Obsolete Hitachi Transistor Substitute Confirmation

Thread Starter

noynek

Joined Oct 27, 2017
3
Good day Everyone.
'm not as strong as I'd like ot be ( Yet) in electronic circuits.
I'm currently trying to find a suitable ( easily avaialble and relatively inexpensive ) substutute for a Hitachi.2SD1922 TO92 Transistor .

It is an OEM transistor used in a nissan ECM's to switch the fuel pump Relay coil to ground. I ideduced that (I hope i'm right ) from the fact that Ive had to change a few when the Fuel pump relay stops switching via the ECU

Ive read online how to look for a suitable subs but I wonder how much Icbo Iebo and Iceo will affect performance for the Substitute.

Ive deduced that the the SANYO 2SC3070 Could be an approprite Substitue but the DIfference in Emmitter and Collector Cut off currents has me uncertain.

Could someone please review and let me know if this is an approprite choice and or sugest another that may work ?

Best Regards
Kenyon
 

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RichardO

Joined May 4, 2013
2,271
It looks like you are going to have a hard time finding the 2SD1922.

You may have to make your own. :(
The 2SC3070 may work as a replacement but I think that you should find a part that has at least 40 volts for the Vce breakdown voltage. Since the 2SD1922's seem to fail a lot you may also want to find a transistor that can withstand higher collector currents.

Use the replacement transistor and add your own diode and zener. Use a 1N4001 0r 1N4002 for the diode and a 1N 5256B for the zener diode. Wire the diodes as shown on the 2SD1922 data sheet.
 

GopherT

Joined Nov 23, 2012
8,012
Thanks. Excuse me if it seems obvious to someof you.

But then what would be the accurate way to find a real substitute for the 2SD1922 ?

A subsitute will likely work ok but the added diode and zener are there to protect the device from automotive-like situations (noise, spikes, ...).
 

RichardO

Joined May 4, 2013
2,271
A subsitute will likely work ok but the added diode and zener are there to protect the device from automotive-like situations (noise, spikes, ...).
The zener diode is a way of clamping the collector voltage to protect against back EMF of a solenoid. The advantage is that it lets the inductor voltage rise above the power supply voltage which reduces the time constant.
 

absf

Joined Dec 29, 2010
1,948
I found this 2SD789 which is slightly better than the D1922 but you have to put in the diode and zener as mentioned by RichardO. The only transistor with the diode built-in was the HOT used in TV sets.

But I think any transistors with a Vceo>60V , Pc=1W and Ic>1A should be fine as 2SDxxx are for Audio Freqency applications. 2SC3070 should do the job too..

Allen
 

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Last edited:

RichardO

Joined May 4, 2013
2,271
It occurs to me that you may also want to add a small heat sink to the transistor if there is a safe way to do it mechanically.
You have to make sure that vibration will not move the now heavier transistor causing it to break its leads.

Something like this:


upload_2017-10-28_9-46-28.jpeg
 

Thread Starter

noynek

Joined Oct 27, 2017
3
A subsitute will likely work ok but the added diode and zener are there to protect the device from automotive-like situations (noise, spikes, ...).
I contemplated that after it was brought to my attention, thanks
It looks like you are going to have a hard time finding the 2SD1922.

You may have to make your own. :(
The 2SC3070 may work as a replacement but I think that you should find a part that has at least 40 volts for the Vce breakdown voltage. Since the 2SD1922's seem to fail a lot you may also want to find a transistor that can withstand higher collector currents.

Use the replacement transistor and add your own diode and zener. Use a 1N4001 0r 1N4002 for the diode and a 1N 5256B for the zener diode. Wire the diodes as shown on the 2SD1922 data sheet.
I thought that this is what I may have had to do, you answered one of the other questions I had in my mind, which was, what Zener and Diode to use? .. Truth is from what I have seen most 2SD1922's have faild due to incorrect connection on the ECU terminal. It has typically occured when persons install the ecu and engine in a non OEM Chassis then "wire up" the ECU and incorrectly apply a +12V source to the correspondingg terminal on the ECU not understanding that it's a control signal designed to switch an external relay by pullin to ground one side of the relay coil.
The zener diode is a way of clamping the collector voltage to protect against back EMF of a solenoid. The advantage is that it lets the inductor voltage rise above the power supply voltage which reduces the time constant.
Makes perfect sense since this does switch an autmotive relay. before this, I would have overlooked the necessity of the Diodes. I understand how they operate but it wasn't second nature to me to make this observation
It occurs to me that you may also want to add a small heat sink to the transistor if there is a safe way to do it mechanically.
You have to make sure that vibration will not move the now heavier transistor causing it to break its leads.

Something like this:


View attachment 138214
Hmm food for thought .

I found this 2SD789 which is slightly better than the D1922 but you have to put in the diode and zener as mentioned by RichardO. The only transistor with the diode built-in was the HOT used in TV sets.

But I think any transistors with a Vceo>60V , Pc=1W and Ic>1A should be fine as 2SDxxx are for Audio Freqency applications. 2SC3070 should do the job too..

Allen
I'll look into the 2SD789 transisitor as well. Which ever one is easier to get and cheaper in my neck of the woods is the one I'll go with..

-------
Thanks to all you guys for replying I really appreciate it.

Again
I really appreciate the feedback, I feel more educated now. My backround is really Mechanical Enineering. Sometimes I wish I did Electrical instead. :oops: Electrical is just my own personal hobby so I'm learning as I go

Cheers
 
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