HP 5370B - Page 1
Forum section: electronics / repair

author: cncjerry
author_rank: Unknown
timestamp: February 26, 2024, 07:37:36 pm
content: I bought this 5370B for a great price and it reinvigorated my love for time-nut stuff. Almost cost me my life as I missed the top step of 23, outside, hard wooden, stairs going down to my office. Nothing broken, just torn... Do you believe I hit three times? Actually rolled and was in the air again. 911, ambulance, the whole thing. 2nd time I fell on those stairs, my wife is trying to kill me.Anyway, the 5370B was working perfectly. I shut it off and it wouldn't power up. Fans run. Investigation leads me to the 10V reference. Looks like an HP part. The HP part is LH0070-1H. It has 16V DC coming in with ground and very little coming out. That feeds the opamps that turn on the regulators. All voltages are then referenced to this 10V. Without the 10V, nothing, and it is held at zero until power is applied, then the 10V comes up and that brings up the regulated voltages. The unregulated voltages are fine. I pulled out the small blue tantalums on the board, including C5, they all measure fine, no change. Resistance to ground there without the caps is 7.7K.I have 10V standards, I don't know how much current they can deliver.Thoughts? I was thinking of pulling it out, putting 10V on that line, current controlled, to see if she powers up.ThanksJerry

author: Dr. Frank
author_rank: Super Contributor
timestamp: February 26, 2024, 07:58:07 pm
content: You may pull out the supply card and feed the circuit with the intended voltage, to see outside, if the LH0070 is ok.I think so, as I got a 198x 5370B as well, and the semiconductor components are extremely durable.Recently, one tantalum shorted and shut down the oscillator board, and nothing else worked , due to lack of μP clock.What's the display doing?

author: KE5FX
author_rank: Super Contributor
timestamp: February 26, 2024, 07:58:33 pm
content: Ouch.Watch your step, falls are no joke. That's how we lost Barrie Gilbert (edited for spelling).Makes sense to feed it an external 10V source and see what happens, assuming you can't test the LH0070 by powering it up with no load. ADR01 could be a good replacement, given what the brokers are asking for the LH0070.

author: cncjerry
author_rank: Unknown
timestamp: February 26, 2024, 09:23:05 pm
content: Falls, yes, I had a close one. Big mistake was just not falling. I tried to run my feet back under myself as I was going forward. Big mistake as I accelerated, hit, rolled, flew, hit, rolled slid, smacked my face on the bottom stair & deck. I had enough time to think, "when is this going to end?!?"Anyway, I lifted the output of the 10V reverence, applied my own, and everything came up. I found 16 of them on ebay for $15.I hope the other 10 boxes I've turned on lately are so simple. I wasn't in the lab for a while and it seemed like everything was pissed at me:1) 5335 counter threw error 4 after power cycle;2) 3325 has offset issues;3) 3336 I got working, had a loose power cable;4) TD-784 scope the screen is rolling and I love that shutter plane display;5) TDS-3054 scope (recovered but needs to stay plugged in),6) 3586-a, 3586-b, 3596-c all have power issues, aren't coming up or partially;7) 4375(?) LCR, acting weird, probably powerand oh, a 5371 that I powered on just to hear the jet engine fan, shut off after 5 minutes and that was it. I have two, one with a blow H/V supply so I can swap that in, but why? Haven't used it.Someone will invariably say, "should have brought them up on a variac" but I think that only works with really old paper caps, could be wrong. So I have my future retirement all setup.It's been a tough month, plus my wife got COVID and with my separated ribs, if I had to cough, it would have been hell on earth.Thanks for the input and reading the back story, who was Barry Gilbert?Jerryp.s: anyone know if that reference is used in any other HP gear? LH0070? Maybe one of the above?

author: KE5FX
author_rank: Super Contributor
timestamp: February 26, 2024, 10:23:33 pm
content: Quote from: cncjerry on February 26, 2024, 09:23:05 pmBarrie was the 'G' in 'MC1496G.'TheWikipediaarticle sells him short; he was more or less a Renaissance man. Losing him on the heels of Jim Williams and Bob Peasewas a real bummer, so you don't want to follow in his literal footsteps. (I understand that he died in a fall at home but I never heard any actual details.)

author: cncjerry
author_rank: Unknown
timestamp: February 26, 2024, 11:58:37 pm
content: I can't get the voltage ref for a week or so and would like to have this box. I have two standards handy, but I don't want to modify anything. They both take a pair of 9v batteries. I have 16.2 available inside the 5370b that feeds the reference that is in there. I also have a bunch of LM399's around but I can't find a decent opamp to go with it in my stash. I have other calibrators but the way things have been failing, I hate to turn them on without going over them completely. This think failed at the worst time.ThanksJerry

author: cncjerry
author_rank: Unknown
timestamp: February 27, 2024, 03:55:36 am
content: I looked at using the same 16.2V for my voltage reference as used for the original in the 5370. Issue is they start with 20v and use a 315ohm dropping resistor then a 16.2V zener diode as a regulator. As soon as I attach my spare 10V reference, the 16.2V drops to an unregulated 8.4V. So I guess my reference board is drawing around 25ma. I can adjust the value of the 315ohm resistor but I don't like doing too much surgery on these old boards as the pads lift. I guess I'm going to have to let it sit until the new reference get's here.Jerry

author: cncjerry
author_rank: Unknown
timestamp: February 27, 2024, 05:36:10 am
content: John, I was able to get some of the Lh0070-1H parts, the add read 16 of them, I'll see when they get here. I'll also look at the ADR01. I have a bunch of LM399s and I thought I would build a little circuit card and put that in. I can't remember what is in a 3457a, I thought that had a little card in it with a lm399. I have a pair of them and can sacrifice one until the other part gets here.