Murex Miget wire speed fault

[the snooper]

do a search on google for an alternative match

 

[Retroanaconda]

Ah yes, there are a few hits which suggest MJ15015 as an alternative for a BDX18. RS do stock those, although typically they're not in their core range.

The datasheet for the GO Semiconductor MJ15015 that RS supply does show that the collector and the emitter connections are reversed on this compared to the datasheet for the (I assume) Comset Semiconductors BDX18 I have here.

They both claim to be a TO-3 case.

Will this be a problem do you know?

 

[shenion]

Datasheets show two pinouts for BDX18. One shows case is collector, the other shows case is emitter (Cosmet).

Case as collector is most common, a common replacement is MJ2955

Tracing the circuit, it looks like the case is the collector (connected to emitter on NPN driver.).

 

[Retroanaconda]

Bit of a pain that they didn't design a way of being able to tell which your unit is.

If the case-as-collector is more common, and given your reasoning above, I guess I should go with that one.

Thanks

 

[R Kraft]

It would make it run at full speed, with no control.
One of the RS transistors should work, It's just, a big low gain transistor.
An NTE219, or an ECG219 should work.
Even an MJ2955 would probably work,and it seems RS carries them.
Robert

 

[Retroanaconda]

I will get hold of an MJ2955 and let you guys know how I get on. Thanks again for all the help, much appreciated.

Cracking forum you have here

 

[Retroanaconda]

'twas a good shout chaps.

I soldered in the new MJ2955 and gave it a test. Seems to work a dream, I can dial the wire feed from practically nothing all the way up to full speed

Thanks again, much appreciated. Can get on with the business of learning to weld now!

 

[the snooper]

good result