barbetta 3105 schematic

[oc disorder]

Juan mentioned the Polytone ..I've tried to clean this up a bit here it is Polytone PA 378

[lowell]

Good news. Don't know what kept me from checking the bias... but in any case I checked the tweeter PA bias and there was very little current running in those mosfets. In the datasheet it says .25ma (.00025A). So I tried the bias pot and got those where they should be. The tweeter now works. SO, I then tried the same approach with the woofer PA and there is no current AND the bias pot does nothing. So I swapped LM391 chips. Now the woofer works and the driver transistor bases are at +1.1v/-1.1v. I'll be ordering a couple LM391 ICs. Now to dive into the other one. Thanks for all the help! Oh, and here's an updated tweeter PA schematic. There are some slight corrections from the previous one.Namely the P8N20 SOURCE connections. Also, the ballast resistors are 2.2ohm NOT 22ohm. Glad I caught that when biasing the thing!!

[lowell]

Gonna search online... But littlediode.com says they don't have any. If anyone knows any other suppliers pls let me know!

[g1]

littlediode.com says they don't have any.

They have them on their UK ebay store: Integrated Circuit, Transistor items in LittleDiode store on eBay!

[Jazz P Bass]

Don't know if they have a minimum: LM391N100 NATIONAL SEMICONDUCTOR HI-VOLT 100V AUDIO AMP / DIP-16PINS
LittleDiode: LM391N100 Integrated Circuit x 1 pieces | eBay

[lowell]

Just ordered... but found different ebay supplier eedesigner. Claims they are NEW. So we'll see won't we! And chose these cause faster shipping and only about $4 each.

[g1]

I think I can speak for JazzP when I say we were trying to find you a source that was NOT coming from China. I doubt these are NOS, so they may be counterfeit, there is not enough demand for anyone to go into production for these.
The higher price ones from little diode may be NOS, which would explain the higher price. They seem to be a very reputable seller with 100% positive feedback from over 36,000 transactions.
Either way, it's not a big deal to lose a couple bucks, but if it doesn't work you can't be sure it was a good part when you buy "new" obsolete parts from China.
In your case at least you have another good working chip, so you should be able to verify whether the replacement works.
Good luck!