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Old 8th Aug 2020, 5:37 pm   #1
Bufo Bill
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Default HP 180A: chances of repair?

Hi all, I have a HP180A donated by a well respected forum member. As I recall he needed some space so gave this to me halfway through repair. He had checked the CRT worked, recapped it and checked most of the components bar the diodes, I think.

That was a few years ago now.

My question is, what chance have I got of getting this to work again? The high voltages would probably give me trouble with measurement, I have an AVO 8 MK III, and a modern hand held DMM, I don't think the AVO will measure high enough and I know the DMM won't.

As we have established earlier, I am a sucker for vintage tech but I'm not trained in electronics and a bit of a greenhorn still.
So; is the project a goer or not?
Cheers from Bill.
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Old 8th Aug 2020, 7:35 pm   #2
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Default Re: HP 180A: chances of repair?

HP180A.
Well worth getting going.
The tube in these is absolutely first class, better than the comparable Tek one. I suppose that as HP came much later into making oscilloscopes, they felt they had to produce something really good.

All voltages are within range of your DVM or Avo 8 except for the tube, at 2950V and the PDA. Normally not necessary to measure the PDA at 12Kv. Either it works or it doesn't. For the 2950v, I made up a series resistor chain in a PVC tube to double the top Avo range to 5000v. Although that sounds dangerous, it is from a high impedance oscillator and with usual care should give you no worries. I and others have posted details of such probes and its calibration in the past. Under Telequipment D75/D83 I think.

The things that frequently fail are the Low Voltage power supply regulator neon tubes. (Which also affect the trigger action enough to give trouble and a very mysterious fault). I have posted alternatives for them in the past (see Philips PM3262 I think). The later HP180C/D uses a zener stabiliser and also current limiting. You will need a stock of 100ma/500ma fuses when fault finding on the HP180A/B series.
In the usual Timebase plug-in HP1821, be very careful of the tunnel diodes. It uses two 5ma and two 10ma ones. Not available anymore, but the Russian ones do just as well (GI304 and GI305). But under no circumstances measure a tunnel diode on the ohms range; you will destroy it. I and others have posted notes upon this in the past.

The later TB modules HP1825 and HP1824 use ECL trigger, similar to the HP1707 and HP1740 portable oscilloscope.
These oscilloscopes are all transistor, circa 1968. The manual quotes HP numbers. I and others have lists of the commercial equivalents. Nothing difficult, all commodity types, except for a couple of germanium high speed types 2N964/ASZ21, for which it is said Silicon can be used.
If you are stuck for these unusual parts, I may be able to help.

The manuals available on the web are limited. I have manuals for most of the main frames and most of the plug ins for all the versions of these scopes. Main frames HP180, 181, 182, 184. Y-plug in HP1801, 1802, 1803, 1804, 1805, 1807, 1808. TB plugin HP1820, 1821, 1823, 1825 all generally 50Mhz or 100Mhz. Sampling HP1810 to 1Ghz, and Spectrum Analyzers 8558 and 8559 and TDR 1815-7. Also the special wide band HP183 MF with 1830 and 1840 PI.

They are real delight to use, though showing their age in reliablility. But access and servicablity is good. I suspect they are less well known than Tek because the manuals are much more difficult to find. As you can tell, I like them.
wme_bill
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Old 8th Aug 2020, 8:02 pm   #3
Bufo Bill
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Default Re: HP 180A: chances of repair?

Wme_bill, thanks for the support, your advice is most welcome. The one thing on my side that I didn't mention is that I have a manual and circuit diagram for the 180 mainframe, so that's something. I have the HP1801 and I think the1821 as you say. Will try and get some pics up soon.
Cheers from Bill.
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Old 8th Aug 2020, 9:07 pm   #4
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Default Re: HP 180A: chances of repair?

I've used 180 family scopes for many years, and they are a delight. The trace is crisper than Tek used to give. The flood gun grat illuminator is gorgeous.

Trigger setup is touchy. These scopes founded the legend that no HP scope has ever triggered on anything. This is a very useful legend... it keeps prices down.

Bill's warned you of the tunnel diodes and ohms ranges.

The other thing to be careful about can kill you, and others around you. In the 1801 Y amplifier plug-in, look on the back panel. The plate deflection drive transistors are TO-5 cased ones sitting on ceramic insulators on a bracket to heat sink them. That ceramic is Beryllia, = Beryllium Oxide. Safe as a solid. Deadly as inhaled dust. Do not risk breaking them or scraping them.

David
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Old 8th Aug 2020, 9:16 pm   #5
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Default Re: HP 180A: chances of repair?

Crikey, will definitely be taking care there then! Cheers David.
Bill.
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Old 8th Aug 2020, 10:45 pm   #6
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Default Re: HP 180A: chances of repair?

Quote:
Originally Posted by WME_bill View Post
HP180A.
The things that frequently fail are the Low Voltage power supply regulator neon tubes. (Which also affect the trigger action enough to give trouble and a very mysterious fault). I have posted alternatives for them in the past (see Philips PM3262 I think). The later HP180C/D uses a zener stabiliser and also current limiting. You will need a stock of 100ma/500ma fuses when fault finding on the HP180A/B series.
wme_bill
Do you mean to keep a stock of 300mA, 375mA & 2A fuses? that is what is fitted inside my 180A, they thoughtfully put them behind a clear plastic cover so you can see the flash when fault finding and think there goes another couple of £'s of fuses.
I've pulled the power supply board from mine as the lower value fuses (300ma/375ma) are getting expensive, just haven't got round to attempting to test it outside the scope.
The military manuals for the 180A (AN/USM-281A) on the web are much better than the rubbish scanned by Agilent (now Keysight).

I've recently acquired an early 183B (rack mount version) thankfully that appears to uses a different power supply board and appears to be working.
It came with a 1831A direct plug-in which I can't find much info on (apart from the brochures of course). I've since bought a set of 1830A/1841A plug-ins to go with it, these are supposed to be working, but were described as having switch problems.

David
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Old 9th Aug 2020, 1:35 am   #7
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Default Re: HP 180A: chances of repair?

Remember that the 183 mainframe and its plug ins 1830 and 1841 are not at all compatible with the main part of the 180 family.

These wide bandwidth scopes run very hot and were definitely less reliable than the plain 180. models. That was the cost of the wider bandwidth at the time.

David
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Old 9th Aug 2020, 7:45 am   #8
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Default Re: HP 180A: chances of repair?

Isn't there a 180A going on the forum at present, it's in a bit of a tatty state but maybe good for parts. As a relative novice I've tried fixing a few vintage scopes, it isn't too hard Bill, knock yourself up a EHT probe, pretty easy to do with some bits of PVC pipe etc, it's only a few resistors and bits and bobs.

Andy.

Edit the scope that's FS is a 182, not 180, my mistake.
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Old 9th Aug 2020, 9:11 am   #9
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Default Re: HP 180A: chances of repair?

182 is a 180 to all intents and purposes.

It takes all the same plug-ins as the 180, it just has a bigger screen and later designed power supplies.

Focus isn't as crisp as the smaller screen, though.

David
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Old 9th Aug 2020, 10:43 am   #10
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Default Re: HP 180A: chances of repair?

Just to spoil the party, I had about a dozen of these and I thought they were rubbish. Mind you, didn't think much of the Tek 7704's either, particularly the rack mount version.

It is the plug ins, the 1821 I think has a PCB fixed at an angle in the chassis, with many many wires attached to both sides of the board. Can't remember if soldered or plug in now. Then there is the cable form stretched along the edge of the board making access, or even moving the board nearly impossible. The plug in outputs are a couple of slide type contacts to the mainframe, so having an extender is near impossible.

Some were nice and had plug in tunnel diodes, some were soldered.
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Old 9th Aug 2020, 10:59 am   #11
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Default Re: HP 180A: chances of repair?

Bill, as David says, (He's the Forum's respected Guru on HP gear), the EHT voltage can be lethal. With any 'scope its best to be safe than sorry. Most Oscilloscope & TV enthusiasts get their hand on a decent 2nd hand EHT Voltmeter such as the Rank Bush Murphy 30KV model. Mine, tatty cosmetically, was picked up for something like a tenner, a few years back, and is still working fine.
I've just recently recalled working on 180A's back in the 60's, and I vaguely seem to remember that they had a problem with Ga diodes in the LV PSU circuitry, and that mod kits were bought out for RAF versions.
There must be heaps of experienced Forum guys in the West Midlands(my old stomping ground) who could possibly mentor you in your project, and advise on obtaining a decent 2nd hand EHT Voltmeter.
Back in my Cosford days we just had a lovely big black bakelite AVO EHT Probe for working on 'scopes, (OH I , and a pair of super thick rubber gloves) . Plus all work surfaces & close flooring were covered in "EHT Proof" black rubber matting.

Regards, David
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Old 9th Aug 2020, 11:34 am   #12
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Default Re: HP 180A: chances of repair?

With an EHT probe, whether home-made, bought from a shop, new or second-hand the first thing you do with it is to ry to measure a known high voltage. Make sure that the meter you use is on the actual range you're going to use when measuring the full unknown voltage...... This is critically important because some voltmeters change input impedance on different ranges. Not all do, but some.... just enough to cause confusion. This can cause a sudden tenfold change in the scaling factor of your probe which will definitely send you off on a wild goose chase. Autoranging DMMs can go batty when this happens.

So get to know your EHT probe, get to know it with the meter you choose to use with it, and then stick to that meter.

Keep your EHT probe clean and scrupulously dry

Really good EHT probes have a protective ground connection and some form of voltage limiter to protect the voltmeter often with a ground resistor.

In simple ones, if the voltmeter connection plug comes out, it goes to full EHT voltage, theough via a big series resistor. Id the voltmeter ground comes loose, the voltmeter etc all floats at full EHT. Bet the voltmeter insulation isn't rated for THAT!

Don't be scared.

I did these things as a thirteen year old building my first scopes and somehow survived (idiot's luck!) No guidance, but I had to work them out for myself.

Oh, those scopes i did had mains derived EHT, something that really is deadly and scares the bejasus out of early telly people.

Anyway, an HP 180 is:

A) very fixable compared to later models
B) well worth fixing. Not as a financial concern, but for wht it can do for you.

David
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Old 9th Aug 2020, 1:17 pm   #13
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Default Re: HP 180A: chances of repair?

Quote:
Originally Posted by Radio Wrangler View Post
Remember that the 183 mainframe and its plug ins 1830 and 1841 are not at all compatible with the main part of the 180 family.

These wide bandwidth scopes run very hot and were definitely less reliable than the plain 180. models. That was the cost of the wider bandwidth at the time.

David

Thanks, I'm aware that the higher bandwidth 183x & 184x plug-ins aren't usable with the 180A. The 183B covers are full of holes to help with cooling and it also has a small fan fitted at the back, something the 180A doesn't need. I know some people don't like test gear with fans.

David
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Old 9th Aug 2020, 1:28 pm   #14
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Default Re: HP 180A: chances of repair?

Quote:
Originally Posted by woodchips View Post
Just to spoil the party, I had about a dozen of these and I thought they were rubbish. Mind you, didn't think much of the Tek 7704's either, particularly the rack mount version.

It is the plug ins, the 1821 I think has a PCB fixed at an angle in the chassis, with many many wires attached to both sides of the board. Can't remember if soldered or plug in now. Then there is the cable form stretched along the edge of the board making access, or even moving the board nearly impossible. The plug in outputs are a couple of slide type contacts to the mainframe, so having an extender is near impossible.

Some were nice and had plug in tunnel diodes, some were soldered.
What did you not like about them apart from the servicing issues you mention?
Some of the 1821A plug-ins have the wiring soldered to the boards, others have individual connectors & pins.
HP did recommend fitting sockets if a tunnel diode needed replacing, to help prevent damage from soldering.

David
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Old 9th Aug 2020, 1:42 pm   #15
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Default Re: HP 180A: chances of repair?

Quote:
Originally Posted by David Simpson View Post
I've just recently recalled working on 180A's back in the 60's, and I vaguely seem to remember that they had a problem with Ga diodes in the LV PSU circuitry, and that mod kits were bought out for RAF versions.
Regards, David
That's interesting to know, mine isn't one of the oldest as the power supply regulator board is a Rev C version. The blown apart transistor has already been changed along with a failed 2N3055 pass transistor. I hoping I can't get it working again as the scope is labelled as having the less common P7 CRT.

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Old 9th Aug 2020, 2:18 pm   #16
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Default Re: HP 180A: chances of repair?

P7 phosphor was the option of choice for a frame to be mostly used with a spectrum analyser plug-in. EG 8558A

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Old 9th Aug 2020, 4:11 pm   #17
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Default Re: HP 180A: chances of repair?

I was sorry to read that Woodchips didn't like his dozen 180A's. To me, having initially worked on Hartley 13A's, then enjoyed working on their replacement - CT436's,( but they were still on the heavy side), it was a joy to work on 180A's. Plug-in modules being a new experience to me, apart from ARC52. But this was all 50 odd years ago. Some years back, a VMARS chum bought a CT436 at a ARS junk sale for £5 & gave it to me. Still works fine, & has kept in cal.
So Bill, keep working on your 180A & enjoy it. It was once a SOTA compact trend-setter.

Regards, David
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Old 9th Aug 2020, 8:45 pm   #18
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Default Re: HP 180A: chances of repair?

Quote:
Originally Posted by Radio Wrangler View Post
P7 phosphor was the option of choice for a frame to be mostly used with a spectrum analyser plug-in. EG 8558A

David
My 180A with P7 option dates from around 1969, this predates the spectrum analyser plug-ins. The only spectrum analysers in the 1969 catalog are the 140/141 series with 8553/8552 plug-ins and the 851/8551.
I can just about read the part number on the CRT (5083-0932), this is not mentioned in the manual I have, the 180C/D manual has different part numbers for the CRT's (but not the one I have).
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It was built at the South Queensferry site (U pre-fix on SN plate).
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Old 9th Aug 2020, 8:53 pm   #19
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Default Re: HP 180A: chances of repair?

Some more pictures of the boards in my 180A, all of which have connectors to help with servicing, I have noted some on the wiring colours have faded (same thing has happened in my 606B), I made notes when pulling out the LV regulator board.
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And the fuse holders, it keeps blowing both the 300mA & 375mA fuses at the moment.
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David
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Old 9th Aug 2020, 9:05 pm   #20
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Angry Re: HP 180A: chances of repair?

Many years ago I owned a 182 'scope: excellent machine. Unfortunately, switched it one day and no trace. Reason: no EHT. Reason: failure of the HV transformer. Obtained a price from HP for a replacement xfmr.: cost was well into the £hundeds. Sadly, that condemned it to the scrap pile; yes, tears were shed. At that time, was one of the best 'scopes I had ever used - and much better than Tek. 'equivalents'.

Al.
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