Need help identifying a large TO-3 "transistor"

[Scruit]

Compaq Portable 286 power supply, there are two identical TO-3 packages labelled "102528" with Linear Tech logo.

Anyone know what these are?

https://imgur.com/a/gUJ7Fpn

 

[Someone]

Someone suggests that you contact Analog Devices because they now own Linear Technology.

 

[daver2]

My gut feeling is a linear voltage regulator. But I haven't found the coding for decoding the part code.

Dave

 

[Scruit]

I'm going to try wiring it up to my component tester, see if it can figure it out.

 

[Ruud]

It does help to find out what they do by looking where the connections to the pins lead to. And isn't there schematic available? I mean, Compac isn't an unknown brand.

 

[wrm]

I see your question (and the answers) on Reddit etc.

The 8088 PSU has one LM317. Maybe your PSU has two? Trace the schematic, but if there are three pins and the one is an input and the other is an output and the third has a resistive divider hanging off of it -- LM317.

 

[Scruit]

OOooOOOh... "resistive divider" were the magic words. Tracing the circuit shows that both of these TO-3s are in parallel, and they go through independent diodes to the "+12v" and "+12v Mon" outputs. But what I also see is something in that circuit that looks like a resistor array, 6 pin (SIP)

Resistance between pins

1 and 2 = 120ohm
2 and 3 = 10k
1 and 3 = 1.12k

4 and 5 = 1.0k
5 and 6 = 120ohm
4 and 6 = 1.12k

No connection between pins 1/2/3 and pins 4/5/6.

When you said "resistive divider" that clicked - that's what this device is.

Also, the input of the two TO-3 devices is one of the outputs of the big transformer, so I suspect the transformer is intended to output a little over 12v and these are "high" current 12v voltage regulators that make it spot on.

I will try testing them as vregs. Hopefully they still work.

 

[Scruit]

It does help to find out what they do by looking where the connections to the pins lead to. And isn't there schematic available? I mean, Compac isn't an unknown brand.

Compaq is definitely not not an unknown brand, but the definitely hold their schematics and part#s close to their chest.

 

[Chuck(G)]

Given that Compaq used the LM338K in the original Portable PSU, I suspect that the LTC part is the LT338. Also see discussion here Also note, on the LT338 datasheet, the first page starts out with paralleling the little buggers to get more current.

 

[Scruit]

Given that Compaq used the LM338K in the original Portable PSU, I suspect that the LTC part is the LT338. Also see discussion here Also note, on the LT338 datasheet, the first page starts out with paralleling the little buggers to get more current.

I will have to look at the board again and soo if that pinout makes more sense than the standard TO-3 where the case is ground and the two pins are in/out.

Thank you! This is a great lead!