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Jon,

Yes, I'm familiar with the "harmonica" connectors. The 7704A uses them extensively as well as the plugins and that makes taking the 7704A apart quite a bit easier. The 7514 uses a half dozen of those to the Main Interface, but there are many, many individual slide-on connectors that must be removed in order to remove that board. The manual mentions those but I didn't realize there'd be so many of them!

Yes, I could clean it with IPA and can remove sub-boards and clean them; however, the plugin socket side covers are in very bad shape and I'd like to have the Main Interface board out to better see what I can do about that. If I had a complete set of covers, then that might not be necessary but if I have to try and find a substitute method for those, then having that board out where I can access it directly will be much better.

Thanks,
Barry - N4BUQ

Barry I have no experience on 7514, but most 7000 mainframes use single or double row inlune black Molex or AMP flat ribbon cable to PCB connectiors, one name is "harmonica" style.

BEWARE!! over the decades the thin plastic deterioration causes breakage or crumbling of the connectors plastic!

VERY haed to fix.

If gentle rocking does not release then the pins may he frozen to the recipticles.

In fact removal may nit be needed, perhaps just a water or isopropyl alcohol wash can clean up the PCB.

A photo of the dirty board and close-up of connector will be useful

Bon courage

Jon

I'm in the process of cleaning up a very dirty 7514 (apparently belonged to Southern Railway at one time and was stored in a fairly dirty environment). As part of that, I want to remove the Main Interface board and that involves removing many, many of the single-ended push-on connectors (the type that attach to the small pins that typically interconnect individual boards).

I removed a couple of these with a small hooked tool but that doesn't seem to be the most effective way to remove them because uneven pressure on one side or the other doesn't let the connector pull straight up. I'd imagine a hooked tool with a slot in it to clear the pin and allow even pulling pressure but I don't exactly have such a tool.

Is there a better way to do this? Needle-nose pliers? Unfortunately, I need to remove about thirty of forty of these so am looking for a "best method".

Thanks,
Barry - N4BUQ

On 2022-05-05 6:17 a.m., David Aurora wrote:

I think 2 should be ok based on my tests so far. And yeah, the base model should do just fine, although I grabbed the 25MHz one just to have more bandwidth if I need it for something else.
The seller has come back to me and it sounds like he’s going to do the right thing, apparently his kid packed it up for him trying to help out and left the foam out. Shit happens, but he genuinely seems to be trying to sort a replacement so I’ve got to give him points for decency.

I hope you don't return the damaged unit. Most likely it would go to landfill and as someone else pointed out, it's full of irreplaceable stuff that could drive another display one day (per parallel thread).

IMHO you should still open an eBay case for this within 30 days of receipt of the item. You may wish to wait until close to the end of the 30 day period if you want the buyer to have a chance to sort things out some other way. It does no harm and may do some good.

<>

David

I think 2 should be ok based on my tests so far. And yeah, the base model should do just fine, although I grabbed the 25MHz one just to have more bandwidth if I need it for something else.

The seller has come back to me and it sounds like he’s going to do the right thing, apparently his kid packed it up for him trying to help out and left the foam out. Shit happens, but he genuinely seems to be trying to sort a replacement so I’ve got to give him points for decency.

Is two channels enough, or do you need Z-axis modulation too?

I'm still betting that even the lowest end Picoscope (at 10 MHz) is vastly more bandwidth than this application requires. I'd be surprised if this needed more than 1 or 2 MHz.

-- Jeff Dutky

Thanks for the reply Ozan, I checked the values of the components in the multi and they are all in spec, also the square wave is there and opposite phase between sections as it should be thanks.

I posted in the other thread that while looking for solutions I noticed that Picoscopes allow you to create probes with your own scaling, AND by default the grid is 10 x 10, so in theory once the scaling is set we should be able to get a 1:1 readout. I'll order one with my parts orders today and do some probing when it arrives to see what works best

Actually yeah, good point. I've got a nice clean display just probing in plain old XY. Appropriately scaled in software that's a super simple solution.

This is why I was hoping to tap the amplifier signal Pre final amp. If I remember correctly from the last time I looked at the schematic (it has been a while) The pre tube driver stage is not differential. It is signal ended. Also the 200Vdc supply is only used in the tube driver stage. This being the case the HV transformer is no longer needed because you don’t need the -4Kv supply or the 200 Vdc supply. This is not used in the collector supply for sure. This would also solve the failing HV transformer issues and would really set these units up for a long run. The low voltage supply is a pain to rebuild but it is just time consuming and not difficult.

Zen

It really seems to be that the dead simple solution is just to tap the deflection signals off through the necessary attenuation/diff to single ended conversion and plug the XY in a USB scope. I really don't see the need for doing your own A/D and writing software to drive it all?

From what I've seen, the problems revolve around getting the CRT (pretty? much unobtanium), and replacing the CRT with either an LCD display installed in place of the CRT, or using an external XY display as a readout.

One thing you could do (and I've seen it done) is to take an STMicro Disco board, add an op amp to scale the signal tapped off from the deflection amplifiers, digitize that with the processor's A/D converters (fast enough, perhaps), and then use the built in display (cell phone size) to display the curve data.? Once digitized, the virtual com port on the board could be used to transmit data over to a PC (USB interface), and then displayed on a PC.? No remote control, just remote display.

Another option would be to take a larger display and use it, but you're getting into problems with a round CRT bezel and a rectangular display.

another option would be to have some fast A/D converters driving a processor, which could store the data points, and then either drive a display or a CPU.

Note that any of these options involve programming at a minimum, or hardware.

A fourth option would be a pair of fast A/D converters driving an FPGA for memory, and then perhaps using that FPGA to drive an LCD display, although it would be easier to put a FIFO on the A/D converters (if needed) and then have the display controller in either the processor or a separate chip, all depends on the display.

All of the above are possible, all of the above require some effort, not inconsiderable.

Harvey

Yeap, I don't have any idea why some E-bay sellers simply refuse to pack
items decently. They're idiots if they think that the buyers aren't going
to complain to Ebay and get their money back.

A warning though, a lot of E-bay sellers will drag their feet about
refunding your money and will ask you not to file a claim with ebay but
then they'll string you along until it's too late to file a claim. My
advice is to go ahead and file a claim with Ebay/PayPal. If the seller
sends another CT or somehow "makes it right" then you can mark the claim as
being resolved. But considering the shipping time from the US ( I assume
that that's where you bought the CT) to Australia, it could be weeks before
you get a replacement item and by then it might be too late to make a claim
with E-bay/PayPal.

I read your posts on EEVblog, and I'll just add that my 576 was packed
in multiple layers of big sheets of some kind of blue high density foam
about 2" thick in a large cardboard box and was shipped halfway across the
US and arrived in good condition so Foam In Place packing isn't absolutely
necessary. I used to work in a place that used foam in place packaging and
UPS still managed to mangle many of those packages so FIP by itself is no
guarantee that your item won't be damaged. I personally never use FIP, I
cut a hollowed out square of foam to fit around the knobs, meters etc and
tape that over the front and then pack my items well and I've shipped stuff
all over the world and never had a damaged item. (knock on wood!)

On Wed, May 4, 2022 at 8:28 PM David Aurora <
electronics@...> wrote:

Yep, Ebay so hopefully I have protection there, though nearly 24 hours
since it arrived I still don't have a response from the seller. It's a damn
shame because otherwise the thing is immaculate, and it even came with
original printed manual and a spare faceplate. For literally a couple of
dollars of foam this thing would have gone for years more

I'm definitely happy to collaborate (as long as I have a unit to work with haha, if this one goes back to the seller I don't know when I'll get another one). When I found this board and saw all the posts about the topic I thought there would be a solution in there somewhere but it seems like something people thought about but never followed through on. So if I can help get us to a concrete solution that everyone can benefit from I'm happy to help

I definitely think there is a place for tapping off the 0.5V/div (or 0.1V,
or whatever) vert and horiz signals from the unique and interesting
electronics and feeding both a digital display and something with network
connectivity so you can pull pngs, or whatever. The 576 offers the hope
that you could also tap off the important settings (like the fibre
display), the 577 (as I have) does not make that part particularly easy.
However, saving traces so you can match parts, etc certainly seems
interesting to me.

I've pondered this as a solo project, but I wonder if there is more hope of
actually getting traction if there were people who shared that thought and
were interested in collaborating (I know it's a double edged sword) - one
could easily contemplate driving an outboard display (e.g. a Tek 620, or
another scope in X-Y mode maybe) from the same analog outputs, without all
the digital stuff. I really looked into this when I discovered the tube on
my 577 was nearly dead, but then I got very lucky and picked up a 5110 from
a friend, so it went to near the bottom of my project list - I know 576
owners are not so likely to be able to find a replacement tube as easily.

My first step was going to be simply buffering the vert and horiz
differential output at the transition from the "interesting/difficult
stuff" to the plate amplifiers, and presenting the output on the back
panel. If there's interest in that, I could pony up a PCB pretty easily and
would be willing to share the prototype (because I always have to order
more than just one.)

Answer on or off list, as you see fit.

"Nay saying" -> /dev/null

On Wed, May 4, 2022 at 7:28 PM David Aurora <
electronics@...> wrote:

Yep, Ebay so hopefully I have protection there, though nearly 24 hours
since it arrived I still don't have a response from the seller. It's a damn
shame because otherwise the thing is immaculate, and it even came with
original printed manual and a spare faceplate. For literally a couple of
dollars of foam this thing would have gone for years more

--
Andy

If you look at the horizontal/vertical amplifier, if it's the type I'm familiar with, it's an emitter coupled differential amplifier with a (possibly) current input.? The differential pair produces an in phase and an out of phase signal.? If you can tap either one of them, there's no need to go differential for your signal pickoff.? You may also want to look at how the 7000 series scopes pick the vertical signal from the amplifier, and see if you can duplicate that.? That would give you a buffered signal output (if you need it).? IIRC, the signal output is not differential, just a copy of one of the sides of the amplifier.

Harvey

As a sidenote, while I've been probing inside my CRT-less unit and weighing up my options, I noticed that the software you get with those cheap Picoscopes allows you to save custom probes with whatever scale factor you want, which would make calibration a breeze. I'm thinking about ordering one today, knocking up a small differential to single ended converter board that can fit inside and trying it out. I downloaded the software for a look and right out of the box it's a 10 x 10 grid, so that's another thing in it's favour.

Yep, Ebay so hopefully I have protection there, though nearly 24 hours since it arrived I still don't have a response from the seller. It's a damn shame because otherwise the thing is immaculate, and it even came with original printed manual and a spare faceplate. For literally a couple of dollars of foam this thing would have gone for years more

I hope that you bought it from Ebay. If you did they'll make the seller
pay for the return shipping (if he wants the scope back) as well as
refunding your purchase price and what you paid to ship it to you. Ebay's
refund policy is one of the big reasons that I choose to buy my 576 through
E-bay. Fortunately my seller did a good job of packing and everything
arrived in good shape.

There are people on here that are more expert than I, but yes, I think
the 576 CRTs are unobtainium even in the US, so you're probably going to
have to start searching all over again.

On Wed, May 4, 2022 at 2:21 AM David Aurora <
electronics@...> wrote:

Following on from my other thread where I was awaiting delivery...

... my 576 arrived today. As soon as I popped the lid on the crate I knew
things were bad- there was zero padding between the crate and the top of
the unit. The bottom was the same, the seller had literally just done a
single wrap of bubble wrap around the sides and shipped it from the US to
Australia as if nothing would go wrong.

Obviously, the CRT has been destroyed, this thing must have been slammed
up and down a thousand times in the past couple weeks.

I've always heard there's practically no chance of finding replacements,
and with my work schedule I have zero time to play around trying to jerry
rig an external display. So my question is, are the CRT's really
unobtainable, if not, how often and what kind of price range do they seem
to pop up in? I can live with one that's a little dim if need be, but if
this is going to just sit here forever waiting for a screen then I probably
need to crate it back up and get it shipped back to the seller immediately.

Ugh, what a day.