EEVblog #693 - AVO Transistor Analyser Teardown

[SeanB]

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".

[G7PSK]

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.

[German_EE]

At 56 next birthday I'm beginning to wonder if I'm the oldest person on the EEV Blog board?

[EEVblog]

Imo a C cell battery would fit perfecly in those battery cans . 

Do you think so? They looked just a bit too small to me - but then again, I don't handle C cells much.

Nope, C cells don't fit.

[Macbeth]

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...

[EEVblog]

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?

Agreed. They're IR (International Rectifier) 2E1 diodes.

Yes, they are back-to-back diodes.

[robrenz]

At 56 next birthday I'm beginning to wonder if I'm the oldest person on the EEV Blog board?

Your not even close

[Dave Turner]

Nope - beat you but younger than robrenz!

[w2aew]

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? 

[rf-loop]

Nice equipment and no FW bugs!

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?

Also in over 60 club.

[ciccio]

At 56 next birthday I'm beginning to wonder if I'm the oldest person on the EEV Blog board?

No, 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

[rob77]

According to http://www.vintage-radio.net/forum/showthread.php?t=78716
the 1289 4.5v cycle battery would yield 3 U10 sized cells. I've not tried it myself but may be worth checking out.

as far as i remember... yes , that should be the case at 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.

[G7PSK]

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.

[bigsky]

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

Sorry for late reply. I didn't exist when this was made. It's definitely ex-military.

The arrow is known as the broad arrow.

See http://en.wikipedia.org/wiki/Broad_arrow

The 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:

See http://www.nsn-now.com/Indexing/ViewDetail.aspx?QString=6625999490872

or http://www.nsncenter.com/PartNumber/40695B

[SNGLinks]

At 56 next birthday I'm beginning to wonder if I'm the oldest person on the EEV Blog board?

I was 68 last July!

[steve_w]

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 memories


regards

Steve W

[coppice]

The thing that gives it away as military is the NATO stock number on the front

The 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.

[(In)Sanity]

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

[(In)Sanity]

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

[ttp]

At 56 next birthday I'm beginning to wonder if I'm the oldest person on the EEV Blog board?

There is at least one older than you

[SeanB]

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

I 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.

[(In)Sanity]

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

I 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.

I 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

[Refrigerator]

I just found my gramp's old resistance meter, maybe i should to a teardown of it ?

[Electronics-Repairman]

I'm 60 & will be 61 in May if spared