[TriEmbed] Substitute transistor

The MacDougals paulmacd at acm.org
Sun Jan 16 09:20:37 CST 2022


The display is buried amongst several layers of things on the control panel.

I am hesitant to try to separate the layers.

There appears to be no impact to the operation of the oven.

 

---> Paul

 

 

From: Shane Trent <shanedtrent at gmail.com> 
Sent: Saturday, January 15, 2022 5:59 PM
To: Paul MacDougal <paulmacd at acm.org>
Cc: TriEmbed Discussion <triembed at triembed.org>
Subject: Re: [TriEmbed] Substitute transistor

 

Do you think the backlight going out would shut down the system? Do you know what voltage rail is used for the backlight?

 

On Sat, Jan 15, 2022 at 1:26 PM The MacDougals via TriEmbed <triembed at triembed.org <mailto:triembed at triembed.org> > wrote:

The display blinked back on at full intensity for a short while yesterday!

I believe it is the back light of the LCD that is the issue.

 

---> Paul

 

 

 

From: TriEmbed <triembed-bounces at triembed.org <mailto:triembed-bounces at triembed.org> > On Behalf Of The MacDougals via TriEmbed
Sent: Saturday, December 18, 2021 3:02 PM
To: triembed at triembed.org <mailto:triembed at triembed.org> 
Subject: Re: [TriEmbed] Substitute transistor

 

I replaced the transistor with an exact match from ebay and a couple of electrolytic caps (at Carl’s suggestion).

The display is still dim.  Oh well.

 

---> Paul

 

 

From: TriEmbed <triembed-bounces at triembed.org <mailto:triembed-bounces at triembed.org> > On Behalf Of The MacDougals via TriEmbed
Sent: Friday, November 26, 2021 9:11 PM
To: triembed at triembed.org <mailto:triembed at triembedorg> 
Subject: [TriEmbed] Substitute transistor

 

My microwave display suddenly went very dim.  I opened it up and found a discolored

spot on a circuit board feeding the display (see attached image).  That component is

marked B1238, so I assume it is a 2SB1238, which is obsolete.

 

https://www.digikey.com/en/products/base-product/rohm-semiconductor/846/2SB1238/30307

Medium power transistor( 80V, 0.7A) 2SB1189 / 2SB1238 Features 1) High breakdown voltage, BVCEO= 80V, and high current, IC= 0.7A.

2) Complements the 2SD1767 / 2SD1859. Absolute maximum ratings (Ta=25C) Parameter Symbol Limits Collector-base voltage VCBO −80 Collector-emitter voltage VCEO −80 Emitter-base voltage VEB O −5 Collector current IC −0.7 C.

 

Anyone want to help me find a replacement?

I dug through my Dad’s stash of old electronics and found a TIP30B, which looks like it might work.

 

 

---> Paul

 

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