Replacing Power modules for KA9100: Heat Sink Questions?

5th beatle

Active Member
Will have a trimpot and emitter resistor adjoining the replacement power module. Do they need their own heat sink protection? Secondlly, when taking the old power modules out, are there any issues or surprises I need to be awre of?
 
Sorry for the confusion. My neighbor is going to try replacing dead TA-100WA with STD03P plus .33 emitter resistor and 200 ohm trimpot. He's a tube guy but wanted to give this a try. Hope this is clearer and the reason for the questions. Thanks.
 
you need more than an STD03P .. you need the complimentary one STD03N and make sure there is a diode across that trim pot if he's doing what I think he is.
I've done it with SAP16N & P's no pot. The SAP16's are obsolete. I have the parts to do this fix but have not got to it yet.

The Darlingtons (STF03's) have to be mounted to the heat sink or they will fry. Trust me I know.
don't have a diagram at the moment. Before he does that I would post a diagram of what he wants to do, if he hasn't done anything like this before.

My .02
John M
 
Hi SicMan,

He does have the "N" modules as well. Has 1-1/4 to 1-1/2" by 3/4" heat sinks plus small circuit boards with which to mount. This will be a first SS project.

Since it is a first, this is why he wanted to know about heat sinking and any issues when removing dead modules.
 
Sounds like he wants to know if you need an insulator (mica, sil-pad or one of the new types whcih I don't know the names for) to mount the transistors on a heat sink. Which you do. The metal on the back of the transistor is also the collector, which are the supply rails. Not having the transistors, if the hole is not insulated, then you need an insert to isolate the screw from the transistor. (or nylon screws, which are not recommended). My.02
 
Sregor,

Looks like there is no insulator in or around hole at top of transistor/metal backing. The other question is what problem(s) may he encounter removing the 2" x 3" box beneath the heatsinks housing the dead modules.
 
Those heat sinks you mention will be too small.
you can mount them to the holes in the large heat sink with mica insulators

Here's a pic of an early experiment with the 9600 you will need to add the Emitter resistors also a 9100 with the SAP16's mounted . on heat sink .. less work
in there I have done 5 of these mods already and the 9600 has been running for 3 years and the 4 9100's have been running 2 1/2 years no probs .. just don't short the speaker wires ..

.. and the diode/pot combo for the 9100 mod .. you talk about

John M
 

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SicMan, if you could post a sketch of this circuit, it would be greatly appreciated and most helpful. I've got a 9100 that's kaput. I understand that the modules are hard to come by and I wouldn't venture a mod like this without specific wiring. Thanks, Terry.
 
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