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.
point,
marking.
tester).
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
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
Toroid, will get back to you tomorrow with the rest.
Gareth.
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.
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.
$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.
"Gareth Magennis"
** 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.
point,
marking.
tester).
perhaps obtained from these people
What are the test parameters of a Peak?
Toroid and no inrush limit device. The Bipolar Bear uses 2SA1695 and
2SC4468 devices.Gareth.
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.
BUZ901/906
parameters.
and
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.
Just realised I've got the old version of the Peak. The new one does more things than mine, like gate threshold voltage.
Gareth.
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.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.
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.
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.
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.
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