What do these capacitor markings mean - in your opinion

[UHU]

Hello - could you help me identify what the markings on this strangely marked capacitor mean - I think the markings read:-

"4.7"
"25s"
"B47"

here is a photo with an arrow pointing to the item in question

The rest of the capacitors I think are:-

"7d 100 16V" = 100uF 16Volts

"7f 10 16v" = 10uF 16Volts

"5c 22 16v" = 22uF 16Volts

"6e 1 50v" = 1uF 50Volts

Any ideas who made these - Lelon?

Am I interpreting these markings correctly?

Regards.

[Agent24]

Re: What do these capacitor markings mean - in your opinion

Probably 4.7uF 25v

The 'random' markings like 6e and 7f are probably date-codes. It looks like that one capacitor is a different brand to the others.

Since there would be no logical reason to use a decimal point in a date-code, so the 4.7 is probably the value. Which means the voltage could be either 25 or 47. 47v is not a standard rating (50v is) Neither is 25uF a standard value - (22uF is the usual)

Also 4.7uF makes more sense as the capacitor is the same size as the 1uF and 10uF parts, while the 22uF and 100uF ones are larger.

[UHU]

Re: What do these capacitor markings mean - in your opinion

I agree - and having measured the dimensions of the capacitors are: -

4.7 - 4.0mm by 5mm Tall (PCB to top)
100 - 6.2 by 5 Tall
10 - 4.0 by 5 Tall
22 - 5.0 by 5 Tall
1 - 4.0 by 5 Tall

So, the size also points towards 4.7uF which I will have to choose and order - I can't think of anything else it might be other than a capacitor - you are right it is different to the rest of the capacitors - wonder if it was a factory rework or was it a design change?

As this is a Burglar Alarm speech dialler connecting to the phone line as well as the alarm control panel signalling outputs I am hoping that none of these capacitors are the non-polarized/bi-polar type which you tend to find in this kind of telephone equipment.

However as far as I know there are no non-polarized capacitors of this SMD type available?

The 100's will probably become Panasonic EEHZA1E101XP while the 22's EEHZA1V220R - the rest I have yet to choose - comments on replacement capacitor choices are welcome.

The reason it is being recapped is that to record the voices (for the alarm calls) and set the telephone numbers to call and other options a regular telephone is plugged into the dialler and the DTMF digit tones are used to navigate voice menus and record alarm messages (location, burglar, fire, power, hold-up/panic etc.) BUT there is tremendous buzzing/sizzling interference being heard in the programming telephone and the dialler is becoming a bit slow in operation.

Regards.

[Behemot]

Re: What do these capacitor markings mean - in your opinion

You can replace them with ordinary THT caps, just cut the leads and bend them. They are much more available and I think of better quality.

[UHU]

Re: What do these capacitor markings mean - in your opinion

Thank you for all your inputs and advice - yes, all the capacitor values / suggestions were correct - all the capacitors have been replaced - as suggested it was simpler, cheaper and better to use regular THT caps (and empty the surplus parts bin at the same time) in many places.

The Vocaliser is back up and running in fact the performance is better than new! Seizes the phone line, picks up the phone and dials out very quickly and reacts to the acknowledgement (DTMF keys being pressed by recipient of the alarm call) instantly - before it did not always "hear" the acknowledgement DTMF tones so it would hang up and call somebody else.

The audible buzzing is massively reduced but not gone altogether - which got me thinking - this is a long explanation/question.

I used to have another Pyronix Vocaliser installed elsewhere (manufactured several years before this one) and it was quiet compared to this one.

When first I installed this one I noted the buzzing (which wasn't as bad as it became before the capacitor replacement) and also noted this buzzing / noisy one had an open sided "ETAL" transformer while the older quieter one had a closed sided "ETAL" transformer.

Between then and now the alarm control panel (that controls the newer noisy Vocaliser) was replaced (newer bigger version of the same Control panel model) and the manufacturer of the Control Panel had decided to change from a linear power supply to a switch mode power supply in the control panel which also made the buzzing worse.

Anyway Noisy Vocaliser has a "ETAL P5100" BUT the Quiet Older Vocaliser according to the picture on the cover of the Pyronix Vocaliser manual had an "ETAL P1200" which according to the ETAL datasheets is "vacuum impregnated".

So, would any transformer experts on this forum know if I changed the "ETAL P5100" over to an "ETAL P1200" would that make the buzzing noise stop?

Is there nowadays an ETAL transformer that perhaps even outperforms the P1200 ?

For instance Broadband/ADSL did not exist when the Vocaliser was first manufactured - are newer ETAL models optimized for ADSL performance - after all ADSL passes around the dialler - there is an ADSL filter installed that is meant to be separating the Dialler from the ADSL signal but it is always better to stop the interference at source (the Dialler) than just filter it out.

ETAL datasheets seem to imply that the 5100 is a cheaper version of the 1200.

Does "vacuum impregnated" basically mean potted in resin while under a vacuum to glue the transformer core laminations together so they can't vibrate?

[Behemot]

Re: What do these capacitor markings mean - in your opinion

That would make sense, different kinds of glues, laminations etc. are used to dumpen noises which transformers and coils may emit.

I only theoretised so far about dealing with transformers where it is kinda difficult to get under the tape and layers of winding when it is already finished. But what about maybe pretty much boiling it in some hot lackquer bath for couple hours? That may make the lackquer get into the capilars between the winding turns…