Thurlby 1905 any good ?  - Page 1
Forum section: electronics / testgear

author: Flump
author_rank: Frequent Contributor
timestamp: May 30, 2014, 11:31:06 pm
content: I have the chance to buy this meternever heard of them before.I dont really need it,just wanted to try it out.are they any good ?

author: tautech
author_rank: Super Contributor
timestamp: May 31, 2014, 01:31:12 am
content: Quote from: Flump on May 30, 2014, 11:31:06 pmThe name rings a bell from the past.Availability of schematics would make the choice for me along with the price.

author: Rufus
author_rank: Super Contributor
timestamp: May 31, 2014, 05:45:53 am
content: 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.

author: nanofrog
author_rank: Super Contributor
timestamp: May 31, 2014, 06:59:52 am
content: Quote from: tautech on May 31, 2014, 01:31:12 amThurlby Thandar Instrumentsperhaps.Thurlby merged with Thandar in 1989 (source).

author: macboy
author_rank: Super Contributor
timestamp: June 02, 2014, 05:04:10 pm
content: 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.

author: macboy
author_rank: Super Contributor
timestamp: June 02, 2014, 05:08:43 pm
content: Manuals attached.

author: Hydrawerk
author_rank: Super Contributor
timestamp: June 02, 2014, 11:11:05 pm
content: It is/was a high quality product probably, but it has no True RMS or autorange. Buy it only if it is cheap.

author: macboy
author_rank: Super Contributor
timestamp: June 02, 2014, 11:59:34 pm
content: Quote from: Hydrawerk on June 02, 2014, 11:11:05 pmSome have True RMS, but I don't think it was common, since the operators manual doesn't mention it.

author: Rufus
author_rank: Super Contributor
timestamp: June 03, 2014, 05:15:47 am
content: Quote from: macboy on June 02, 2014, 11:59:34 pmAs I recall it was an extra cost option.

author: Flump
author_rank: Frequent Contributor
timestamp: June 06, 2014, 04:18:00 pm
content: thanks for the replies and info everyonethanks for the manuals macboythere is a problem with the A (amps) button,it does not stay latched in, I have squirted some cleaner in therewhich 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 oldbit 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 ?

author: Flump
author_rank: Frequent Contributor
timestamp: June 07, 2014, 09:11:48 am
content: Update on thisI have bought it now, i did get it cheapwhich is good because after further testingthere is a segment out on the furthest right LEDI have not looked in to this yet but I am hopingthe LED's are fairly generic, you don't notice theproblem in general 4/5 digit use, I only noticed itwhen going in to the secret 6 digit mode lolIt is very accurate (on dcv and ohms at least)

author: Andy Watson
author_rank: Super Contributor
timestamp: June 07, 2014, 10:13:02 am
content: Quote from: Flump on June 07, 2014, 09:11:48 amI 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! DOHIgnore me, I must have my head on the wrong way today!

author: Flump
author_rank: Frequent Contributor
timestamp: June 07, 2014, 10:49:23 am
content: 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 showi will take a pick later so you can see

author: Flump
author_rank: Frequent Contributor
timestamp: June 07, 2014, 01:54:52 pm
content: here are some pictures of itits is strange how the bottom lights up in pic 1 but not in pic 3

author: Andy Watson
author_rank: Super Contributor
timestamp: June 09, 2014, 02:25:02 pm
content: 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.

author: Flump
author_rank: Frequent Contributor
timestamp: June 09, 2014, 03:33:46 pm
content: hi Andythey are not replaceable like that.I have it all stripped down nowand I dont think i can get replacements for them newhave a look in the forsale section i put awtd post in there

author: macboy
author_rank: Super Contributor
timestamp: June 10, 2014, 02:51:17 pm
content: 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.

author: Flump
author_rank: Frequent Contributor
timestamp: June 10, 2014, 03:40:48 pm
content: 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 pointand I dont need any higher resolution than that,but It would be lovely to sort the display and the amp switch outjust to get it to %100 again.So if you find yourself bored one day and write a step by stepor more detailed how to then I would love to read it.

author: Zad
author_rank: Super Contributor
timestamp: June 10, 2014, 05:18:03 pm
content: 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.

author: jpb
author_rank: Super Contributor
timestamp: June 10, 2014, 06:06:43 pm
content: Quote from: Zad on June 10, 2014, 05:18:03 pmTheir 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.

author: Rufus
author_rank: Super Contributor
timestamp: June 10, 2014, 06:20:29 pm
content: Quote from: Zad on June 10, 2014, 05:18:03 pmTTi 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 thesehttp://www.vintagecalculators.com/html/pdm35_multimeter.htmlI think.

author: G0HZU
author_rank: Super Contributor
timestamp: June 13, 2014, 12:45:06 pm
content: QuoteI 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

author: jpb
author_rank: Super Contributor
timestamp: June 13, 2014, 01:14:39 pm
content: Quote from: G0HZU on June 13, 2014, 12:45:06 pmI 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.

author: G0HZU
author_rank: Super Contributor
timestamp: June 13, 2014, 01:18:40 pm
content: 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.

author: KJDS
author_rank: Super Contributor
timestamp: June 13, 2014, 01:34:38 pm
content: Quote from: G0HZU on June 13, 2014, 01:18:40 pmI suspect that may be Thandar's influence on Thurlby.

author: G0HZU
author_rank: Super Contributor
timestamp: June 13, 2014, 01:45:30 pm
content: Quote from: KJDS on June 13, 2014, 01:34:38 pmVery possibly.The other thing about the mk1 PL320 is that the LED display driver chip has been obsolete for many years and it is a known weak spot on the PSU.I've been inside quite a few of them over the years at work when they go a bit dicky and the usual things I spot are loose screws in the termination blocks (probably work loose over the years and give intermittent connections) and the LED segments are playing up either due to poor/aged solder joints or because of a dead/dying LED driver chip.Taking them apart further is not nice because the boards are all hard wired/soldered and the wires are quite stiff so you either have to unsolder each and every wire connection or try and bend the boards away from the hardware and try and swap out any broken parts. Not good...The later ones are much better built than this