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Telequipment D52.

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Telequipment D52.

Post by Rebel Rafter » Thu Mar 31, 2016 9:38 pm

Hi all, RR here. I've got an old Telequipment D52 scope which I got from an old shop which is closing down this weekend and it appears to be fairly intact inside and apart from one double and two single low voltage electrolytics, C410, C415 & 416 and one germanium transistor, TR401 which someone has replaced with an AC128 everything else seems to be original and while it's filthy with a capital F there doesn't seem to be any corrosion so it was out with the insulation tester and it read over 100 megohms to earth from both live and neutral with the power switch on and there seemed to be no obvious signs of distress anywhere so I rather cautiously switched on at the scope first and then standing well back switched on at the socket and nothing went bang and all the valves lit up nicely so I adjusted the controls and soon got two nice clean traces all nicely focused so it looks like the tube is ok. So I will have to give it a good clean out and a service. Has anyone here had previous experience of this scope? I know it's only a very basic model, I only got it for a friend of mine who wants to learn to use a scope and needs something basic. Anyone got any suggestions of any critical points to watch out for with this model? I can get the manual online. Any suggestions most appreciated, thanks in advance. RR.

 
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Re: Telequipment D52.

Post by boyblue » Fri Apr 01, 2016 1:16 am

Hi RR, nice old Telequipment scope, good for for LF work but never had very good triggerring. It was said in the old days that if a waveform triggerred first time you had to buy all the workshop a pint!. Watch the transformer derived EHT though. it bites!

Peter

 
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Re: Telequipment D52.

Post by Terrykc » Fri Apr 01, 2016 2:17 pm

Google is your friend ...

(Other search engines are available.)

First hit:

http://diyaudioprojects.com/Testeq/Telequipment_D52/Telequipment_D52.htm

 
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Re: Telequipment D52.

Post by Dr Wobble » Mon Apr 04, 2016 6:30 am

I'm working on a S51 and 52 at the moment. One potential problem is the big selenium diodes that Telequipment used in most of their scopes of this era, IE MR409 and the big paper cap, C409 may be dry and on its way out. That said, I've replaced this in some scopes and left as is in others. It's hard to test for leakage unless you have a megga. These two supply the screen and the top end of the potential divider network. I found some Vishay ( BYX10GP -E3/54, 5 for £2.10 from top quality tools) EHT diodes on Ebay and replaced MR409 with one of these with a resistor in series. I used a 470 ohm for no other reason that it sounded right.

Apart from cleaning all switches and pots, it sounds like your lucky and wont need too much doing. The S51 I'm working on, I'm pretty sure has a duff CRT, the S52 has a trace, but it's big and fat, so I think either some of the big caps may be kaput or a resistor somewhere is out or maybe just dirty focus/astig pots.

I have a spare tube ( why are CRT's tubes and not valves? ) for a D52 as well as a few other bits, like knobs etc if you need anything.

BTW, the manual is available free as a PDF online.

Andy.

 
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Re: Telequipment D52.

Post by Rebel Rafter » Mon Apr 04, 2016 10:56 pm

Hi, Andy, RR here, thanks for the offer of some bits, unfortunately I've messed up and posted a reply to your post in the wrong place, I've got two posts on the forum about this scope and I've got them mixed up so apologies for that. Unfortunately I'm too far away from Lincolnshire and a scope tube is a bit too delicate to post but I have a mate who drives all over for work so I'll ask him if he ever goes anywhere near Lincs. Have a look at my other post in the wanted section. If the EHT diodes failed wouldn't good old BY182's do the job? if I remember right they were rated at about 12Kv and I fitted some of those in my big Roband scope in place of the old DY51's that it had. I've got the circuit diagram from diyaudio projects, I'll print out the rest of the manual soon enough, I wish I could find a manual for my big scope as easy as it needs an overhaul. RR.

 
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Re: Telequipment D52.

Post by Dr Wobble » Wed Apr 06, 2016 8:50 am

No worries, will look for display thingy, think the one I have is metal.

Any EHT rated diode should be ok AFAIK, the only thing is to put a suitable resistor in series. How you calculate this am not sure. I suppose that you calculate for max current as you do for zeners etc. So as the current on the EHT screen supply isn't great or that of the focus/brilliance etc controls it also feeds, current wouldnt be that great. Really, it would be easier to measure the current, but not sure about a DMM having 1kv+ on its its current circuit. I used a 470R, which on reflection seems too low a value. Oh and dont forget the resistor needs to be rated for HV.

We need some advise here from the boffins.

Andy.

 
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Re: Telequipment D52.

Post by Rebel Rafter » Wed Apr 27, 2016 9:10 pm

Hi from RR. I've got the rest of the manual for the D52 now but for some reason in the setting up procedure it doesn't show the adjustment procedure for a preset pot labelled as "I.P.S.", circuit reference RV309. Does anyone else know anything about this pot and how to set it up or is it one of those critical things that's set up once for the life of the scope and not supposed to be touched. Well I think mine has been disturbed and I need to know how to set it. Any help most appreciated, thanks. RR.

 
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Re: Telequipment D52.

Post by occiput » Wed Apr 27, 2016 10:36 pm

IPS is the Inter-plate screen - it is intended to prevent cross-talk due to capacitive coupling between the various sets of deflection plates.

In the absence of any line-up instructions, I would measure the mean potential of the Y deflection plates, with the Y shift controls set so that the traces are on the mid-line of the graticule, and adjust the IPS voltage to be somewhere near the average. I don't think it's particularly critical.

As someone who tried to use a D43 in anger for a number of years, I sincerely wish you all the luck in the world. As others have said, getting the timebase to trigger correctly can be something of a black art in Telequipment 'scopes of this era.

 
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Re: Telequipment D52.

Post by Cathovisor » Thu Apr 28, 2016 9:13 am

occiput wrote:IPS is the Inter-plate screen - it is intended to prevent cross-talk due to capacitive coupling between the various sets of deflection plates.

In the absence of any line-up instructions, I would measure the mean potential of the Y deflection plates, with the Y shift controls set so that the traces are on the mid-line of the graticule, and adjust the IPS voltage to be somewhere near the average. I don't think it's particularly critical.

If the OP can supply the type number of the CRT, the instructions for setting up the IPS may well be contained within the data for same. I once recall finding the instructions for setting up an analogue storage CRT within the CRT data sheet - when it was absent from the service manual for the 'scope.

occiput wrote:As someone who tried to use a D43 in anger for a number of years, I sincerely wish you all the luck in the world. As others have said, getting the timebase to trigger correctly can be something of a black art in Telequipment 'scopes of this era.

I have both an S43 and a D75 in my arsenal; both of which have differential Y amplifier plugins fitted. The reason for my wanting a differential plug-in are now sadly lost on me, but the main thing that strikes me is that the D75 is of the era when Telequipment were a brand of Tektronix, and the X amp and trigger module reflects this; I always felt that older Telequipments with their 'stability' controls were very much a John Scott-Taggart sort of design - make every parameter variable.

 
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Re: Telequipment D52.

Post by Rebel Rafter » Thu Apr 28, 2016 8:10 pm

Hi from RR. The scope tube in question is a type: E13-12GH/1324S, made by GEC, also labelled with the M-O valve co. ltd. I think I've got the type right, the old label is a bit rough and it's got some old sticky tape residue all over the type number so it's a bit faint. RR.

 
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Re: Telequipment D52.

Post by Marconi_MPT4 » Thu Apr 28, 2016 8:35 pm

Hi,
Perhaps this may help, according to the Telequipment S54 and S54AR service manual, to set the 'IPS' control adjust as follows.

Inter-plate Shield Potential. Set Time/CM to 0.5ms and STABILITY control fully clockwise. Centre trace with shift controls and adjust TRACE ROTATION for alignment of trace with graticule. Adjust pot for minimum curvature of the trace when re-positioned to the top and bottom of the screen.

As this is the last step in set-up procedure, it is reasonable to assume all other adjustments have been correctly set.

Rich


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