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Old 12th Apr 2019, 9:55 am   #1
MrBungle
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Default HP 180A scopes - anything I need to know?

Potentially got my hands on an HP180A scope in good condition with 100MHz vertical plugin.

Does anyone know of any gotchas with these or preventative maintenance steps I need to take to make sure it's not going to explode on me?
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Old 12th Apr 2019, 2:33 pm   #2
Humber888
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Default Re: HP 180A scopes - anything I need to know?

I've got a couple of 182C and 184A 'scopes and have worked on the odd 180C. These are quite straight forward and generally reliable with a nice trace. You shouldn't run into any Rifa type problems. IIRC the 180A's PSU may use a neon type voltage reference rather than a zener. If so these sometimes get a bit iffy with age.

If your version uses a leaf contact type switch for the beam finder, rather than the later conventional push button, it is worth giving it a dose of switch cleaner. I spent a happy hour tracing why the trace wasn't central only to find the beam finder intermittent.

Be aware that one of the 100MHz vertical plug-ins uses custom ICs to drive the final deflection transistors and these are very hard to replace if duff.

Finally, if by any chance the unit still has its original plastic handle, don't lift the 'scope with it. They were solid plastic which hardened and broke upon applying stress. Normally a 180, etc, of this vintage just has a missing handle or sometimes a replacement strap with a steel band running through it for strength.

Mike
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Old 12th Apr 2019, 4:41 pm   #3
MrBungle
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Default Re: HP 180A scopes - anything I need to know?

Thanks for the tips. Much appreciated. Will bare these in mind when I go and look at it.

This is a relatively early unit apparently so lots of gotchas that will keep me busy (and probably happy!)
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Old 13th Apr 2019, 2:16 pm   #4
WME_bill
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Default Re: HP 180A scopes - anything I need to know?

Mr Bungle,
These are nice scopes with a particularly good tube.
The trigger is good but must be set up properly.
The usual 50Mhz timebase (1821) plug-in uses tunnel diodes. See notes elsewhere on the Forum. But particularly do not try testing with an ohmmeter/Avo. It will destroy them.
The 100Mhz TB (1825) uses ECL for the trigger, which again must be set up carefully. Remains stable provided the power rails are absolutely stable.

The HP180A main frame and also HP181A storage version use little stabilizer neons for each rail, which with age begin to fluctuate enough to stop the trigger working, however much you re-set it. This model also has no overload limitation other than blowing a fuse. So keep a stock of fuses to hand when you start fault finding.
The HP180C and 180D use the now usual zener differential transistor pair on one rail, and all the other rails draw off it. Much better, and it also has electronic overload protection.
I did consider modifying my HP180A power supply to the 180C/D version, but it effectively means a new board.

However Philips suggest on their PM3262/PM3266 family of scopes a modification to replace such neons with a zener/transistor combination. It can fit on the board.
Circuit attached. It is preferable to using a high voltage zener as the temperature coefficient is vastly better and comparable to the neon. Neons replaced from GI,Hivac or Mullard are: the 83v ones V83R4,Z82R7, ZZ1000,8228. For 103v - V103R2. For 116v - V116R2.
You have to change the resistor chain which feeds the transistor base for each voltage, as noted.

Other points. As Humber888 says, the handle is "famous". Replace with a metal strap at once.
All HP scopes seem to use discrete semiconductors which can be replaced up to the 75Mhz models. (PI 1801,PI 1808, 1804 4 channel and scope HP1707).
The 100Mhz models (PI 1805,1809 4channel, scopes HP1740, HP1741) use integrated circuits which are quite irreplaceable.
I have a note of the commercial equivalents of the transistors in these scopes. There is one germanium type as well, usual vhf switching, for which comparable can be found.
For a design introduced in 1966, they seem reliable. Most parts are commodity and similar still are available.
The HP182A is the large screen version and the the HP 184A is the fast storage. Both use the later 180C/D zener power supply.
wme_Bill
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Old 13th Apr 2019, 3:57 pm   #5
MrBungle
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Default Re: HP 180A scopes - anything I need to know?

Thank you for the extensive reply and information. Much appreciated. I will sit down and digest this later today. I’m doing a swapsie for this with a Racal counter tomorrow evening so fingers crossed.
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Old 16th Apr 2019, 1:06 am   #6
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Default Re: HP 180A scopes - anything I need to know?

I've got one of these scopes. It's been in bits down on the floor of the workshop for probably a couple of years now, with all the covers off and some components removed. seeing this thread a few days ago has prompted me to dig it out and take it outside onto the paving to blow out all the muck and dust that's dropped into it using my air blower and magic blowing wand. It looks like I haven't lost any of the parts or the case screws, so I'm going to put it back together and see what happens!
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Old 16th Apr 2019, 3:15 am   #7
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Default Re: HP 180A scopes - anything I need to know?

In the plain old 50MHz Y-amp plug-in, the output transistors are mounted on four white ceramic insulators sitting on a bracket off the rear panel.

BEWARE. That ceramic is beryllia, BeO. Ten micrograms of inhaled beryllia dust is reckoned to have a 50% probability of fatality. Do not drill, crack, abrade, etch or otherwise damage these things.

Small pieces of this stuff are common in RF power transistors, but are sealed inside packages if you're lucky, but may be an exposed part of the package.

David
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Old 16th Apr 2019, 8:37 am   #8
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Default Re: HP 180A scopes - anything I need to know?

Yeah know all about BeO stuff. The scary thing is it takes a long time to kill you. Weeks. Basically like getting stage 4 sarcoidosis instantly.

Many years ago I stopped colleague making a keyring out of an RF PA transistor once. Was literally about to drill a hole in it. The funny thing is that he was a design engineer and I was his IT support guy!

Still haven't gone to see it yet. Rescheduled next Sunday.
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Old 16th Apr 2019, 5:59 pm   #9
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Default Re: HP 180A scopes - anything I need to know?

Dear Mr Bungle & Radio Wrangler,

Just to give you, and others, some reassure re the beryllium oxide issue you have been discussing, just in case they come into contact with similar items.

Acute beryllium disease is akin to a chemical pneumonitis and more often associated with inhalation of fumes or contact with soluble beryllium compounds. It requires a relatively high level of exposure to the extent that it has only be reported from beryllium manufacturing workers and even then has been extremely rare since the end of the 1950s with better occupational exposure controls.

Removal from exposure with supportive care is usually curative for acute disease. Fatalities have occurred and reported to be ~10% of cases in the reported 1950s foundry incidents. I'd expect us to do a lot better than that now if an acute case occurred.

Chronic beryllium disease (CBD) is the big problem, and that comes from repeated exposure to levels (usually) above the occupational health limits. These limits have been progressively lowered over the last 50 years to try to eliminate any cases.

CBD is an unusual disease as it is immune mediated and linked to a known gene variant. An inflammatory response in the lungs creates a granulomatous response (Mr Bungle this can be mistaken for sarcoidosis).

You are quite correct, therefore, to discourage any machining of beryllium materials outside of a controlled process area; this includes beryllium metal, beryllium alloys and beryllium ceramics (beryllium oxide).

However, intact beryllium ceramic insulators are perfectly safe to handle, and gross damage is unlikely to yield particles of a size that can be effectively inhaled; therefore risk from such items properly handled is very remote.

Hope that helps to set your minds at rest if you do come across any of these items.

Nick.
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Old 16th Apr 2019, 6:48 pm   #10
MrBungle
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Default Re: HP 180A scopes - anything I need to know?

Thanks for this - much appreciated.
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Old 16th Apr 2019, 11:13 pm   #11
Radio Wrangler
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Default Re: HP 180A scopes - anything I need to know?

Thanks.

I understand one of the worst incidents in electronics came after someone used abrasive coated paper to sand the surface of some large berylia-insulated transmitting valves in order to clean off some surface contamination. This released beryllia dust into the atmosphere of a building

David
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Old 16th Apr 2019, 11:27 pm   #12
MrBungle
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Default Re: HP 180A scopes - anything I need to know?

That really doesn't surprise me. I hate to think how you'd decontaminate that.

The HP 180A is unfortunately off. I got sight of it today in a photograph and it has been dropped on the front at some point. The chassis is clearly bent. Don't fancy my chances with it as it's a good 150 mile round trip. Also don't want to give up my counter for it.
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Old 17th Apr 2019, 8:06 am   #13
Radio Wrangler
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Default Re: HP 180A scopes - anything I need to know?

I had a clear-out a couple of years ago and gave my 180 scope collection to a young guy at work... including a spectrum analyser plug-in. So I can't help out, I'm afraid. He left about a year ago to go do a PhD.

David
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Old 17th Apr 2019, 10:29 pm   #14
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Default Re: HP 180A scopes - anything I need to know?

As only too typical with things of this nature, watch for high value resistors under high potential stress being not quite what they were- there have been several differing detail iterations of carcase PSU design, my on-the-way-to-the-granulator rescue dog had 5x 6M series resistors as EHT feedback (one other version has a single big 30M resistor here), one of these had gone O/C, resulting in a small, bright, hummy trace as the EHT power oscillator reached for the giga-volt gong using the ripply raw DC rail. A replacement VR37 restored normality, EHT rectifier and PDA multiplier seem none-the-worse for their ordeal.
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