Trace Elliot schematic confusion, BUZ 900 series questions

[jvcmarine]

Trace pb250.pdf

I am ready to order parts for my Trace Elliot PB250 power amp.

I have attached the schematic.

I have a few questions.

The amp originaly was built using 2 K135 and 2 J50 for outputs.

Comparing the schematic to the PCB layout, I see that on the PCB all four of the

TO-3 cases (source) are connected along the common trace on the PCB connecting

the spkr output, four source connections, continuing on to the feed back to R7.

On the schematic attached, I don't see any connection of source from TR6/8 to

TR7/9.

Am I missing something here????

Concerning the BUZ900 series replacements from SEMELAB, the data sheet does not show the case configuration of the TO-3 replacement.

Is the BUZ900 series TO-3 replacement the same pinout as the old K135/J50 TO-3 can?????????????

Maybe I am easily confused here, so any help appreciated,

Vin Collins

[Steve Conner]

All I know is, since these are lateral MOSFETs, the can/tab is always the source. And since they don't need ballast resistors, all four cans will be connected to the speaker output. I've built lateral FET amps where the whole heatsink was live with the speaker signal.

The Semelab ones must have the can as the source too. It's for semiconductor physics reasons. On a lateral MOSFET, the back side of the die that gets soldered to the can just happens to be the source.

So the only possibility is that they have switched the remaining two pins, which would be silly, since they know a lot of people will buy them as replacements for the old Hitachis.

[Enzo]

The missing connection just looks like a drawing oversight.