MPS-U45 Transistors

[TVisitor]

I'm trying to gather up some parts for repairing a Gottlieb System 80
machine. This machine has a 74LS139 which goes through a 7416
invertor which drives a MPS-U45 transistor as a pre-driver for 2N3055
transistors that drive a solenoid.

Since a schematic is worth a 1000 words, check out the far right of
this diagram: http://www.pinrepair.com/sys80/bhdriver.gif

Here, look at MPS-U45 Q54. You don't see it on the diagram, but it
drives a 2N3055 several feet away (under the pinball machine's
playfield). It's mostly identical to the Q57 / Q58 pair just a little
further down in that same diagram.
The driving logic for these are over in http://www.pinrepair.com/sys80/bhcpu.gif,
specifically the 74LS139 & 7416's on the upper right.

My questions:

1. MPS-U45's are not cheap. I am having a problem finding them, or
their replacements. Can I use something else instead?

2. Instead, is there a reason I can't drive the 2N3055 by itself
directly off the 7416's? Would I need some extra logic?

 

On Dec 3, 5:14 pm, TVisitor <tvisi...@gmail.com> wrote:

I'm trying to gather up some parts for repairing a Gottlieb System
80
machine. This machine has a 74LS139 which goes through a 7416
invertor which drives a MPS-U45 transistor as a pre-driver for
2N3055
transistors that drive a solenoid.

Since a schematic is worth a 1000 words, check out the far right of
this diagram: http://www.pinrepair.com/sys80/bhdriver.gif

Here, look at MPS-U45 Q54. You don't see it on the diagram, but it
drives a 2N3055 several feet away (under the pinball machine's
playfield). It's mostly identical to the Q57 / Q58 pair just a
little
further down in that same diagram.
The driving logic for these are over inhttp://www.pinrepair.com/sys80/bhcpu.gif,
specifically the 74LS139 & 7416's on the upper right.

My questions:

1. MPS-U45's are not cheap. I am having a problem finding them,
or
their replacements. Can I use something else instead?

Yep - crosses to NTE272. It's just a modest NPN Darlington. Should be
able to find something at ON Semiconductor. Being a solenoid pre-
driver probably doesn't need any speed, just current gain.

2. Instead, is there a reason I can't drive the 2N3055 by itself
directly off the 7416's? Would I need some extra logic?

If it was OK to _not_ have it, don't you think they would leave it out
in the first place?

GG

 

[Phil Allison]

"TVisitor"

My questions:

1. MPS-U45's are not cheap. I am having a problem finding them, or
their replacements. Can I use something else instead?

** Yep - the TIP110, 111 or 112 are very similar and also TIP120,121 or
122.

Should be readily available and low cost.

Note: the pin out is different, though both have the collector as the tab.

From the front, it reads: EBC for the MPSU45 and BCE for the TIPs.

2. Instead, is there a reason I can't drive the 2N3055 by itself
directly off the 7416's?

** Bad idea.



........ Phil

 

[Ross Herbert]

On Mon, 3 Dec 2007 17:14:21 -0800 (PST), TVisitor <tvisitor@gmail.com>
wrote:

I'm trying to gather up some parts for repairing a Gottlieb System 80
machine. This machine has a 74LS139 which goes through a 7416
invertor which drives a MPS-U45 transistor as a pre-driver for 2N3055
transistors that drive a solenoid.

Since a schematic is worth a 1000 words, check out the far right of
this diagram: http://www.pinrepair.com/sys80/bhdriver.gif

Here, look at MPS-U45 Q54. You don't see it on the diagram, but it
drives a 2N3055 several feet away (under the pinball machine's
playfield). It's mostly identical to the Q57 / Q58 pair just a
little
further down in that same diagram.
The driving logic for these are over in
http://www.pinrepair.com/sys80/bhcpu.gif,
specifically the 74LS139 & 7416's on the upper right.

My questions:

1. MPS-U45's are not cheap. I am having a problem finding them, or
their replacements. Can I use something else instead?

2. Instead, is there a reason I can't drive the 2N3055 by itself
directly off the 7416's? Would I need some extra logic?

Those old Motorola package transistors such as the MPS-U45 have the
unfortunate EBC pinout arrangement whereas the more common modern
TO126 case types, for which there are many which would be suitable,
uses the ECB pinout.

Firstly the data for your desired MPS-U45
http://www.datasheetarchive.com/pdf/2453676.pdf

I would suggest a Zetex BCX38C would be a good drop in replacement
http://www.zetex.com/3.0/pdf/bcx38a.pdf
(don't be fooled by the small E-line package, they handle heaps of
power)

Now, depending upon your location, you may not find Zetex devices all
that readily available. I am guessing you might be in the US so to
help you locate a US supplier try one of the links here
http://www.zetex.com/9.0/9-1-1a.asp?areaid=2&countryid=223&country=United+States

You could also try Newark
http://www.newark.com/jsp/Supplier+Direct+Ship/All+Supplier+Direct+Ship/ZETEX/BCX38C/displayProduct.jsp?sku=76K2637

stratus46@yahoo.com suggests the NTE272, which is fine, and while it
is a direct replacement for the MPS-U45, you might not like the price
asked by such suppliers as Jameco who want USD11.80 ea for 25+.
http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=273199

 

[TVisitor]

True! But I don't like to assume why a designer does something -
sometimes strange things do happen (or, 25 years later, there may be a
better way to do it it such that I could ditch the predriver).

On Dec 3, 10:32 pm, stratu...@yahoo.com wrote:

2. Instead, is there a reason I can't drive the 2N3055 by itself
directly off the 7416's? Would I need some extra logic?

If it was OK to _not_ have it, don't you think they would leave it out
in the first place?

GG

 

[Eeyore]

TVisitor wrote:

True! But I don't like to assume why a designer does something -
sometimes strange things do happen (or, 25 years later, there may be a
better way to do it it such that I could ditch the predriver).

The 2N3055 doesn't have very much current gain on its own.

Graham