Capacitor polarity?

[kirstyd]

Hi all .Can anyone tell me which end of these red caps is positive .there are no markings that i can see.

[wireman]

Type elkomold into the search box at the top of the page.

[Sideband]

If my memory serves, I think the 'castellated end' is negative.

[ms660]

If that's in a Hacker I think the castellated end is +ve.

Lawrence.

[Hartley118]

Best to connect your voltmeter across it with the set running. That’ll tell you the positive end.

Martin

[Station X]

Originally Posted by Sideband

If my memory serves, I think the 'castellated end' is negative.

Originally Posted by ms660

If that's in a Hacker I think the castellated end is +ve.

Lawrence.

Well that'll get the OP confused!

Try this link as alluded to in post #2:-

https://www.vintage-radio.net/forum/...ad.php?t=25759

[ms660]

Originally Posted by Station X

Well that'll get the OP confused!

Try this link as alluded to in post #2:-

https://www.vintage-radio.net/forum/...ad.php?t=25759

https://vintage-radio.net/forum/atta...4&d=1404667310

https://www.vintage-radio.net/forum/...5&d=1472223916

Lawrence.

[Analogue man]

If one end of the can is metal and the other end is rubber then it is the rubber end which is + it will also usually be the end with the indented ring around the can.

[kirstyd]

yes its a hacker cavalier .the castellated end just has the wire coming out .the other end has a black rubber cap [making me think that was negative] with the wire coming out of that .i will take another photo tmro

[Diabolical Artificer]

Connect a DMM to chassis/ground, meter on continuity, check each end of the cap. The end that beeps and has no big DC resistance is negative.The rubber bung is a give away too = positive.

Andy.

[dazzlevision]

The attached TCC data sheet will explain all.

[Station X]

[ms660]

Just as I thought, the castellated end is +ve, in the OP's photo the Grey wire connects to the cathode of the valve's triode.

Lawrence.

[Lucien Nunes]

I was going to say, surely it is obvious from the circuit which end is which?

As it happens I was testing some Elkomolds the other day. I usually take a dim view of them and routinely replace, but I was interested to see that all of the dozen or so that I tested were, at the moment, functioning perfectly with good leakage, ESR and capacitance readings. They fared better than the red/black Plessey PCB moulded-case elkos of the same age, of which about 40% were U/S, some completely non-functional.

Only if all three main parameters and seal condition are good would I ever consider leaving vintage electrolytics in circuit.

[AD360 Rob]

These confused me first time I came across them (In a Hacker Cavalier) After fitting replacements, I found I'd wired them all the wrong way by assuming they followed what I considered to be normal practice with positive at the rubber bung end.

[kirstyd]

here are photos of the ends . Seeing them for the first time i assumed that the black end was negative . The blue ones are what i had in mind for replacements

[Lucien Nunes]

i assumed that the black end was negative

And you were right. But if in doubt, just trace the circuit, the end going coming from the valve cathode must be positive and the one going to ground the negative.

If you are interested to date the machine, don't forget that the capacitors you are about to snip out will usually give you a date a few months prior to construction. At the bottom of the print it will say TCB/xx where xx is the alphanumeric date.

The Vishay axial caps (formerly BC, formerly Philips) are my regular choice too.

[kirstyd]

Thanks everyone for the usual expert advice

[kirstyd]

Hi all
Well i have been busy changing capacitors and some resistors powering up after each procedure. All went well until today when i changed the two 820K resistors on the valve sockets .One of them was reasonably ok but the other was way out so i replaced both . i put the valves back in and switched on but there were no signs of life . I checked over the work i had just done [the two 820K resistors ] but all was ok . The only other thing i had touched was the valves so i had a look at them wiggling them around and cleaning the pins then swapping the two ecl86s over that's when the thing came to life . I then swapped them back and sure enough it was dead again . I tried the valve in another machine [A fidelity one valve job] and got nothing so it seems I have a dead valve but what did surprise me was that even with only one working ECL86 the Cavaliers amp still had a good output. I wont run it again till i have a working valve

[Lucien Nunes]

Because of the way this phase splitter works, the valve whose triode is the preamp will still work and deliver (reduced) output even if other valve's triode (used as the inverter) is dead. But if the valves are swapped to make the dead triode the preamp, there will be no output. However, if one pentode section is dead it should still work with them either way round, unless (e.g.) the output transformer is open-circuit on one half, in which case the dead valve in the socket with the good winding and vice versa would give no output. So it's worth a double-check of the DC voltages when you put the new valve in, to ensure all is well other than the valve.

When encountering a major malfunction like no output, it's usually worth checking DC voltages as a first move, before swapping valves etc, as there is often a clear pointer to the problem that can be traced in seconds.