Obsolete Hewlett Packard Transistor

[shrtrnd]

I've got a blown HP 1853-0233 (proprietary) transistor in an HP 3437A.
It's obsolete. Some guy told me he thinks a TIP42 is supposed to be the equivalent.
With no 1853-0233 data sheet available, I consider that a crap shoot.
Anybody know anything about a definitive 1853-0233 equivalent that's available?

 

[dorke]

This site has it for 5$
and this one for 3.6$

 

[shrtrnd]

Yeah. Thanks.
I know it's available as an original part.
It won't make any sense to you (or me, or anybody else who actually repairs these things),
but the owner has specific requirements as to component vendors.
I should have mentioned that I know the original part can still be found. I just can't buy from them for this job.
The owner would pay for a scrap unit for me to salvage it from, before allowing me to spend the .68 cents I can
actually buy this part for if I was allowed to.
I was hoping for verification of an equivalent that I can substitute.
I do appreciate your taking the time to search for the ones you found though. Thanks

 

[dorke]

From the service manual
It is a PNP 40Watt T0-220 manufactured by HP designation Q2.
Is this part of the power supply?
Can you post the schematics ?

 

[davenn]

The owner would pay for a scrap unit for me to salvage it from, before allowing me to spend the .68 cents I can
actually buy this part for if I was allowed to.
I was hoping for verification of an equivalent that I can substitute.

explain to the stupid owner that a substitute is never going to work as well as an original

 

[shrtrnd]

I'm on a 'more important' job right now, so I set this off to the side for a while.
I have to dig deeper into the schematics to see what that 1853-0233 is for, later.
The Q2 (TO-220) 1853-0233 emitter is tied to the base of Q1 (TO-3) 2N3791.
The Q2 collector is tied to connector J2, pin 5, on the main CPU/Logic board, I have to trace that out.
The Q2 base is physically cut-off, not connected to anything.
There's damage to the power supply, and this is incidental damage, looks like.
*steve*, you're an engineer. It might work different where you are, but us techs can't tell our engineers here anything.
Techs and Engineers here are surfs to the nobles running things. Kind of gives you an idea why companies
move their operations to China (if they want to stay in business).

 

[dorke]

Well,
Please post a clear schematic of that logic card.

I would imagine the only reason to keep on using that "museum instrument" is
it is a part of an old automatic measurement system with HP-IB software,
with no budget to replace/update

 

[shrtrnd]

It's a long story, but can't post diagrams or pictures from this computer.
I'll figure it out, was just trying to see if anybody heard of an equivalent for the 1853-0233.
Pretty good analysis of the instrument's purpose.
Think NASA and the old Voyagers. They were surprised to find one still active beyond Pluto, but had
used an early microprocessor they had long ago obsoleted. Instead of spending billions to create a modern-day
equivalent, NASA quietly bought-up all the surplus microprocessors in salvage businesses (before they knew
what was going on, to up the prices),and rebuilt the Voyager support system for pennies on the dollar.
Sometimes you can't just replace/update one instrument. It costs millions or billions to recertify to meet specs for the entire interconnected system.

 

[dorke]

The Q2 (TO-220) 1853-0233 emitter is tied to the base of Q1 (TO-3) 2N3791.
The Q2 collector is tied to connector J2, pin 5, on the main CPU/Logic board, I have to trace that out.
The Q2 base is physically cut-off, not connected to anything.
There's damage to the power supply, and this is incidental damage, looks like.
.

Well,
I think you may have the Q2 pins mixed:

Emitter is indeed tied to Q1 base.
Base is connected to J2 pin5
Collector is connecetd to GND via chassis(TO- 220 metallic case with no isolator?)

Does this make any sense?

 

[shrtrnd]

It's still on a back-burner right now, lemme take a look at it.
Going by looking at the actual picture on the fold-out page, Figure 7-6 Rev A Pages 7-19 7-20.
(I'm still on that rush job, so I don't have time right now to check the schematic vs the actual wiring.)
And now looking at the instrument,... that isn't what I have.
.... great. Probably got me a specially modified unit. (Or some other revision).
Thanks for taking a look at this dorke, lets me know I've got more work to do on this than I thought.

 

[(*steve*)]

There is mailing list dedicated to repair of old HP and Agilent hardware.

Of you're not familiar with it I'll look out up.

It was a Yahoo group from memory.

 

[(*steve*)]

It is called hp_agilent_equipment, it is a yahoo group, but I can't verify it still exists at the moment.

 

[shrtrnd]

Thanks *steve*, made a note of it.
I scrounged our salvage unit yard and came up with two of these HP 3437A's
Non-functioning, but the 1853-0233's are good. I'll strip them for the parts I need to get this unit going.
So I have the original OEM parts I require to do the job now.
Thanks davenn, dorke, and *steve* for your input.

 

[dorke]

Another thing,
Q2 is part of the 5V regulated digital voltage of the unit.
It is the driver of the series-pass Tr. Q1 in the regulator.
It also serves as part of the current limit and Over-voltage limit circuit .

If you are lucky,
the failure in the P.S wasn't such that the 5V rose to a level that would destroy multiple digital ICs.
Before you start replacing devices,better check the 5V voltage ,The LM358 and the uA723 regulator .
and Q1 as well.

 

[shrtrnd]

Definitely on my to-do list. Thanks dorke.