Philips GM 4249 AC bridge

[Refugee]

This was a skip find in the mid 1980s and worked with a good magic eye back then. Due to a poor workshop and lack of time it has been left in storage since then.
The magic eye has been staring at me for too long and it is time to check it out and fix it if needed.
I have cleaned it up and sorted out the dried grease in the variable capacitor and a cap reform will be next.
It has got a lovely thermal fuse with a bed spring on it and a strange "mint" capacitor that looks like it may be a green mustard capacitor.
With the type of capacitors and only the electrolytic and one or two mica types perhaps it only needs a reform.

[AlanBeckett]

That looks pretty much like the standard beast for the era, and is similar to several others. Geany has a Thread currently running about a different one and there've been others. I've got several myself, both Valve and Solid State.

However, despite spending some 45 years in the Electronics Industry I would guess that the number of times I used one in anger could be counted on the fingers of one hand. The usual methodology for a suspect Component was simply to change it. The only time I used a Bridge was to select Capacitors for an application which required a non-standard value, or to check/select an Inductance.

So, what were they used for? They can't have been cheap, although possibly the areas I worked in were 'peculiar'.

Alan

[pwdrive]

We had a Hunts capacitor bridge in the workshop I worked at, we too hardly ever used it as regarding run of the mill service work, however they are handy for capacitance value checks when building tuned circuits etc ie: checking min to max capacitance on variable capacitors and trimmer capacitors if their original specified value is unknown.
Worth getting going whichever way.

Lawrence.

[tiv48]

"The magic eye has been staring at me for too long "
rob t

[Refugee]

It is looking at me all bright eyed like an angel eye now

   

I have had a go at working out the Dutch service manual and operating manual and it looks like it would have been sold with a probe or two that you dipped into liquids to measure them.
What I did establish back in the 1980s is that it can be used to measure an unknown capacitor against a known one and this is still true today. The maximum ratio being plus or minus 10. It also has a resistance bridge mode too although not as accurate as my bridge Megger but you don't have to wind it.

   

Now it is time to look into finding a can of hammer finish silver paint to do the cabinet after I have cleaned the inside of the dial.

[Refugee]

I have now checked out the resistance bridge section and it is working fine although not as accurate as my hand cranked Megger one with its 4 digit decade box bridge arm. In spite of this it still shows up high quality resistors from boxes of bits very well.
It is just the inside of the glass and a coat of paint and it is all done.
As it was made to measure the resistance of liquids and not really for capacitors I have to fit a reference capacitor and one that is under test and it then reads off on the scale quite accurately the catch is that it does not have a switched capacitor internally. Although it looks nice it is not quite as convenient as the Hunts type in use.
I am now looking for a capacitor decade box to plug in for full functionality.

[pwdrive]

A good all round bridge is the Marconi TF2700 if you ever come across one.

Lawrence.

[AlanBeckett]

.... or an Advance BR1 which is remarkably similar

Alan

   

[pwdrive]

So it is, not come across the Advance one, I have the Marconi, it's got a dodgy pot but I can get it to work ok, works well on low value pf and uh.

Lawrence.

[Refugee]

If I see a full stand alone LC bridge I will go for it.
The way to tempt fate is to go to the trader whom sold me that lovely giant Megger for a tenner for the case. If knows what an item is he charges 20 quid.
He sometimes has items of physics lab gear and has had resistance decade boxes in the past.
I will keep an eye out.