R&S Polyskop (SWOBII)

[Sean Williams]

I really should be locked up somewhere safe!

Another late night on eBay brings a pair of these beasties home!

Onto more interesting stuff. One of the pair at least shows some form of trace, the second, nothing!

Thus far we have CRT voltages on the base, that are broadly in agreement with the manual (well, the focus volts are a bit low, but that should result in a less than pin sharp trace)

Shorting the cathode to G1 reveals no picture, so I guess the final anode voltage is missing.

Its one hell of a job to get to the power supply in this monster - perhaps a spot of lunch, and a cuppa first!

Would be interested to hear of anyone else that might have worked with these.

Sean

[Sean Williams]

As suspected the EHT supply for the final anode is missing - so, out comes the CRT, and much cursing and shouting I find the underside of the power unit.

There are three Sentercell rectifier sticks acting as a tripler unit, in conjunction with some big, and I mean big caps this is all supplied by a 1.7KV winding on the mains transformer.

I guess its time for some new diodes - the surge limiting resistor (50K) is open circuit, so I guess one of the sticks is now sick....

More fun, but why have one that works, when you can have two!

[G0HZU_JMR]

I've never actually looked inside one of these but I have used the SWOB and SWOB II variants in the past for testing various RF filters.

These units require a fair degree of user experience to get the best out of them and the quality of the trace is usually less than inspiring especially when you turn the marker pips on. However, I think I used the earlier version the most (huge RF connectors!) and the SWOB 2 was definitely nicer to use with a better display quality and I think it had regular N connectors.

The company had loads of them on the shelves but most people shied away from using them because the user interface isn't particularly intuitive and also (on SWOB 1) the display wasn't great and was very flickery.

New (frustrated) users of Polyskop SWOBs could often be spotted as they usually resorted to wiggling the various controls at random trying to get the display to show what was expected

Sorry my post isn't particularly helpful but I have spent a fair bit of time using these in the past and I felt a bit nostalgic

[Sean Williams]

No problems! - to be honest, im not expecting greatness from something of this age, or size!

This SWOB 2 has the chunky Desifix connectors - I also picked up a pair of adaptors that let me use PL259s (not a connector of choice either!)

None the less, build quality is superb, lots of silver plate, a whole platoon of valves, and a 14" crt to display with, if nothing else they are a talking point!

Cheers
Sean

[ppppenguin]

Originally Posted by Sean Williams

....lots of silver plate, a whole platoon of valves, and a 14" crt to display....

and a hernia

Many years ago, I was about 18 at the time, I used a Videoskop, the low frequency cousin of the Polyskop. It was a revelation to see the frequency response of video amplifiers on the screen.

[PJL]

I have a largely working polyskop III but that's semiconductor. I also bought a few boxes of dezifix adaptors on ebay. The markers work quite well on this version. I have replaced about 100 small electrolytics and still managed to miss a few buried deep in the master oscillator...

It gets very occassional use but makes a good table.

[Sean Williams]

I hope to have "first light" on this as soon as I receive the diodes from Jeffrey - the CRT voltages all look to be about right, so I am fairly confident.

My main reason for buying them was the lack of a project, especially seeing the spare time I currently have..... One will also prove useful when playing with the RA17 - will be nice to check all the bandpass filters.

I doubt I will go to the extreme of returning the units to "as new" condition for one the sheer number of expensive (read audiophool) valves it contains, secondly, given the limited application I have for it, coupled with what looks like an unobtainable cavity oscillator may be a step too far...

Still, its the first vintage repair work I have done in absolutely ages.

[Julesomega]

How is this coming on Sean? I have the Manual (English) and a Sweep Section Oscillator and Tuning assembly surplus to requirements

[Sean Williams]

It isn't, I passed them onto Mike down in Exeter, once i had them in the shack, I realised just how much room they took up!

[6AL5W-Martin]

hello Sean,

**** happents to all SWOB III, there are some Tantal Elkos inside.
Find them all and replace with others...
In my SWOB III there was a short cut of the -16V, I found it in the lin-log- plugin, it have on the ground board 2 Tantal blocks, one of them was shorting to ground. Some parts in this SWOB are critical in handling, like the thermo block of the lin-log Plugin, there is a little heater to warm up the dual Fet and 2 diode to +58°C

greetings
Martin

If you need any applications, I havea large collection of the books, SWOB self, and some of the plugins and oscillator boards.

greetings
Martin

http://www.wellenkino.de/swob

[Julesomega]

I like your Wellenkino site, Martin. I wonder what other Messgeräte you have there, hidden from view?

[6AL5W-Martin]

I`m still building the site, andere Messgeräte, there is some things from Philips, Rohde&Schwarz, Grundig, Plisch, generators, sweepers, tube voltmeter, mili-ohm-meter and so on.
The centre of my hobby is restoring and collecting heavy warm scopes.

greetings
Martin

[Herald1360]

Originally Posted by Sean Williams

One will also prove useful when playing with the RA17 - will be nice to check all the bandpass filters.

And will also be exactly what they were set up with at the factory...... at any rate they were in the early '70s.