Racal 9010 600MHz Decade Divider

[Techman]

Yet another item as I go through the recent 'lot' of old radio and electronics stuff. I went into the loft to find an appropriate Bulgin connector lead for it and on first power up I noticed that the front panel light briefly lit up quite brightly and then settled down to normal brightness. I note that this indicator lamp is powered from the +/- 5 volt supply, so probably capacitors charging/reforming after probably decades of non use - it didn't do it again after several power off and on cycles. I can hear internal relays clicking when operating the control knob. I know nothing about this type of unit and have never seen one before. I've not opened it up yet.

Edit: I should have put in the title that it's the model 9010.

[factory]

It's a frequency divider, they were used to extend the range of lower frequency counters, it uses the exact same power supply section as some counters of the same age, hence why it's so heavy for it's size, note the +220V rail that is still needed, but only to activate other supplies.

The circuit is based on a tunnel diode & Plessey divider IC, this was also found in some higher frequency counters.

David

[Techman]

Thanks David and also Mike for updating the thread title. It's important for this to be fully correct for anyone in the future who's researching this unit, as there's absolutely no other information on it out there other than a manual, which is how I deduced where the panel lamp was fed from.

From the manual I'd assumed that this unit was for the purpose that David confirmed, although I'd not come across anything like this before. Anyway, I've connected an equally vintage signal generator and frequency counter and have confirmed that the unit does actually work. The first picture shows the counter fed with 40MHz from the generator and the second picture shows the counter fed via the divider unit and you'll notice the change in position of the decimal point. The random difference in the last numbers is just general slight warm up drift, which is normal and to be expected.

I'll post the pictures in the next post.

[Techman]

Pictures.

[Vintage_RC]

Good to see another Racal 9839 frequency counter out there. I have had mine in regular use for 20+ years. It was a cast off from the company I was working for at the time.

[Techman]

Yes, the 9839 originated from the same person as the rest of this gear and I was pleased to get a good working Nixie tube type counter. It already goes up to at least 560MHz, so not exactly a candidate for this divider unit, but just used to prove the equipment. Testing it against other counters, it's pretty much accurate once it's warmed up.

Here's the innards of the decade divider, top and bottom.

[factory]

The 9839 counter uses the exact same Plessey divider IC too, along with the tunnel diode, but the rest of the counter is updated to use TTL & more compact.
With both of these the tunnel diode is a tiny part, that almost looks like a droplet of paint on a wire, these are very fragile, heat & incorrect testing will ruin them.

I've actually got a pair of 9010 dividers, one of which works fine, from memory the other has a faulty power supply, there is a description of how the power supply regulator circuitry works in the 9024 manual, it only differs in the power switch (it switches two DC rails, for a standby mode, instead of the mains), the 9010 has a link from the +12V output to activate the +5V rail, the +5V is needed for the +5.4v & -12v rails, this is probably why I never got the fault diagnosed, I didn't realise the interdependence of the supply rails at the time.
Also I noted the DC fuses are the exact same values for the 9010 & 9024, which seems odd as the 9010 has a lot less circuitry.

Some pictures taken over 4 years ago of the insides of the faulty 9010, strangely I don't have the metal panel/cover with the attached spanner, no idea why, for future reference mine is ex-mil and has the stock number 10S-6625-99-117-5251.

The power supply, as used in quite a few other Racal counters.



Amplifier & first divider stage board, the tunnel diode is hidden on the back along with some surface mount capacitors.



Buffer board, this has a second divider stage.



And the remote control board, only found in the 9010 & 9011, the 9012 & 9013 use a front panel switch attenuator.
Transistors Q8 & Q9 are used for option 5, which isn't fitted here.



David

[Vintage_RC]

Attached is a photo of my 9839 connected to my Quartzlock 2A frequency standard modified to also act as a GPSDO.

[Joe_Lorenz]

Obviously a beautifully made set, still going strong! Those Racals must have been quite expensive. BTW: Please can anyone explain why they mounted that spanner inside?

Joe

[factory]

I've no idea, there is no mention of the spanner in the manual, nor any pictures of the underside where it's located.

Mine is refusing to cooperate, the power supply rails are all correct with the exception of the -12V supply, this never gets below -11.3V, tolerance is +/-0.1V for all the rails. I've got the two PCBs removed as per the manual.

I've checked all the parts in that section, R27 fell apart last time I worked on it, R29 was slightly high at 3.7k and the pot is measuring at 12k, but it's not open.
When the pot R30 is adjusted, the base voltage of Q13 is behaving very differently, to the same part in the +12V supply. The +12V one (Q3) is always slightly more positive than the emitter, the -12V (Q13) is OK for part of the adjustment range, but then goes below the emitter voltage level, the transistor checks OK, a new part behaves exactly the same.

I'm beginning to wonder if this one ever worked correctly.

David

[Joe_Lorenz]

David, if it was mine I'd be inclined to investigate if there were any tantalums (tantali?) electrolytics present. Always suspect!

[factory]

With the two plugin boards removed, there is only one tantalum left in circuit, it's across the output of the -5.4V rail, which is working OK. The can capacitors check OK too, both for ESR, capacitance and ripple voltage.
I did check the ceramic capacitor on the output of the faulty -12V rail, it was removed as I couldn't measure it in circuit, it tested fine, those are Murata parts.
Power consumption of the faulty unit at the moment, without the plugin boards is approx 6W.

David

[factory]

Originally Posted by Joe_Lorenz

Obviously a beautifully made set, still going strong! Those Racals must have been quite expensive. BTW: Please can anyone explain why they mounted that spanner inside?

Joe

I think I've worked it out, the input BNC assembly is much longer than normal (mine is just an ordinary BNC connector), I suspect it's a fuse holder, as the higher frequency counter front ends have very little protection against people accidentality transmitting into them.

You should also note the fuses can be damaged on removal, I have a HP "N" fuse holder that has this problem, the glue failed between the glass & the fuse end caps, rotating them till the fuse wire snapped.
I wonder if there might be spare(s) hidden somewhere in the bracket holding the spanner.

Here is the same spanner attached to the back of a Marconi freqeuncy convertor, the front has the extended input connector.



David

[Techman]

Originally Posted by factory

With both of these the tunnel diode is a tiny part, that almost looks like a droplet of paint on a wire, these are very fragile, heat & incorrect testing will ruin them.

strangely I don't have the metal panel/cover with the attached spanner, no idea why,

David

Yes, I was looking for the position of the tunnel diode on the board layout in the manual and it wasn't shown, so assumed that it was possibly tacked on the print side somewhere - I didn't remove any of the boards when I opened it up for the photos. Seeing as it seemed to be working I decided not to disturb things unnecessarily.

I was waiting to see if anything would be said regarding the spanner, and it's interesting to note that as well as yours not having that same spanner, yours also doesn't have that part of the chassis plate that it's attached to either. I also wondered why it wasn't mentioned in the manual and wondered if I'd missed it and ran through it again to check.

[Techman]

Originally Posted by Vintage_RC

Attached is a photo of my 9839 connected to my Quartzlock 2A frequency standard modified to also act as a GPSDO.

Excellent - love it!

I really ought to get myself set up with a frequency standard.

[factory]

Originally Posted by Techman

Yes, I was looking for the position of the tunnel diode on the board layout in the manual and it wasn't shown, so assumed that it was possibly tacked on the print side somewhere - I didn't remove any of the boards when I opened it up for the photos. Seeing as it seemed to be working I decided not to disturb things unnecessarily.

I was waiting to see if anything would be said regarding the spanner, and it's interesting to note that as well as yours not having that same spanner, yours also doesn't have that part of the chassis plate that it's attached to either. I also wondered why it wasn't mentioned in the manual and wondered if I'd missed it and ran through it again to check.

Mine is still open, I'm not sure where the cover went, haven't found it yet, nor have I fixed the power supply problem.

Compare these pictures showing the front of mine, all the BNCs are identical, your unit has the BNC fuseholder on the input.



And the hiding place of the tunnel diode, it's on the back along with the surface mount ceramic 'chip' capacitors. Extra picture of the Plessey SP630F ECL divider.



David