Author Topic: Racal Dana 1992 - fresh from ebay (Read 13637 times)

Thomas · « **on:** April 22, 2014, 03:45:19 pm »

Hi there,
Just thought I'd throw out a picture of my latest ebay purchase, so here you go:

Seems to be in good shape, even the buttons are good. Just a little cleaning up, that's all

Bryan · « **Reply #1 on:** April 22, 2014, 05:17:07 pm »

Bought one off Ebay awhile, back great unit. Something about actual LED displays that I like. May want to have a look at http://youtu.be/g862Xy_VXcY , and make yourself a 10Mhz standard for even better accuracy.

David Hess · « **Reply #2 on:** April 22, 2014, 05:53:50 pm »

I picked up a 1992 from Ebay as well and it only required cleaning of the front panel switches to restore correct operation. It is my best counter currently although it only has the TCXO option. I prefer LEDs as well.

At some point I will build a GPS disciplined reference for it and my other counters but as it is, it is more accurate than I routinely need.

Thomas · « **Reply #3 on:** April 22, 2014, 07:08:17 pm »

Definitely agree on the display, and I like the general look and feel of the instrument. Not much wasted space on that front panel

But I just realized they forgot to include Duty Cycle measurements? Oh well, I have other instruments for that.

Mine has options 02M and 04E. That's ovenized reference and GPIB, right?

Anyway, more pictures:

Internal overview.

Don't like the bulge on top of the smaller of those electrolytics, will be replaced.

GPIB board.

Vgkid · « **Reply #4 on:** April 22, 2014, 10:30:08 pm »

That is a nice looking counter, you answered the question that i was going to ask earlier(about the time base).

lowimpedance · « **Reply #5 on:** April 22, 2014, 11:24:08 pm »

These are nice little counters.
Check the 680 uF electros at the rear (+/-15v rails), they are prone to drying out giving random readings with no input.

David Hess · « **Reply #6 on:** April 23, 2014, 02:39:36 am »

Here is a photo of the inside of my 1992 which has the optional TCXO. The capacitors on mine show no bulging.

Vgkid · « **Reply #7 on:** April 23, 2014, 03:45:01 am »

I figured that the TCXO would smaller than it is.

David Hess · « **Reply #8 on:** April 23, 2014, 04:54:59 am »

The TCXO in the HP 5315A which I have is about the same size. Here is a photo of just the 1992 TCXO with a pen for scale and the full HP 5315A with TCXO which is at the top and left of the center.

I recall that the 1992 OCXO is 5 MHz and the printed circuit board on the bottom is a frequency doubler. I have seen them for sale on Ebay occasionally but it would be less expensive to add a more modern 10 MHz OCXO if one were inclined to do that. The external reference option includes a fascinating sampling phase comparator allowing it to lock to submultiples of 10 MHz.

There is enough room in the 1992 case to add an entire GPS disciplined oscillator if one were so inclined.

I think the HP 5334 and HP 5335 at 2 nanoseconds are the closest HP equivalents. The HP 5315 and HP 5316 lack interpolation limiting them to 100 nanoseconds.

Vgkid · « **Reply #9 on:** April 23, 2014, 06:01:08 am »

That is a rather interesting choice in oscillator manufacturers, but then again these would be most likely be either kept in a rather temp stable environment, or externally locked.

PA0PBZ · « **Reply #10 on:** April 23, 2014, 06:45:37 am »

Quote from: Thomas on April 22, 2014, 07:08:17 pm

Don't like the bulge on top of the smaller of those electrolytics, will be replaced.

That is most likely just a piece of bulged carton on top. Better check before you replace the cap.

Thomas · « **Reply #11 on:** April 23, 2014, 07:04:27 am »

I did check it. Capacitance and ESR seems fine, 5400uF and 40mohm.
The top plastic cover is probably squeezed by the heat shrink tubing, that's all.

These electrolytics are subjected to quite a lot of heat there, between the transformer and the ovenized reference

BloodyCactus · « **Reply #12 on:** July 09, 2014, 01:12:39 am »

just got my 1992 off of ebay. Got some caps and buttons to redo all the know issues. Actually my buttons seem ok right now, half the number pad has no numbers. I plan on replacing all the button switches anyway, since we know they go bad I dont see the point in leaving them in even working.

I believe I have rom 4.04? I will dump my roms + gpib rom later on. Apparently I have options 55 + 4E, so it should have an ovenised can in there too. sweet.

I hooked it up to my rigol test point, rigol was saying it was output 999.999khz and the 1992 was reading 999.995xx, after running for about an hour.

David Hess · « **Reply #13 on:** July 09, 2014, 01:20:16 am »

Quote from: BloodyCactus on July 09, 2014, 01:12:39 am

just got my 1992 off of ebay. Got some caps and buttons to redo all the know issues. Actually my buttons seem ok right now, half the number pad has no numbers. I plan on replacing all the button switches anyway, since we know they go bad I dont see the point in leaving them in even working.

What replacement buttons did you find?

On mine most of the buttons worked poorly but I found that taking them apart and cleaning the contact surfaces on the inside restored proper operation. It looked to me like there was flux remover residue inside on the surfaces but maybe someone sprayed them with contact cleaner at some point.

BloodyCactus · « **Reply #14 on:** July 09, 2014, 01:32:17 am »

dont these buttons have the nasty little rubber piece that disintergrates and perishes?

see muvideo's teardown on the buttons

https://www.eevblog.com/forum/reviews/racal-dana-1992-teardown/

BloodyCactus · « **Reply #15 on:** July 09, 2014, 02:16:49 am »

a quick poke around shows all my chips datecoded to 1989, week 44 seems to be the latest datecode I can see, which puts it around november/december 1989! my roms are the same muvideo uploaded, 230867 rev b.

edpalmer42 · « **Reply #16 on:** July 09, 2014, 02:23:50 am »

Quote from: BloodyCactus on July 09, 2014, 01:32:17 am

dont these buttons have the nasty little rubber piece that disintergrates and perishes?

Maybe. Nobody knows why one counter has good switches and another has bad ones. It could be a change in the formulation of the rubber in the switch, the cleaning fluids used, the environment that the counter was used in, or something else entirely. I have two 1992 counters. One works fine but on the other, every switch has failed. One of the custom ICs failed on that one, so it's just a parts donor.

Since the original switches aren't available and yours are working fine, I'd say leave them alone.

Ed

BloodyCactus · « **Reply #17 on:** July 09, 2014, 12:36:50 pm »

thanks Ed, I was under the impression all the 1991/1992 models had bodgy buttons.
I wonder if its a time of manufacture thing. mine stems from late 1989, I've seen pics on the web of some peoples boards with 1985 datecodes..

edpalmer42 · « **Reply #18 on:** July 09, 2014, 03:00:52 pm »

Unfortunately, I don't have date codes from my units and it's not convenient to pull the working unit apart. It's installed in a stack of equpment that I would have to disconnect and unstack to get at the 1992. I'll have to remember to check that the next time I dig into the stack.

Ed

Andy2 · « **Reply #19 on:** July 09, 2014, 05:46:15 pm »

Nice! I have the 1998 1300MHz counter, which is very similar. I bought it for £50 at a rally about 10 years ago and noticed that the seals on the ovened reference osc had been broken. However, I had recently built a Droitwich-locked standard so it was easily tweaked back onto frequency (it was about 2 Hz out). It has run faultlessly since then. I agree about the LED displays, they are bright and easily visible from all angles, unlike LCD.

Thomas · « **Reply #20 on:** July 10, 2014, 08:31:24 am »

I bought these switches from Digikey: http://www.digikey.com/product-detail/en/EVQ-21509K/P12227SCT-ND/593531. Ordered before I received the counter.
But I haven't replaced them yet, the original ones are working fine. Will probably replace them later.

Mine seems to be made in July 1987, "07.87" is stamped on the right chassis casting.

Melt-O-Tronic · « **Reply #21 on:** July 10, 2014, 04:33:37 pm »

Those are the right switches, for sure. I have a 1991 and a 1992 and had some new key caps laser cut & engraved. I made extras and bought a couple extra sets of switches with the intention of listing them on eBay as a complete repair kit, but I'm too lazy to list them (I mean too busy! Yeah, that's it!).

BloodyCactus · « **Reply #22 on:** July 10, 2014, 04:54:38 pm »

the switches I ended up getting were

101-TS7311T1607-EV made by Mountain Switch

http://www.mouser.com/ProductDetail/?qs=sGAEpiMZZMsgGjVA3toVBBTb8bj5TiiQf5z2HYgjptA%3d

which were 13mm instead of the 9.5mm ones, as i was not sure how tall. they do have the 9.5mm ones.

http://www.mouser.com/ProductDetail/?qs=sGAEpiMZZMsgGjVA3toVBFFf203LvpB4U9vfkmEoH6E%3d

edpalmer42 · « **Reply #23 on:** July 10, 2014, 05:04:12 pm »

I have an Advantest Spectrum Analyzer that has an odd keyboard. Some of the tactile switches have an actuator. It happens to be a cross just like the Racal one, although it's a different switch. But some of the other switches just have a completely flat top. With this type of switch, all you need is a spacer of the correct height to reuse the old key cap.

Does anyone know where we could find tactile switches with a completely flat top like the orange one in the attached picture?

Ed

David Hess · « **Reply #24 on:** July 10, 2014, 05:12:40 pm »

If you were reusing the original buttons, it looks like the switch or the button would need to be modified to fit together.

I figured I lucked out since cleaning the inside of the switches on mine with a cotton swab and alcohol was enough to restore operation.


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Author Topic: Racal Dana 1992 - fresh from ebay (Read 13637 times)

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