looking for a surface mounted diode

[Dream to fly]

Sorry guys but I am grasping at straws and I am in need of a surface mounted diode that has the numbers 220 7AA on it.  That is all the info I have and am just throwing a dart hoping it can hit.  Any help would be appreciated.  It is an engine control module that was connected improperly and let the smoke out. 

[EricJ]

A pic might help.

 

[Dream to fly]

A pic might help.
 

It's too tiny to picture. It's about the size of a large pinhead

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[Marauder]

It's too tiny to picture. It's about the size of a large pinhead

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Give us some idea what it is mounted on and a picture of the assembly that holds it. Could be any number of diodes.


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[EricJ]

2 hours ago, Dream to fly said:

It's too tiny to picture. It's about the size of a large pinhead

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Those little ones can be difficult to rework, e.g., replace, without proper equipment and experience.   Even experienced techs generally don't like working with that stuff.  

But, yeah, an assembly pic might still help, plus anything you might know about the circuit.

 

[Dream to fly]

Give us some idea what it is mounted on and a picture of the assembly that holds it. Could be any number of diodes.


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If from a diesel PCM. It protects the transistor that controls the ground to the glow plug relay.

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[Dream to fly]

Big problem is there is only one other diode on the board doing the same job. That is where I got the number from. I'm guessing it has been over stamped with a builders code. I really wish things could be simple. There is no reason a diode has to be secret.

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[Marauder]

Big problem is there is only one other diode on the board doing the same job. That is where I got the number from. I'm guessing it has been over stamped with a builders code. I really wish things could be simple. There is no reason a diode has to be secret.

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Replacing surface mount components can be problematic especially if the board has been damaged. It looks like there was a small overheat/melting on that component. That may have damaged the trace making the replacement difficult if not impossible. Even if you can find the component, not sure how you plan on attaching it. Chances are the board was wave soldered.

I will see if any of the EEs I know can tell us what component this is.

Have you looked at the cost for buying a replacement PCB?


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[ArtVandelay]

Sorry guys but I am grasping at straws and I am in need of a surface mounted diode that has the numbers 220 7AA on it.  That is all the info I have and am just throwing a dart hoping it can hit.  Any help would be appreciated.  It is an engine control module that was connected improperly and let the smoke out. 

The 220 may be the maximum voltage rating, try looking for diodes with 7AA.


Tom

[Dream to fly]

Replacing surface mount components can be problematic especially if the board has been damaged. It looks like there was a small overheat/melting on that component. That may have damaged the trace making the replacement difficult if not impossible. Even if you can find the component, not sure how you plan on attaching it. Chances are the board was wave soldered.

I will see if any of the EEs I know can tell us what component this is.

Have you looked at the cost for buying a replacement PCB?


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The PCM is out of a 2000 power stroke. It has been discontinued and the aftermarket has discontinued it too. Repair shops including cardone are backed up months. I have the equipment to do the work. I own a wave table, hot air torch, rework solder station, and I can repair the trace. Doing the work is not my problem getting the part is.

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[1964-M20E]

any chance of using another diode with the same electrical parameters and solder the leads to the pads where the original diode is?

 

On less critical things I have just grabbed a basic diode from the box and soldered it in and all was good.  This maybe different.

 

 

[orionflt]

have you tried digikey?

[bob865]

mouser if digikey doesn't have it.

[Dream to fly]

have you tried digikey?

Never heard of it. I will check it out now thanks


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[larryb]

Joe:

I am an EE. The thing with simple power electronics is that any part that meets or exceeds the specs will work fine. And we can guess at the specs from the application. You said this diode is the protection diode for a relay.  Any diode > 50V and 2A should be fine. So what I would do is measure the size of the good component with a caliper. Then go on the Mouser site, link below, and filter on the package size. Just find an in-stock diode with the greatest electrical specs that fits in the board footprint. May as well buy 10 while you are at it. If you post the size here I can make a part recommendation for you.

 

Note that if the board was used after the diode blew the transistor driving the glow plug relay could also have been damaged since the protection diode is now missing. If you can identify that part it might be good to buy a few of them at the same time. The driving transistor would work for a few cycles after the diode was damaged but it eventually would be damaged from the inductive kickback from the relay. A relay drive transistor is similar to the diode. Any part that fits the footprint, has the same pinout, has a current rating > 2A, voltage > 50V, and the same type (NPN) will work.

 

https://www.mouser.com/Semiconductors/Discrete-Semiconductors/Diodes-Rectifiers/Diodes-General-Purpose-Power-Switching/_/N-ax1mp?Keyword=diode&FS=True

[N201MKTurbo]

It looks like a SOD-123 package.

 

 

 

[Dream to fly]

Joe:
I am an EE. The thing with simple power electronics is that any part that meets or exceeds the specs will work fine. And we can guess at the specs from the application. You said this diode is the protection diode for a relay.  Any diode > 50V and 2A should be fine. So what I would do is measure the size of the good component with a caliper. Then go on the Mouser site, link below, and filter on the package size. Just find an in-stock diode with the greatest electrical specs that fits in the board footprint. May as well buy 10 while you are at it. If you post the size here I can make a part recommendation for you.
 
Note that if the board was used after the diode blew the transistor driving the glow plug relay could also have been damaged since the protection diode is now missing. If you can identify that part it might be good to buy a few of them at the same time. The driving transistor would work for a few cycles after the diode was damaged but it eventually would be damaged from the inductive kickback from the relay. A relay drive transistor is similar to the diode. Any part that fits the footprint, has the same pinout, has a current rating > 2A, voltage > 50V, and the same type (NPN) will work.
 
https://www.mouser.com/Semiconductors/Discrete-Semiconductors/Diodes-Rectifiers/Diodes-General-Purpose-Power-Switching/_/N-ax1mp?Keyword=diode&FS=True

Ok. I will do that. Thank you very much. This forum saves the day again. I have the transistors. But the diodes I couldn't cross and wasn't sure what was a good replacement.

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[N201MKTurbo]

The transistors are most likely MOSFETs. So N-channel or P-channel. the lack of a heatsink dictates a low Rds On MOSFET. Then you should know the gate threshold. some are optimized for TTL drive and some are not and require a higher gate voltage.

[Dream to fly]

The transistors are most likely MOSFETs. So N-channel or P-channel. the lack of a heatsink dictates a low Rds On MOSFET. Then you should know the gate threshold. some are optimized for TTL drive and some are not and require a higher gate voltage.

They are NPNs and it's a stupid simple circuit but very much needed in the driver's pool of today's driver. When a positive input is detected from the ignition being turned on the transistor grounds a solenoid/relay to power the glow plugs also starting a count down on a timer circuit. At the end of 20 seconds the timer interrupts the base signal and shuts off the solenoid/relay. I could just have added a push button to the dash like most would do but that is against my every grain and the truck is really clean. Besides that, it puts control in the driver seat. I like keeping somethings original. The problem was the owner tried to replace his own glow plug relay and besides having the battery still connected he forgot to turn the ignition off. So connecting cables wrong and crossing a grounded circuit that handles .5 amps tried to carry for an instant 50amps. The truck was brought to me after being towed to three shops that for whatever reason could not get it to start. One went so far as to hand the customer a 6in of 2 gauge wire and showed him where to jump across the relay for a few seconds then start the truck..... Appreciate all the input.

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[peevee]

Dude that's gonna be a bitch to solder. Junkyard ECU?

[EricJ]

Also, it looks like there's a conformal coating on the board, which will have to be removed around the component before replacing.

But, generally, yeah, just stick a reasonably spec'ed diode on there and see if it works.

FWIW, diodes don't fail very often.   Replacing the diode may not fix the problem, either because the diode isn't actually failed or because whatever caused it to fail is still bad.

 

[thinwing]

There is a conformational coating...use heavy duty aluminum foil to protect any side components before heating with your rework gun.Magnification is a huge help...many times component values become apparent.Heating evenly and the component is easily lifted of after burning thru the coating..goodluckgood luck

[thinwing]

I would try a 22 v,2 amp Shottkey surface mount as a replacement

[Dream to fly]

I would try a 22 v,2 amp Shottkey surface mount as a replacement

I'm just getting home from towing so I look tomorrow. Appreciate the help.

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[Dream to fly]

This hit a cord with me but here is the finished working repair.  To those who thought it was silly, a waste of time, or dam near impossible here is the finished job.  7 minutes of total time.  It took a month to find the parts and get the parts but the repair was easy.  I understand that most people on this forum or any other forum for that matter really don't know the capabilities of the others on the site.  But I am really tired of hearing negativity towards everything.  If you feel so compelled to shoot down an idea just to add content do me a favor record yourself and play it back repeatedly.  See if it gives you pleasure. 

Aviation is a rewarding field.  So are many others, but non of the fields including rocket science is out of the grasp of anyone with the willingness to learn, read and TRY.  I believe if it has been built by man it can be fixed my man.  It might not be cost effective and that is a good argument to have, especially if other better options are available but in some cases that is not the case and that is when people like myself find it a challenge to resurrect the broken.

AS FOR THOSE THAT HELPED ME THANK YOU A MILLION TIMES!!!  This website is absolutely the best!