure. Slaving another amp via the send isn't likely but a failing speaker or poorly wired/connected load might be the reason. Check this out, if just for educational purposes. Quite interesting. http://www.4qd.co.uk/serv/MOSFETfail.html Gareth. Mostly pertaining to motor control applications. My experience is limited to audio applications. Some similarities exist thought. Still a good read for failure modes. Isn't a speaker a motor? Gareth. It can be perceived as a sound motor. -- Live Fast Die Young, Leave A Pretty Corpse |
#30
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Gareth Magennis is xxxxxxxxxxxx
On Sat, 09 Apr 2011 09:42:02 +1000, Phil Allison wrote:
"Gareth Magennis" Check this out, if just for educational purposes. Quite interesting. http://www.4qd.co.uk/serv/MOSFETfail.html ** Got nothing WHATSOEVER to do with LATERAL mosfets !!! These are completely different animals to switching mosfets. Originally invented by Hitachi and sold in TO3 packs as 2SK ( N ch) and 2SJ ( P ch) numbers as the perfect output devices for audio amplifiers. Power amp makers in the UK, Australia and NZ pounced on them and for a while in the mid 1980s, MOSFET amps were the industry standard. I cried the day Hitachi quit manufacturing the 2SK49 / 2SJ135 pairs. I have one old SCS 350w/ch power amp that uses them. I acquired it with a blow channel back in the late 90's. It wasn't easy back then to find replacements. I imagine it's probably a lot easier these days to find NOS replacements. Maybe even a sub is made today? -- Live Fast Die Young, Leave A Pretty Corpse |
#31
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Gareth Magennis is xxxxxxxxxxxx
"Phil Allison" wrote in message ... "Gareth Magennis" Isn't a speaker a motor? ** And chaulk an cheese are the same too. ****wit. ... Phil Oh and there's me thinking a motor is a device that converts electrical energy into mechanical energy. ****wit. |
#32
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Gareth Magennis is xxxxxxxxxxxx
On 4/9/2011 9:06 AM Meat Plow spake thus:
On Sat, 09 Apr 2011 00:43:51 +0100, Gareth Magennis wrote: "Meat Plow" wrote in message news On Sat, 09 Apr 2011 00:12:23 +0100, Gareth Magennis wrote: "Meat Plow" wrote in message news On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote: Interestingly the customer said that the amp went DC and fried his speaker - the amp has no relay or DC protection. My little bit or research so far indicates that dv/dt failure in industrial motor applications can be down to pulling the power cable off a stalled motor, zapping the gate/substrate connection in a nanosecond. Might this also apply to a faulty speaker in this kind of audio amp which burns short then eventually self disconnects? I also understand extremely electrically noisy environments can also induce this failure mode. The customer is daisy chaining this amp with another one via the FX send, I'm wondering if this has any chance of being the cause of the failure. Slaving another amp via the send isn't likely but a failing speaker or poorly wired/connected load might be the reason. Check this out, if just for educational purposes. Quite interesting. http://www.4qd.co.uk/serv/MOSFETfail.html Mostly pertaining to motor control applications. My experience is limited to audio applications. Some similarities exist thought. Still a good read for failure modes. Isn't a speaker a motor? It can be perceived as a sound motor. It *is*, in fact, a motor. Which, technically speaking, is anything that converts electrical energy to mechanical motion. So by this definition, even solenoids and piezo transducers are motors. Now, it's not a motor in the conventionally-understood sense--something that produces rotary motion--but it is, nonetheless, a perfectly good motor. -- The current state of literacy in our advanced civilization: yo wassup nuttin wan2 hang k where here k l8tr by - from Usenet (what's *that*?) |
#33
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Gareth Magennis is xxxxxxxxxxxx
On Sat, 09 Apr 2011 13:23:48 -0700, David Nebenzahl wrote:
On 4/9/2011 9:06 AM Meat Plow spake thus: On Sat, 09 Apr 2011 00:43:51 +0100, Gareth Magennis wrote: "Meat Plow" wrote in message news On Sat, 09 Apr 2011 00:12:23 +0100, Gareth Magennis wrote: "Meat Plow" wrote in message news On Fri, 08 Apr 2011 10:17:06 +0100, Gareth Magennis wrote: Interestingly the customer said that the amp went DC and fried his speaker - the amp has no relay or DC protection. My little bit or research so far indicates that dv/dt failure in industrial motor applications can be down to pulling the power cable off a stalled motor, zapping the gate/substrate connection in a nanosecond. Might this also apply to a faulty speaker in this kind of audio amp which burns short then eventually self disconnects? I also understand extremely electrically noisy environments can also induce this failure mode. The customer is daisy chaining this amp with another one via the FX send, I'm wondering if this has any chance of being the cause of the failure. Slaving another amp via the send isn't likely but a failing speaker or poorly wired/connected load might be the reason. Check this out, if just for educational purposes. Quite interesting. http://www.4qd.co.uk/serv/MOSFETfail.html Mostly pertaining to motor control applications. My experience is limited to audio applications. Some similarities exist thought. Still a good read for failure modes. Isn't a speaker a motor? It can be perceived as a sound motor. It *is*, in fact, a motor. Which, technically speaking, is anything that converts electrical energy to mechanical motion. So by this definition, even solenoids and piezo transducers are motors. Now, it's not a motor in the conventionally-understood sense--something that produces rotary motion--but it is, nonetheless, a perfectly good motor. My reference was to the failure modes of motor speed control mosfets. They aren't the ideal comparison to the failure modes found in audio power amps using lateral or bipolar mosfets. None the less the 4QD read was enlightening. Lots of things can be considered motors if you think outside the box. Anything that conveys motion can be considered a motor. -- Live Fast Die Young, Leave A Pretty Corpse |
#34
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Gareth Magennis is xxxxxxxxxxxx
"Meat Plow" I cried the day Hitachi quit manufacturing the 2SK49 / 2SJ135 pairs. I have one old SCS 350w/ch power amp that uses them. I acquired it with a blow channel back in the late 90's. It wasn't easy back then to find replacements. I imagine it's probably a lot easier these days to find NOS replacements. Maybe even a sub is made today? ** Finding NOS for those numbers is nigh impossible now. But the Semelab BUZ900 and BUZ905 lateral mosfets are near identical. Where devices operate in parallel, best not mix the numbers up - particularly if there are no source ballast resistors. ..... Phil |
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