Telequipment S31 - UK Vintage Radio Repair and Restoration Discussion Forum

stuart_morgan_64 · 13th Mar 2017, 10:57 am

I have one of these which is basicly working. Displays a sine wave, which is good as it would be a pain to replace parts to find the tube is low.

What I would like to know is, what are the most liable parts to fail which should be replaced as at the moment I wouldn't like to leave it for long periods.

I found the 1A mains fuse blown, on variac with A meter i found it was drawing about 500 to 750ma

Many thanks

dave cox · 13th Mar 2017, 4:53 pm

Personally, I would run a vacuum cleaner over it, less to catch fire that way!
I don't see any paper caps in there ...

dc

Gridiron · 13th Mar 2017, 5:33 pm

The capacitors with the diamond logos look like Wima types, these could have reliability problems.
Mike.

HamishBoxer · 13th Mar 2017, 7:05 pm

Unless you are unlucky, most scopes just sit there with very little use. Certainly all the old ones I have had have had a good CRT, inc my 1930's Cossor 339A.

TrevorG3VLF · 13th Mar 2017, 7:34 pm

I have a S51B with a blown fuse. There was a thread which suggested replacing the EHT rectifier with half a dozen 1N4007 diodes in series and replacing the EHT reservoir capacitor. It is not on my priority list at present.

MotorBikeLes · 14th Mar 2017, 12:49 am

As already mentioned, those brown Wima capacitors mostly on the time/cm change switch WILL almost certainly all be leaky.
The long brown HT rectifying diodes tend to lose efficiency, resulting in a loss of EHT. If low (compare with values in manual) replace with a high voltage diode and series resistor (try 4k7).
Low HT can of course be a low emission rectifier valve, easily replaced.If I recall, all other valves are ECF80, you may need the odd replacement.
Then you will have a super little 'scope, a world leader in its day for value for money combined with quality.
Les.

britishrocket · 27th Mar 2017, 10:49 pm

I have got two of these so will be watching your progress with interest.

I blew mine out with compressed air to get rid of the dust. I'm almost finished making a cap reformer and have the ht diodes in case the eht sticks are shot.

Carl.

stuart_morgan_64 · 28th Mar 2017, 11:08 am

I have it all working, however the trace isn't always stable, there seems to be ripple on the HT and the HT caps are getting warm, none in stock so will order. I replaced the caps as in Gridiron reply, some did seem an a very poor shape, some split. So far so good.

britishrocket · 29th Mar 2017, 11:22 am

Interesting to hear all that. Did you do any reforming of the electrolytics before you switched it on? One of the caps on the time/div switch on mine is split. Most of then look dodgy so I plan to replace them.

stuart_morgan_64 · 29th Mar 2017, 2:13 pm

I did reform, but s they are warming up I will just empty the cans and put some new caps in. There were a few split ones, mainly inline with inputs.

WME_bill · 29th Mar 2017, 4:28 pm

S31. I have a S32A, introduced a few years later than the S31 as an improved version.
I had to replace one of the polystyrene TB capacitors, non-linear sweep; C18, the 8uf electrolytic in the Y Amp for the 150V rail; and one of the little neons which protect the grid of Y Amp valves during warm up, the lead out wire was broken. No trouble at all with the EHT rectifiers, STC stick style K8/50. Not found necessary to reform electrolytics either.
It is a very nice little scope, handles well even now and deservedly swept the market 1960 to 1966. wme_bill.

britishrocket · 3rd Apr 2017, 11:11 am

I'm starting to think I should just plug mine in through a limiter and see what happens....

13th Mar 2017, 10:57 am	#1
stuart_morgan_64 Heptode Join Date: Aug 2004 Location: Woodbridge, Suffolk, UK. Posts: 501	Telequipment S31 I have one of these which is basicly working. Displays a sine wave, which is good as it would be a pain to replace parts to find the tube is low. What I would like to know is, what are the most liable parts to fail which should be replaced as at the moment I wouldn't like to leave it for long periods. I found the 1A mains fuse blown, on variac with A meter i found it was drawing about 500 to 750ma Many thanks Attached Thumbnails

13th Mar 2017, 4:53 pm	#2
dave cox Nonode Join Date: Jan 2009 Location: Bristol, UK. Posts: 2,062	Re: Telequipment S31 Personally, I would run a vacuum cleaner over it, less to catch fire that way! I don't see any paper caps in there ... dc

13th Mar 2017, 5:33 pm	#3
Gridiron Heptode Join Date: Apr 2010 Location: West Midlands, UK. Posts: 663	Re: Telequipment S31 The capacitors with the diamond logos look like Wima types, these could have reliability problems. Mike.

13th Mar 2017, 7:05 pm	#4
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: Telequipment S31 Unless you are unlucky, most scopes just sit there with very little use. Certainly all the old ones I have had have had a good CRT, inc my 1930's Cossor 339A. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

13th Mar 2017, 7:34 pm	#5
TrevorG3VLF Rest in Peace Join Date: Apr 2011 Location: Matlock, Derbyshire, UK. Posts: 1,378	Re: Telequipment S31 I have a S51B with a blown fuse. There was a thread which suggested replacing the EHT rectifier with half a dozen 1N4007 diodes in series and replacing the EHT reservoir capacitor. It is not on my priority list at present.

14th Mar 2017, 12:49 am	#6
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	Re: Telequipment S31 As already mentioned, those brown Wima capacitors mostly on the time/cm change switch WILL almost certainly all be leaky. The long brown HT rectifying diodes tend to lose efficiency, resulting in a loss of EHT. If low (compare with values in manual) replace with a high voltage diode and series resistor (try 4k7). Low HT can of course be a low emission rectifier valve, easily replaced.If I recall, all other valves are ECF80, you may need the odd replacement. Then you will have a super little 'scope, a world leader in its day for value for money combined with quality. Les.

27th Mar 2017, 10:49 pm	#7
britishrocket Retired Dormant Member Join Date: Nov 2016 Location: Forres, Moray, UK. Posts: 83	Re: Telequipment S31 I have got two of these so will be watching your progress with interest. I blew mine out with compressed air to get rid of the dust. I'm almost finished making a cap reformer and have the ht diodes in case the eht sticks are shot. Carl.

28th Mar 2017, 11:08 am	#8
stuart_morgan_64 Heptode Join Date: Aug 2004 Location: Woodbridge, Suffolk, UK. Posts: 501	Re: Telequipment S31 I have it all working, however the trace isn't always stable, there seems to be ripple on the HT and the HT caps are getting warm, none in stock so will order. I replaced the caps as in Gridiron reply, some did seem an a very poor shape, some split. So far so good.

29th Mar 2017, 11:22 am	#9
britishrocket Retired Dormant Member Join Date: Nov 2016 Location: Forres, Moray, UK. Posts: 83	Re: Telequipment S31 Interesting to hear all that. Did you do any reforming of the electrolytics before you switched it on? One of the caps on the time/div switch on mine is split. Most of then look dodgy so I plan to replace them.

29th Mar 2017, 2:13 pm	#10
stuart_morgan_64 Heptode Join Date: Aug 2004 Location: Woodbridge, Suffolk, UK. Posts: 501	Re: Telequipment S31 I did reform, but s they are warming up I will just empty the cans and put some new caps in. There were a few split ones, mainly inline with inputs.

29th Mar 2017, 4:28 pm	#11
WME_bill Octode Join Date: Oct 2007 Location: Exeter, Devon, UK. Posts: 1,554	Re: Telequipment S31 S31. I have a S32A, introduced a few years later than the S31 as an improved version. I had to replace one of the polystyrene TB capacitors, non-linear sweep; C18, the 8uf electrolytic in the Y Amp for the 150V rail; and one of the little neons which protect the grid of Y Amp valves during warm up, the lead out wire was broken. No trouble at all with the EHT rectifiers, STC stick style K8/50. Not found necessary to reform electrolytics either. It is a very nice little scope, handles well even now and deservedly swept the market 1960 to 1966. wme_bill. Last edited by WME_bill; 29th Mar 2017 at 4:48 pm.

3rd Apr 2017, 11:11 am	#12
britishrocket Retired Dormant Member Join Date: Nov 2016 Location: Forres, Moray, UK. Posts: 83	Re: Telequipment S31 I'm starting to think I should just plug mine in through a limiter and see what happens....