Volume fault ? Trio 9R 59D

[Station X]

Where has 500 (units not stated) come from?

The meter is on the ohms X1 scale and it's reading about 0.7 indicating a resistance of 0.7 ohms.

Did you zero your meter before using it? Touch the leads together and adjust the OHMS ADJ. pot until the needle sits at zero at the right hand end of the scale.

If you want to measure 500k (500,000 ohms) I suggest setting the meter to the X10K scale which means you'll have to multiply the reading (read from the ohms scale) by 10,000. So a reading of 50 would indicate 500,000 ohms.

[Humptydumpty]

Graham sorry i dont know how to read off the scale .
What i do know would not buy me a penny candle .
But compare the tags - tag 1 and 2 and 2 and 3 the one side the reading is very low .And i do set the needle before test each time. On X1K on tags 1 and2 it reads 5.5 on the 3 and 2 tags it reads 17 . Have did have to turn the pot in the other direction to get both readings .The meter is old and need an analog .

[Station X]

If you're measuring resistance, which you are, the scale to read off is the green one. Note it reads from right to left and is very cramped at the left hand end.

On the X1K range a reading of 5.5 would indicate 5,500 ohms or 5.5 kohms. A reading of 17 would indicate 17,000 ohms or 17 kohms.

What reading do you get between tags 1 and 3 on the X10K range?

[Humptydumpty]

Graham with the test meter set on ohms X10 and needle set to zero .
With red test lead on the tag 1 and black lead to tag 3 i get zero reading
Thats with the pot turned up, and with it also turned down .

[Station X]

The maximum resistance you can usefully measure on the X1 range is about 1000 ohms or 1 kohm. A good pot will measure 500 times that ie 500,000 ohms or 500 kohms.

Repeat the test using the X10K range.

Try it on the old pot and a new one so you can see the difference.

[Station X]

I see you've edited your post to read X10 instead of X1.

You need to use the X10K range though.

[Humptydumpty]

On x10 and old pot i get no readings at all on any combo of tags .
But on the new pot i get 500k it just about moves on the far left to the 500 k mark .
To read the old pot i need to be on X1K setting .Remember this old pot is still in the set could the wiring to the board and other things create a problem?

[Station X]

If you test the new pot on the X10K range you should get a reading near to 50 which multiplied by 10k, ie 10,000, gives a value of 500k or 500,000. This is much better than trying to read the cramped left hand end of the scale. Do this with the old and new pots.

There will be no problems checking the old pot in-situ as it's isolated DC wise.

[Humptydumpty]

Graham there must be a problem i get no readings onX10K on the old pot
On the new one i get 50 k like you say .
Just waiting for the mini audio wire to come .I will remove the old pot and replace it for a new one.The wire thats there now is to short to work on .I will attach all the wires before it goes in to the face plate .I think you have done all possible to explain to me how the meter works .I have just ordered a new multimeter . This way it will be easy to read it off .But i will still need to multiply by what ever setting its on .Thank you for now . Trev

[Station X]

That looks like a prefectly good analogue (moving coil) meter to me.

If you're using the X10K scale the reading needs to be multiplied by 10,000 or 10k.

50 X 10,000 is 500,000 or 500k which is correct.

Your results measuring the old pot indicate a crack in the track, so replace it.

A tip when measuring resistance, or indeed voltage, is to start with the meter on the highest range, in this case X10K, and progressively switch down the ranges to X1 stopping at a point where the scale is easiest to read.

If you have problems interpreting the reading on an analogue meter, you might like to consider purchasing an Auto-ranging digital meter. You just set it to read resistance and the result is displayed along with any suffix such a 'k' or 'M'.

Some people don't like auto ranging meters, but I'm quite fond of mine.

[Humptydumpty]

Graham it was exactly like the other set i had first .
I removed the pot and opened it up to find the main part inside was cracked though the centre .

[Humptydumpty]

Originally Posted by Station X

If you test the new pot on the X10K range you should get a reading near to 50 which multiplied by 10k, ie 10,000, gives a value of 500k or 500,000. This is much better than trying to read the cramped left hand end of the scale. Do this with the old and new pots.

There will be no problems checking the old pot in-situ as it's isolated DC wise.

Just checked again by per your instructions .Set on X10K i am getting more like 45 - 47 k its a 470 k on the new pot . I will try the pot once more thats in the set .

[Humptydumpty]

As per last post Test old pot readings are - All readings are all 100 ohm any combo 1 and2 1 and 3 2 and 3 and not 45--47 .

[Humptydumpty]

No more test to be done .I find there is a problem on the old pot. .If i test the new pot i can see the problem . The readings are as you said only not 50ohm but 47 ohm .It is a 470k pot
So the old one reads not 500k or 470k . The reading i get is 100.ohm on top scale X10K why is it reading 100ohm ?.
The pot is out ,and a new one in place ,just need to solder the pcb Wednesday ..Talk lWed after its in . If you are about Graham..I have ordered an auto test meter .

[Station X]

If you're seeing a reading of 100 on the X10K scale that indicates that the pot is measuring 1 million ohms or 1 Megaohm which is twice the correct value and shows that the pot is faulty. 100 x 10,000 = 1,000,000.

I spoke of an auto-ranging meter. An auto test meter may be something for working on automobiles.

You can see my own auto-ranging meter in this thread:-

https://www.vintage-radio.net/forum/...ad.php?t=42194

Note that it has a single resistance range denoted by the Ω symbol.

[Humptydumpty]

Nice bit of kit Graham . Still waiting for mine to arrive . I was mixed up over the 100ohm and now way could i work it out in my head . Another thing on this meter of mine i can see 1x, 10x , and 1,000x , and 10,000x but what is the 1x for is that to read right from the scale?.I will cal back later on today .Off to finish the job i started yesterday .I am not happy with it .The wire is a little to large although its the same type Phil sent me . But i have to have things in three lots and purchased othe wire as well .Dont seam to find solid i core shielded wire anymore.It was al stranded hat i found .

[Station X]

Originally Posted by Humptydumpty

Another thing on this meter of mine i can see 1x, 10x , and 1,000x , and 10,000x but what is the 1x for is that to read right from the scale?.

I assume you mean the analogue meter pictured in the current thread?

What's actually shown on the range selector switch is X1, X10, X1K and X10K. Think of 'X' as meaning "times". You multiply or times the scale reading by the figure against the pointer on the range switch.

So if the scale reading is 50:-

On the X1 range the measured value is 50 ohms. 50 times 1.
On the X10 range the measured value is 500 ohms. 50 times 10.
On the X1K range the measured value is 50,000 ohms. 50 times 1000.
On the X10K range the measured value is 500,000 ohms. 50 times 10,000.

As I've said before if you're uncertain of the value switch ranges until the pointer sits at a useful point on the scale.

FINAL ANSWER

[Humptydumpty]

Thanks for that i will put it in my note pad and keep a page in the meter cover. Graham its done . The pot was as we said faulty . Volume working as it should now . Last night i did a postmortem operation on the old pot . And i can see a part of the carbon track that was very shiny .And only one 1/4 of it had carbon showing i think this was the place it was doing nothing .I did take pictures but its hard to see the track .So Graham this is another post you can put to bed for now . My next job is to recap the Trio no1 .