Scope purchase advice

[WaveyDipole]

Thanks Bill. I haven't given up on that telequipment D61a quite yet, but I think you were right from the start. I will need a scope to see what is going on in there. I've spent hours on it already and michael might be right about it being a calibration issue. On the other hand I don't want to go there until I'm sure its not a fault, so a bit chicken and egg I guess.

Anyway I thought if I get another one I could always sell the D61a if need be (spares or repairs if I can't get it going). As it happens, I posted in the wanted section earlier and when I got home I had a couple of replies. One of them was an offer from a member who has a working Gould/Advance OS3500 for a very reasonable price, complete with power cable and probes. I will probably have this off him. There's a working Hameg 604 coming up on eBay as well with just a few hours to go, so I'm keeping both options open. There is also a Telequipment D66a as a fallback, but then there's also that once bitten feeling as well.....

I wasn't aware that all those model of Teks had tunnel diodes, nor did I realise that the A and B versions had ICs. According to Wikipeadia, some tunnel diodes are still being manufactured, although I guess matching the spec migh be an issue. However, I had a look on eBay and found a couple listed (1N3716 and AEY25) - at £10 each! I suppose that's a small price to pay for a nuclear radiation proof component!

[Radio Wrangler]

The HP1740 uses (then) fast logic, not tunnel diodes. They made a big thing of it after the fun with the tunnel diode in the HP1821 timebase plug-in for the predecessor 180 series.

The 1740 does have custom microcircuitry in some critical places.

http://www.hpl.hp.com/hpjournal/pdfs...Fs/1975-12.pdf

and the details of the very fast ECL trigger IC is in the article on the 275MHz member of the family.

Interesting to see that it uses the same CRT as the 180a... I've got a spare one of those...


David

[Radio Wrangler]

Oh, the Cossor CDU150 is rather a nice 2 channel scope. 35MHz. Forget the dual timebase, it's a bit limited so count it as a single timebase. All regular through-hole components, manuals available. Cheap as chips, though none inside. Tough as well.

One thing... Avoid analogue storage scopes. They aren't suited to general use. Specialised beasties for special occasions, and rather easy to damage when used in 'normal' mode.

David

[WME_bill]

WaveyDipole. Thanks to RadioWrangler for reminding me about the Cossor CDU150. Nice scope, no IC's nor tunnel diodes. Everything on separate PCB panels, so easy to service. Meets all my criteria. The Cossor 4000 and CDU120 are virtually the same as the CDU150, which was the military specification version.
The trigger delay, instead of a second TB was used by most makers around 1970. Awkward to use, so soon replaced by the true dual TB which HP and Tek had used from the start. I am not sure which one was first. Does any-one know?

I never mentioned Solartron. In valve days, the CD1014, or the military CT436 version (6Mhz DBeam) and the CD1400 15Mhz DBeam still often turn up. But beware of the Trigger delay TB plug-in CX1444 on the CD1400, which uses a tunnel diode, while the basic TB CX1443 does not.

The transistor Solartron are more difficult as the CD1740 (a very pretty 50Mhz scope, but not blessed with utmost reliability) uses tunnel diodes, and the A100 (30Mhz) special ICs as well. By 1972/74, Solartron were fully caught up with their digital voltmeters and had passed all scope manufacture over to another part of Schlumberger :Enertec in France The Enertec 5222 does not use tunnel diodes or special ICs'.
The Telequipment valve D43, S32 or variants often turn up. Change the capacitors, remember the EHT is mains derived, and they work reasonably well.
Incidentally, I have manuals for all the scopes I mentioned, except very little on Hameg or Hitachi.
The D61 was produced I believe for the bottom end education market, and uses diode switching so as to provide X-Y and other facilities with least number of panel controls. Makes it particularly confusing to service as you have found.
The D65/D66/D67 seem to be the Tektronix design teams' effort to meet the TV service market under the Telequipment name and price. Not brilliant, but others might know more about them.
Advance, like Philips, go in for large tightly packed boards, so not easy to service. Good luck if you get your Advance OS3500. I have one sitting on my "to do" pile, but I need a magnifying glass now to find my way around the boards.
Tunnel diodes: the AEY25 (Siemens/Philips) and 1N3716 (GE) are equivalents.
wme_bill

[WME_bill]

Scope Purchase advice_ Philips PM3260
Just seen the comments by Skywave and Dickie about ICs, which these scopes do indeed use.
The PM3260 family of 1975 use thick film hybrids, with a very sophisticated travelling wave tube which must have cost a fortune. Also similar models with tweaks in other features: PM3261, PM3265. 120 or 150Mhz.
The PM3262 family of 1979 use special custom ICs. Also with tweaks: PM3263, PM3264, PM3266. 100Mhz.
The PM3240 family of 1977 (50Mhz) use a single type of IC, which I suspect is a selected and re-packaged CA3045 or CA3127 commodity transistor array.
All use horrid switched mode power supplies operating directly of the mains. Each model has a different design of PSU, so I suspect they had much trouble getting it reliable.
Hence my suggestion of the PM3217 of 1983 (50Mhz), with a 24v based PSU.
Dickie: You were asking for a manual for the PM3260, but I believe you have got one now. If not, or for most of the other models, let me know. wme_bill.

[Dickie]

Thanks Bill, I do now have a manual for the PM3260. As a result I also have a good working PM3260 'scope that is sitting idle, but thanks to your comments about it the chances of me finding a new owner for it are rather small (only joking).

Nobody has yet suggested the Gould-Advance OS3000A. These are a straightforward 2-channel 50MHz scope, all discrete with no funny bits inside. I always found them very easy to work on. Apart from the EHT potting compound dribbling out after a few years they had no major weaknesses.

[woodchips]

Question, what was the fun with the HP1821 timebase tunnel diode? Not heard about that before.

Ordinary tunnel diodes are not rare, and £10 isn't that bad, a similar speed IC will be very similar. Ordinary are the ones to 100MHz or so, ones used in the type 7T11 are not ordinary!

Always the Tek 7000 series, early ones had linear PSUs.

[Radio Wrangler]

The 1821 timebase and the single timebase version used tunnel diodes as the bistable element in the trigger circuits. The diodes exhibited an ageing characteristic and needed regular adjustment. If the unit was calibrated annually and set up by someone who knew what they were doing, all was OK, but some units were subjected to frantic twiddling of the random kind, (a close cousin of The Phantom) and the trigger systems were left sort of working, which frustrated the users.

Out of this a reputation grew and grew. Some people would rather gnaw their left leg off than try to use any HP scope, While I've never had a problem despite using even the models with actual tunnel diodes in them over 30+ years. I've fixed a few failed transistors but all in power supplies.

Put simply, ALL available second-hand scopes have at least one component in them which can now only be sourced from a donor instrument. I handle this by not paying so much money for any one that it would break my heart if it failed irreparably, plus I try to get two of each model so I have spares back-up anyway. Beyond that I don't worry about tunnel diodes, ICs or CRTs made where now there are only featureless plains of tract housing... and I get on with enjoying using them for however much life they have left.

I may be a bit biassed. In 1991 I was on the design team of an HP oscilloscope. It was a modular plug-in unit that went in a system mainframe for the US navy. Everything was driven via deeply nested menus on the system monitor and control panel. It was tolerable under automated control, but it was very very painful to try to use manually. I wouldn't recommend one. It was done for the US navy to squeeze a necessary function into a huge set of racks to automatically test their equivalents of our 'Whizz-Bangs' 'Oooh-Nasties' and 'Floggle Grommits' Always assuming their Sgt Bilkos (like our CPO Pertwees) hadn't already flogged them off on the black market.

David

[WaveyDipole]

Originally Posted by Dickie

Nobody has yet suggested the Gould-Advance OS3000A. These are a straightforward 2-channel 50MHz scope, all discrete with no funny bits inside. I always found them very easy to work on. Apart from the EHT potting compound dribbling out after a few years they had no major weaknesses.

Was the problem with the potting compound an issue for the OS3500 as well?

[Radio Wrangler]

As a university student in the early 70's I wound up with a brand new Gould OS3000 for my final year project work. Even new it used to make disquieting flashover noises every now and then. It worked perfectly though, but I'm not surprised to see EHT problems mentioned whenever this model is mentioned.

David

[Dickie]

Originally Posted by WaveyDipole

Was the problem with the potting compound an issue for the OS3500 as well?

I don't believe so. It's not a big problem anyway. You just have to clean it out and repot. An easy fix.

[dave cox]

My favourite scope is a tektronix 7603 - I quite often see these on ebay going for sub £100 with basic plugins (7A18 amp 75MHz 2 or 4 trace + 7B53A dual time base, the most common configuration). A big and heavy scope although it doesn't take up as much bench real estate as you might think (unless you get the rack version). By far the most common of the 7000 series and in continuous production for decades !

In my book this is the absolute business and is only beaten on bandwidth and portability !!

This model has a big screen and a linear PSU but the trace does not seem to be as sharp as some of the earlier scopes. There are plenty of custom IC's in it although I've only seen / heard of issues with the vertical monolithic amplifier (seen once, probably a bond wire failure, it gets rather hot) and the vertical channel switches (typically down to hot-plugging an amplifier- an absolute no-no). Of course additional plugins can extend the capability but they are getting hard to find so don't buy a mainframe on the basis that you WILL be able to get the plugins that you want !!

PS: do not try and post one of these, it will end in tears.

dc

[G0HZU_JMR]

I would always recommend the Iwatsu SS-5710 and SS-5711 scopes from Japan. These were made in the late 1980s and are 60MHz and 100MHz respectively and have four channels and can be bought cheaply and are extremely well made and very reliable.

Based on decades of using all the usual mainstream analogue scopes from the big names like Tek, HP and Philips etc, the 1980s Iwatsu SS-571x models are (in my opinion) way ahead of anything else in the areas that matter to the home user who is on a tight budget. i.e. solid build quality and japanese reliability. They are really nice to use as well with very good quality controls and a decent CRT.

In my opinion all of the major players in the analogue scope market lost their way from the late 70s onwards in terms of build quality. So instead of the bulletproof controls on the scopes of the 60s and 70s you ended up with fussy little plastic knobs, plastic control shafts and timebase knobs that wore out way too quickly or simply broke off or even fell off.

By comparison the Iwatsu SS-571x scopes from that era still had the ruggedness and quality that a decent scope 'needs' in order to give a long service life. Iwatsu still make analogue scopes today

I would also recommend the classic old Tek 465 as a good buy but only if you are happy to service/repair it yourself as they are so old. I use one as my main
analogue scope. If it ever went BER then I'd happily replace it with an Iwatsu SS-5711 if I couldn't find another decent 465 or 475.

The only other advice I can offer is that I would recommend you consider favouring something reasonably 'small' in terms of footprint and portability because the typical hobbyist today can now buy all kinds of test gear on ebay really cheaply. Therefore bench or shelf space can quickly get used up. Also, if you like working in silence then avoid anything with a noisy cooling fan as this can quickly become annoying and tiring.

[glowinganode]

I'd second Jeremy with Iwatsu.
I was given a basic 15 MHz dual channel one 15 years ago with a faulty timebase, leaking trim cap in the timebase.
Since being mended it has been absolutely reliable, and has outlived at least two other scopes. In fact I now only have the Dynamco as an emergency back-up.
I'd also recommend Hitachi scopes.
Do try and get the D61 going as it's a nice little scope, if you get stuck with it I'll gladly look it over.
Rob.

[WME_bill]

Iwatsu. Interested in G0HZU Jeremy 's suggestion of Iwatsu. I have always heard well of them.
But they would fail one of my criteria: No manuals available.
Perhaps he has the manuals for the two models he mentions, SS-5710 and SS-5711, available. I would be very glad to have a copy so as to learn something new. wme_bill

[G0HZU_JMR]

Hi Bill
The SS-5710 manual is available for free download at Elektrotanya.com

http://elektrotanya.com/iwatsu_ss-57.../download.html

The SS-5711 manual is here:
http://elektrotanya.com/iwatsu_ss-57.../download.html

It is a combined user/maintenance/service manual and is about 10Mb in size
If you have not used this site before then you might get confused by all the tempting clicky buttons that are really just adverts. You need to look for this bit of text below on the webpage in the link above and click on the plain text 'Get Manual'

NOTE:
The Get Manual text doesn't appear straight away because they want you to read the adverts first. Give it a few seconds and the text will appear just below the preview image of the manual

Click the preview picture to see bigger size.
The preview is worse quality than the original pdf.

This file is downloadable free of charge: Get Manual
(You are not logged in, only 2 downloads per day possible for you.)

[woodchips]

David, thank you. I bought several 1821s some years ago and on a quick test all seemed to work fine. I only bought them for the five tunnel diodes they used, similar to any used in the up to 100MHz bandwidth scopes of that era.

I am not convinced by Jeremy's point about flimsy post 1970 scopes and then recommended something small. They seem to be connected, the large 54x etc scopes had the space for large knobs and buttons. Customers want more facilities and they all need buttons and controls, and to fit them they have to be smaller. QED. There doesn't seem to be any solution to this problem.

The bigger problem is the packing density in the smaller scopes, I have found them to become almost impossible to service. Something like the Gould OS300 is simple, the Tek 485 is anything but.

[Radio Wrangler]

Woodchips, Fingers haven't got any smaller.

Unfortunately the more modern machines handled this with deep layers of menus and a formally structured human interface design with one knob to twiddle things, one pair of up/down keys. You played an adventure game in the menus to find the parameter you wanted and twiddled the knob. Need to change something else? Ha! back into the jungle of menus.

Fortunately even HP/Agilent and Tek worked out that their users weren't happy, and the past several years have seen the return of the scope with lots of single-function knobs in a triumph of ergonomics over styling.

Oh, there were 4 OS300s auctioned last night at about a tenner each.

David

[MotorBikeLes]

I had a batch of new Iwatsu manuals some time ago. I think I still have two new ones, but not sure which ones. I sold some off on Ebay a couple of years ago. I just saw that I have two new HP 1740A manuals (found whilst looking if any spare iwatsus).
Recently when calibrating a TQ S2A dual timebase, I was having a struggle to see the two triggering pulses that have to aligned on a ramp. I was using a 50MHz D755, so decided to tlook instead with my 35MHz HP 1703 portable storage scope.
Trace sharpness very much better, setting now straightforward. The D755 uses the same CRT as the Tek 465B I think.
I really like those HP CRTs with internal graticule illumination.
I really ought to have a look at the 250MHz HP scope that I bought 18 years ago, just before moving away from my main customer base.
Les.

[WaveyDipole]

Funnily enough I saw a couple of Iwatsu go on eBay recently but ignored tham because I couldn't find any information. Jeremy, thanks for the links.