Finals for HW-7?


Norman Lee:
Hi there!  I have an HW-7 with broken leads on one of the finals, and want to insert a new pair of finals.  Trouble is, the part number is a Heath house number - 417-224, and the circuit also says MP5U05.  Can't find this anywhere so presume it's long since been discontinued.  Can I use substitutes recommended for the HW-8 (such as the ubiquitous 2N2222A!)?  Please help if you can
With kind regards from winecountry South Australia
Norm vk5gi

William J J Hoge (I go by my first middle name "John"):
The P/N is MPSU05, Mike Papa Sierra Uniform Zero Five.  It can be replaced with an MPS06 (same die, screened for higher Vce).  Both parts are out of print.  I suspect that you could use a BD139 as a replacement, but check the pin out before installation.

William J J Hoge (I go by my first middle name "John"):
Opps, that should be MPSU06.

Dale Hunt:
The BD529 is also listed as an equivalent.

Dan's Small Parts and Kits (
lists the MPSU05 in his closeout section for $2 each.

I'm not familiar with the HW-7 (I have the HW-8 instead)
but unless there is something odd about the output circuit
a transistor such as the 2N4427 or 2N3553, or any of the
ones designed for CB use should work.  There are a number
of Japanese transistors in this category, such as the
2SC2078, 2SC1957, etc.

A 2N2222 or 2N2219 should handle the current and voltage,
but may not have as much output.  (The power dissipation
may be a bit low unless you have a good heat sink.)  
One of my favourites is the RCA 4013, which is a TO-39
case designed for 3 watts output on CB.

Dale Hunt:
Hmmm...  $15 shipping for international orders would make
the parts rather expensive though.  I wonder if I have
any in the junkbox...


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