Is this component an SCR?

Thread Starter

Rahulk70

Joined Dec 16, 2016
511
Hello,

Found this circuit board from an 1980s old humidity controlled chamber. This definitely looks like a temperature regulator of some sort. It has a M logo which means made by Motorola. It has the labels E03G-3-9 and 8739. Does anyone have any info on what this part is?

Thanks in advance.
 

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schmitt trigger

Joined Jul 12, 2010
330
Those stud packages were very commonly used for both SCRs and Triacs during the 70s and 80s.

8739 is the manufacturing datecode:
The 39 week of 1987.
Unfortunately the other numbers are house numbers, they don’t follow the Motorola’s catalog part numbers for thyristors; MCR, MAC, HEP or a JEDEC 2N-xxxx
 

MisterBill2

Joined Jan 23, 2018
7,285
The device has numbers, and possibly letters, and maybe even a trademark. Those will provide information that may even lead to a data sheet. The exact same packages could have an SCR, a triac, or a transistor.
Just be very careful with the force applied to the terminals because that glass seal is prone to breaking, and then you have a chunk of scrap metal.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
511
What the reason for query?
Is the unit not working?
Max.
Yes, it was removed from a functional unit. But because the machine itself was from the 80s it was to be discarded. So, I salvaged some parts that I found useful. You are right it is an SCR.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
511
Those stud packages were very commonly used for both SCRs and Triacs during the 70s and 80s.

8739 is the manufacturing datecode:
The 39 week of 1987.
Unfortunately the other numbers are house numbers, they don’t follow the Motorola’s catalog part numbers for thyristors; MCR, MAC, HEP or a JEDEC 2N-xxxx
I thinks a Motorola Case 253-03 style SCR (stud version). So, after some digging found the shorter lead is Gate, long is cathode and body is Anode. After feeding the Gate-cathode with a 1.32V from a NiMH cell via a 10 ohm resistor I was able to get the Anode to cathode to conduct. Without the battery connection it doesn't conduct so confirmed. Thank you so much for the information.

Though I wish I could find the datasheet to determine the voltage and current specifications for the Thyristor/SCR.
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
511
The device has numbers, and possibly letters, and maybe even a trademark. Those will provide information that may even lead to a data sheet. The exact same packages could have an SCR, a triac, or a transistor.
Just be very careful with the force applied to the terminals because that glass seal is prone to breaking, and then you have a chunk of scrap metal.
You mean the portion of the thyristor where the gate-cathode is attached is glued with glass?
 

Thread Starter

Rahulk70

Joined Dec 16, 2016
511
YES, that shiny colored section on many of the devices is a glass hermetic seal. Some brands may use epoxy of some kind, but many of them have glass hermetic seals
Glad you mentioned it because I had a hard time getting the SCR out for the picture. In case I decide to pull it out in the future I'll be careful. It could be glass I have a feeling. Looks very glossy.
 
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