For all the Metrix crazies: have a few GX5000's left. If you're interested, PM me.
No you don't ! I don't see them in your ebay shop !!
... that means they are not ready for sale... that means they are broken !
Mine is too but there is no service manual for it anywhere ! Contacted Metrix directly and they said "yeah we remember that one, but have no info on it as we outsourced its R&D, we didn't design it ourselves ". Bummer
Actually like new, in a carry bag. With manual (user, not service). But there are quite of a few of those on eBay, I'd rather wait a bit
Spotted a couple of old Racal frequency counters on eBay.
There is this 520 - https://www.ebay.co.uk/itm/384663905868 - This is the version with individual lamps in a vertical column. Starting bid is £20.
Racal 836 6 digit ***** **** 30MHz -- https://www.ebay.co.uk/itm/324991526216 BIN at £150. No thank you.
I know nothing about the sellers or the
I won't be bidding or making offers on either one.
The former is the first frequency counter I ever used.
From memory, it topped out around 10MHz.
Like so?
I've also bought some Soviet 74188 clones to try & fix the second 5340A control board (according to the manual there are four in total, two of which are on the control board), still waiting for them to arrive.
Earlier this week I got the rare opportunity to work in the lab for a day, while I was there I had a read of the manual for the Expro 60/80 programmer & it will read/write the 74188, but knowing my luck the ancient PC that it is part of, will be dead/emit smoke/or HDD corrupted by now.
David
I'm going to use National Semi DM8577s. I found a few NOS parts. They are read compatible with the '188 but do not program the same way.
I have no idea about programming the Soviet clones. Presumably they program like the TI 74188??
If my device works (that is a bigif) I will have a couple of partly populated PCBs available at cost. (about $20 + shipping) There are still some DM8577s on eBay. . .
Has anyone ever tried this style of test clips (accidentally spotted on eBay while looking for something else)? Any good?
Yep got 2 sets of those. Quality is ok and they are working well. Not like some other micrograbber I ordered.
Like so?
Wow thanks a lot for the video !!
So yours exhibits the very same problem, except 10 times worse : frequency is jumping around by the kHz rather than tens or hundreds on mine.
So... maybe that means it's normal and my unit works just fine ?! Being a pulse generator, it's not meant / expected to have any kind of stability in frequency when used in continuous mode ?
Must be that... OK cool, so if it's normal, that's one less TE that needs fixing, great !
Thanks for your help !
....snip....
I would have made a close-up picture of the screen to prove I am not lying about frequency and signal amplitude. Sadly just before doing that, I tried fiddling with the adapter to see if I could shove it in a bit more to make sure the trace does not go unstable right as I am trying to photograph it and... as I was grabbing the adapter, I got ZAPPED !!! Yes this generator tried to kill me !!!
So no close-up picture for you sorry... instead I immediately pulled the plug !
Checked with the DMM for resistance between the two line terminals in the power socket, and chassis/enclosure.... no short, got 5Mohms and slowly climbing.
So I am not touching this generator for now !
Think I will retrofit an IEC power socket hidden at the back (to not ruin the looks of the face plate), and get myself a life saving earth connection....
Will look at the schematic of the generator to see if there is maybe some failing cap that could explain the mishap...
As for the DM8577, I'm avoiding ancient Nat Semi/TI parts, the Soviet clones should be a bit newer. Strange how the Nat Semi parts on ePay-UK are marked as both DM8577N & DM74188AN if they can't be programmed the same way.
David
....snip....
I would have made a close-up picture of the screen to prove I am not lying about frequency and signal amplitude. Sadly just before doing that, I tried fiddling with the adapter to see if I could shove it in a bit more to make sure the trace does not go unstable right as I am trying to photograph it and... as I was grabbing the adapter, I got ZAPPED !!! Yes this generator tried to kill me !!!
So no close-up picture for you sorry... instead I immediately pulled the plug !
Checked with the DMM for resistance between the two line terminals in the power socket, and chassis/enclosure.... no short, got 5Mohms and slowly climbing.
So I am not touching this generator for now !
Think I will retrofit an IEC power socket hidden at the back (to not ruin the looks of the face plate), and get myself a life saving earth connection....
Will look at the schematic of the generator to see if there is maybe some failing cap that could explain the mishap...
Catching up still......
Looking at your previous posts on the Metrix 920, it seems to have two capacitors to ground (aka the case) and looking at the back of the mains inlet there are two dubious looking capacitors on the sides of the inductors, I would be amazed if these weren't wax paper deathtraps/smoke bombs.
And the DMM will be of no use here, you need a proper DC insulation tester at 250V or 500V to check them, but probably best to just change them for some class Y rated capacitors anyway.
David
Try setting the width a bit lower. You have not allowed anytime for the transitions and it may be confusing the unit.
As for the DM8577, I'm avoiding ancient Nat Semi/TI parts, the Soviet clones should be a bit newer. Strange how the Nat Semi parts on ePay-UK are marked as both DM8577N & DM74188AN if they can't be programmed the same way.
David
I was nearly caught out by that. The ones I have are factory marked DM74188AN DM8577N. I was initially using the TI Databook. I have one around here somewhere and it was easier to find on the web. Mostly because I was curious, I did an extensive search and found the DM8577N in a National book. Much to my horror, they are "Pin Compatible" but very different internally.
....snip....
I would have made a close-up picture of the screen to prove I am not lying about frequency and signal amplitude. Sadly just before doing that, I tried fiddling with the adapter to see if I could shove it in a bit more to make sure the trace does not go unstable right as I am trying to photograph it and... as I was grabbing the adapter, I got ZAPPED !!! Yes this generator tried to kill me !!!
So no close-up picture for you sorry... instead I immediately pulled the plug !
Checked with the DMM for resistance between the two line terminals in the power socket, and chassis/enclosure.... no short, got 5Mohms and slowly climbing.
So I am not touching this generator for now !
Think I will retrofit an IEC power socket hidden at the back (to not ruin the looks of the face plate), and get myself a life saving earth connection....
Will look at the schematic of the generator to see if there is maybe some failing cap that could explain the mishap...
Catching up still......
Looking at your previous posts on the Metrix 920, it seems to have two capacitors to ground (aka the case) and looking at the back of the mains inlet there are two dubious looking capacitors on the sides of the inductors, I would be amazed if these weren't wax paper deathtraps/smoke bombs.
And the DMM will be of no use here, you need a proper DC insulation tester at 250V or 500V to check them, but probably best to just change them for some class Y rated capacitors anyway.
David
Thanks for doing my work Dave !
Just looked C11 and C12 in the parts list... they are indeed paper caps ! They are 10nF 10%.
Will replace them of course !
Will keep the old caps so I can test them later for fun and educational purposes...
Hell I could cobble a crude tester together easily I guess !
After all these caps are simply subject to mains AC ! So all I need to test them in a relevant manner, is to connect the to mains and measure the leakage current, eh ?
Just need to put a series resistor to limit the current to a safe value, I don't know, less than 500mA, since my Metrix meter has a 500mA current range / fuse.
Will open up the generator in the coming days, if I can sort out this problem right now, why wait... there are enough things to do and fix in this lab for me not to post pone repairs I can do quickly and easily !
Also does the Metrix TV related gen you have, also have these two cRapacitors on the mains inlet?
David
Tidied these away into the component drawer units bought from work, was surprized to see what RS used for the filling inside the wee boxes.
David
Try setting the width a bit lower. You have not allowed anytime for the transitions and it may be confusing the unit.
Not sure what you mean ? 10MHz, 100ns period, pulse 50ns wide so 50% duty cycle, 50ns "off" time... isn't that plenty enough to "recover" ?!
Unit can do 50MHz to boot, so a period down to 20ns. So at 100ns I am really not pushing it
Anyway, just tried it. 20% duty cycle this time, so 20ns pulse and 80ns off.
Result is exactly the same, no better or worse, status quo.
But it was my first good excuse to use my shiny new coax cables and adapters !
Boy it's so nice to have all the cables and adapters you need at your disposal, in a just few seconds everything is connected up properly like a pro, no more scope probes banana adapters and bits of wires hanging ! I am a pro now !
However I have a new problem now... looks like my Metrix Nixie counter has a problem with its LF / 1Meg input ! Signal is only 10MHz so it can take it no problem. However it would not register / count anything at all, only zeros on the Nixies, even though I have good signal amplitude, 5Vpp unloaded, and no matter how I fiddled with the input "sensitivty" pot/control. Plus, when I connect the counter, I can see on the scope that the signal goes haywire. Big drop in amplitude + it becomes completely out of shape, looking like a wiggly triangle, no more a rectangular pulse at all ! If I use the HF / 50R input instead, all is well.
So, the LF front-end has a problem.... some more repairs in the queue !
This counter is not easy to work on I fear, very compact in there. It's not going to be fun I think...