Test Equipment Anonymous (TEA) group therapy thread

[McBryce]

Mouarf.... trying to fix a VCR, first one in my life, never worked on these things before...
It was given to me and I thought hell, would be cool to (try to...) fix it as an exercise and to have at least one VCR around, you never know when you might need one... seeing as I tend to like old stuff, who knows, might come handy one day.

Anyway. First it did not power up at all. Was bloody RIFA. Removed it, works fine now. don't have VHS tapes but the old guy who donated the VCR also donated a tape of Star Wars the Phantom Menace.

Anyway it plays the tape... audio is just fine, I can hear the movie sound track just fine, but no video ! 

I tried using SCART and video composite on two different LCD monitors equipped with these I/O, and every time the same answer : " No sync ", and a black screen, so not happy.

Looked at the schematic, have partial ones, not the main board sadly... but have the one for the rear panel PCB that carries the I/O connectors, and plugs right angle to the mother board.
I see that the video composite signal comes from a chip on this board, and is served to both the RCA jack AND the SCART connector. Apparently SCART has both RGB and composite signals available. I don't know which one the monitors actually use when I ask them to display SCART. Anyway, at least if make some sense that both SCART and composite would not work...

Anyway, I scoped the composite signal on the RCA jack, and to me looks like a I do have my composite signal ?!  So why doesn't it work ?! 

I know squat about video let's be clear.... I simply looked at Google to find diagrams of what it should look like. I have my negative sync pulse, about 5us as it should. Total frame length is about 64µs as measured with the cursors, which is what it should be about. So as far as sync goes, the LCD monitors should be able to detect a signal eh ?! 

My two main worries that might explain the problem (?!), tell me what you think :

- Noise... as you can see from the video clip below and my screenshot, there is lots of noise... but that could just be my probing setup which is more than awful of course, not having a BNC to RCA adapter nor even a coax cable.. so just using my probe in x1 and a little contraption made from recycled RCA jacks. It's too ugly to be showed here, don't want to stoned.

- Looks like there is a HF signal superimposed on everything, whose vertical excursion spans the entire composite signal... looks like faint squiggly lines at the top and bottom of the waveform.  This does not show on wave form diagrams I see on the net.. however I understand there are two combined signals on these things, "luminance" and "chrominance", so maybe what looks like squiggly lines is just one of those two signals and everything is fine . I am so clueless it's painful.

- Voltage levels : 99% of the diagrams I found do NOT indicate voltage levels. Instead they use funny "IRE" units, whatever that means, to give the proportions of the various parts of the signal, but not actual voltages. Proportions look fine on my signal, I find. Video content is about 2+ as high as the sync pulse.
The rare diagrams I found that did indicate voltage levels, showed a 1Vpp excursion, but I get as you can see 2.5Vpp or so ! 

It's so horrible to hear the sound track of Star Wars but not being able to see the video even though I can see it on the scope !!! 

Anyone here with working knowledge of composite signals ? I am in Frog land so I guess we are talking SECAM, though from what I see, SECAM / PAL / NTSC have very similar looking wave forms...

First thing you do whenb fixing a VCR is make sure the head is clean, no dirt in the grooves and the surface should be shiny enough to see your reflection. Then check that the read heads are still electrically connected and that the coils haven't started detacting from their core. These are common issues on old VCRs. If the head is in any way damaged you're probably going to have to fix it, because I doubt you'll find a replacement now.

McBryce.

[AVGresponding]

Some ebay tat:


This is just asking for a "not as described" claim:  https://www.ebay.co.uk/itm/304284980455





One of these little TTi scope/meters that Specmaster has:  https://www.ebay.co.uk/itm/373844430587





More TTi. Are these things any good?:  https://www.ebay.co.uk/itm/265480929487





Early multimedia laptop, could do with a bit of a clean:  https://www.ebay.co.uk/itm/373848009899





To describe the pricing here as "optimistic" would be a huge understatement. This seller has some strange ideas, some of their stuff is quite well priced:  https://www.ebay.co.uk/itm/255303176816





Absolutely terrible description might result in a real bargain for someone here:  https://www.ebay.co.uk/itm/255311820788

[mnementh]

Getting to this point involved moving a dozen or so heavy-ass 1m² cartons

The effort is splendid, except that it sounds a bit flat. Was there only area and not volume to those cartons?     

No, it were the dwagon what fell flat.    And as I sat down just now with my coffee, it was the first thing I noticed too.  And I knew instantly that you would be right along to keep me honest, unless another of the usual suspects beat you to it. 

mnem
Actually, I find that oddly comforting... 

[tonyalbus]

Absolutely terrible description might result in a real bargain for someone here:  https://www.ebay.co.uk/itm/255311820788

[/color][/size][/b]

Thanks! 

[BU508A]

Anyone in need of a new display for a Fluke 8840A / 8842A?

There is a new batch (made by AHOL) available:

https://www.eevblog.com/forum/buysellwanted/ebay-led-display-module-fluke-8840a42a-(diy-kit)-replace-broken-damaged-vfd/msg3915332/#msg3915332

[TERRA Operative]

Jarid.. 'The Tekwiki' ??  for a none tekboy (for now) .. i google like 20 tekwiki's ?

For me it's the first result when I search for "Tekwiki" https://w140.com/tekwiki/wiki/


David

This is the one.

If you don't have an account, I can upload any files etc on your behalf.

[Robert763]

Simpson 467 DMM with 5kV probe and case cheap BIN on ebay UK
Ex US military AM/PSM 45 kit
www.ebay.co.uk/itm/194698170035

Edit gone already!

[Kosmic]

The bad news is the megaphase cables I got for free...well I got what I paid for. They are total junk above ~3 GHz.  Worst of all, they all seem to have anomalies right in X band towards the lower end of Ku band....RIGHT where I want to work of course. 
.
.
Check out this Narda 2-18 GHz coupler!

Nice coupler.
'One tip: do NOT fall for Gore test cables. They are in my company lab and I came to hate them. They transmit torque with every movement and work loose the connector at my VNA in no time!

Ideally I'd like to find a pair of the cables it would have come with new. But those are megabux, when they are available at all.  Any other recommends for the epay saved search? 

I can recommend Suhner Testflex/Sucoflex and also some from Radiall.

Thanks for the recommendation. I just found 2 Huber & Suhner Sucoflex 104 for 25$ each 

[tonyalbus]

Absolutely terrible description might result in a real bargain for someone here:  https://www.ebay.co.uk/itm/255311820788

[/color][/size][/b]

Thanks! 

[edit] TVA does VAT in frence

Hi sir,
Sorry but I must to cancelled your order.
This is not the device.
This is an ad only for one customer to pay the VAT on his purchase...

Sorry.
Best regards,

[capt bullshot]

Question time.

How to measure jitter on a scope (TDS784C) that doesn't seem to have an obvious delayed sweep function? Unless it's called something different and I'm too dumb to work it out......?

Horizontal Menu -> first select Timebase Main (slow enough to include the desired delay time), then Intesified (to visually choose when the delayed sweep shall happen), then Delayed Only (to show the delayed sweep), or use Delayed Runs ... after Main to set the delay time.
This method is quite common to digital Tek scopes, you'll find it similar on other models.

[mnementh]

OK so the two main things I would try to improve on your knobs, what jumps at me, are :

- White dot is too big, larger diameter than the original. Either too much paint, or you did not measure it accurately enough, or you did but the printer did not manage to do it properly in which case you need to compensate for that by asking it to make a smaller diameter so that once printed it ends up at the appropriate diameter.

Thanks for your observations.

Yes, due to the nature of the 3D printed surface it can draw paint away in very tiny "channels". That's all that is. The best way (searching for perfection now) is to:

Sand the button with very fine sandpaper, Prime the button (or part), Sand again, Prime again, Sand once more, Paint with gloss black, Use toothpick to "dot" the dimple

^^^ all this is for a perfection part that makes or breaks the restoration. Would be needed for a museum piece with a knob or button entirely exposed in all ways but the back.

- On your first pic the narrow side of the button is clearly undulating like mad, not straight at all. I guess it's inevitable with a 3D printer that melts plastic.... maybe printing the button more slowly would improve it, but you will always get ridges anyway, even if the overall shape is straight, as can be seen on the underside of the button.

Personally, if you are intending to make a better match (already good IMO), I'd only bother with the top 5 to 7 mm as that is the only part of the knob visible, why wast e all that effort on parts that are not normally seem

Yes that was caused by trimming with a knife - not the printer. As Specmaster said, almost 75% of the button's body is not visible (never seen) when the bezel is installed, so it doesn't really matter. But yes if you want to talk absolute perfection sanding would be the way to go.

I want to take this as a challenge Vince. I want to see how good I can make it look after it comes off the build plate. I need to buy some glossy paint. I already have airbrush primer which will work great for this, and very fine sandpaper.

Stay tuned ...

P.S. I just ordered Tamiya gloss black & gloss white

WARNING: MUCH TINKER-DWAGON NERDITY FOLLOWS!   

I've made more than a few such parts, particularly making one kind of knob or button match others on a project when I worked at the Ding & Dent appliance store. First, you want wet-dry silicon carbide sanding sheets or better yet, sanding films and/or polishing films if you have a hobby shop or auto painting supply house nearby. 

If you didn't know, they make an assortment for modelers (there is a similar product for automotive "mirror-finish" hand-sanding) on a plastic film backing specifically to be extra-consistent and flexible so they can be laid on glass for flat sanding or rolled around a bit of dowel for concave sanding; the kits will usually start at like 120-180 grit and go up to 2200-3000 grit.

Wet-sanding with a piece of glass under the paper is key to getting flat areas smooth without swirls and scratches; I've used this tactic to restore optical clarity to lenses and filters from equipment that are gouged or burned. For concave sanding you want to sand under running water if you can. Wrap the sanding sheet around something with as close to the original arc as possible. I've used use a dowel, pill bottle, copper pipe/fittings, or even a long 3/8" drive socket; whatever it takes to get the right arc.

The hardest part with little knobs and buttons is getting a good finish without taking away too much material; I can't tell you how many times I've gotten a good-looking finished part, then put it in place and see it is conspicuously too small compared to its cousins.

3DP/FDM parts always have striations from the deposition process that you need to deal with. As your part is already the right dimensions, the usual solution offered in the 3DP groups is to apply a thin layer of epoxy all over the part, then sand it smooth. You need to be extra careful around the paint dimple; it is easy to fill it in completely. This thin layer of epoxy also offers the benefit of serving as a good primer for model and spray paints.

   

Also, for roughing out parts, one of the best tools you can have in your arsenal is the large foam-backed emery boards and diamond files from the Nail Care dept at the Px. Depending on the shape of the part, the buffing pads (made similarly to the emery boards above, or as square sticks of rigid foam with polishing grits applied) they offer can also be useful. Be mindful that due to their slightly flexible nature, all these foam-backed abrasives tend to round off corners and make flat surfaces slightly convex if using by hand.

just make sure you hide them from SWMBO, or you'll never have them when you need them. 

If you know all this, just regard it as "advice for those playing along at home". It's this kind of "fiddly-bits" work that I find most rewarding about this sort of project, and I've done a lot of it.

mnem
 

[capt bullshot]

First day at the new job today. I've quit my previous job basically due to being bored.
So most probably less time for TEA and general eevblog forum during the next months.

[Kosmic]

Simpson 467 DMM with 5kV probe and case cheap BIN on ebay UK
Ex US military AM/PSM 45 kit
www.ebay.co.uk/itm/194698170035

Edit gone already!

Hmm that's where that thing is going. I got the 5KV adapter in a lot of connector. I don't have the meter myself.



If anyone want it, just pay shipping and it's yours.

[Specmaster]

First day at the new job today. I've quit my previous job basically due to being bored.
So most probably less time for TEA and general eevblog forum during the next months.

Wish you good luck at the new job, what are you doing?

[capt bullshot]

First day at the new job today. I've quit my previous job basically due to being bored.
So most probably less time for TEA and general eevblog forum during the next months.

Wish you good luck at the new job, what are you doing?

Thanks!

Job offering was "embedded software", but they found out I can do hardware too and will most probably make use of this in addition to firmware development. Product are sights of various kinds, including plain optical daylight, night and thermal vision, nowadays there's electronics and software in this stuff that you'd think "It's optical only" at the first glance.
I don't know yet all detail, but I think all the interesting stuff (e.g. infrared vision aka thermal camera) will be covered by general non-disclosure.

[mansaxel]

I must remember to try the Tek 2465B (ex-BBC with TV option) sometime.

Dang, now you make want a waveform/vector scope (specialised CRO to look at video signals technically ) a bit more.

Trouble is, they're tightly tied to the video standard, so Never Twice (the) Same Colour ones are uninteresting to me, as are SD-SDI ones now that we're running 3G-SDI and up at work.

[Kosmic]

First day at the new job today. I've quit my previous job basically due to being bored.
So most probably less time for TEA and general eevblog forum during the next months.

Congrats ! hope you are going to have fun.

I wish I could do the same. But with my current compensation and 4 work days / week, it's hard not to loose something by switching to a more interesting position. I guess I got golden handcuff now

[AVGresponding]

Absolutely terrible description might result in a real bargain for someone here:  https://www.ebay.co.uk/itm/255311820788

[/color][/size][/b]

Thanks! 

[edit] TVA does VAT in frence

Hi sir,
Sorry but I must to cancelled your order.
This is not the device.
This is an ad only for one customer to pay the VAT on his purchase...

Sorry.
Best regards,

Whaaaat? That's some amateur-hour shit right there, I'd complain to ebay, not that they'll do much

[mnementh]

Mouarf.... trying to fix a VCR, first one in my life, never worked on these things before...
It was given to me and I thought hell, would be cool to (try to...) fix it as an exercise and to have at least one VCR around, you never know when you might need one... seeing as I tend to like old stuff, who knows, might come handy one day. (SNIP)
It's so horrible to hear the sound track of Star Wars but not being able to see the video even though I can see it on the scope !!! 

Anyone here with working knowledge of composite signals ? I am in Frog land so I guess we are talking SECAM, though from what I see, SECAM / PAL / NTSC have very similar looking wave forms...

   

Vince -

Assuming you aren't just dealing with a signal format mismatch problem, my gut reaction here is that your monitor is the problem, not anything crucial in the VCR as you are getting video out, just not getting sync. The sync timing is critical; a PAL monitor will usually not sync on a NTSC signal or vice-versa. While many monitors I've had can do both NTSC and PAL formats, a switch usually needs to be flipped in hardware or firmware. I have no direct experience with SECAM but pretty sure the same applies.

Double-check the format of your tape and that it matches your VCR; VHS tapes are different depending on whether the local market uses NTSC, PAL or SECAM. You should be able to figure out what format your VCR uses by the model number and the market it was made for if it isn't actually stated on the dataplate.

If your VCR, tape and monitor all match the same format, then the problem is likely simple loss of sync due to incorrectly reading the tape. The first clue is in the name of the format: VHS. It stands for Vertical Helical Sync, and essentially the head records video at an angle across the face of the tape. Beta also records this way; it just uses a different track density and sync mechanism.

The GROSSLY oversimplified explanation is that it reads/records a line of video information diagonally across the tape; this includes a line of raster video with chrominance and luminance information and at the beginning/end of that information are sync pulses. If the tracking is totally out of whack or heads are not aligned properly, or one or more is dirty, those sync pulses are lost. This would manifest on a analog monitor as a distorted picture with tearing until the tracking/alignment is restored. However, with your digital monitor, the sync isn't there so it just goes to blue-screen/black screen.

First thing I'd try is to see if you can find some tracking buttons/knob on the front of the unit or remote. If you do and still no joy, then you need to look for some service videos on cleaning the tape path and adjusting the head azimuth (which is actually adjusting the feed rollers as the tape wraps around the head). Also look for excessively loose/damaged tape guides/rollers that might be locating the tape in the wrong place on the head assembly.

To actually correctly adjust the azimuth death-nuts requires a scope, but truth be told that is time-consuming and dependent on the unit, procedures can differ because of how the machine processes the signal for auto-tracking and audio sync.

Alternately, you can dig around in your stuff or try to borrow a old CRT TV/monitor with Composite input. You can also try feeding your Composite signal into the green channel of a monitor/TV with RGB inputs; many times they will sync on a Composite signal and give you a monochrome image you can use for diag.

Good hunting!

mnem
 

[capt bullshot]

Congrats ! hope you are going to have fun.

Thanks!

Time will tell. Topics look quite interesting and fun, but apparently there's similar product manager / decision taking structures as with the old job. So one most probably can't always get the most interesting or fun projects because the decisions what projects will be done are made by managers and/or MBAs, not engineers.

I wish I could do the same. But with my current compensation and 4 work days / week, it's hard not to loose something by switching to a more interesting position. I guess I got golden handcuff now

Depends, I wouldn't have changed the job if I had only a handful of years left to retirement, as the old one was "Mostly Wally, sometimes Dilbert" and "We did nothing today and still get paid" during the last few years. Plenty of time for personal projects while on work time, but in total the situation was quite dissatisfying. Witnessed too many management decisions that were obviously wrong to all the engineers, but the engineers were forced to follow, ...

[Kosmic]

Depends, I wouldn't have changed the job if I had only a handful of years left to retirement, as the old one was "Mostly Wally, sometimes Dilbert" and "We did nothing today and still get paid" during the last few years. Plenty of time for personal projects while on work time, but in total the situation was quite dissatisfying. Witnessed too many management decisions that were obviously wrong to all the engineers, but the engineers were forced to follow, ...

Hehe I guess it's the norm, I got plenty of that right now. I decided to not care that much about work. I try to help people and just have fun.

[mansaxel]

First day at the new job today. I've quit my previous job basically due to being bored.
So most probably less time for TEA and general eevblog forum during the next months.

Gute Fahrt, Käpt'n!

[mnementh]

First day at the new job today. I've quit my previous job basically due to being bored. So most probably less time for TEA and general eevblog forum during the next months.

Congrats ! hope you are going to have fun.

I wish I could do the same. But with my current compensation and 4 work days / week, it's hard not to loose something by switching to a more interesting position. I guess I got golden handcuff now

Damn... I need to mug you and steal your job. 

mnem
 

[mansaxel]

First day at the new job today. I've quit my previous job basically due to being bored.
So most probably less time for TEA and general eevblog forum during the next months.

Gute Fahrt, Käpt'n!

Very late addition: Just as the Captain and his ship are leaving port, a Citrôen Traction Avant skids to a halt on the quay, a very hung-over naval officer jumps out and shouts "Fette Beute!" to properly send the Captain off.

(For those to whom the reference is not obvious, make sure you get the TV series edition, not the movie cut.)

[capt bullshot]

First day at the new job today. I've quit my previous job basically due to being bored.
So most probably less time for TEA and general eevblog forum during the next months.

Gute Fahrt, Käpt'n!

Very late addition: Just as the Captain and his ship are leaving port, a Citrôen Traction Avant skids to a halt on the quay, a very hung-over naval officer jumps out and shouts "Fette Beute!" to properly send the Captain off.

(For those to whom the reference is not obvious, make sure you get the TV series edition, not the movie cut.)

Though it was raining today, luckily my workplace isn't under the sea