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New toy for the workshop! HP 54600a

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Lloyd
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Just taken delivery of a new piece of test equipment, well, new to me! It’s a HP 54600A 100Mhz scope, I’ve had my eye on one of these for a while, there are 2 where I work still in daily use!

This particular one has been doing the rounds on eBay for god knows how long, it was on for £140, so I stuck it on my watch list, and eBay does this weird thing where it’ll send me a message saying ‘the seller has sent you a special offer of ##% off (item name..)’, which can be rather handy! It had been dropped to £112, so I stuck in a very cheeky counter offer of £85, expecting to be told to bog off, but surprisingly it was accepted! It arrived today, complete with a cover for the front, pouch on top, instructions, an X10 probe and some other bits.

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BE27E3B9 A890 4AD1 A508 7B8F3BD72B4B
78E554C3 22D4 4FC5 95FF 4D9D34B1C0F0

Although it was sold as working, I doubt it had been switched on in a long time, first power up produced a line bouncing up and down in the middle of the screen, not good! A few more power cycles and it suddenly gave the HP logo and start up screen, but only an inch tall, and when the graticule appeared there was an error message about ‘illegal operation’ and no buttons did anything. Another power cycle, and it started up properly, with both traces responding! So it’s looking good so far, although I’ve not tried any inputs yet.

There is a PAT test sticker on top with a date of August 1996! So it’s probably been out of use for a very long time. The squished display is a known fault, apparently caused by tired caps on the display PCB, so that’ll be the first thing to tackle, as well as giving the whole thing a damn good clean.

Why did I want one of these? Purely because I liked the ones at work, they have a nice clear display, and they seem to stand up to daily abuse with all the controls still operating well, the encoders seem to last longer than the ones in the old Tektronix TDS scopes we have lying around, and even some of the Lecroy’s have crappy encoders now too, and what’s more, it has Tetris built into it!!!! That in itself passed many boring hours on night shift!

36B5ED4E AFEA 4EB1 A01D 6652047DF901

 Regards 

Lloyd. 

 
Posted : 07/01/2022 2:53 pm
turretslug, crustytv, Mikey66 and 6 people reacted
Cathovisor
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Posted by: @lloyd

There is a PAT test sticker on top with a date of August 1996! So it’s probably been out of use for a very long time.

More likely nobody's bothered to test it.

 
Posted : 07/01/2022 3:50 pm
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Sundog
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Looks like you got a bargain. 😀 

 
Posted : 07/01/2022 5:30 pm
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Mikey66
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That's a great find. 👍 

Best regards

Mike

 
Posted : 07/01/2022 7:07 pm
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Sundog
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I'm sure it'll be a great addition to the workshop, where I'm sure you do lots of things. Do you anticipate it to be of much use for vintage TV/Radio?

 
Posted : 07/01/2022 7:56 pm
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Lloyd
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Well, it’s currently in bits! Sorted the squished display, it was an O/C cap in the vertical stages, 10uF 16V, I also changed the cap next to it which was a 1000uF 16V, it might have been ok, but I’ve changed it anyway.

There has been some burn ups on the main board, which are a bit concerning, 3 SMD tants have turned into ash, and taken themselves out of circuit, no idea what value they were, and amazingly they don’t seem to be affecting anything! All the others of the same size are marked ‘105 35k’ so 1uF 35v, unless I’ve got that wrong, so I’ll probably order a load of them and change every single one on the board, as if 3 have gone, then the rest are suspect too, and I don’t want them damaging anything irreplaceable on the main board! I had a similar problem with an Apple MacBook Pro, which went off with a bang one night when plugged in to charge, that was a couple of tants across a 12V rail going short, recovered that one with a load of new caps and a fuse.

So now I’m on to the cleaning, surprisingly it’s not that dirty inside! Just a few con webs, and it looks like some liquid may have got in at the very back, it didn’t get on any of the boards, just the metal chassis and some of the cables, there’s a bit of mould growing on some of the cables but nothing terrible.

 

 

C10B8174 16ED 4004 8973 42F5BB056C99
6D353652 39FC 407B 9664 2D1A148048F2
1AC5275F 6FCC 44CC A843 978E07B179DB
DFF5FB22 7078 48B0 877F B9A4C80B8BB0
A5BA08A6 E811 4786 A460 BF5722E5219C

I’ve started making a video of its repair too, so I might post that somewhere eventually! 

Regards,

 Lloyd.

 

 

 
Posted : 07/01/2022 8:21 pm
Lloyd
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@sundog 

I've not really given it much thought! I hope it'll be of use, so long as it displays waveforms correctly from TV and radio circuitry, it should be of use, the inputs are rated up to 400V, so should be good for probing around video stages. I'm sure you can set it to give an actual frequency readout on screen, as well as using the cursors for taking exact measurements (saves me having to do any maths, which I'm crap at!!).

Regards,

lloyd

 
Posted : 07/01/2022 8:28 pm
Sundog
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@lloyd Great you've got it fully working now.

Re-reading my previous comment makes me sound cynical, that was not my intention at all. I'm just reminded of how infrequently the 'scope was pulled out from under the bench to fix faults, in the day.

But the landscape is different now. The 'scopes are so much better now with fast warm-up (boot-up) time and bright displays that trigger nicely. Also faults are more diverse now, sometimes requiring rather more skill to solve, than in the equipment's heyday. And they don't take up half the bench!

 
Posted : 07/01/2022 8:43 pm
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Nuvistor
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@sundog 

Surprising how we all work in different ways.

I used the scope a lot in the 70’s for bench work, took it on calls at times if I thought it would save a 26 inch CTV being taken back to the workshop. It was on the bench and switched on if I was in the the workshop. Even take quick DC readings while chasing waveforms, all in one piece of test equipment. it was a decent Telequipment dual beam  15Mhz bandwidth unit. Used it doing my radio trades exam 1968 or 69, chasing no video, the invigilator walked past and did a double take when he saw it displaying the video IF signal on the final IF anode, fault was an o/c detector diode.

If accurate voltage reading were required then of course the multimeter was used.

Happy days.

Frank

 
Posted : 07/01/2022 9:25 pm
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Sundog
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@nuvistor I never did take a scope out on the road for TV servicing, my tools and spares boxes were heavy enough!

I fully agree about fixing it in the field where possible - and on a single call. Where the other engineers would book a return call with a replacement UHF tuner, I ensured I had a stock of AF139 and BF180 front-end transistors. I was quite comfortable with RF as I was active on 70cm and 23cm amateur bands with entirely home constructed equipment.

 

Funnily enough our dialogue has reminded me of an "scope event" from the distant past:

At a part time evening job I had a hybrid Pye monochrome TV to repair. I can’t remember the model. Even though the business had a CRT re-gunning facility in the basement, they had no scope. After quite a bit of measurements I declared that I couldn’t fix this without one.

The business proprietor asked what the problem was and I said that the frame timebase was unlocked. Then obviously the fault is in the sync separator or the timebase he said.

The sync separator voltages were a bit off but I’d checked all the component values and nothing seemed awry.

Reluctantly a scope was borrowed from a friendly business and I started probing. The demodulated video had a distorted and low amplitude vertical sync period. How could this happen?

My probe slipped onto another track and suddenly there was a pulse at field rate. Checking the schematic, this was the AGC line. Surely there must be some kind of time-constant to prevent this from happening? Indeed there was. A capacitor whose task was to help integrate had become disconnected.

The manager still wouldn’t buy a scope.

 

 
Posted : 08/01/2022 6:03 pm
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Lloyd
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It’s funny how boss’s don’t like buying useful equipment for their staff! Where I work, we have just been given the go ahead to spend £1500 on new soldering equipment! So that’s gone on new JBC soldering stations, we also needed some new VNA’s last year, so we got some new Keysight ones at £16k each, sadly I didn’t get one, so I’m stuck with an old one, which is ok, it’s better than the ones that we had before (of which I blew up 7 of them!) which were Anritsu ones, that apparently cost £60k! Those Anritsu’s are all on their last legs now, power supply faults keep popping up, not to mention the other favourite ‘ warming up - please wait’ appearing on the screen, and never going away, that one also means certain death for it! The repair bills are crazy, I was told they wanted £10k to fix the last one, which was declined. 

I did have to get the scope out recently just to set up a TV, it called for it in the manual of a Bang and olufsen MX2000, where I had to set the green by looking for an 85V peak to peak waveform on one of the test points, I did try cheating with a multimeter, but it didn’t work! I do already have a few scopes kicking around, the main workhorse being a Hameg 203-7, it doesn’t have any fancy features! But it did ok for that particular instance. 

Regards,

 Lloyd 

 
Posted : 09/01/2022 9:53 am
Nuvistor
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@sundog 

The only tuner I didn’t have any success repairing was the 1043 varactor, in the finish I bought a couple new and then sent the faulty ones away for repair, MCES in Manchester were excellent. They always seemed to fail intermittent, I know some had success resoldering but not me, I always had a good one on the van, it was cheaper than having call backs.

Other tuners were not a problem, usually the RF amp would be faulty after an electrical storm.

 

Frank

 
Posted : 09/01/2022 12:25 pm
Sundog
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I joined a Japanese manufacturer right after that but nothing really changes, it was repairing Sanwa and Mitsumi UHF tuners. I set up a sweep arrangement for alignment. If you inject a sawtooth into the tuning terminal and trigger a scope with it, the demodulated output shows the amplitude response. A variable frequency generator can be input to check the performance over the bands.

 
Posted : 10/01/2022 8:14 pm
Lloyd
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More fun and games with this thing, and not Tetris! Yesterday evening I went into the workshop (as I do every night, because I have no life!!) and fired it up, thought ‘why not check its calibration against my function generator!’ So dug that out of the cupboard and connected it up. It was all looking rather good for a minute or 2, then up pops a little message in the corner again ‘address error : 4e902310H’ accompanied by none of the controls responsive, the display of the waveform was still responsive though.

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So I did the usual, turn it off and back on again, but this time I was left with a blank screen, ‘oh heck, what’s happened now?!’ More power cycles didn’t bring it back either!

Earlier, over the weekend, I’d got rid of all the error messages popping up by pulling the HP-IB interface module off, and luckily this time removing it brought it back to life, I gave it a good test, and all seems well now. I think the module is probably duff, as on the start up screen it always says ‘no module installed’ even when it is. The module has one of those Dallas non volatile SRAM things in it, so I guess the internal battery has snuffed it, and probably bricked it. Never mind, I probably wouldn’t ever have used the module anyway! I might take it to work and plug it into one of the scopes there and see if it does the same thing!

 Regards 

Lloyd 

 
Posted : 11/01/2022 7:04 pm
crustytv
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Hi Lloyd,

Bummer about the fault manifesting, but equally good that you have a way out of it.

If you're anything like me, this module fault may start to bug the heck out of you, and you will just have to navigate the black-hole to investigate it further. These type of faults make for wonderful content, just look at the entertainment CuriousMarc gives us with his HP escapades.

Keep us updated on the 54600a shenanigans 👍 

p.s.

Posted by: @lloyd

Yesterday evening I went into the workshop (as I do every night, because I have no life!!)

You and me both, I woke up early this morning, my mind started chattering, no chance of getting back to sleep, so at 5am I was in mine editing CNC geometry jobs. 🙃 

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Posted : 11/01/2022 7:21 pm
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Lloyd
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Oh no, Chris! I know the feeling, waking up too damned early, and then your brain refusing to just be quiet and let you get back to sleep! I have this thing where Tuesday is always the worst day of the week, even my new boss has a name for it now, 'tired Tuesday', it's title says it all!! and it's always caused by me waking up too early! I've been following your progress with the PCB CNC, your doing great with it, I certainly couldn't do it, I don't have the patience for all the computer side of things! I remember having to use Autocad at college (20 years ago!) and it was a nightmare.. I never did get to grips with it!

I've gone into the workshop again, the scope is working well without the module, so I stuck it back on again (with the power off of course!) and immediately the scope starts playing up, blank screen on the first attempt, second attempt and it booted up then shortly afterwards showed another error message, this time a slightly funny one 'Illegal operation : OH', oh indeed!!! a bit more poking can cause errors simply by pressing on the module, which says to me it might be down to the connector, so I'm going to have a look there first, even though the connector looks clean, and the soldering looked ok.

Regards,

Lloyd.

 
Posted : 11/01/2022 8:10 pm
Lloyd
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Good news!! The module’s not dead!

I first tried cleaning the contacts in the connectors on both the module and the scope, no change, so then I reflowed the solder on the connector in the module, this got me some results! First power up after that, with just the naked board of the module connected it came up on the start up screen! 

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Bad news, a message popped up saying all the calibration data was lost, and defaults had been loaded 🙁 no idea why that would happen just from plugging the module in! Never mind, the manual shows how to run the self-calibration, and it sounds fairly easy, just need to get some BNC cables. The only noticeable effect of the lost data is that channel 1 doesn’t settle on the centre line with no input and the vertical offset set to zero, whilst channel 2 does. 

anyway, here’s some photos of the module with no case on, there’s not much in it! I also have no way of testing the other end of it, as I have no HP-IB things to plug into it! 

C4F84482 2D58 4D78 B353 363BB72600DF
FE340063 E413 4112 B6A9 5D996EFA61FF

Regards 

Lloyd 

 
Posted : 11/01/2022 10:49 pm
crustytv
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If you've not got these yet, I've just uploaded to the test equipment section of the library,

  • Interface Modules for HP 54600-Series Instruments Data Sheet.
  • HP 54600A & 01A Series Programmer for QuickC

No idea if it's of any use.

CrustyTV Television Shop: Take a virtual tour
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Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek

 
Posted : 11/01/2022 11:05 pm
Lloyd, Nuvistor, Lloyd and 3 people reacted
Lloyd
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Cheers Chris, I’ll have a look at those! 

regards,

Lloyd

 
Posted : 12/01/2022 10:25 am
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