ST2000 Transistors

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northwind

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My ST2000 (The old back one, not the ST2000+ which is the newer grey one) Has stopped working, I opened it up and one of the power transistors is getting very hot, so its time to replace it.

The only service manual I can find is for a ST2000+ which suggests they are "TRANSISTOR FET LRFZ34 60V 30A" Looking on RS, I can find these: STMicroelectronics 60V 30A, Dual Schottky Diode, 3-Pin TO-220AB STPS30L60CT | RS Components Would they be ok as a replacement?

Anyone else had this issue? Apart from the power transistor the board looks ok, so hopefully its just that that needs replacing.

Thanks!
 
look at the number on top of the transistor, don't rely on the later model using the same device. It's getting hot because it is working hard, but it is a power power transistor designed to work hard, and it may be within it's normal operating range, or it might be getting too hot because it is passing too much current. Unfortunately you don't have a comparison to decide which it is. It's unlikely to have failed just a bit, power trannies really go when they go, and usually its because another component has failed first allowing the transistor to draw too much current. Typically this is failed resistive devices but can also be capacitors going short circuit, or shorted turns on motor windings.
 
The 4 FETs are an H bridge which drives the motor forward or reverse. 2 FETs should be on for fwd. The other 2 for reverse. 1 getting hot and no motor movement means something's wrong!
 
I think a fist step is to ensure the motor can turn. Then disconnect the motor and try on 12v both ways. In an H set up of course we would expect 2 transitors to be conducting so 2 getting hot. ol'will
 
Yes, disconnect one leg of the motor and disconnect the unit from power then power the motor/ram in both directions. Preferably monitor the current if you can.
 
If you need to remove a component have a look at the low melt solders . I used to do a lot of console and laptop repairs and it was amazing for removing chips and components without the need for heatguns and excessive heat. Chip quick it called
 
Rhylsailer99 said:
If you need to remove a component have a look at the low melt solders . I used to do a lot of console and laptop repairs and it was amazing for removing chips and components without the need for heatguns and excessive heat. Chip quick it called
Click to expand...

Thanks for the suggestion of ‘Chip Quick’ I have a couple of transistors to replace so will place an order for it.
 
northwind said:
Thanks for the replies, the motor works fine, connected it to my bench psu and it happily moves in and out not drawing more than an amp, the transistor gets hot even without the motor connected..
Click to expand...
You need to find out what is drawing the current that is causing the transistor to get hot. (y)
 
Just change the transistors, at least the one getting hot plus the one working on the same motor terminal. The current making it hot is probably coming from the other transistor on the same terminal.

You could check the 5V regulator to make sure it is working.
 
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