BUZ901P BUZ906P replacements

[MarkusBass]

I switched and put the IFPR in place of BUZ. The sound came out perfect. I get the sound out for 30 minutes

I wonder who advised you to replace lateral MOSFETs with vertical ones. Everyone knows that this will not work. This is mainly due to thermal runaway of vertical MOSFETs. You need a power amp specially designed for this type on MOSFETs. Otherwise the amp will work (maybe) 1 minute, 1 hour, or 1 day.

Sorry, but this will not work. You have to buy lateral MOSFETs. You can buy them from ebay, or from China.

Mark

[J M Fahey]

Oi Alan, tudo bem?

Mmmmmhhhhhh , acho que não

I switched and put the IFPR in place of BUZ
the sound came out perfect
I get the sound out for 30 minutes
after the relay tripped and the sound stop

Please read all the thread, specially posts # 16, 19, 20, 21, 23, 24, 27

You can NOT easily replace Laterals (2SK.. , BUZ... ) with Verticals/Switching (IRFP) .
Adding / increasing emitter ballastv resistors is NOT enough, amp works for an hour or a day and then "mysteriously" blows, as MarkusBass shows.

Better than EBay or China, buy straight from the source to get guaranteed good parts:
Exicon Lateral MOSFETS - Why use Exicon?

They will probably send you to "a shop" , EXICON .... which I guess is themselves

You can buy straight from them with your International Credit Card.

Being a small simple package with just a couple parts inside, Corréios might even send them straight to your home, without problems at the Alfândega .... the order will probably be under tax free 50U$ anyway.

[alansom]

okay
even if I modify the legs of iIRFP (reverse sugunda with the third)?

[J M Fahey]

You don't have a leg problem.

You have a bias problem.

You have a thermal problem.

Lateral (BUZ... , 2SK/2SJ... ) need 200/300mV fixed bias and are thermally stable.

Vertical (IRFP... ) need 3500/3800mV , thermally tracking heat sink temperature, and are thermally unstable. (inestável têrmicamente e precissam de correção permanente) .

Besides, Laterals are very fast (they are designed for switching) and if you use more than one pair, each transistor needs a series gate resistor, very close to the gate leg (I use 1k with a leg twisted and soldered straight to the transistor leg) or they self-oscillate (auto oscilam) at many mHz frequency , overheat and burn.

You can design with Verticals, but must do so from the beginning, also a special PCB thinking about track length, as if it were an RF cicuit; you can not just plug them into a Lateral designed circuit and expect them to work.

Worst is that they will seem to work ... and then explode.

People avoids them because they are "expensive" ... well, they are not, just U$10 to U$ 15 each; you repair the amp and they work forever, or until owner does something stupid ; compare that to retubing an SVT : 6x6550 ... which might be repeated every year even with regular use.

Now that is expensive.
40U$ to 100U$ each one.

Just get the Exicon transistors and repair that amp the proper way

[alansom]

Thank J M Fahey

I just bought 6 pairs in the UK and should deliver in 3 or 4 days
but The SPENDING WAS TOO HIGH TO ME THAT LIVE IN BRAZIL


BECAUSE HERE IN BRAZIL
EVERY 1 GBP 3.8 VALLEY REAL

FICO ALL WITH TRASPORTE 140 GBP = 532 REAL

THIS AND EQUAL TO SPEND 532 USD

[alansom]

problems not just out there rsrsr
have a Ampeg SVT 4 Pro that the sound is coming out cutting and giving some explosions in sound
and not meeting what it is

[J M Fahey]

Well, the Ampeg SVT4 is designed for Switching Mosfets, so replacements can be easily found in Brazil.
If you are in São Paulo, Multicomercial, in Santa Ifigênia (Rua Timbiras?) probably has them.

As of the MESA amp, it's a beast of an amp, very expensive but justifies being repaired.

Also has a lot of transistors, 6 pairs or 12 units will add up fast.

Newark in USA has BUZ901/906 at U$20 and U$15 each, plus shipping, which adds up to a stiff bill, some U$210+shipping.

I know Brazil very well, I travel there every few months (next probably in April or May) and certainly for ExpoMúsica in September or October.

Profusion shows gbp 5.60 each, or U$ 8.63 each, some U$104 + freight .

I just hope Customs does not want to charge 60% fixed tax on that , although you have U$50 tax free, you should pay on the difference.

Just remember to use a Lamp Bulb Limiter, and be very careful making sure 10 times that amp is working perfectly before releasing it, something burnt the old transistors (in fact I think some will still be fine, measure them one by one "outside"), you may also have *other* bad parts there.

If you burn them again you will suicide, which is easily done by shouting "viva Boca Juniors" in the middle of the Corinthians or Flamengo torcida, he he.

[alansom]

Thank you very much for Info
the buz arrived
paid the minimum rate

now I colocalos and Midir all tensions
I had to change the
lm7915, lm7815, LM7805
now he does not present the shortest

However when i turn it and it turns out not sound
I Realized que arming and disarming is the reley
and the valves do not reach very hot

will be I have to adjust bias?

[alansom]

hello
I'm looking at the q12 q11 and
2 and has mps 4126
Scheme and ask the ecg159
will be what makes the sound does not come out?
I switched tripot and now works
I I the regulated 375v in v1
but the v2 not reach 390V
but get 380,381v
and standard this?
Still no sound from
I Realized que When the gun relay and encanto in p6(tube) leg
sound comes from the boxes but not v2 sound comes

[Jazz P Bass]

The ECG159 is pin for pin compatable with the MPS4126.
It is a valid replacement.

[J M Fahey]

Amigo, também acrescenta o texto original em Português, você escreve com erros e o Tradutor não sabe o que fazer com isso e não faz sentido.

Friend also add the original text in Portuguese, you write with mistakes and the translator does not know what to do with it and does not make sense.

[monto]

hey guys sorry about bumping an older thread but I was wanting to ask, I noticed in my award session sessionette 75 (1985) guitar amplifier it contains a BUZ901P and a BUZ905P in the output stage. should it really be using BUZ901P and a BUZ906P instead? also, are there general common signs of what happens to your amplifer if there is a fault with these components (eg. sound cuts out? or is it more likely you wouldn't get any sound at all? or some other symptoms?) ... many thanks!

[J M Fahey]

Imagining possibilities is endless, please post what problems your amp is actually showing today and we move from there on.

[Jazz P Bass]

I noticed in my award session sessionette 75 (1985) guitar amplifier it contains a BUZ901P and a BUZ905P in the output stage. should it really be using BUZ901P and a BUZ906P instead?

What voltages is the amplifier running at, + & -46Vdc?

As the only difference in the two MosFets is the Drain - Source Breakdown Voltage (900/905= 160Vdc /// 901/906= 200Vdc) and 46 volts is nowhere even close to either one, I would have to say the number mismatch is o/k.

As to possible problems: when those MosFets blow, oh you'll know it.
There is no almost.

[monto]

What voltages is the amplifier running at, + & -46Vdc?

As the only difference in the two MosFets is the Drain - Source Breakdown Voltage (900/905= 160Vdc /// 901/906= 200Vdc) and 46 volts is nowhere even close to either one, I would have to say the number mismatch is o/k.

As to possible problems: when those MosFets blow, oh you'll know it.
There is no almost.

hey thanks a lot for the response
ah ok so I think it is what you said, around 50V (to be honest im not too hot at this stuff but there is a manual here: http://www.award-session.com/pdfs/SG...structions.pdf

could I ask something else, regarding if you bought an amplifier from 1985 (ie. 30 years old), would you not change the 2 mosfets just for peace of mind so to speak (as it's hard to know how much use they have had in the past etc) or is that just paranoid do you think, and it's more a case of 'if it aint broke, don't fix it' ?
ps. I am going to change all the electrolytic caps as there are only 11 of them in the circuit. I think the amp is actually using the original caps, so I doubt they are in the best shape they could be in. (plus the amp does sound a bit noisier/more hum than usual, so I think a cap job is in order)