Phonoland

Hi Folks,

I'm progressing the repair of my DOA Jukebox, She powers up now and displays "ERROR C", (believe this is related to coin board, probably only dirty IR LEDs)... Very happy to have got this far...

My question is, what Transistors are Grounded to the Heat-shield? Or are all the transistors isolated from grounded heat-sink (by the clear plastic things that sit between the thermal paste and the back of the transistors called 'Mica Sheet Insulators')

Guy I rescued this from had the plug wired arese ways and this main board removed...
happy it's operating
any advice appreciated..

" Mica's" when used are insulators--some transistors are grounded at the mounting tab, others are not. White, or (IMHO) better yet clear, silicone is an insulator/and is used as a heat dispenser. Ron Rich

Ron Rich wrote:" Mica's" when used are insulators--some transistors are grounded at the mounting tab, others are not. White, or (IMHO) better yet clear, silicone is an insulator/and is used as a heat dispenser. Ron Rich

And of course you know that insulated shoulder washers are needed as well, right Ronnie baby?

Hi Mattie,
Yep--that or, nylon screws & nutz !! Ron Rich

Ron Rich wrote:Hi Mattie,
Yep--that or, nylon screws & nutz !! Ron Rich

Personally, I never use those nylon binders, they're crap. - heat tends to make them lose "grip" or "stretch".
I always metal fasteners, and lockwashers, and even if the collector of one transistor is at ground potential, I always use a mica insulator anyway, slathered on both sides with heat sink "grease".

Now... In answer to my own question

The both 'middle' pairs of transistors screwed vertically and horizontally to the heat-sink don't require Mica Sheet Insulators
only Heat sink compound is needed... However if unsure, a safe bet is to put Mica Sheet Insulators on all...
See Pic as reference....