Audison LRx

[Deadly Sones]

Good morning,

First time working on an Audison amp... I can't seem to pull a part number from any of the 6 power supply transistors. I'd think IRF3205 would be fine???

Thanks in advance.

 

[jfet]

hi it's BUZ110s

 

[Deadly Sones]

Hmmm... never had those in an amp before... where can I get them??

 

[Deadly Sones]

Neither Digikey or Mouser have them... can I just use 3205 as replacements?

 

[Perry Babin]

The drive circuit generally determines what you can use. For a typical drive circuit using emitter-follower pairs, you can use virtually anything if you use the appropriate gate resistors. 47 ohm is typically used with the 3205.

 

[Deadly Sones]

I'll have to change the 10 ohm to 47 then, if I can't get original transistors. Thanks Perry.

 

[Perry Babin]

You can use lower value gate resistors. It will stress the drivers a bit more but it's not generally a problem.

It's odd that they used 10 ohm with those originals.

Measure the resistance from the emitters of the drivers to the pad for the gate of the FETs. Do you read only 10 ohms?

 

[Deadly Sones]

Even octopart doesn't list any authorized dealers for the factory ones. I guess I'll try replacing the 10 ohm with 47 ohm gates and install 3205s and hope for the best. Thanks everyone.

 

[Perry Babin]

The BUZ10s are very old. They were used in the oldest Punch amps (pre HD) that used FETs.

 

[Deadly Sones]

I get 100 ohms. They have a pair of paralleled 180ohm resistors (R11). I get 90ish ohms across them plus the 10 ohm in series with it. So from gate pad to the emitter I have little over 100 ohms

 

[Deadly Sones]

Awww I see... now I know why no-one ever wants to work on these things, lol Pic and info you requested on previous page.

 

[Deadly Sones]

The closest values I have are 60.4ohm ones. could I just replace the 180 ohm with 60 ohm? and leave the 10 ohms in circuit? The drive circuit survived. That would get me to about 40ohms gate to emitter.

 

[Perry Babin]

That should be OK.

 

[Deadly Sones]

OK, thanks Perry. Have a nice night sir.