TEK 212 Oscilloscope.

[MotorBikeLes]

I was inclined to take the Lion route with this, but then common sense took over and the 2/3AAs have been ordered.
I have dismantled it ready and need to reinstate the bits I removed when I connected it for an external 12v supply.
However, I have spotted a minor problem.
When I bought it or shortly after I got a copy of the military service manual . When I had a difficult to solve trace switching problem, I eventually realised mine was a later number, with completely different circuit in that area. I bought a correct pdf manual from ArteK. The military manual gives the correct values for C210 and C212 in the circuit snippet posted earlier. However, the correct manual has DIFFERENT values from the military version, and it does not show ANY options. These are the details:-
Military, standard, 110-126v @ 58-62Hx. C210 = 1.7UFd, C212 = 3.3UFd.
Military, option 1, 220-250v, 48-52Hz. C210=1.0, C212=2.0.
Military, option 2. 90-110v, 48-52v, C210=2.2, C212=4.4
Late model,110-126v, 58-62Hz, C210=3.3,C212=3.3.
HOWEVER, mine is clearly marked 90-110, 48-52Hz.
I don't remember what the original caps were (I will probably find them soon), but my question is, what values for C210 and C212 should I use? Considered suggestions please.
Les.

[RogerEvans]

Les,

If you have the 1800mAH capacity 2/3 AA cells (which is what I have) there is a good reason to stick with the original capacitor values (not the late model). When I put my battery pack together I had a quick look on the web and you will find that trickle charge for NiMnH is not more than 0.05C or 90mA. The 1uF capacitor for C210 gives around 80mA at 240V, but to be more accurate you could work out the difference between average current per half cycle and RMS current. C212 supplies the current when the scope is powered on so stick with the original values.

The major decision is 110V or 240V? If you opt for 240V you will need to change the mains filter capacitors which according to the manual will be 200V rated. If you go for 240V then 1uF and 2uF (or 2.2uF if it easier to find) should be fine, if you opt for 110V 50Hz then the original capacitors should be OK even though the current will be a little less because of 50Hz vs 60Hz. Mine is fine with the original capacitors in place. If you worry about these things, the mains slide switch is only rated at 125V RMS.

Regards,

Roger

[MotorBikeLes]

Roger, thanks for suggestion. I will only be using 230-250v at 50Hz. I will try to check the currents generated at trickle and used by scope in operation when it all comes together. I was confused by some irreconcilables in the manuals' values, but I can see some possible reasons. The earlier ones were 600mAH capacity, later version 700mAH, small but maybe significant difference. Do Nicads have a higher safe trickle charge current than NiMH I wonder?
I am thinking of using a new curly mains lead from a shaver with the smaller 2 pin socket for the supply to the unit, if I can locate a suitable socket. I have an old Braun shaver I may cannibalise.
Les.

[RogerEvans]

Les,

The information I found was from something like 'batteryuniversity', it suggested 0.1C -> 0.2C for trickle charging NiCad but only 0.05C for NiMnH. I wonder if there were complaints from the field that the early ones took too long to charge.

Roger

[6AL5W-Martin]

Originally Posted by MotorBikeLes

Mods, I just spotted that I got the topic heading wrong. It is a TEK 212, NOT a 221 as written. Sorry, please change.
Les.

the 221 use also 2 Packs of 5pcs AA size NiCd Cells. But the Pwer Supply is different it accept all volatages from 90 up to 230V~ so there is nothing to change.

From this little scopes there was five models:

the 211 is a 0.5mc single channel
the 212 is the same but 2 channels
213 is a 1mc single channel with onscreen DMM, it have 2 batteries "D" size
214 is like a 212 but storage
221 is a single channel 5mc and useful for any voltage.

222, 222A and 224 are little DSO, the obsolete lead batteries can be replaced by 4pcs of enersys cyclone 2v 2,5Ah

Batteriepacks of 5pcs AA can be found in the bay.
The restoration of this µTek is always a little expensive, but the instruments self also. They go mostly for more then 100,-€ in the bay (not restorated!) so they are worth to get their batterie packs.

Most significant problems are copper lines demolition by battery acid on the boards of 211, 212, 214 and 221. Except 213, it have 2 large holes for the fat D cells, to the acid will flow in the downside case, not in the board.
222, 222A and 224 hat a seperated battery room, it protect the sensitive boards from acid damages.

picture.

212, 213, 214, 221 and 222. The 211 I will find later anywhere, still searching to get one

restoration of the probes.
Attention: all µTek are made to test high voltage rates, look at the selector of vertical sensitivity. 50v/div, some them can eat 100v/div ! They are build for not groundet work, so the little probes, including the ground crocodiles, have to be high isolated. Have a special look at this to make shure the little scope will be safety when using the high voltage features. The little DSOs 222, 222A and 224 have also isolation amplifiers, they will allow you a high voltage also between the both crocodiles.

greetings
Martin

[MotorBikeLes]

Martin, too much information there (he said enviously).
While I wait for the 2/3AAs to arrive, I thought I had better put it back to stock (but 230v 50Hz), but can't find the missing bits, so I thought I would order new caps for C210 and C212. They are specified at 400v DC wkg. Are these suitable?--

PANASONIC ELECTRONIC COMPONENTS - Film Capacitor, 2.2 µF, 630 V, PET (Polyester), ± 5%, ECQE(F) Series

The Panasonic ECQE(F) series are general purpose, radial leaded metalized polyester film capacitor. ECQE(F) series capacitors have non inductive construction using metalized polyester ...

A spec sheet is here:--
http://www.farnell.com/datasheets/425842.pdf
Not much space, but I may be able to squeeze them in. Not much choice, but at first glance these seem more than adequate.
Les.