Test Equipment Anonymous (TEA) group therapy thread

[TERRA Operative]

True, but then you need to wear earplugs when you check operation at high volume, unless you like rocking out to sine and squarewaves.

[Vince]

No high volume for me !  The buyer will find out.

I test at low levels, that I can stand. How many 303 sellers bother scoping the output, measuring the amplification and check the waveform ?
None that I saw. I am already well above the average seller here, I don't feel guilty ! Sorry ! 

100mVpp and that gives me 4.0Vpp at the output,and it's already quite loud as it is to be honest !

I don't see why anyone would try to use anywhere near the max power of this amp, unless he wants to lose his hearing, it's pure madness.

[tautech]

Oh you just can't imagine how fed up I am with this thing and how impatient I am to see it go out the door...

   

Be angry at yourself, your mistake did this ! 

[Vince]

You are missing the point. 

[Specmaster]

No high volume for me !  The buyer will find out.

I test at low levels, that I can stand. How many 303 sellers bother scoping the output, measuring the amplification and check the waveform ?
None that I saw. I am already well above the average seller here, I don't feel guilty ! Sorry ! 

100mVpp and that gives me 4.0Vpp at the output,and it's already quite loud as it is to be honest !

I don't see why anyone would try to use anywhere near the max power of this amp, unless he wants to lose his hearing, it's pure madness.

The real loudness will vary of course depending on the sensitivity of the speakers being used. Most true Hi-Fi speakers will require a relatively high output wattage to deliver much volume, whereas speakers from a say a average domestic music system are high sensitivity, because they are designed to make the most in terms of sound level from very low output wattage amplifiers. This why such systems normally steer well clear of giving any real specifications that mean something. Normally they will quote output power with either Peak watts or Music Power Watts and Hi-Fi will always quote it in terms of RMS watts with low level of distortion, but other sound system have a far higher level of distortion and noise levels.

[tautech]

You are missing the point. 

Really ? Your probe point missed its mark, did it not ?

You need get some better probes and some with only the very point exposed like when you have the condom on a scope probe or when you go probing anything SMD you'll need wear sunglasses to protect yourself from the blinding flashes.

Better tools and better techniques save us all immense amounts of grief and time. 

[Vince]

No high volume for me !  The buyer will find out.

I test at low levels, that I can stand. How many 303 sellers bother scoping the output, measuring the amplification and check the waveform ?
None that I saw. I am already well above the average seller here, I don't feel guilty ! Sorry ! 

100mVpp and that gives me 4.0Vpp at the output,and it's already quite loud as it is to be honest !

I don't see why anyone would try to use anywhere near the max power of this amp, unless he wants to lose his hearing, it's pure madness.

The real loudness will vary of course depending on the sensitivity of the speakers being used. Most true Hi-Fi speakers will require a relatively high output wattage to deliver much volume, whereas speakers from a say a average domestic music system are high sensitivity, because they are designed to make the most in terms of sound level from very low output wattage amplifiers. This why such systems normally steer well clear of giving any real specifications that mean something. Normally they will quote output power with either Peak watts or Music Power Watts and Hi-Fi will always quote it in terms of RMS watts with low level of distortion, but other sound system have a far higher level of distortion and noise levels.

Interesting. So you mean a 100W hifi speaker will actually be much less efficient than a 100W cheap speaker ? It will convert less of that 100W into actual sound pressure, and more into heat dissipated in the speaker coil ?

[Vince]

You are missing the point. 

Really ? Your probe point missed its mark, did it not ?

 

Actually no it did not. It was well in place and when it was, I tried holding it steady with my left hand while trying to operate the camera with the right hand to take a picture of the scope screen for Zoli. Once I had taken the picture and moved my right arm into place to put the camera back onto the bench... that's when the left arm moved a bit and the probe wandered a little bit and .... SPARK !

Better tools and better techniques save us all immense amounts of grief and time. 

Yes I am learning Tautech, I am learning a bit more every day !
As for equipment to get, the list is so long that it's difficult to forecast when such or such particular piece of equipment will get purchased next.

Anyway, I found the problem and the fix is under way. See schematic. One of the two beefy wire-wound 0.3 ohms resistors died open-circuit, well, reads 2Megs or something...

Now after looking at my stock of sub ohm resistors, I came with two solutions, pictured below. Either I put x3  0.1R resistors in series, which would give me the closest to the nominal value... so that's the favoured option... or, put two 0.56R in // , which would give 0.28R, which is less than 10% off the nominal value, which is probably on paar with the tolerance of the original resistor I bet....


However I am not too sure what these two 0.3R do. Are they current shunt that tell the amplifier about over-current condition so it can shut / calm down the output ?  If so, I guess the value is not so critical, being 5 or 10% off will I guess trigger the protection a tas later... but just a tad, the amp is unlikely to self destruct eh ?!  And even if it did, it would be the user's fault for listening too loud to his music !

Or do they hae another purpose, in which the absolute value maybe is not so critical, but where maybe it would be important for the two resistors to be MATCHED ?

Hmmmm.... I guess in order to avoid all these risks and ifs and buts... I should just go for the 3x0.1R in series option to get back to the nominal value and sleep on both ears tonight.

See ? I am getting good  / quick at fixing these driver boards already ! 


As for the replacement transistors, I think I will go for the 2N5320 / 5322 because they are available easily, though very expensive.
The BC 441 / 461 must be too old, they aren't as easy to find. "Dada" is thinking the same it seems, they sell the 2N not the BC.

[Specmaster]

@Vince, never mind, we have all been there sometime or other, I seriously doubt that there is anyone on this forum who can honestly claim that they have never caused a problem while probing before. 

[Vince]

Thanks Spec !

OK I went for the 3x0.1R in series option. Just soldered that in place, quick test..... driver board is back alive !

NO MORE PROBING on this amp now !

Tomorrow I will order the transistors.

The smell of victory is getting stronger ans stronger !

Whatever money I get for this 33/303 pair, it will be well deserved ! 


Oh, forgot... it goes without saying that I don't feel comfortable playing around with low value WW resistor and NOT even be able to actually meeasure them accurately !
A 4 wire capable bench DMM is on the cards, has been for a long time.

For now I make do with my Fluke 11. Has a 0.1 ohms resolution, and I know for a fact that it's voltage and resistance measurements are way more accurate than it's advertised spec of... horrible %.
So I short the leads, get a solid / stable 0.2 ohms, then when I measure my 0.1 resistors I get a solid 0.3 ohms reading on the display, which is  better than no test at all, but still I dream of 4 wire measurements in the lab, regularly ! 

[tautech]

However I am not too sure what these two 0.3R do.

They are series series conductors and very important in the signal path. WW they are too and maybe wound on ferrite cores.
Of the OC ones snap one in half to see what the former is.


While you might be happy with the preceding, it's very valuable learning that stands us all in good stead for whatever the future throws at us.
Liking your steady progress Vince. 

[Vince]

On another note, some good news : after much delay and fear of getting lost or damaged... I finally, finally received my Rochar Niksee DMM type  A.1466 !!! 

It was well packaged but still there is some minor metal work needed : front top right corner of the top cover (see close-up shot below) is out of shape. It's totally inconsistent with a shipping damage, given the way that it was packaged. Still, didn't notice it in the sellers pictures.... but for 10 Euros the thing, complete and in good overall nick other than being super dirty.... I am still over the moon, so happy to have secured this puppy !

Will make it look as good as can be of course.

At the back we have a pritner output, cool... especially since this meter has good resolution, 20,000 counts I think, so probably a decent accuracy to match that as well. So would be cool to use it for some data logging.

Also at the back, we see stickers from the " CNES " institute. It's French for " Centre National d'Etudes Spatiales ", the public body that does research related to space stuff.
So pretty cool ! This meter has a nice history.... these stickers are there to stay 

One thing that shocked me with this meter, is the big range switch on the right side / plugin.

It is VERY hard to turn and VERY loud !  CLUNK CLUNK CLUNK !! 
It feels solid and indestructible for sure !
Either it's intentional or it needs some lubrication.... the truth probably lies somewhere in between...

Sadly I can't play with this thing just yet as the bench is full of QUAD Stuff which I want to 100% finish before I can work on anything else.

So since it will take quite some time before I get to play with it, I wanted to post a quickie about it just to say the drama with the courier is over and I finally got it, and in one piece.

[Specmaster]

Thanks Spec !

OK I went for the 3x0.1R in series option. Just soldered that in place, quick test..... driver board is back alive !

NO MORE PROBING on this amp now !

Tomorrow I will order the transistors.

The smell of victory is getting stronger ans stronger !

Whatever money I get for this 33/303 pair, it will be well deserved ! 


Oh, forgot... it goes without saying that I don't feel comfortable playing around with low value WW resistor and NOT even be able to actually meeasure them accurately !
A 4 wire capable bench DMM is on the cards, has been for a long time.

For now I make do with my Fluke 11. Has a 0.1 ohms resolution, and I know for a fact that it's voltage and resistance measurements are way more accurate than it's advertised spec of... horrible %.
So I short the leads, get a solid / stable 0.2 ohms, then when I measure my 0.1 resistors I get a solid 0.3 ohms reading on the display, which is  better than no test at all, but still I dream of 4 wire measurements in the lab, regularly ! 

You don't need to have 4 wire capability, all you need is a decent 2 wire meter with a Null function, short the leads together, press the null button and it will reset the display to read zero, then measure your .3ohm resistor and your meter will display .3ohms. A 4 wire meter is just spending more money, unnecessarily.

Edit, Come on, you have all of those lovely Metrix hand held DMM's, stick you meter probes in one of them, select ohms range, short the tips together, and pre the REL button just before you measure your 0.3ohm resistors and your done, no need to waste more money on a 4 wire meter...

[Zoli]

...
Interesting. So you mean a 100W hifi speaker will actually be much less efficient than a 100W cheap speaker ? It will convert less of that 100W into actual sound pressure, and more into heat dissipated in the speaker coil ?

Efficiency in the speakers are characterized by SPL(sound pressure level; sound pressure @1W&1m, IIRC); typically in the 80-100dB range.
Driver trannies: you can try BD139-40, if you manage to get the lowest rated ones(h_FE:40-100, typically -6 suffix); those would be much more easier to install. Higher rated ones(h_FE>100) can cause problems...
Square wave: look decent, something I would expect from a good 70-80's amp.

[Specmaster]

Interesting. So you mean a 100W hifi speaker will actually be much less efficient than a 100W cheap speaker ? It will convert less of that 100W into actual sound pressure, and more into heat dissipated in the speaker coil ?

If you check out the magnets on the speakers, you will notice that cheap speakers will have far smaller and less powerful magnets than those on decent quality Hi-Fi speakers. This means that Hi-Fi speaker requires more wattage to produce enough energy in the voice coil to overcome the effect of the strong magnet.

[vk6zgo]

Interesting. So you mean a 100W hifi speaker will actually be much less efficient than a 100W cheap speaker ? It will convert less of that 100W into actual sound pressure, and more into heat dissipated in the speaker coil ?

If you check out the magnets on the speakers, you will notice that cheap speakers will have far smaller and less powerful magnets than those on decent quality Hi-Fi speakers. This means that Hi-Fi speaker requires more wattage to produce enough energy in the voice coil to overcome the effect of the strong magnet.

The large speakers used in the late 1950s & '60s had very large magnets, & were efficient, plus were used in massive, efficient enclosures.
With the fashion for "bookshelf" speakers, enclosures reduced radically in size.

This made the enclosures less efficient, plus the speakers were smaller, & had to use some clever engineering to get reasonable bandwidth.
The trade off was poor overall efficiency, hence the high electrical power required in modern amplifiers.

The advent of power semiconductors made this relatively easy to do, so modern Hi-Fi systems get away with small enclosures.
The upside is we don't have to work around big, obtrusive boxes in our loungerooms.

[Messtechniker]

If you check out the magnets on the speakers, you will notice that cheap speakers will have far smaller and less powerful magnets than those on decent quality Hi-Fi speakers. This means that Hi-Fi speaker requires more wattage to produce enough energy in the voice coil to overcome the effect of the strong magnet.

The large speakers used in the late 1950s & '60s had very large magnets, & were efficient, plus were used in massive, efficient enclosures.

Fully agree. Still using some 12-in. Tannoy Monitor Gold speakers
in large enclosures. Something like 70 cm x 40 cm x 35 cm.
Also very much liked the larger version with 15-in. Tannoy speakers
in something like 170 cm x 80 cm x 70 cm. Quite some umpf....
especialy at the low end:scared:

A 1 W amp is enough for a jolly good volume in a 40 sqm room.

Normally my Tannoys are connected to a 50 W power amp which
is absolute overkill. But nowadays power amps do not come
any smaller than this. Had to doctor the volume pot to increase
its usable range.

[TERRA Operative]

Boooooo.

I'm trying to get sticky labels to label all the 3.5" floppy disks I'm using for my test gear and retro PC, BUT.... Of the two Japanese brands of labels that are advertised for floppy disks (one being a 3M brand...) BOTH turned out to be complete crap and do their best to peel themselves off the disks within minutes of sticking them down. Turns out the adhesive is 'temporary adhesive for easy removal', completely the opposite of what you want for labelling disks..... Complete crap. 

So, a check of Amazon.com found me some Avery 2" x 2-3/4" sticker labels with strong adhesive, and says they will ship them to Japan, and even gives a shipping cost (not terrible), perfect I'll get those.

Nope! Amazon says they'll ship these to Japan in the search results page and in the actual listing but when I go to pay, it says NOPE, no shipping to Japan for YOU!. BOOOOOOO!   



Anyone want to do me a shipping favour?

[Black Phoenix]

Do they ship to China?

[Neomys Sapiens]

Boooooo.

I'm trying to get sticky labels to label all the 3.5" floppy disks I'm using for my test gear and retro PC, BUT.... Of the two Japanese brands of labels that are advertised for floppy disks (one being a 3M brand...) BOTH turned out to be complete crap and do their best to peel themselves off the disks within minutes of sticking them down. Turns out the adhesive is 'temporary adhesive for easy removal', completely the opposite of what you want for labelling disks..... Complete crap. 

So, a check of Amazon.com found me some Avery 2" x 2-3/4" sticker labels with strong adhesive, and says they will ship them to Japan, and even gives a shipping cost (not terrible), perfect I'll get those.

Nope! Amazon says they'll ship these to Japan in the search results page and in the actual listing but when I go to pay, it says NOPE, no shipping to Japan for YOU!. BOOOOOOO!   



Anyone want to do me a shipping favour?

can do: PM

[Neomys Sapiens]

You don't need to have 4 wire capability, all you need is a decent 2 wire meter with a Null function, short the leads together, press the null button and it will reset the display to read zero, then measure your .3ohm resistor and your meter will display .3ohms. A 4 wire meter is just spending more money, unnecessarily.

Ok, the URL seems to suffer from malignous redirection and some flunkie is posing as our friend Specmaster here!

Else it would be crystal clear that everyone should have at least one desk multimeter with 4 wire capability AND that the requirement to measure resistances below 1 Ohm is a perfectly good reason to aquire a milli/micro-Ohmmeter!

[Ice-Tea]

Else it would be crystal clear that everyone should have at least one desk multimeter with 4 wire capability AND that the requirement to measure resistances below 1 Ohm is a perfectly good reason to aquire a milli/micro-Ohmmeter!

You woke my inner Ferrengi.

https://www.ebay.de/itm/144799654046?hash=item21b6bb609e:g:IfAAAOSwvxNjaP9Z

[Specmaster]

You don't need to have 4 wire capability, all you need is a decent 2 wire meter with a Null function, short the leads together, press the null button and it will reset the display to read zero, then measure your .3ohm resistor and your meter will display .3ohms. A 4 wire meter is just spending more money, unnecessarily.

Ok, the URL seems to suffer from malignous redirection and some flunkie is posing as our friend Specmaster here!

Else it would be crystal clear that everyone should have at least one desk multimeter with 4 wire capability AND that the requirement to measure resistances below 1 Ohm is a perfectly good reason to aquire a milli/micro-Ohmmeter!

Nope it is I alright  , but I was under the distinct impression that Vince was looking to raise some Euro's not spend some, and for measuring resistances of the value that he was looking at, there is no need for a 4 wire meter. I have 3 such meters myself and I can't recall ever having to use them in such fashion, 2 wire has always been good enough, especially once the lead resistance has been nulled out of the readings. I like to only really buy what I need, but then again, I'm not in the same position of a lot of friends here who are single, I have to keep SWMBO happy as well 

[Neomys Sapiens]

You don't need to have 4 wire capability, all you need is a decent 2 wire meter with a Null function, short the leads together, press the null button and it will reset the display to read zero, then measure your .3ohm resistor and your meter will display .3ohms. A 4 wire meter is just spending more money, unnecessarily.

Ok, the URL seems to suffer from malignous redirection and some flunkie is posing as our friend Specmaster here!

Else it would be crystal clear that everyone should have at least one desk multimeter with 4 wire capability AND that the requirement to measure resistances below 1 Ohm is a perfectly good reason to aquire a milli/micro-Ohmmeter!

Nope it is I alright  , but I was under the distinct impression that Vince was looking to raise some Euro's not spend some, and for measuring resistances of the value that he was looking at, there is no need for a 4 wire meter. I have 3 such meters myself and I can't recall ever having to use them in such fashion, 2 wire has always been good enough, especially once the lead resistance has been nulled out of the readings. I like to only really buy what I need, but then again, I'm not in the same position of a lot of friends here who are single, I have to keep SWMBO happy as well 

I was almost going so write a taunting reply akin to 'which spouse would not be perfectly happy about an improvement of the in-house measurement capabilities' when suddenly the view of my ex-SWMBO snarling at me 'I do not want to live in a f****** laboratory' appeared in my mind. So, duh.

[factory]

On another note, some good news : after much delay and fear of getting lost or damaged... I finally, finally received my Rochar Niksee DMM type  A.1466 !!! 

It was well packaged but still there is some minor metal work needed : front top right corner of the top cover (see close-up shot below) is out of shape. It's totally inconsistent with a shipping damage, given the way that it was packaged. Still, didn't notice it in the sellers pictures.... but for 10 Euros the thing, complete and in good overall nick other than being super dirty.... I am still over the moon, so happy to have secured this puppy !

Will make it look as good as can be of course.

At the back we have a pritner output, cool... especially since this meter has good resolution, 20,000 counts I think, so probably a decent accuracy to match that as well. So would be cool to use it for some data logging.

Also at the back, we see stickers from the " CNES " institute. It's French for " Centre National d'Etudes Spatiales ", the public body that does research related to space stuff.
So pretty cool ! This meter has a nice history.... these stickers are there to stay 

One thing that shocked me with this meter, is the big range switch on the right side / plugin.

It is VERY hard to turn and VERY loud !  CLUNK CLUNK CLUNK !! 
It feels solid and indestructible for sure !
Either it's intentional or it needs some lubrication.... the truth probably lies somewhere in between...

Sadly I can't play with this thing just yet as the bench is full of QUAD Stuff which I want to 100% finish before I can work on anything else.

So since it will take quite some time before I get to play with it, I wanted to post a quickie about it just to say the drama with the courier is over and I finally got it, and in one piece.

Got loads of catching up to do, had unusable internet since last Wednesday night, down to dial-up speeds or worse, this site & many others just don't work properly or time-out.  Finally back online with a temporary 4G hub, had to connect my phone to the PC to use it's WiFi, as the 4G hub has no network port. 

Good to hear you got the Rochar DVM finally, mine must be the export version as the panel is labelled in English, still not had a look at it. You just need to find the ohms plug-in at a reasonable price now.

Someone on the radio forum found these connectors, that should fit the one on the back (if you don't want to replace it), they just need an earthed mains cable fitting and a three pin plug, thankfully mine came with one.
https://www.ebay.es/itm/131440976335

David