Source for BUZ901P, BUZ906P N & P-Ch MosFET's?

[nevetslab]

I have a Mesa M-Pulse 600 Bass Amp with failed BUZ901P and BUZ906P N-Ch & P-Ch Lateral MosFET's. So far, I haven't found a source (apart from on ebay). Checked with Audiolabs of Georgia and initially it looked like they had a cross for them Exicon ECX10N20 and ECX10P20 Lateral MosFET's, but shows up no stock when I went to order them. A further cross are Renesas 2SK1058 and 2SJ162 parts.

I had our purchasing dept at CenterStaging LLC here in Burbank check with Gibson, who owns Mesa these days, but no luck on those parts or replacements.

Anyone have better suggestion then ebay?

Also, looking at the schematics for the M-Pulse 600, there are no instructions on setting bias level on the replacement set. Where do you typically bias these to?

mesaboogie-m-pulse-360-600-schematics.pdf

The 1N4739 Zeners are 9.1V 1W, and the 1N750 is a 4.7V zener, seen in the bias leg of the output stage.

[Jon Snell]

There are alternatives available made by Exicon.
I have used them in the past as the BUZ range have been obsolete for years.
https://gb.profusion.uk/uk/ecx10n20
https://gb.profusion.uk/uk/ecx10p20

https://www.exicon.info › PDFs › ecx10n20
https://www.exicon.info › PDFs › ecx10p20

If you buy from fleabay or the amazun who knows what you will get.

[g1]

Here is a link to their US site: https://us.profusion.uk/int/catalogs...lt/?q=exc10n20

[nevetslab]

There are alternatives available made by Exicon.
I have used them in the past as the BUZ range have been obsolete for years.
https://gb.profusion.uk/uk/ecx10n20
https://gb.profusion.uk/uk/ecx10p20

https://www.exicon.info › PDFs › ecx10n20
https://www.exicon.info › PDFs › ecx10p20

If you buy from fleabay or the amazun who knows what you will get.

Many Thanks, Jon! I just got thru placing an order for 10 pcs each on the Ecxicon ECX10N20 Select and ECX10P20-Select. Had trouble with getting registered with them, but after getting all that done, and placed the order, paid via PayPal, the Sales Order form showed they DIDN'T use my billing address as I had entered it . Used the Shipping Address instead. Shouldn't make any difference, but just one of those pesky issues that kept going in circles while filing out the form. Oh well.

I probably should have ordered far more than 10 pcs each so I'd have enough to screen/batch for having a matched set installed.

Yesterday, I found a seller local to me (El Monte, CA) who had (3) 5-pc pairs of new 2S1058's and 2SJ162's, and ordered 10 pcs of each. Then by the end of the day, I got an email from the seller indicating they are coming to me from Hong Kong! DAMN! Seller DID at least have a 99.1% Positive Feedback rating, but, the parts have NO MFGR markings, just faint Part Numbers on them. So, that may be a wasted $200 payment made. Hope not.

Still interested in what nominal bias current to select, not having a working amp to compare to.

[x-pro]

Still interested in what nominal bias current to select, not having a working amp to compare to.

Start with a voltage of 10 mV across a single 0.22 ohm resistor at either transistor. If the “bias setting” allows. And also no load, no signal.

[Jon Snell]

You will find that 10mV between points A and B with no signal and no load is suffucient, it's class B.

[x-pro]

Jon Snell, if this is a statement to me, I wrote that this voltage should be measured at one of the resistors.
You can take the data on Bias setting from the service manual of Ampeg SVT-4 Pro, STV-5Pro. The output stage circuit is similar there.
There it is specified for one resistor with 0.47 ohm resistance- 25mV. In the Mesa schematic, the resistor is 0.22.

[Jon Snell]

Jon Snell, if this is a statement to me, I wrote that this voltage should be measured at one of the resistors.
You can take the data on Bias setting from the service manual of Ampeg SVT-4 Pro, STV-5Pro. The output stage circuit is similar there.
There it is specified for one resistor with 0.47 ohm resistance- 25mV. In the Mesa schematic, the resistor is 0.22.

Half of the resistance = half of the voltage drop for the same current.
1/2 X 25mv = 12.5mv but 5mv is prefered as it stays cooler.

[J M Fahey]

***Yesterday, I found a seller local to me (El Monte, CA) who had (3) 5-pc pairs of new 2S1058's and 2SJ162's, and ordered 10 pcs of each. Then by the end of the day, I got an email from the seller indicating they are coming to me from Hong Kong! DAMN! Seller DID at least have a 99.1% Positive Feedback rating, but, the parts have NO MFGR markings, just faint Part Numbers on them. So, that may be a wasted $200 payment made. Hope not.***

Cancel sale/payment NOW. Serious.
That guy is just doing "drop shipping"
He does NOT have the stuff, never did or will.
You chose him over others to AVOID. buying from Hong Kong, EBay, AliRxpress, etc. based on his address.
This counts as scam.

He pays, say, $120 (or less) and pockets the difference.

99.1% positive rating means NOTHING.

If buyers is happy, his good rating stays.
If very unhappy and demands refund, he *may* get it but only if he leaves a positive comment.

Be firm with your complaint and make it clear you did NOT want Hong Kong parts, at any price.

Sorry.

Maybe you lost $200 ☹️

[nevetslab]

Earlier this week, having finally finished with the latest batch of inventory amp repairs, I got to use this cute little Peak Atlas DCA75 Pro Semiconductor Analyzer to get readings on all the 2SK1068 N-Ch and 2SJ162 P-Ch MosFET's that I bought before getting Jon Snell's info on the source for the Exicon ECX10N20 and ECS10P20 MosFET's. Granted, this DCA75 can only make readings at low voltages and currents, being powered by a single AAA battery.

All of the unknown mfgr's 2SK1068's and 2SJ162's measured fine, and actually had closer matching in the Gm reading than those of the Exicon parts. I'm about to set up the Hameg HM8042 Curve Tracer, along with another setup for measuring the parts for Vgs at a 50mA Drain Current and 40 to 80V Drain-Source Voltage. So, making progress. I'm also going to have a look at the voltage and current levels in the Ashdown ABM900 which uses the BUZ901P and BUZ906P Lateral N & P-Ch MosFET's. Output stage circuit very similar to that of the Mesa Pulse 600 amp, as seen in thread #6 above.

I've attached the readings made with this Peak DCA75

I haven't yet installed the software for this Peak DCA75.

I've yet to see any of our Ashdown ABM900's fail.

MosFET Testing Results_72424.doc