125 - MARCONI Universal Bridge TF2700: Restoration and test

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I got this MARCONI Universal Bridge TF2700 cheaply from eBay. It is an LCR meter, I think my unit was built around 1971 and the battery that was left in it was probably from 1995. It leaked (of course) and that part is the restoration of this meter because otherwise this bridge seems to works just fine.
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0:00 Intro
0:46 battery leak
2:11 opening
3:09 inside
4:26 function knob
4:56 first power
5:29 how to use it
8:29 testing a cap
11:27 another cap
12:39 who is right?
16:42 inductor test
18:26 external AC
19:32 adding bias
20:43 restoration
21:41 battery choices
23:39 final test

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Опубликовано:

6 авг 2024

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Комментарии : 15

@hullinstruments Год назад

Test equipment... Specifically bridges... Were an addiction of mine for years. 😁

@DucatiMTS1200 11 месяцев назад

Super video. I just got one so your video will help speed me up repairing the instrument. I used to use one of these bridges when I was an electrical apprentice back in the 70's! My unit is cosmetically immaculate, but the oscillator is unserviceable. Thanks for a very informative video. You speak excellent English. Cheers, William.👍

@TheHWcave 11 месяцев назад

Thanks for the kind words. Apart from the battery my unit was fully working, so I was lucky. I use the bridge quite often. I recently made a video about how I used it to check MLCCs. None of my other LCR meters allowed that kind of testing. The oscillator is not terribly complicated and by testing the components you should be able to find what is wrong. As a start, does it even get power? And the socket for ext AC and ext DC have contacts that interrupt the signal from the internal oscillator when something is plugged in. It could be that these contacts fail to close or are dirty so that even with nothing plugged in no oscillator output reaches the bridge.

@t1d100 Год назад

A super find. Kudos.

@hullinstruments Год назад

0:30 "some markings from the previous owner in fluorescent paint on the top... NICE" That can be up there with another well-known RU-vid electronics tagline "BLOODY HELL". Bur said in an accident that almost sounds like singing

@ivolol Год назад

To get a better test of a battery's voltage, you can put a 1k resistor (for a roughly suitable ~9ma with a 9V) across the battery to get some normal current flowing, and then measure its voltage.

@TheHWcave Год назад

Yes, I agree. One should always measure battery voltage under (representative) load. For what its worth, I just tested again with the battery inside the TF2700 using the method described @23:00 (10MOhm range and R INT DC) and it's still 10.05V

@TheDefpom Год назад

Retest after you recap the unit, those old blue caps from Phillips could well be bad by now

@TheHWcave Год назад

Appreciate the tip, you have done way more restorations and are probably right. To be honest, whenever I recapped old test equipment as a precaution, I found that the vast majority of electrolytics are better than their reputation. Those few that were bad were also clearly obvious so (bulges, gunk spills ...). To be fair, I tested the extracted old caps only for capacitance and ESR, and they were still acceptable. I did not test for leakage. But for the DATRON 1030a, I did test the large caps for leakage and they turned out ok . Of course, every cap manufacturer (and production run) is different and if a cap is still good today, it does not mean it still be a year later. So for peace of mind, I should do a recap. .

@TheDefpom Год назад

I think I was looking at that on eBay…. Lol

@TheHWcave Год назад

We share the same hobby and hunting ground..