Finding a suitable replacement for transistor from HP Agilent Keysight schematic

[dlucy67]

I'm digging into a piece of HP gear, a 3466A digital multimeter, and I need to understand how I'd find a suitable replacement for a given transistor. My question is more of a "how to do this" one versus a "which part do I need in this specific case" question.

For instance, I've got a TO-92 at Q906 which has less-than-helpful silkscreen printing on it and the parts list in the schematic hasn't helped me so far. For those of you who know HP Agilent Keysight gear well, how should I decode the following line from the parts list into a real, specific transistor? Once I've got that, I know how to find a replacement (based on cross ref or just parameters):

Ref    HP PN    Description                     Mfr   Mfr PN
A4Q906 1853-0016 TRANSISTOR PNP SI TO-92 PD=300MW 28480 1853-0016

Googling 1853-0016 doesn't give me anything useful and I don't want to just drop a random transistor in there. Where can I take the above info, look it up, and yield a datasheet or at least the critical parameters to then go look for a replacement transistor?

[w2aew]

I'm digging into a piece of HP gear, a 3466A digital multimeter, and I need to understand how I'd find a suitable replacement for a given transistor. My question is more of a "how to do this" one versus a "which part do I need in this specific case" question.

For instance, I've got a TO-92 at Q906 which has less-than-helpful silkscreen printing on it and the parts list in the schematic hasn't helped me so far. For those of you who know HP Agilent Keysight gear well, how should I decode the following line from the parts list into a real, specific transistor? Once I've got that, I know how to find a replacement (based on cross ref or just parameters):

Ref    HP PN    Description                     Mfr   Mfr PN
A4Q906 1853-0016 TRANSISTOR PNP SI TO-92 PD=300MW 28480 1853-0016

Googling 1853-0016 doesn't give me anything useful and I don't want to just drop a random transistor in there. Where can I take the above info, look it up, and yield a datasheet or at least the critical parameters to then go look for a replacement transistor?

According to the cross reference information located here:
http://www.sphere.bc.ca/test/hpparts.html#cross

The 1853-0016 is electrically equivalent to a 2N3638

The specific page I found this on is:
http://www.sphere.bc.ca/test/hpdata/hp-xref81-1.jpg

This same site has cross reference info for Tektronix part numbers too:
http://www.sphere.bc.ca/test/tekequiv.html

[PA0PBZ]

Googling 1853-0016 doesn't give me anything useful...

If I google 1853-0016 the second result says the equivalent is NTE159: http://www.weisd.com/test/GenericParts_WEISD_view.php?editid1=1853-0016
googling NTE159 shows me a lot of places where I can buy this.

But anyway, it is just a generic audio PNP, so I guess almost anything will work.

[timb]

The other way to do this, when you can't find the part online or through a cross reference is this: Look through the parts list and find another transistor with the same part number. Unless it's a big power transistor, odds are it's used elsewhere on the board (this saves on inventory costs). Locate it on the board and remove it, then use one of those $20 Chinese transistor testers on it. This will tell you if it's a PNP, NPN, what the HFE is and what the base current is.

You can then either use a multimeter or scope to measure voltages between the base-collector and collector-emitter of the broken unit. (Or deduce it from the schematic.)

With that information you should have enough information to pick a suitable replacement.

[dlucy67]

According to the cross reference information located here:
http://www.sphere.bc.ca/test/hpparts.html#cross

The 1853-0016 is electrically equivalent to a 2N3638

The specific page I found this on is:
http://www.sphere.bc.ca/test/hpdata/hp-xref81-1.jpg

This same site has cross reference info for Tektronix part numbers too:
http://www.sphere.bc.ca/test/tekequiv.html

Brilliant! Exactly the answer I was hoping for. Thank you!

[dlucy67]

If I google 1853-0016 the second result says the equivalent is NTE159: http://www.weisd.com/test/GenericParts_WEISD_view.php?editid1=1853-0016
googling NTE159 shows me a lot of places where I can buy this.

But anyway, it is just a generic audio PNP, so I guess almost anything will work.

I must have fat-fingered the number as I searched for it. You are exactly right. Thanks!

[dlucy67]

Look through the parts list and find another transistor with the same part number. Locate it on the board and remove it, then use one of those $20 Chinese transistor testers on it. This will tell you if it's a PNP, NPN, what the HFE is and what the base current is.

You can then either use a multimeter or scope to measure voltages between the base-collector and collector-emitter of the broken unit. (Or deduce it from the schematic.)

With that information you should have enough information to pick a suitable replacement.

Great! Thank you!

[JFJ]

According to the cross reference information located here:
http://www.sphere.bc.ca/test/hpparts.html#cross

The 1853-0016 is electrically equivalent to a 2N3638

Hewlett Packard specify the same electrically equivalent transistor in their June-August 1981 issue of "Bench Briefs" magazine.

There are more cross reference tables, and lots of servicing tips, in the other issues of Bench Briefs that can be found here:
http://www.hparchive.com/bench_briefs.htm

[dlucy67]

There are more cross reference tables, and lots of servicing tips, in the other issues of Bench Briefs that can be found here:
http://www.hparchive.com/bench_briefs.htm

Fantastic. Thanks!

[vk6zgo]

The other way to do this, when you can't find the part online or through a cross reference is this: Look through the parts list and find another transistor with the same part number. Unless it's a big power transistor, odds are it's used elsewhere on the board (this saves on inventory costs). Locate it on the board and remove it, then use one of those $20 Chinese transistor testers on it. This will tell you if it's a PNP, NPN, what the HFE is and what the base current is.

You can then either use a multimeter or scope to measure voltages between the base-collector and collector-emitter of the broken unit. (Or deduce it from the schematic.)

With that information you should have enough information to pick a suitable replacement.

As a comment on this.
Sometimes Manufacturers use the same device in a critical & a non-critical application to save on inventory.

If you find another one in a non-critical spot,steal it for the original position.

You can often then use a generic device in the non-critical position.

[dlucy67]

This has helped considerably and I've found a replacement for 1853-016, but the second transistor I'm chasing down is HP part number 1854-071 which, using the above-referenced HP charts, crosses to a CP4071. I can't seem to find a datasheet on the CP4071 (to help me find an equivalent replacement based on the specs).

The device itself has some markings, but I can't find an Internet match for simple combinations of those, either.

I've used a B&K 530 semiconductor tester, verified the 1853-016 is a PNP and the 1854-071 is NPN. Both devices seem to pass the leakage tests on the B&K 530, but I'm keen to drop a temporary replacement in for the 1854-071 at Q908, just to see if the flickering behavior changes at all.

Anyone know what a CP4071 crosses to? Or where I might find a datasheet?

Thanks!

[G0HZU]

Not sure if this is the same part number as it has two zeroes ahead of the 71 but I had several 1854-0071 NPN devices exhibit a 'flickery' failure mode in my old HP8405A vector voltmeter.

You can read about my exploits in the link below.
See the symptoms in posts #30 and #31 and then on post #32 you can see I found a cross reference to a 2N3391 in my old HP431C manual.

http://www.vintage-radio.net/forum/showthread.php?t=102117&page=2

eg one of them says 4-071 TI 726B on it. The other says 4-071 TI 723E on it.

They are probably Texas Instruments parts and the ones that failed developed a flicker mode that was temperature dependant.

I just used BC547B parts to get it working but I would like to find the correct parts at some point. So I'm interested if you find what these parts are!

[JFJ]

Anyone know what a CP4071 crosses to?

1854-0071 transistors (with the same 4-071 marking as in your picture) are listed on eBay:
http://www.ebay.com/itm/391373647073

[dlucy67]

Not sure if this is the same part number as it has two zeroes ahead of the 71 but I had several 1854-0071 NPN devices exhibit a 'flickery' failure mode in my old HP8405A vector voltmeter.

...
I just used BC547B parts to get it working but I would like to find the correct parts at some point. So I'm interested if you find what these parts are!

Very good pointers, thanks!

I found an on-hand transistor with good enough specs, swapped it in there (for the Q908), and the flickering remains. I'll replace the remaining transistors in the LED segment driver, just to see if that solves the problem. If not, we must have different issues.

[edavid]

I believe 1854-0071 = 2N3704

[dlucy67]

I've replaced all the LED driver related transistors with good equivalents, but I'm still getting getting the flickering and the entire range of units LEDs at lit, although dimly, at the same time.