Help with an unknown component.

[Oaksey321]

Hi all. Just a quick question. Can anyone identify this for me. After hunting on Google I've drawn the conclusion that it's a capacitor. I'm probably wrong though. So a little help of what it is and what rating it would be would be fantastic thank you.

Kev.

[Station X]

I see that you've posted this in the record player section rather than in Components and Circuits. You might get a better response if you told us what equipment the component came from and its position in the circuit.

[ms660]

Thermistor, a VA1077.

Lawrence.

[Oaksey321]

Hi. It's out of a boots audio Eg 0300 stereo amplifier. I couldn't say where in the circuitry it's from as I'm a novice. I recieved the unit this morning and it was rattling around inside. I can see where it belongs on the circuit board, so I'm trying to find if I can get a replacement from anywhere.

Thanks again. Kev.

[camtechman]

As Lawrence has identified, it's a Mullard Thermistor (a component that changes its' ohmic value) used in amplifiers to control over heating of other components but now obsolete.

However, from the look of the side shown in your photo, it may be retrievable.

Could you turn it over to show the other side and we'll be able to advise.


Tony

[Oaksey321]

If you're wondering if the solder connection is still on the other side, it's not. It's still attached to the leg which is on the circuit board. However, I've attached a pic.

Kev.

[camtechman]

KEV,

I have restored a few in the past, with a success rate of about 40%.


What I'm about to explain will require a good level of soldering skill, especially quick de-soldering & soldering technique and previous experience of using Silver Solder and a good quality soldering iron and solder tips.


Obviously one side (let's call that the good side) still has solder bonded to the component's solder pad but don't do anything to it at this stage because, if the other side (the bad side) won't allow solder to bond to it, then give up!

But there may still be 50/50 chance of making contact to the 'bad' side.

Using de-soldering wick, place the wick on the bad side contact pad and with a soldering iron, place the soldering iron tip on the wick and, at the same time, drag the soldering tip and the wick towards & away from the bottom edge of the thermistor.

If that leaves even a smidgeon of a silver surface, there is every chance that fresh solder will bond to it. NOTE: IT MUST BE SILVER SOLDER! Then do the same process to the good side

Then apply two pre-tinned copper wires, one each side as quickly as possible so it doesn't lift the Silver Solder from the thermistor contact pads.

However, the actual thermistor may be knackered from a previous overload due to another fault in the amplifier.

Good luck.

[Station X]

Sorry to be a pedant, but silver solder is a hard solder which you'll never melt with a soldering iron. It needs a blow torch.

What's needed here is soft solder with some silver content. Silver loaded solder?

[Refugee]

I fixed one of those many years ago. I did not remove the old solder and just dabbed a new pre-tinned wire onto the existing solder quickly and with minimum heat.

[camtechman]

Refugee,

The OP has advised that the 'bad' side has no solder on it (see 2nd pic provided)

Station X

Thinking it through, yes, it needs to be as you state.
I've been spoilt with the small reels of what my late Dad left me and they are different types of silver compound solders (he used them for both jewellery & other jobs)

[crackle]

Would it be possible to clean of the black paint on the bad side and solder to that location. Then some silver loaded (conductive) paint could be used to help reconnect to the area where the original solder has stripped off the conductive coating.
Failing that then maybe tie a tinned coper wire to the bad side with nylon thread and coat the wire and the bad side of the thermistor with conductive paint.
These are only ideas I would try as a last resort.
Mike

[Michael Maurice]

Apparently this component works well