EEVblog #693 - AVO Transistor Analyser Teardown - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: December 17, 2014, 03:11:57 am
content: Dave tears down a 1962 vintage AVO Transistor Analyser.The auction score video:

author: SeanB
author_rank: Super Contributor
timestamp: December 17, 2014, 04:24:12 am
content: I have the baby brother of that one, it fits in the box in the middle.

author: ratdude747
author_rank: Regular Contributor
timestamp: December 17, 2014, 06:50:03 am
content: A note: The two connectors to the battery board ARE latched... if you look, there are two barrel spacers bolted to the inside of the compartment that hold the plug in the socket.

author: Lightages
author_rank: Unknown
timestamp: December 17, 2014, 07:05:00 am
content: My first thought when seeing those flatish devices marked 1R is that they were diodes. I would never have thought them to be capacitors. Are you sure Dave?

author: digital
author_rank: Contributor
timestamp: December 17, 2014, 08:22:02 am
content: Dave please replace that condenser and do a video of the tester working I am sure a lot of others would enjoy it.Regards

author: G7PSK
author_rank: Super Contributor
timestamp: December 17, 2014, 09:05:15 am
content: Hi Dave, To make AA batteries fit you need a stack of coins to fit under the spring and on top of the cell.I have a whole load of 1950's to early 1970's transistors I can send you to test all brand new and unused.Your unit could well have been unused as the military have the habit of storing equipment just in case they have a war and then after forty years or so realise that it is out of date, I have had a few bits of kit unused ex military.

author: German_EE
author_rank: Super Contributor
timestamp: December 17, 2014, 09:29:52 am
content: Dave, I am almost certain that your analyser is ex-military. The secret is the brass plate which shows a small arrow pointing upwards, this was the symbol for the War Department in the UK (now called the Ministry of Defence). Now that we know you are dealing with a military device it explains the build quality including the laced wiring, the chunky switches and the rubber seals.I was Sagan's age when this unit was manufactured

author: jipihorn
author_rank: Contributor
timestamp: December 17, 2014, 10:08:21 am
content: "Love a good set of balls"Brilliant.J.

author: nathanpc
author_rank: Unknown
timestamp: December 17, 2014, 10:45:44 am
content: I would love to see a video of you replacing those oldcapacitorscondensers and playing around with it analyzing some transistors.

author: fcb
author_rank: Super Contributor
timestamp: December 17, 2014, 11:33:21 am
content: I think you'll find all AVO stuff of that vintage is equally well built.What is slightly puzzling (mainly because I don't know the history of the UK<>ADF agreements) is why it has the UK MOD plaque on it.

author: JackOfVA
author_rank: Unknown
timestamp: December 17, 2014, 12:25:54 pm
content: Battery holders appear to be based on 7 or 9 pin vacuum tube sockets and shields.Yes, please see if you can make it work - would make a great 2nd part video.

author: R_Gtx
author_rank: Regular Contributor
timestamp: December 17, 2014, 01:08:39 pm
content: I hope Dave doesn't just swap the leaky dustbins with modern replacements, but correctly, as with all vintage equipment, re-stuffs the original cans.

author: c4757p
author_rank: Super Contributor
timestamp: December 17, 2014, 01:20:33 pm
content: Ew, god, restuff the cans? I hate it when people do that. This is a tool, and a beautiful piece of engineering, not some wanky painting or something - its beauty comes from the practical, functional design, not the specific shape and size of the capacitors... Hiding nice, modern parts inside crusty old ones seems to me a bit of an insult to the spirit of the engineering work that went into building this in the first place. Do you think, given a choice between a modern capacitor from 2014 and one of the caps that were available in the 1960s, the original engineers would have chosen the latter?

author: Macbeth
author_rank: Super Contributor
timestamp: December 17, 2014, 01:25:36 pm
content: Quote from: Lightages on December 17, 2014, 07:05:00 amI instantly thought this too...

author: Refrigerator
author_rank: Super Contributor
timestamp: December 17, 2014, 01:32:19 pm
content: Imo a C cell battery would fit perfecly in those battery cans .

author: c4757p
author_rank: Super Contributor
timestamp: December 17, 2014, 01:33:51 pm
content: Quote from: Refrigerator on December 17, 2014, 01:32:19 pmDo you think so? They looked just a bit too small to me - but then again, I don't handle C cells much.Quote from: Macbeth on December 17, 2014, 01:25:36 pmYup, those look like diodes to me.

author: Macbeth
author_rank: Super Contributor
timestamp: December 17, 2014, 01:34:13 pm
content: Quote from: German_EE on December 17, 2014, 09:29:52 amDefinitely Ministry of Defence. I also wonder about that "MOD" sticker Dave thinks is for recording modifications. I think it is for some other M.O.D. purposes myself.The arrow you speak of is also printed on the clockface of UK military watches, ration packs, belt buckles, etc, etc.I have to hand it to AVO, they made fantastic old school meters like the AVO-8 in their bakelite cases with hand wound resistors, and hand painted and calibrated dials with parallax mirror. I would say a whole magnitude in quality above an old Simpson.

author: German_EE
author_rank: Super Contributor
timestamp: December 17, 2014, 02:37:45 pm
content: Wikipedia says that the War Department / War Office became the Ministry of Defence in 1964, after this unit was manufactured. 'MOD' on the inside plate is therefore to mark MODifications 1-25.

author: Andy Watson
author_rank: Super Contributor
timestamp: December 17, 2014, 02:57:59 pm
content: Quote from: Lightages on December 17, 2014, 07:05:00 amAgreed. They're IR (International Rectifier) 2E1 diodes.

author: RobertoLG
author_rank: Frequent Contributor
timestamp: December 17, 2014, 03:36:39 pm
content: Dave here are some battery adapters, maybe you are interested for future use, dunno anyways here is the linkhttp://www.amazon.com/C-sized-Adapter-Shells-AA-Battery/dp/B000855034

author: w2aew
author_rank: Super Contributor
timestamp: December 17, 2014, 04:06:09 pm
content: Gee - I hope I look as good as that thing does when I'm that old. Oh wait, I *am* that old! I was born the same year that it was born...

author: Dave Turner
author_rank: Frequent Contributor
timestamp: December 17, 2014, 04:59:35 pm
content: According tohttp://www.vintage-radio.net/forum/showthread.php?t=78716the 1289 4.5v cycle battery would yield 3 U10 sized cells. I've not tried it myself but may be worth checking out.

author: Electronics-Repairman
author_rank: Contributor
timestamp: December 17, 2014, 05:32:06 pm
content: Yes Dave please fix it,I'd love to see it working.

author: PA4TIM
author_rank: Super Contributor
timestamp: December 17, 2014, 07:05:47 pm
content: CT models are military models/versions. I have a CT38, a huge avo VTVM , CV is also a militairy thing, many tubes have a CV number. I have seen those MOD plates on many english militairy stuff. Like on Murphy's (ao on a 1949 version) and Racals. I do not think it stands for modification.

author: fcb
author_rank: Super Contributor
timestamp: December 17, 2014, 07:45:53 pm
content: Those MOD plates do stand for MODification - they are (or were) very common on gear here in the UK, you often see them with numbers punched out/scratched or ticked indicating which mods have been performed. I've seen brand new gear delivered with a few of these punched out before.

author: SeanB
author_rank: Super Contributor
timestamp: December 17, 2014, 07:56:11 pm
content: That is a standard depot level mod plate. Basically used if there was a manufacturer field upgrade issued, which would be implemented by a service depot, and then they would punch the level done with a small circular punch to obscure the required number. You might have a unit that has eg only mod level 3 done, while an older unit might have levels 1 and 2 done, as it would be serial number dependant as to which mod is applied. In a device like this there would likely be no mod state as the unit would be returned to manufacturer for servicing and upgrade, and would not have the sticker done but the version would be in a serial number range.Can be very confusing in having items which are use specific, such use being determined by the mod number. Thus you can have an indicator that has 2 varieties, one for use in a particular application but only if it has the specific mod level applied by the service base. The other one looks identical, but is not usable in this application as the mod state is different. Was often used with RPM indicators where there were 2 different gearboxes in use, and they were slightly different in the RPM output drive, such that you would get a slightly wrong indication if you used the wrong gauge. Pilots tent to get a bit tetchy if the 3 gauges are not in the same position at a specified power level with good engines, even more so when it is a dual indicator and a split needle is an indication there is about to be a loud bang and the big fan keeping the pilot cool is about to stop. Had to go to the stores and pull all the stock to get the right mod state, and sent the old one back as " not suitable for mod statexx".

author: G7PSK
author_rank: Super Contributor
timestamp: December 17, 2014, 09:15:30 pm
content: Those batteries are half a No.8 cell. No.8 cells were very common at one time for pocket torches, two cells in a cardboard tube giving 3 volts. I was trying to remember the No8 cell name earlier but could not, I used to use them in torches many years ago in my first torch a black with silver stripes Ever Ready torch made from aluminium. I was nearly ten years old when that unit left the factory.

author: German_EE
author_rank: Super Contributor
timestamp: December 17, 2014, 10:07:02 pm
content: At 56 next birthday I'm beginning to wonder if I'm the oldest person on the EEV Blog board?

author: EEVblog
author_rank: Unknown
timestamp: December 17, 2014, 10:12:59 pm
content: Quote from: c4757p on December 17, 2014, 01:33:51 pmNope, C cells don't fit.

author: Macbeth
author_rank: Super Contributor
timestamp: December 17, 2014, 10:15:35 pm
content: SeanB - Interesting, I think I would give up and leave those labyrinthine logistics to the NCO in charge of the Quartermaster's Store.My eyes are dim, I cannot see...

author: EEVblog
author_rank: Unknown
timestamp: December 17, 2014, 10:18:20 pm
content: Quote from: Andy Watson on December 17, 2014, 02:57:59 pmYes, they are back-to-back diodes.

author: robrenz
author_rank: Super Contributor
timestamp: December 17, 2014, 10:37:47 pm
content: Quote from: German_EE on December 17, 2014, 10:07:02 pmYour not even close

author: Dave Turner
author_rank: Frequent Contributor
timestamp: December 17, 2014, 11:10:53 pm
content: Nope - beat you but younger than robrenz!

author: w2aew
author_rank: Super Contributor
timestamp: December 18, 2014, 05:07:33 am
content: Well, there are at least a few of us in the over-50 club. Didn't I see a poll in the past that asked the forum member's age?

author: rf-loop
author_rank: Super Contributor
timestamp: December 18, 2014, 07:26:28 am
content: Nice equipment and no FW bugs!Quote from: w2aew on December 18, 2014, 05:07:33 amAlso in over 60 club.

author: ciccio
author_rank: Frequent Contributor
timestamp: December 18, 2014, 11:42:58 am
content: Quote from: German_EE on December 17, 2014, 10:07:02 pmNo, I'm older than you: 64, 65 next birthday.I used AVOmeters model 8 at work in the 70's, bough one second-hand, kept it as a decoration in the lab shelves for 20 years and sold for 5 times the price I've paid it...Best regards

author: rob77
author_rank: Super Contributor
timestamp: December 18, 2014, 12:51:19 pm
content: Quote from: Dave Turner on December 17, 2014, 04:59:35 pmas far as i remember... yes , that should be the caseat least it was like that when i was a kid and i was taking apart batteries (30+ years ago)btw... the marking 3R12 for the 4.5V battery is because it's 3 times R12 inside... and R12 is the same battery as U10 is.

author: G7PSK
author_rank: Super Contributor
timestamp: December 18, 2014, 03:17:32 pm
content: There is a company here in the UK that still sells R12 or U10 batteries but at £4-70 each I would not use them as AA will fit if you put 1 or 2 coins of the right size under the coil spring as packers/spacers and wrap the AA's with some masking tape to centralize them. That meter also allows for external power so that is the easiest and cheapest way to go. AVO liked to use odd ball batteries, the AVO I have takes two 3R12 and a funny 1.5 volt sqaure shaped cell with screw terminals on top, I just use a D cell with wires soldered on the batteries last for 5 or more years. I had thought of using a 9 volt instead of the two 4.5 volt but the resistance range uses both 4.5 and 9 volt with the 1.5 used for offset on the AC ranges.

author: bigsky
author_rank: Regular Contributor
timestamp: December 18, 2014, 09:13:24 pm
content: Quote from: German_EE on December 17, 2014, 09:29:52 amSorry for late reply. I didn't exist when this was made. It's definitely ex-military.The arrow is known as the broad arrow.Seehttp://en.wikipedia.org/wiki/Broad_arrowThe stencilling on the cover (visible in the first 15 secs of the video) is also a giveaway. The 13 digit number on it (6625-99-949-0872) is virtually guaranteed to be a NATO stock number, and indeed it's in the databases:Seehttp://www.nsn-now.com/Indexing/ViewDetail.aspx?QString=6625999490872orhttp://www.nsncenter.com/PartNumber/40695B

author: SNGLinks
author_rank: Regular Contributor
timestamp: December 19, 2014, 04:06:20 am
content: Quote from: German_EE on December 17, 2014, 10:07:02 pmI was 68 last July!

author: steve_w
author_rank: Regular Contributor
timestamp: December 19, 2014, 09:42:28 am
content: The thing that gives it away as military is the NATO stock number on the front, the first 4 digits is the group/ class, 6625 = test equipment next 2 numbers is the country code, 99 = UK (00, 01 = USA, 66 = Australia 14 = France) the rest is sequence numbers that dont mean much to techos.Hope that jogs some memoriesregardsSteve W

author: coppice
author_rank: Super Contributor
timestamp: December 19, 2014, 10:11:25 am
content: Quote from: steve_w on December 19, 2014, 09:42:28 amThe thing that gives it away as military is that its an expensive hand made device to do not very much. Any civilian lab with enough need for transistor testing to invest in serious equipment for the job bought something like one of the Tektronix transistor curve tracers. They cost a lot, but they also did a lot.

author: (In)Sanity
author_rank: Regular Contributor
timestamp: December 19, 2014, 02:05:10 pm
content: I rather like this tear down. It's a device that you can't just run out and buy and tear apart, or that your likely to see at any time. Would love to see it up and running just for the sake of doing so. Age wise I'm guessing I have a year or two on Dave but not caught up with Alan. I have one of the old Sencore Cricket transistor testers that still works perfect.Jeff

author: (In)Sanity
author_rank: Regular Contributor
timestamp: December 20, 2014, 07:48:08 pm
content: OK, now I'm just sad that nobody else has commented on this video. Guess I must be getting old and stuck in the past. This stuff is great..but it would appear I'm in a small group of people that think so. Ohh well, I like my group.Jeff

author: ttp
author_rank: Regular Contributor
timestamp: December 21, 2014, 07:17:23 am
content: Quote from: German_EE on December 17, 2014, 10:07:02 pmThere is at least one older than you

author: SeanB
author_rank: Super Contributor
timestamp: December 21, 2014, 07:53:32 am
content: Quote from: (In)Sanity on December 20, 2014, 07:48:08 pmI have it's baby brother, which fits inside the battery casing. TYear down of that is likely to be destructive though, it was assembled from the face out and does not come apart easily once laced up.

author: (In)Sanity
author_rank: Regular Contributor
timestamp: December 21, 2014, 05:08:35 pm
content: Quote from: SeanB on December 21, 2014, 07:53:32 amI just wish more people were interested in the origins and history of the electronics industry. Very few people build anything anymore with just a few transistors. I myself am guilty of throwing too much technology at the simplest of problems.Jeff

author: Refrigerator
author_rank: Super Contributor
timestamp: December 21, 2014, 06:21:48 pm
content: I just found my gramp's old resistance meter, maybe i should to a teardown of it ?

author: Electronics-Repairman
author_rank: Contributor
timestamp: January 01, 2015, 12:13:52 pm
content: I'm 60 & will be 61 in May if spared