Please post a picture of ALL AXIAL electrolytic caps soldered onto the TS1500 board here. I really need your help. I lost these two (2) caps' correct arrow positions with its value 50V 1uF.
Hello dessony
I haven't opened my TS1500 and I am trying to avoid this.
But if you have a multimeter this might do the job for you.
Just measure resistance between the pads and 0V (middle pin of 7805). If it's near 0 Ohm and the other pad isn't near 0 Ohm (or use the beeper of it) then the one near 0 Ohm is minus and the other is plus.
On a TS1500 (or any Sinclair based computer) this will tell you the direction.
Be aware that this will not help on EVERY schematic. Only if it's used the way Sinclair did (buffering voltages or keeping a pin low for a while like either the 1uF reset capacitor)
Kind regards Paul
In theory, there is no difference between theory and practice. But, in practice, there is.
Ah, but don't forget, the TS1500 uses 4116 DRAM chips which need +12V and -5V as well as +5V. So for the DC-DC switching converter circuit which may use "series" coupling capacitors (I'm not in a position to have a look at a schematic at the moment)
neither capacitor leg may be connected to 0V.
And watch out for the -5V rail, as the positive lead of the capacitor connects to 0V.
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Everything is solved after a few minutes of studying the TS1500's schematic and the TS1500 board with its switching power supply section removed! The C30's positive side goes to a C24's positive side, a D4's anode side and one "leg" of a L4. The C31's positive side goes onto a ground pad area. So the C30's and C31's positive sides must be looking at an area of the 7805 (now, switching mode chip) ground pad and its edge. And, it is now confirmed!
Unpolarised electrolytics are available too. Perhaps this is a question for Mark - can you substitute an equivalent value unpolarised for a polarised cap?
sirmorris wrote: ↑Mon Jun 19, 2017 9:06 am
Unpolarised electrolytics are available too. Perhaps this is a question for Mark - can you substitute an equivalent value unpolarised for a polarised cap?
A quick answer which no doubt others will elaborate on.
Polarised caps back then and possibly even now were usually cheaper and smaller than equiv' non-polarised caps which would have delighted Clive and their electrical properties lend them more to DC circuits, non-polarised tend to be used in AC circuits as opposed to DC and also audio devices, the most common being loudspeaker cross-over units (so Mrs Moggy as a former Wharfedale speaker crossover unit assembler tells me. )
In simplistic terms, an unpolarised electrolytic capacitor is two normal (polarised) capacitors connected back to back.
So as Moggy says, the unpolarised types may be larger and more expensive compared to normal (polarised) capacitors.
But, yes, they can be used. In practice however, the smaller range of values, voltages and case sizes is not so good.
There is also the question about maintenance of the diaelectric. Not a problem for normal (polarised) capacitors, as they have a DC voltage that does this. But if a unpolarised type is used in a DC circuit, will the diaelectric of the reverse connected capacitor degrade over time? I don't know the answer.
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
I lost these two (2) caps' correct arrow positions with its value 50V 1uF. 
Standby alert 
The C30's positive side goes to a C24's positive side, a D4's anode side and one "leg" of a L4. The C31's positive side goes onto a ground pad area. So the C30's and C31's positive sides must be looking at an area of the 7805 (now, switching mode chip) ground pad and its edge. And, it is now confirmed! 
SOLVED! 
