Electronics > Metrology

10V reference needed from my box

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cncjerry:
Hi, I have an HP 5370b that uses 10V ref from an LH0070-1h.  The LH0070 failed and the box won't turn on.  5370b references all voltages to that 10V.  If I apply 10V, the box comes up.  I have parts coming but they can take a while.  I've tested a couple of refs I have, and the issue is the 16.2v regulated that is on that board, cant take much current draw as the 16.2v zener is fed by 315ohm resistor.  I don't want to do much surgery on the board.   The LH0070-1h is a .02% device.  I can live with .1% for now.  I can use a couple of 9v batteries to get ~18V but would need milliamp current draw again.

Here's what I have on-hand:

1) Qty 5 LM399H.
2) a reference module from an HP 3455 volt meter.  This is the A11 board and I think that is an LM399 on it.  It uses 29.5V.  I've tested it and it's stable but I don't have 29.5V handy in the 5370.  Just +/-15, 5.4 and 5v.
3) I have some opamps around but not an lt1001 as in the LM399 reference design I've seen. I have handy: LT1007, LMH6703, lt1677, AD706, op176(?), op(27), TL5532, TL5534, TL082, and probably others.  there is an lm725H on the hp 3455 reference board.

I have lots of  precision resistors, etc.  If I had to drop the power, I have 3045 regulators handy.

So can I put something together with that above or do I wait?

Thanks

Jerry

Kleinstein:
One could use the LM399 reference without the heater. The reference it self can get away with rather low low current. For the amplifier the AD706 should be OK.
The LT1007 / OP27 and LT1677 are similar and should also work, if the resistors for the gain from 7 to 10 V are relatively low value.
The heater for the LM399 needs quite some current and may thus not be feasible at low power.

David Hess:

--- Quote from: cncjerry on March 01, 2024, 09:42:55 pm ---I've tested a couple of refs I have, and the issue is the 16.2v regulated that is on that board, cant take much current draw as the 16.2v zener is fed by 315ohm resistor.
--- End quote ---

Are no other supply voltage available?


--- Quote ---I don't want to do much surgery on the board.   The LH0070-1h is a .02% device.  I can live with .1% for now.  I can use a couple of 9v batteries to get ~18V but would need milliamp current draw again.

Here's what I have on-hand:

1) Qty 5 LM399H.
2) a reference module from an HP 3455 volt meter.  This is the A11 board and I think that is an LM399 on it.  It uses 29.5V.  I've tested it and it's stable but I don't have 29.5V handy in the 5370.  Just +/-15, 5.4 and 5v.
3) I have some opamps around but not an lt1001 as in the LM399 reference design I've seen. I have handy: LT1007, LMH6703, lt1677, AD706, op176(?), op(27), TL5532, TL5534, TL082, and probably others.  there is an lm725H on the hp 3455 reference board.

I have lots of  precision resistors, etc.  If I had to drop the power, I have 3045 regulators handy.
--- End quote ---

Do you have any trimmer potentiometers?

An LT1007 or OP27 can often replace an LT1001 directly.

I might just divide the regulated 16.2 volts down to 10 volts and buffer it with an operational amplifier follower.

cncjerry:
16.2V is available all the time, regulated with a 16.2V zener off a 315r dropping resistor.  The other voltages come up when the 10v reference comes up.  Interesting approach to turning on power.  I have trimmers of all types, 10turn type.  I have capacitors of all types. The opamps I mentioned I believe are mostly single rail type.  I also have a 2.5V reference smd device, it is either AD or LT.  I'll post the number.

If the heater on the LM399 takes more than 10ma then that would probably knock the zener out of regulation.

cncjerry:
one other thing, I tried to use the regulated 16.2 dropped down by the lt3045 but it wasn't very stable.  Setting it precisely was very difficult, I would have to rig up a two stage resistance for the set pin.

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