HP3336 repair (part identification)

Hi

My HP3336 display shows "OSC. Fail" :-(
One thing may be clear: No chance without a manual, but i have a part
in suspicion. A linear IC numbered "1826-00021" on the upper left
board, that i shorted :-( while changing the fan.

What is it ? I cannot find anything about it.


Andreas

 

[Dan Rae]

LM310H



Zerogunner@gmx.de wrote:

Hi

My HP3336 display shows "OSC. Fail" :-(
One thing may be clear: No chance without a manual, but i have a part
in suspicion. A linear IC numbered "1826-00021" on the upper left
board, that i shorted :-( while changing the fan.

What is it ? I cannot find anything about it.


Andreas

 

[Winfield Hill]

Dan Rae wrote...

LM310H

A true Blast from the Past.

Further info: The LM310H was a voltage-follower IC in a
8-pin metal can, with a 20MHz f_T and a 30V/us slew rate,
which was very good for its time, when ICs did not have
high-speed PNP transistors available. The LM310 used an
elegant NPN-only signal-pathway trick, possible only in
voltage followers.

The LM310 operated from +/-15V supplies and featured a low
input bias current for its time, 2nA, using super-beta BJT
input transistors; at 125C the LM110 bias was only 10nA.
It had a modest 2.5mV offset voltage (trim on pins 1 and
8, wiper to Vcc on pin 7). The LM310 used standard opamp
pins, but no external connection to pin 2 (the follower
connections were internal). It had a class A output stage
with 2mA sink current, and pin 5 was a "booster" available
to double this current. Zout = 0.75 ohms + 2.3uH.

The LM310 replaced NSC's older LM302 voltage-follower IC.
The LM310 was 2nd-sourced by TI, Intersil, AMD, etc., but
they're all gone now. It can be replaced with a suitable
high-speed JFET opamp, such as an old Analog Devices AD845
or the faster AD825 (most LM310 replacement candidates have
less than its 20MHz -3dB bandwidth).

Thanks,
- Win

whill_at_picovolt-dot-com

 

[Walter Harley]

"Winfield Hill" <Winfield_member@newsguy.com> wrote in message
news:c3p8ij01qlq@drn.newsguy.com...

Zout = 0.75 ohms + 2.3uH.

Win, what makes for such a high inductance? There aren't any inductors in
there on purpose, I presume; and I would think that the leads only amount to
a couple of nH, at least modeling them as straight wires. In big-picture
terms the current goes in the Vcc or Vee lead, maybe it makes one or two
loops on the chip, and goes out the output, so I could think of it as an
air-core inductor (ignoring the steel TO5 case, maybe that's a bad idea)
with d ~= 0.1" and n = 2 turns; still only get a small number of nH.

Is the "inductance" actually just a rising resistance with frequency, due to
the diminishing amount of gain and thus of feedback? That is, is this just
"notional" inductance, or is it actually storing energy (or behaving as if
it were, like a gyrator)?