Old oscilloscope TESLA BM463 teardown - Page 1
Forum section: electronics / testgear

author: vomocij
author_rank: Newbie
timestamp: April 11, 2015, 08:09:10 pm
content: Hello everyone.My first post here, please excuse my bad English. But i wanna try to share a topic here.Last year i got this old big tesla oscilloscope BM 463 made in Czechoslovakia.Description: Dual Channel 0-20MHz, resolution 20mV - 10V /div, power 110/220V or battery 11-15V, Dimensions(WxHxD) 370 x 280x 430 mm Weight 15,2kg.It is almost fully working just a few things is not in best condition.(front main power switch is broken, one range time base is not working)Photo:From above:Time base switchFrom below: (here is 2 tubes from imputs amplifier PC88 (triode) and 2 tubes from "trigering" PCC88 (double triodes))Main tranformer:With grid on:

author: Vgkid
author_rank: Super Contributor
timestamp: April 11, 2015, 09:16:15 pm
content: Thanks for the teardown, interesting to see the transistors mixed with a few electron tubes

author: HighVoltage
author_rank: Super Contributor
timestamp: April 12, 2015, 01:13:37 am
content: It seems like this TESLA company did built almost everything.Impressive pictures, thank you for sharing.Is that CZECH language printed on the scope?Any idea of how old it is?

author: xrunner
author_rank: Super Contributor
timestamp: April 12, 2015, 01:23:23 am
content: GOOD FIRST POST!

author: vomocij
author_rank: Newbie
timestamp: April 12, 2015, 07:38:29 am
content: Yes, the scope have Czech labels. We need to make everithing in these days, because we can't travel or import anything outside our country. Firstly, I was thinkig it was 50s vitage, but it is from 70s-80s. TkansHere is manual:http://www.docdroid.net/x62u/bm463.pdf.html

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 12, 2015, 08:17:08 am
content: Thanks for posting this. Very interesting. Its amazing what was produced under the Warsaw Pact with little resources.

author: stephunk
author_rank: Contributor
timestamp: April 12, 2015, 08:39:45 am
content: Interesting thing is, that despite of wide component base which Tesla had, most of their products seemed like DIY.Can´t help myself, but when i see TEK465(also 70-80´s) and this BM463, there is apparently a huge difference in approarch to design. Few years ago i also thought, that Tesla made miracles, but you are right, a miracle was, that tesla made something at all in that era.BTW, nice picturesEdit: And the unit is also in very good visual shape!

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 12, 2015, 09:20:39 am
content: You'd be surprised. Cossor in the UK made stuff along similar lines and it worked really well. They didn't have the constraints of availability either.Looking at Tek, they made some longevity problems in their products over the years by being too clever (tunnel diodes). I've got a 453 with triggering problems on the bench at the moment... Mind you it is about 45 years old so I shouldn't really complain

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 12, 2015, 09:45:25 am
content: Weird, I don't see what the tubes would be doing that transistors couldn't. Maybe they had only BJTs, and needed them for voltage followers?Tim

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 12, 2015, 10:12:50 am
content: Tubes have higher grid impedance I understand (I'm lacking in tube knowledge past the basics so this might be wrong), were more reliable than early transistors and they probably couldn't get FETs then. They were probably faster as well. Early versions of my Tek 453 had nuvistors in the channel amps and there are a couple of rectfier tubes in it now. Bear in mind they were state of the art 1966-1975ish and that bit of Europe was 10-15 years behind everything else due to export regs elsewhere.

author: vomocij
author_rank: Newbie
timestamp: April 12, 2015, 11:04:59 am
content: The scope have 10mV/div. I think, back than tranzistors are not that good... or they use tubes because they are more linear.. ? I don't know.I was realy surprised, because there is not any ICs! (For this reson, I was thinking this scope was manufatured in 50s.) I don't now why they not use some, because TESLA manufatured their own ICs copied from world (like Proc. 8080 or 74 logic)

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 12, 2015, 02:54:48 pm
content: Possibly. Tubes did stay on the market in some test gear.No ICs (or at least common ICs) is good. You can still fix them then!I'll do a teardown on my Tek 453 and post it as a comparison when I get some time.

author: vomocij
author_rank: Newbie
timestamp: April 12, 2015, 04:46:25 pm
content: It would be interestingthanks.I was just surprised, because there is no ICs. I don't know why.

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 12, 2015, 04:57:20 pm
content: Probably more expensive than discretes.

author: daqq
author_rank: Super Contributor
timestamp: April 13, 2015, 09:53:23 am
content: Thanks for the teardown! It's always nice to see Tesla stuff.QuoteBeing a giant state owned monopoly helpsyup, Tesla manufactured everything, from consumer radios, TVs, to military stuff, parts for it included.

author: ModemHead
author_rank: Frequent Contributor
timestamp: April 13, 2015, 11:57:25 am
content: What is the purpose of the blue stuff on all the solder terminals?

author: smjcuk
author_rank: Frequent Contributor
timestamp: April 13, 2015, 12:01:56 pm
content: Probably insulation or a marker to say that loom has been ibspected or completed.

author: vomocij
author_rank: Newbie
timestamp: April 14, 2015, 07:33:31 pm
content: Yes, i think so. Insulation or marker. Tkanks daqq

author: SaabFAN
author_rank: Frequent Contributor
timestamp: April 15, 2015, 02:47:09 pm
content: Reminds me of old Radar-Equipment I saw on a swedish destroyer in Stockholm once.Nice teardown. Only one thing missing: Pictures with glowing tubes.

author: david77
author_rank: Frequent Contributor
timestamp: April 15, 2015, 06:19:33 pm
content: Nice scope, thanks for the pictures.It looks very much like German made stuff of that vintage, the two Siemens scopes I own look very much like it, actually. They also have that home-built taste about them and Siemens certainly was at the cutting edge of technology.What I find interesting is that stuff made in Poland, Hungary, the GDR or the Czech Republic always looks very western compared to the russian Klingon style technology. That's true for the parts as well as the styling of the case.

author: orbanp
author_rank: Regular Contributor
timestamp: April 16, 2015, 03:26:39 pm
content: Looks like to be a really nice scope!It is probably from the early '70s.Fairly advanced for a 20MHz unit with tunnel diode base triggering circuit and delay line in the vertical amp!Do you have the schematics as well? The manual did not contain it!The missing time base at one setting is probably just dirty switches.Do not flood any of the wafers with contact cleaner, just use a Q-tip wetted with the contact cleaner and just wipe the metal pads.Peter

author: vomocij
author_rank: Newbie
timestamp: April 18, 2015, 06:00:28 pm
content: Yes, I found some schematic:http://www.docdroid.net/xrap/bm463.pdf.htmlUps :/ I' ve already clean the switches. I did not care about the one range, it is propably bad cap.Thanks guys