Tutorial on RCS 901 frequency counter

[sobell1980]

Hello all

Just acquired this RCS frequency counter timer 520mhz. I've never used one before so a beginners guide to its functions or tutorial would be helpful. I've used sig gen and oscilloscope as part of my repairs. Looking for do's and don'ts. Can I use the same lead from my scope? Does anybody have a copy of a user manual? I just like to know how to use my equipment and all its functions.
Many thanks
Dave

[Julesomega]

The 1MΩ input is suitable for a scope probe, and 80MHz will cover the majority of the work you are likely to do.

[factory]

There seems to be a general lack of manuals or information on RCS products, here is another thread with a repair of a RCS 901 & some reverse engineering of the faulty area.

https://www.vintage-radio.net/forum/...d.php?t=102912

David

[turretslug]

Is that the same RCS as the Radio Component Specialists sometime of Croydon? I was aware that they did a range of components and surplus decades ago and a few branded things, but hadn't realised that anything as sophisticated as this was involved. Before my time though, really.

That looks like a rather nice, comprehensive and potentially useful tool, and thank goodness the clock folk haven't vultured it!

[PETERg0rsq]

Is this quick guide to its functions I produced be any use?

Only way to damage it is to connect it to too high a voltage when in 50 ohm input modes!

Do not transmitt into it!!!!

When using a frequency counter, always "sanity check" the reading! That means is the reading what you would expect?

If not then do not trust the display, as they can pick up on harmonics, or interference if present.

If the display is not stable, then again ask why not, as they usually need a decent noise free input signal.

Finally, only as accurate as the reference source, if using internal ref, then think how accurate is that, best to use a good external reference of known accuracy. With a good reference, this will be as accurate as the latest frequency counters

[Granitehill]

Originally Posted by turretslug

Is that the same RCS as the Radio Component Specialists sometime of Croydon? I was aware that they did a range of components and surplus decades ago and a few branded things, but hadn't realised that anything as sophisticated as this was involved. Before my time though, really.

That looks like a rather nice, comprehensive and potentially useful tool, and thank goodness the clock folk haven't vultured it!

I think it might be "Radio Control Specialists Ltd" who produced rather fine model control kit from the 1960s on. They were in Bath Road in Hounslow.
Perhaps they diversified into testgear - but I've not seen anything other than counters. They used to advertise occasionally in Wireless World - around the 1970s-80s, I think.

[Philco-Pete]

I believe you are correct granitehill. I donated this counter to Sobell 1980 and IIRC it was indeed built by that RCS.
As far as it’s accuracy goes here is a picture from last week of it displaying the 10MHz output of a GPS RX. Not bad for a counter 40+ years old

[Nymrod121]

Nice counter these; Ambit (Brentwood) had one in their R&D environment which they kindly lent to me when I was working on development of high-end FM tuner modules during the mid-late '70's.
If one's interests are likely to increase in terms of frequency, a divide-by-10 prescaler might be worth considering (anybody remember the Plessey SP8629? - yes, it was actually a ÷100). For domestic radio work, perhaps not ...
Cheers
Guy

[Julesomega]

Originally Posted by Nymrod121

a divide-by-10 prescaler might be worth considering (anybody remember the Plessey SP8629?)

It may well use one for the switchable prescaler as shown in the images

[Nymrod121]

Indeed ... I note from Jeremy/Pamphonica's quoted thread that circuit & service information seemed rare so I wonder what was involved in the 'scaler' switchable option?

[Vintage_RC]

As a user of RCS (Radio Control Specialists) radio control gear in my model aircraft back in the 1960's and 1970's I can confirm that the RCS counter/timer was made by them in Hounslow. As far as I know they didn't make any other test equipment.

[factory]

There are pictures & a manual for a RCS model plane/boat guidance system here;
https://www.rcgroups.com/forums/show...5&postcount=43
The last page has the address for Radio Control Specialists Ltd. as National Work,s Bath Road, Hounslow, Middlesex.

However I just noticed the top right hand corner of the 901 counter/timer has the name as RCS Electronics, searching for this finds an advert in Wireless World (Nov 1978) for a company that made test gear including; an off-air frequency standard, a function generator and a range of counter timers (from a 32MHz 5 digit version to a top of the range 8 digit 1.2GHz version).
https://www.americanradiohistory.com...-Page-0124.pdf
The address given for R.C.S. ELECTRONICS is, 6 Wolsley Road, Ashford, Middx.

Edit: that advert in WW Nov 1978 has the address spelt wrong, an earlier advert has it as 6 Wolsey Road, TW15 2RB, page 22 of WW Oct 1977;
https://www.pearl-hifi.com/06_Lit_Ar...77/1977-10.pdf
Possibly this factory with the clock hands on the front;
https://chthomas.com/2017/11/28/univ...-ashford-sold/

David

[Nymrod121]

Gosh ... that's an amazing bit of research, David. Seeing those pages from W.W. gave me a real nostalgia kick - thank you!
Guy

[Vintage_RC]

The owner of RCS was Eric Falkner, a friend of mine. As I said above it was the same RCS as the radio control equipment, I should know, Eric offered me a job working on the development of the range of test equipment. The different address may have been a new site for making the test equipment, I'm not sure.

[factory]

Originally Posted by Vintage_RC

The different address may have been a new site for making the test equipment, I'm not sure.

It might be they because they needed to move to a bigger factory.

I wonder what happened to them, the address in Ashford is being converted into residential use, that's why I linked a website showing it before, as google street-view shows it behind wooden building site fencing.

David

[sobell1980]

Wow, thanks so much everyone for the replies. Especially the download info pdf file. I hope to have a play with it this week. I shall let you know how I get on.

Dave

[Vintage_RC]

Out of curiosity I used Google street view to take a look at 6 Wolsey Road. There are major building works taking place (when the photo was taken) at what looks like it might have been a factory unit in the past.

I visited the R/C works in Bath Road back in the day on many occasions and they would have been pushed for space to manufacture a range of test equipment as well.

[Philco-Pete]

As a footnote to all the recent interesting posts regarding these counters I have just discovered that the PCB with 6 Nixies and a load of TTL that I rescued many years ago from an idiot would-be clock builder* is from one of the same RCS models. It has had the gating and timing logic removed but retains the counters and Nixie drivers; I couldn’t resist it having a quick play with it so I restored the modified tracks around the 7490 decade counters and powered it up. Only about 150V available from the little HT generator module that was attached to it - it’s a but dim and some of the Nixie numerals struggle to illuminate properly but it was fun to see it counting again. If anyone wants to give this a home it’s yours for the price of postage- drop me a PM
Regards Pete
* I have nothing against Nixie clock builders per-se ( I have built a few myself and still have a nice example at work) it was just the vandalism of a working piece of test gear which didn’t even result in a finished clock that I found galling in this case.

[TonyDuell]

That row of wire links between the 2 rows of ICs would seem to be in place of 7475 ICs which could be used to latch the count value and thus keep the display stable when the thing was counting.

Am I close?

[Philco-Pete]

Spot-on Tony!
(See attached picture of the 901 innards)