Test Equipment Anonymous (TEA) group therapy thread

[Specmaster]

You could always print some 

NOT GOING THERE

 

Well not for a while yet, never say never!

And you'll be right there with me. 

Well they say don't they, "Great minds think alike and fools seldom differ!"  Thing is by joining the club later, we can learn by others mistakes and so get it right. 

[med6753]

You could always print some 

NOT GOING THERE

 

Well not for a while yet, never say never!

And you'll be right there with me. 

Well they say don't they, "Great minds think alike and fools seldom differ!"  Thing is by joining the club later, we can learn by others mistakes and so get it right. 

Sounds good to me!  I'll keep using that excuse.   

[tggzzz]

ENOB depends on signal level on this as the noise at some input attenuator settings is terrible. It's only a cheapy. However I can measure down to about 45dB down on a large signal which is good enough to anti-peak the harmonics. Anyway I just did this quickly as it's lunch time and it's looking much better. So harmonics are down 30dB on this which isn't terrible for an analogue function generator. The sine is looking much better now too.

I'd say performance is about the same as a 3310A. Edit: but cheaper and easier to fix!

Anything to avoid filling in my tax form, or confronting my well justified visceral fear of faultfinding my Datron 4903...

Here's the Analog Discovery with the HP3310A at three different levels, ~30Vpp, ~3Vpp, and ~0.3Vpp.
At higher levels the 9th harmonic is the worst (only -55dBc), but most are better than -63dBc.
At lower levels the 3rd hamonic is only -55dBc.

EDIT: re-uploaded three different screenshots, doh!

[worsthorse]

A whole lot of small scale TTL logic on that board!  Sorry for the sideways photo.    Will fix that tomorrow, too.

Not TTL - RTL. There are a lot of Fairchild uL923 JK flip flops on that board. They run at up to "2m/c" on 3.6V.

The microLogic family was the first available set of integrated circuits.

Count yourself lucky they didn't use the analogue /2 and /5 circuits in the Tek 184

Indeed it is RTL not TTL. Careless typing on my part. But I fear not for I designed stuff in both RTL and ECL back in the day. And if the logic doesn't work, I can always haul out the Tek 308 to analyze it!   

[bd139]

ENOB depends on signal level on this as the noise at some input attenuator settings is terrible. It's only a cheapy. However I can measure down to about 45dB down on a large signal which is good enough to anti-peak the harmonics. Anyway I just did this quickly as it's lunch time and it's looking much better. So harmonics are down 30dB on this which isn't terrible for an analogue function generator. The sine is looking much better now too.

I'd say performance is about the same as a 3310A. Edit: but cheaper and easier to fix!

Anything to avoid filling in my tax form, or confronting my well justified visceral fear of faultfinding my Datron 4903...

Here's the Analog Discovery with the HP3310A at three different levels, ~30Vpp, ~3Vpp, and ~0.3Vpp.
At higher levels the 9th harmonic is the worst (only -55dBc), but most are better than -63dBc.
At lower levels the 3rd hamonic is only -55dBc.

That's pretty excellent actually. Better than some of the wein bridge oscillators I have seen. Thanks for the data.

Also no thanks for making me consider purchasing an Analog Discovery. Has a lot of interesting capabilities that does and doesn't take the whole bench up!

Edit: so minor update. Went through cal and found some offset issues. That allowed me to kick everything down to 40dBc.

[PA0PBZ]

Here's the Analog Discovery with the HP3310A at three different levels, ~30Vpp, ~3Vpp, and ~0.3Vpp.

Maybe I DO need new glasses, but I see no difference between the 3 pictures 

[tggzzz]

Here's the Analog Discovery with the HP3310A at three different levels, ~30Vpp, ~3Vpp, and ~0.3Vpp.

Maybe I DO need new glasses, but I see no difference between the 3 pictures 

Look again!

Not sure how I managed to create three different files with the same image, but clearly my cockup.

Thanks.

[PA0PBZ]

Look again!

Now even I can see the difference! 

[tggzzz]

That's pretty excellent actually. Better than some of the wein bridge oscillators I have seen. Thanks for the data.

Even better when I've changed my original post to give the correct information; thanks PA0PBZ!

Also no thanks for making me consider purchasing an Analog Discovery. Has a lot of interesting capabilities that does and doesn't take the whole bench up!

Provided you can live with 30MHz bandwidth and a GUI interface, it is a surprisingly flexible and useful piece of kit. I suspect it could be JavaScripted to be low-end ATE. Download the waveforms software; you can play with it in demo mode, under Windows or Linux.

If you can, get an educational discount. (But it would be cost-neutral for you: you could sell several boat anchors that can be replaced by the AD )

I find the complementary advantages of a Tek 485 (bandwidth, simple/fast interface) and AD (DSO/AWG with 14 bit ADC/DAC) to be compelling.

[factory]

See below 

That is a massive fail. I would expect a linear supply if it was going to fail to suddenly output nothing.....not jump up to 56V. Can you imagine what would happen if you had a 3.3V logic board connected when that happen? That would be spectacular flames that would make bd139 proud. 

Have you noticed how many Mastech power supplies I  have owned? I've fixed a lot but owned precisely ONE and that was a very long time ago

All the cheap ones are nasty as fuck. There's usually a cost cutting thing in them which goes bang pretty quickly. I was going to write a detailed rant about this but decided that a visual explanation is better:



I have fixed at least 5 that have done this over the years. And 3 with other problems, usually someone shorted the output diode by connecting a battery the wrong way across it 

Edit: for some absolutely stupid reason the failed position of the relay is always full voltage. I don't know why they do that. The whole design works rather well apart from that gigantic cock up. I suspect these are "cut and paste" designs mostly. I've seen several variants with exactly the same schematic.

Mine is nothing like that at all, it has 4 transformer taps, 2nd tap comes in around 6.5V, 3rd tap 15.5V and 4th tap at 24V. I have used it quite a bit and it has so far given me sterling service. The last time I saw the particular model I have it was listed around the £100 mark but at that kind of money I'd rather get a 2nd hand TTi unit or similar.

There was a Isotech branded dual version of that Mastech PSU in the bin at work a few years ago, I pulled it out and found despite being a bit battered it was working, but when I heard the click of the relays I remembered those failures, so back in the bin it went. 

Bigclivedotcom did a video a while ago of one of the cheap higher current ones after finding out about one that had caught fire.



David

[bd139]

Yeah those switchers are a bit scary. The majority of the cost of these power supplies is the shipping so they are constantly optimising for lowest mass. The SMPS gets pretty close to minimum mass. Also cheapest price. Never connect something you care about to a shit power supply.

[factory]

Grabbed a small stash of HP type screws a while back too. It is getting harder to get anything non metric or Whitworth. We still get some UNF and UNC's turn up on gear so with pain some can be sourced locally but the pain level is rising.

Looking at the feet I made them a bit chunky but it will make it stable if you are floating it I guess.

They're pretty solid feet. Don't think they are too chunky at all. I've never seen an authentic one before that isn't smashed to bits and I don't think anyone has so they look fine  . Thing is rock solid on them.

As for American screws, we have these guys who do not insane quantities of screws of all sorts: https://www.spaldingfasteners.co.uk/ ... For 10x 6-32 washers, 5x 6-32 7/8" pan head screws and 5x 6-32 1/4" countersunk it was £2.76 including delivery and arrived in 2 days

If you don't mind waiting for them to be made, ACCU have a much wider variety of fasteners; https://www.accu.co.uk/ common sizes are more readily available.

I bought some #6-32 3/16" screws for the side covers of HP TE, I've already used some for the 333A to replace some incorrect thread ones that had been force fitted by a previous repairer im-pairer, I'm guessing they lost the original side panels too as they look home made.


David

[factory]

Yeah those switchers are a bit scary. The majority of the cost of these power supplies is the shipping so they are constantly optimising for lowest mass. The SMPS gets pretty close to minimum mass. Also cheapest price. Never connect something you care about to a shit power supply.

If they do burst into flames it would be wise to never leave one running unattended either, better still bin it and get a decent one.

Are these compact Xantrex/Sorensen XPD 60V 9A PSU's any good? I bought this one to eventually replace my cheap Rapid Electronics one and provide a higher voltage range, I did briefly have the Xantrex version but it was DOA (stuck in current limit), thankfully the seller was able to replace it with the Sorensen one, which is indentical apart from the output terminals/binding posts.



David

[bd139]

Xantrex ones are quite decent I understand. Same sort of league as the TTi ones.

I tend to hit RS and buy a Meanwell switcher if I need some juice however.

[xrunner]

Now another radio restoration - a Yaesu FRG-7000 shortwave receiver for $35. Couldn't pass it up. Dirty but appears to be working OK. Needs an alignment and the freq. display is off by 2 kHz, but no big deal should come back after work is done.

[factory]

And today's bench project, the Tektronix Television Test Signal Generator:



Tomorrow, I will put up a separate thread on this one but here's one photo of the inside:



A whole lot of small scale TTL logic on that board!  Sorry for the sideways photo.    Will fix that tomorrow, too.

That looks very nice, can't be many of those left, apart from the manual there isn't much on the Tek wiki for it either;
http://w140.com/tekwiki/wiki/067-0601-00

I have a Tek type 141 PAL TV signal generator in my collection, will add some pictures when I get round to repairing it.

David

[mnementh]

Yeah those switchers are a bit scary. The majority of the cost of these power supplies is the shipping so they are constantly optimising for lowest mass. The SMPS gets pretty close to minimum mass. Also cheapest price. Never connect something you care about to a shit power supply.

That there sounds like a VERY compelling candidate for 10 Laws of TEA No 12...

It is FOR SURE the reason I gladly suffered the hernia-inducing addition of those two 200VA Lambda CC/CV linears to my own workbench...

mnem
*out widda family*

[mnementh]

Huh... The whole frontend of that thing is just SO cheap & cheesy looking... but still, I find something about it endearing.

Maybe it's the fact it is so shamelessly lowest-possible BOM GREEN LED (even the linear scale)... it doesn't try to hide the Hulk-juice, it OWNS IT.



Except I'll bet the current side of that scale is even cheesier RED LEDs, isn't it...? 

mnem
*maybe it's memories of prehistoric Drake and Uniden C-Band receivers on the shelf*

[Specmaster]

Yeah those switchers are a bit scary. The majority of the cost of these power supplies is the shipping so they are constantly optimising for lowest mass. The SMPS gets pretty close to minimum mass. Also cheapest price. Never connect something you care about to a shit power supply.

Yeh, to be fair though, as Clive points out, the actual units do appear to quite well designed and built electrically. The weak link as is the case with almost all Chinese kit like this is A/ The mains lead, being undersized and copper plated Aluminium strands along with a possible sleeved earth pi, which when fully pushed into the socket then looses the earth connection  and B/ The low voltage leads are of low quality and have very poor terminations. I would expect anyone on this forum would be aware of these issues and do the right thing by replacing both power and low voltage leads anyway.

The actual fire was more then likely the result of either loose internal connections to the banana sockets and/or the poor terminations of the cable to the banana plug itself.

The power supply itself does not have any relays in its as it a switched mode unit and so does not have any transformer taps to switch in and out. I have the very same model as the one Clive was looking at except its a 30V 5A output. Personally I would never like to use it much above 3A if I needed more than I'd get the next size unit up as I always think its best to under run these things anyway, nothings going to last long if it is constantly running at or near its theoretical maximum.

The other one I have is a proper linear power supply with a stonking great big transformer at is heart with the relays, which is my preferred and go to power supply the switcher only comes out to play if I need higher voltage or a second unit to replace temporarily, 2 rails in the DUT. I've had mine for 3 years without any problems at all, but I always double check the connections before switching them on.   

[factory]

Edit: boring one but my TG210 arrived. Perfect condition. Nothing wrong with it at all. £35 well spent.

Every bench at work had TTI TG215 function gens built in, only difference being an added LCD, but most people preferred the older Farnell Sine/Square oscillators with the larger frequency control. I must confess I swapped mine for an extra bench multimeter in the last couple of years we were repairing electronics.


We also had matching TTI bench multimeters and their excellent dual 30V 2A PSU's built in, the only bit of kit we didn't use much were the 20MHz Leader CRO's, being built in the controls were too far away to make them useful.

David

[Specmaster]

If they do burst into flames it would be wise to never leave one running unattended either, better still bin it and get a decent one.

Are these compact Xantrex/Sorensen XPD 60V 9A PSU's any good? I bought this one to eventually replace my cheap Rapid Electronics one and provide a higher voltage range, I did briefly have the Xantrex version but it was DOA (stuck in current limit), thankfully the seller was able to replace it with the Sorensen one, which is indentical apart from the output terminals/binding posts.

(Attachment Link)

David

Personally I wouldn't give it bench space, it is just such a crude unit, doesn't even support a fine and a course adjustment on either the current or the voltage sections.

Like mnem says you are better off with a far higher quality unit, but and here's the rub, I fully expect that even with a top flight unit such as a TTi etc there is always going to be a possible failure mode that could result in damage to the DUT, nothing and I mean nothing apart from using batteries to power the equipment, could result in an over voltage situation in the event of a failure occurring, so its best to never leave anything connected to power supply unattended. 

[factory]

Huh... The whole frontend of that thing is just SO cheap & cheesy looking... but still, I find something about it endearing.

Maybe it's the fact it is so shamelessly lowest-possible BOM GREEN LED (even the linear scale)... it doesn't try to hide the Hulk-juice, it OWNS IT.



Except I'll bet the current side of that scale is even cheesier RED LEDs, isn't it...? 

mnem
*maybe it's memories of prehistoric Drake and Uniden C-Band receivers on the shelf*

Nope, presumbly to keep costs down they used those nice GREEN LED's for the current scale too, both the voltage & current controls are multi-turn with a connector on the back for remote control, it also has an OVP control too. 


I did prefer the smaller colour-coded binding posts on the Xantrex one, maybe I can change them.


As usual it was footless when I got it, but I sorted that with some rubber feet from the local hardware store's closing down sale, need to do a teardown with pictures at some point.

David

[bd139]

Yeah those switchers are a bit scary. The majority of the cost of these power supplies is the shipping so they are constantly optimising for lowest mass. The SMPS gets pretty close to minimum mass. Also cheapest price. Never connect something you care about to a shit power supply.

Yeh, to be fair though, as Clive points out, the actual units do appear to quite well designed and built electrically. The weak link as is the case with almost all Chinese kit like this is A/ The mains lead, being undersized and copper plated Aluminium strands along with a possible sleeved earth pi, which when fully pushed into the socket then looses the earth connection  and B/ The low voltage leads are of low quality and have very poor terminations. I would expect anyone on this forum would be aware of these issues and do the right thing by replacing both power and low voltage leads anyway.

The actual fire was more then likely the result of either loose internal connections to the banana sockets and/or the poor terminations of the cable to the banana plug itself.

The power supply itself does not have any relays in its as it a switched mode unit and so does not have any transformer taps to switch in and out. I have the very same model as the one Clive was looking at except its a 30V 5A output. Personally I would never like to use it much above 3A if I needed more than I'd get the next size unit up as I always think its best to under run these things anyway, nothings going to last long if it is constantly running at or near its theoretical maximum.

The other one I have is a proper linear power supply with a stonking great big transformer at is heart with the relays, which is my preferred and go to power supply the switcher only comes out to play if I need higher voltage or a second unit to replace temporarily, 2 rails in the DUT. I've had mine for 3 years without any problems at all, but I always double check the connections before switching them on. 

On the build quality, yes and no. A lot of the problems on these, as per the linear ones, occurs on the little front panel terminal board wiring. The binding posts are usually well attached and fit for purpose but the wire that joins the regulator board to the front panel is plated chinesium core and it corrodes. After a few years the strands break off then the thing goes up in smoke. That’s actually what killed my first mastech linear that was used to fast charge RC NiCd batteries.

If they do burst into flames it would be wise to never leave one running unattended either, better still bin it and get a decent one.

Are these compact Xantrex/Sorensen XPD 60V 9A PSU's any good? I bought this one to eventually replace my cheap Rapid Electronics one and provide a higher voltage range, I did briefly have the Xantrex version but it was DOA (stuck in current limit), thankfully the seller was able to replace it with the Sorensen one, which is indentical apart from the output terminals/binding posts.

(Attachment Link)

David

Personally I wouldn't give it bench space, it is just such a crude unit, doesn't even support a fine and a course adjustment on either the current or the voltage sections.

Like mnem says you are better off with a far higher quality unit, but and here's the rub, I fully expect that even with a top flight unit such as a TTi etc there is always going to be a possible failure mode that could result in damage to the DUT, nothing and I mean nothing apart from using batteries to power the equipment, could result in an over voltage situation in the event of a failure occurring, so its best to never leave anything connected to power supply unattended. 

Indeed. This is one reason I have a crowbar between my radio and the power supply  . One fail and poof goes a not insignificant investment. Power supply I use for that is a TTi PL154. That just trickle charges the internal SLA so it works off grid.

[factory]

If they do burst into flames it would be wise to never leave one running unattended either, better still bin it and get a decent one.

Are these compact Xantrex/Sorensen XPD 60V 9A PSU's any good? I bought this one to eventually replace my cheap Rapid Electronics one and provide a higher voltage range, I did briefly have the Xantrex version but it was DOA (stuck in current limit), thankfully the seller was able to replace it with the Sorensen one, which is indentical apart from the output terminals/binding posts.

(Attachment Link)

David

Personally I wouldn't give it bench space, it is just such a crude unit, doesn't even support a fine and a course adjustment on either the current or the voltage sections.

Like mnem says you are better off with a far higher quality unit, but and here's the rub, I fully expect that even with a top flight unit such as a TTi etc there is always going to be a possible failure mode that could result in damage to the DUT, nothing and I mean nothing apart from using batteries to power the equipment, could result in an over voltage situation in the event of a failure occurring, so its best to never leave anything connected to power supply unattended. 

The Xantrex/Sorensen unit does have multi-turn voltage & current controls.
It's got to be slightly better than the Rapid Electronics unit (I seem to be lacking in pictures of that), which only has single turn controls, plus crappy hard to see LCD's and the binding posts are shit too. 
If I had space I would have something like a HP 6274B under the bench.

David

[bd139]

It wasn’t a Rapid HY1803D was it? That was the least bad Mastech I fixed