Thurlby 1905 any good ?

[Flump]

I have the chance to buy this meter
never heard of them before.

I dont really need it,
just wanted to try it out.

are they any good ?

[tautech]

I have the chance to buy this meter
never heard of them before.

I dont really need it,
just wanted to try it out.

are they any good ?

The name rings a bell from the past.
Availability of schematics would make the choice for me along with the price.

[Rufus]

I bought one in 1983. Hasn't had much use recently because I have better.

I calibrated it for the first time last year - wasn't far out. The only issue it has had is some kind of intermittent connection which prevents the processor booting properly, a tap on the side of the case has always fixed it so I never bothered to look further.

Handbook and service manual are kicking around on the web.

If it is working and cheap it will be worth the money.

[nanofrog]

The name rings a bell from the past.

Thurlby Thandar Instruments perhaps.  Thurlby merged with Thandar in 1989 (source).

[macboy]

It's a decently good meter, with nice mathematical capabilities, like ax+b scaling, and dB display. It uses a poor-man's version of the LM399 heated zener reference, the LM3999, which is the same die in a TO-92 plastic package without any thermal insulation. Mine developed a fault where a tantalum cap on the -15V supply went short circuit, a simple fix once you find it. Mine has True RMS AC (via an analog devices AD637 in metal package) which is AFAIK an undocumented feature... no mention of this option in the user manual, but the service manual shows the two variations.

A couple gems:

• It has a hidden 6.5 digit mode, press "**" then "5 1/2".
• There is a header inside that has a RS-232 (TTL level) serial output at 2400 baud (8N1), sending the contents of the display each time it updates (about 2.5 time/second). It is output only... no command input. I rigged up a USB-to-serial converter with an optocoupler for isolation, so that I can do simple data logging. Just open a serial terminal and log to a file. Simple.

[macboy]

Manuals attached.

[Hydrawerk]

It is/was a high quality product probably, but it has no True RMS or autorange. Buy it only if it is cheap.

[macboy]

It is/was a high quality product probably, but it has no True RMS or autorange. Buy it only if it is cheap.

Some have True RMS, but I don't think it was common, since the operators manual doesn't mention it.

[Rufus]

It is/was a high quality product probably, but it has no True RMS or autorange. Buy it only if it is cheap.

Some have True RMS, but I don't think it was common, since the operators manual doesn't mention it.

As I recall it was an extra cost option.

[Flump]

thanks for the replies and info everyone
thanks for the manuals macboy 

there is a problem with the A (amps) button,
it does not stay latched in, I have squirted some cleaner in there
which helped for a few mins but then it went back to how it was.

I have put a bid in for it but not bought it yet, but it is a lovely old
bit of kit i would like to bring back in to daily use.

Does anyone have any experience on replacing the switches or a source to get them from ?

[Flump]

Update on this

I have bought it now, i did get it cheap
which is good because after further testing
there is a segment out on the furthest right LED
I have not looked in to this yet but I am hoping
the LED's are fairly generic, you don't notice the
problem in general 4/5 digit use, I only noticed it
when going in to the secret 6 digit mode lol

It is very accurate (on dcv and ohms at least)

[Andy Watson]

you don't notice the
problem in general 4/5 digit use,

I doubt that the segment is wired up. It's advertised as a 4½ or 5½ digit meter, the half means that the most significant digit will be either 1, or 2 (look at the maximum scale length), so segment "F" is not used.

Edit. Did you say "furthest right"? You did!  DOH Ignore me, I must have my head on the wrong way today! 

[Flump]

hi andy, it does look like its wired up because part of it displays,
think of a led figure 8 , its the top left vertical line that does not show

i will take a pick later so you can see

[Flump]

here are some pictures of it

its is strange how the bottom lights up in pic 1 but not in pic 3

[Andy Watson]

Since you will be unsoldering it to replace it, why not swap over two of the digit strobes to confirm that the fault is with display and not some quirk of the software - you say it is only noticeable in the "hidden" mode.

[Flump]

hi Andy

they are not replaceable like that.

I have it all stripped down now
and I dont think i can get replacements for them new

have a look in the forsale section i put a
wtd post in there

[macboy]

The missing segment is definitely not a 'feature' of the firmware. On mine, all segments of the last digit work fine. You could replace all 8 digits with something else that you rig up yourself. It is a simple common anode arrangement with 8 digits multiplexed. You would wire all the segments (a to f and decimal) of all digits to the segment outputs on the board, then connect the anode of each digit to the corresponding output on the board. You could even use a different color display if you liked.

[Flump]

Thanks macboy but thats totally over my level of electronics,
I would need a step by step guide to do that.

The display is perfect at 3 decimal places after the point
and I dont need any higher resolution than that,
but It would be lovely to sort the display and the amp switch out
just to get it to %100 again.

So if you find yourself bored one day and write a step by step
or more detailed how to then I would love to read it. 

[Zad]

Thurlby / TTi gear is almost always good stuff. Hardly any presence outside the electronics industry, so you don't see them much in the amateur / hobbyist field.

What is particularly curious though, is just how unlike Clive Sinclair's other products these are. From day 1 and his "hifi" products, through the TV, computer and C5 era, pretty much all his products are characterised by being just a bit too cheaply made and too many corners cut. On the other hand, Thurlby gear feels like it was designed by engineers for engineers. Not pretty, but it gets the job done, and keeps on going.

[jpb]

Thurlby / TTi gear is almost always good stuff. Hardly any presence outside the electronics industry, so you don't see them much in the amateur / hobbyist field.

What is particularly curious though, is just how unlike Clive Sinclair's other products these are. From day 1 and his "hifi" products, through the TV, computer and C5 era, pretty much all his products are characterised by being just a bit too cheaply made and too many corners cut. On the other hand, Thurlby gear feels like it was designed by engineers for engineers. Not pretty, but it gets the job done, and keeps on going.

Their power supplies are particularly good, very robustly made and in some ways over-engineered so they are unlikely to fail. I have one and also their counter the TF930. They are not as sophisticated as HP/Agilent gear but they are much cheaper. The counter for instance is 10 digits with reciprical counting and works well, I'd like to have 12 digits and time stamping and 20 psec resolution like the Agilent 53230A but the TTi cost me £200 (ex demo model) whilst the Agilent, even second hand from their e-bay store, is well over £2000.

[Rufus]

What is particularly curious though, is just how unlike Clive Sinclair's other products these are.

TTi are way removed from Sinclair. In 1979 Sinclair Radionics was split up the test equipment section being named Sinclair Electronics and a year later renamed to Thandar Electronics. 9 years later they merged with Thurbly Electronics to form TTi.

The 1905a is a Thurlby product. I bought one six years before the merger.

At a company I worked for my boss bought a Sinclair multimeter for evaluation, he gave it to the cal lab for checking and it was so bad they wouldn't let him have it back. One of these http://www.vintagecalculators.com/html/pdm35_multimeter.html I think.

[G0HZU]

Their power supplies are particularly good, very robustly made and in some ways over-engineered so they are unlikely to fail.

I agree that their recent offerings are very good but the older generation of Thurlby PL320 PSUs aren't very well built at all.

eg the ones built in the early 1990s. I have a few here and we still have some of these old ones piled up in a graveyard at work. They look great on the outside and perform very well but the inner build quality is best described as a 'poorly designed lashup'

The LED displays are notoriously unreliable and suffer all manner of ailments due to the poor quality soldering and the overall 'homebrew look' to the internal construction with wires soldered point to point in a tangled mess.

The later TTI supplies are much, much better and show signs that they finally hired somebody who knew a bit more about production engineering. i.e. they have proper connectors rather than cheapo screw terminals and bared off/soldered wires at each PCB. I assume these are the ones you are referring to because I agree they look to be built to last a long time

[jpb]

Their power supplies are particularly good, very robustly made and in some ways over-engineered so they are unlikely to fail.

I agree that their recent offerings are very good but the older generation of Thurlby PL320 PSUs aren't very well built at all.

eg the ones built in the early 1990s. I have a few here and we still have some of these old ones piled up in a graveyard at work. They look great on the outside and perform very well but the inner build quality is best described as a 'poorly designed lashup'

The LED displays are notoriously unreliable and suffer all manner of ailments due to the poor quality soldering and the overall 'homebrew look' to the internal construction with wires soldered point to point in a tangled mess.

The later TTI supplies are much, much better and show signs that they finally hired somebody who knew a bit more about production engineering. i.e. they have proper connectors rather than cheapo screw terminals and bared off/soldered wires at each PCB. I assume these are the ones you are referring to because I agree they look to be built to last a long time

I must admit that I've not poked around inside my one to check the build quality - the meters are very accurate and it has worked very well externally. My comment was based on the fact that TTi supplies seemed to be ubiquitous in the labs/companies I've worked in without acquiring any negative reputation for build quality. Also I've seen quite a lot of them around still working after years and second hand I've heard good things regarding the "over engineering".

Your direct experience is interesting to hear. Perhaps I'll check what is actually inside my supply if I get time.

[G0HZU]

The old and badly built ones look like this on the outside:

They are really nice to use and I really like the bright display and general performance but the internal build quality is very poor.

[KJDS]

The old and badly built ones look like this on the outside:

They are really nice to use and I really like the bright display and general performance but the internal build quality is very poor.

I suspect that may be Thandar's influence on Thurlby.