Philips SBC850 Multimeter
 

Hi, this is my first post, I have only just registered to the site so hope I am getting this right.
I have an old Philips SBC850 multimeter which I found in the bin. Cosmetically, it's almost like new and the analogue scale works fine. However, someone has used it on the wrong setting or something and fried at least 6 resistors. Would anyone know where I could obtain a circuit diagram since their values are unreadable? Thanks, Stephen

Re: Philips Sbc850 Multimeter
 

Stephen,
post a photo please!
Radiomusem knows only SBC-851, s I think the UTS-001 i.e. can be (very?) similar...

Re: Philips SBC850 Multimeter
 

Hi, and thank you for the quick reply. It looks to me that your SBC851 is a new version of the same thing, it looks very similar but close up the front has slightly different scales, and the pcb inside is totally different. However I appreciate the info as I have wondered for some time about using the sbc-851 to fix my meter.

Philips SBC 850 Multimeter
 

Good morning guys today I found a vintage multimeter, it was from my grandfather, the problem is that there is a burnt resistance. I tried to find information about this resistance on the Internet but only in this forum, in this page, a boy has a problem similar to the mine, and I think now I can help him a bit with the photos of my multimeter, because his has many more resistances burned than mine and I instead only have one burned. My invitation to him is to take photos with better quality, because his photos are blurred and not very magnified. So maybe let's fix two of multimeters ;) Anyway, any of you new, do you have any idea about the resistance you need? Have a good day everyone!

Re: Philips SBC850 Multimeter
 

Hello giacomo16v and welcome to the forums.

It's been over a year since Crowella visited the forums, But you're welcome to post pictures here.

Re: Philips SBC850 Multimeter
 

Sorry, my mystake....so this is the foto:)

Re: Philips SBC850 Multimeter
 

I think the color of resistance are all brown for 1,2,4,5 ......the middle is to much burned and dont know if that is one information for understand something......example.....in commerce the only one resistance that you can find is one resistance all brown if the 1,2,4,5 are brown....somebody have an idea???

Re: Philips SBC850 Multimeter
 

Hello giacomo16v,

What make and model is your multimeter ? it looks similar but not the same as the Philips SBC850 photo.

Saluti,

David

Re: Philips SBC850 Multimeter
 

Are you able to view the other side of the board to see what components the burnt resistor connects to ?

Re: Philips SBC850 Multimeter
 

Hi, never did restore that old meter, however, I still have it, and intend to replace those resistors, when it burnt out, it actually created a dry/disconnected solder joint, therefore none of those resistors were destroyed, can't guarantee their accuracy though, I can measure the resistance for you. Would very much like to speak to you about it.

Re: Philips SBC850 Multimeter
 

Good morning crowella meanwhile I believe you can replace those burnt resistances with the good ones that are seen in my photo and then You should try to understand that last Resistance that burnt to me what kind of value it has.....For example, I know that for sale there are not all the values ​​of resistances imaginable, so it could be that, having the first, second, fourth and fifth brown stripes, it could be that the third is inevitably of a single color.....What do you think

Re: Philips SBC850 Multimeter
 

Close up pictures (use macro mode if your camera has it) of small sections of the PCB would enable all the component values to be identified from their colour codes.

Re: Philips SBC850 Multimeter
 

This is the high resolution photo .... I also tried with a Wood lamp to see if under the burn I could understand what the written resistance was but I could not see anything
:beer:
So the only possibility is to understand if with the 4 brown stripes that are on the unburned resistance, the central strip (the third one) can be of only one possible color, because maybe there is only that on the market.

Re: Philips SBC850 Multimeter
 

The writing denotes the type of diode fitted for example 1N4148.

Interestingly the two resistors connected in series have 13M7 ?? written under them which most likely denotes their combined value. It also appears that all the other resistors have their values written under them. If you snip out the burned resistor you may be able to read its value from the PCB.

Re: Philips SBC850 Multimeter
 

Maybe like this the colors of resistances of the first one one the left, of before, are better. i've create one pdf 4000dpi resolution

Re: Philips SBC850 Multimeter
 

The burnt resistance is disconnected and unfortunately it is not read under what is written, as the board is also burnt, as I said I also tried with a wood lamp to read under the burn but nothing appeared.

For the other resistances just do the calculation of the value from the colors as they are all intact. The only maybe that I will change is the one close to the white variable resistance, as it is well seen, which is a bit burnt underneath and perhaps, even if it is not like the other with all brown stripes, it has not kept its given value by the colors on the stripes.

Re: Philips SBC850 Multimeter
 

Unfortunately, the knob attached to the black variable resistance is attached very strongly and I would like to avoid forcibly detaching it, in order not to compromise the aesthetics of the multimeter, which could be damaged by tele operation.

Re: Philips SBC850 Multimeter
 

I'll leave it to someone with a better value of resistor colour codes than me to determine the values.

Have you determined which ranges work and which ranges don't? With this information it might be possible to determine whether the burned resistor is a multiplier resistor associated with a voltage range, a shunt resistor associated with a current range, or a resistor associated with a resistance range.

Knowing the values of the other resistors associated with the faulty circuit function may enable the value of the burned resistor to be calculated.

Does the meter scale plate give any indication of Full Scale Deflection (FSD) current and internal resistance?

What ranges does the meter have? The same as in post #3?

Re: Philips SBC850 Multimeter
 

To do this I would have to remove the pcb from the plastic container and unfortunately it is very difficult as the knob attached to the black variable resistance is attached very firmly and I risk damaging the outside of the multimeter. Crowella, by chance, can you disassemble the pcb and send us a photo of the electrical tracks?

Re: Philips SBC850 Multimeter
 

yes my multimeter is the same of the post #3

Re: Philips SBC850 Multimeter
 

I'm not suggesting you dismantle anything.

You could fit a battery and see whether the resistance ranges work. Just select each range in turn, touch the test leads together and see if you can zero the scale at the right hand end using the OHMS control.

Then how about measuring the voltage of a 1.5V and 9V battery?

Re: Philips SBC850 Multimeter
 

You must have very good eyesight if you can distinguish 4 brown bands on this burnt resistor !

Re: Philips SBC850 Multimeter
 

I can now see from post # 6 where you think there are 4 brown bands, I am not so sure myself.

Some of the other resistors look like they have 6 bands and others 5 bands, so the burnt resistor could be a 5 or 6 banded resistor but the sixth band is a temperature coefficient value, so it does not matter in terms of the resistance value determination.

From your high resolution photo my old eyes are still struggling with some of the band colours on the various resistors, but from what I can determine they do not obviously appear to be similar values to the Philips UTS-001 circuit resistors.

If the burnt resistor does have 4 browns bands with a band in-between, then that would mean the resistor is 11X (first, second and third colour band digits) multiplied by 10 (4th brown band = the multiplier of 10) where X could be anything between 0 and 9.

In this example the most logical colour for the middle band would be black (0) this then would be 110 multiplied by 10 which is 1.1kohms which is a preferred (standard) resistor value. The 5th (outer/last) brown band being a +/- 1% tolerance band.

But resistors in DVMs may not be preferred values, i.e. they may be special values to suit the meter calibration.

Have you tried measuring the burnt resistor to see if any resistance value can be measured ?

Re: Philips SBC850 Multimeter
 

I still have not tried to measure the burnt resistance because unfortunately I do not have a multimeter with a charged battery to be able to do it, however under the microscope the bands of the burnt resistance can be clearly seen that there are 5, and fortunately the 4 external to the central one can be seen well that the color is brown. Your deduction on the color of the central band gives me hope and I thank you for understanding my little electronic reasoning, and more practical. Now I will look for a way to create a 3 volt battery to power the other multimeter I have at home and measure the burnt resistance. thanks a lot DMcHamon

Re: Philips SBC850 Multimeter
 

Hi, sorry for the late reply, the PCB will come out, I will send what info I can, but need to find the meter again first!

Re: Philips SBC850 Multimeter
 

Hi Crowella! Sorry but only now i have see your answer. So thank you, i'm waiting for your good news!:-)

Re: Philips SBC850 Multimeter
 

Greetings to all from Italy.
I think this discussion is the only one in the world that talks about the SBC850. And of course those who find it are those who have a broken SBC850. Unfortunately, I am no exception, the same broken resistance, soon I will post some photos.
It would be very important for me to repair this multimeter, because it has a great emotional value for me.
I hope that a solution can be found together.

Re: Philips SBC850 Multimeter
 

I took new photographs of my SBC850 and I noticed that it is less burnt than yours, I can partly trace the colors, by exclusion you can get there, can you help me? So we finally fix them!

Re: Philips SBC850 Multimeter
 

Red denotes that the value begins with a '2', but that's not much help.

Is the resistor's value written under it on the Printed Circuit Board (PCB)?

Re: Philips SBC850 Multimeter
 

Your burnt resistor is intact in the attachment to post #15, so a forum member with better knowledge of colour codes than me should be able to determine its value.

Re: Philips SBC850 Multimeter
 

I looked with a powerful lens, after red there seems to be brown, and the last one is definitely brown. I believe that other users can be of help since the resistance above them is burnt, instead on mine you can still see the colors. It's already a step ahead, isn't it?

Re: Philips SBC850 Multimeter
 

There is something written on the PC, but it doesn't read, I should remove the resistance to see if the writing has burnt or is legible.

Re: Philips SBC850 Multimeter
 

Six band resistor calculator here:-

https://www.digikey.co.uk/en/resourc...or-code-6-band

Try reading he values of the good resistors and compare them to what's printed on the PCB.

Re: Philips SBC850 Multimeter
 

Using the calculator I make it 143 ohms 1%, starting with brown, yellow etc, if one tries to read it from the other end, the yellow band then is not a valid colour for the % tolerance.

Re: Philips SBC850 Multimeter
 

Actually looking at the chart in my Post # 23, yellow has a 4% tolerance, so in that case reading it from the other end (the red band) it is 210 x 1,000 so 210kohms at 4%.

This makes it confusing. There is supposed to be a spacing between the bands to enable one to know which is the first/start band but difficult to see the spacing.

Re: Philips SBC850 Multimeter
 

The lower value makes more sense with the failure mode, the higher value would have much less chance of being burnt from measuring voltage with it set to the current or resistance ranges.

David

Re: Philips SBC850 Multimeter
 

I have just found this circuit in a drawer, I know it is a schematic for a Philips multimeter but unsure of the model. It might help locate the part you are looking for or give some direction.
John

Re: Philips SBC850 Multimeter
 

Very good!

If Gtman72 can tell us the resistance and full-scale deflection of the meter in his multimeter we'll know whether it's the correct diagram.

Several resistors there with values commencing 14.

Re: Philips SBC850 Multimeter
 

I don't think that diagram is for the SBC850 as it shows a separate socket for the 2.5A range. Also looking through the pictures in this thread the SBC850 has a 100K pot and x3 ranges instead of the x2.5 ranges shown on the diagram.

David

Re: Philips SBC850 Multimeter
 

Not the correct diagram I’m afraid. It shows a 20k/V version of an SBC 851.

The diagram shows a separate AC/DC switch rather than AC and DC ranges at different positions of the main switch, 2AA cells rather than 1, 4 Ohms ranges rather than 3, and different current ranges. Resistor values will be different.

However, assuming a reasonably conventional circuit with a universal shunt, and comparing the front panel picture in post 3 with the resistor values visible in the attachment to post 15, we can hazard a guess at the missing resistor value.

The resistors at the top of the picture are obviously the voltage range resistors, and unsurprisingly are undamaged. These resistors show that this is a 20k/V meter (for DC).

Resistors close to the missing resistor have values of 143, 1430, and 1.41 Ohms

Unless I’m very much mistaken, these are the universal shunt resistors, and the missing resistor is between the 30mA and 300mA switch positions and should be 14.3 Ohms. The resistors between the two pots are 2840, 274, and 27.4 Ohms. These would match up the resistance ranges seen in post 3 with current ranges of 0.3mA, 3mA, and 30mA. There is no 0.3mA range on the main switch, but the top of the 1430 Ohm would give that range for the highest resistance range.

If this theory is correct, DC voltages will read high by 20 to 30%, current ranges of 30mA and below will read very high, and current ranges of 300mA and above won’t read at all.

If you just short the stub ends of the missing resistor, the voltage ranges should read correctly. If you fit a 15 Ohm resistor, the resistance ranges should be OK, but the 30mA current range will read a bit high. Adding a 330 Ohm resistor across the 15 Ohm resistor should give near enough 14.3 Ohms.

Then again, I might be very much mistaken!

Stuart

Re: Philips SBC850 Multimeter
 

Well done.

That makes the burnt out resistor in post #30 14.3R (Brown, Yellow, Orange, Gold) and the resistor next to it 143R (Brown, Yellow, Orange, Black).

Re: Philips SBC850 Multimeter
 

Probably I'm too late but I have this meter in original working condition, so if you still need any info please let me know!

Re: Philips SBC850 Multimeter
 

Ciao Luca certo che sei utilissimo se il tuo ancora funziona ti prego di postare una foto del circuito dove si vedano bene le resistenze cosi risolviamo tutti!

Hi Luca sure that you are very useful, if yours still works please post a photo of the circuit, where you can see the resistances well so we can solve them all!

Re: Philips SBC850 Multimeter
 

It would be wonderful if you posted some photos of the high resolution resistors, so anyone who has an SBC850 with this problem can solve it !! In the whole web there is nothing like it, only here is there information about it!

Re: Philips SBC850 Multimeter
 

OK I will post pictures of mine when at home.

Regards,
Luca

Re: Philips SBC850 Multimeter
 

Hello all and sorry for the late reply, here you have some pictures of mine.

Re: Philips SBC850 Multimeter
 

More pics

Re: Philips SBC850 Multimeter
 

Thank alot LUCA!!!are you Italian?

Re: Philips SBC850 Multimeter
 

Luca sorry could you shoot another time the photo of this resistor in the pics that i have post? I can't understand the color of the second stripe from right or you can read the value on the board under the resistor?....and that is the resistor that i need 8-\ Thank a lot

Re: Philips SBC850 Multimeter
 

In any way i ask to the moderator of the forum, how is possible that me and luca have the same model of multimeter and some of the good resistor are different?i was good in elettronic a lot time ago.....now i don't remember any things.....:-):-)