EMI scope model 2300 - UK Vintage Radio Repair and Restoration Discussion Forum

Alf Fisher · 3rd Jun 2016, 6:17 pm

Hi folks,

Does anyone have a circuit diagram for the little EMI scope model 2300.

This is the only place I have found it mentioned.

http://www.thevalvepage.com/testeq/emi/2300/2300.htm

Alf

WME_bill · 5th Jun 2016, 6:51 pm

No, I do not have the circuit, and would like one also.
It is not a very sophisticated machine, so it would not be too difficult to trace out the wiring.
Made in 1956, by Industrial Electronics, East Sheen, Surrey, SW14, and marketed as Sonatronic for £39.10.0.
EMI then badge engineered it, and sold it as EMI 2300. Uses Mullard DG7-5 3" tube, with 3 EF91 valves. Y performance was 7cm/V (140V/cm) to 100khz, and 0.7cm/V (1.4v/cm) 20Hz to 2.5Mhz. X Amp 5cm/V to 100khz.
Fine for Television servicing in those far off black and white 405 line days.
wme_bill m0wpn.

David Simpson · 6th Jun 2016, 10:58 am

Hello Alf,
If you scroll down to page 2, you'll see that I have an EMI WM1 scope of similar vintage.

https://www.vintage-radio.net/forum/...d.php?t=111781

Take away the voltmeter, and it may well have similar circuitry & CRT.
I'll look out the Manual pdf.

Regards, David

Alf Fisher · 6th Jun 2016, 3:59 pm

Thank you Bill for the data and thanks David for the link to the WM1 scope.

I picked up this little scope up at the Luton rally a couple of years ago and it has been sitting in the roundtuit pile ever since.

I'll have a look and see how the circuits compare.

Cheers,
Alf

WME_bill · 7th Jun 2016, 5:09 pm

EMI 2300 / Sonatronic 2300 / Industrial Electronics oscilloscope.
Apparently uses three EF91 pentodes. Can you let us know what the tube type is, as that makes quite a difference to the circuit techniques used.

I don't think you will find the EMI WM1 much help, as it uses two power pentodes as a paraphase Y amp, with a transistron (phantastron) TB and triode X amplifier. Tube is ECR30 / VCR139A / Cossor 23D / GEC E4205.
I rummaged through my manuals. Best I could find were:
Cossor 1039 Mark1. Three EF91 and 23D tube. As single Y amp, with transitron TB and paraphase X amp. Circuit on Jon's invaluable Valvpe Page site. As it is a bit eccentric now-a-days to download I attach the circuit.
Cossor 1039 Mark2. Much improved performance, with three EF91 and DH7-91 / 3AFP1 tube. Single Y, transitron TB and Sync valve. circuit attached.
MetroVick CT52/CT84. Two EF91 and 6F33. single Y amp, with Transistron TB and paraphase X amp. Ignore the two extra EF91 and EB91 diode used to give triggered and sync polarity. circuit attached.

Let us know how you get on, as I would like a copy of the circuit please. I see a Sonatronic is currently on offer on ebay. Perhaps you are after that, and hoping to find a manual in advance. wme_Bill

Alf Fisher · 7th Jun 2016, 6:29 pm

Hello Bill,
I realise the circuit of the WM1 will be nothing like the 2300 but I like to study these things.
I had a look inside the EMI 2300 last evening and found 5 valves all mounted horizontally. There are 2 above the CRT and 3 below which are impossible to get out. They all look like Z77 (EF91) but can't be sure about the lower ones until I can get them out to check. Power supplies are a bit simple using a HW tubular selenium rectifier for HT and similar but a longer and thinner one for the EHT. Its all a bit tightly packed. I daresay I will need to replace some capacitors.
I checked a few resistors that are easy to get at and they hadn't gone as high as some of similar age in other equipments.

I will have another look at it in the coming days and let you know what the other valves are and what type of CRT is in it.

Alf

Restoration73 · 7th Jun 2016, 7:48 pm

It would be useful if a circuit turns up. Someone gave me a 2300 on Sunday, looks
mint, just plugged it in and it worked. Prefer the proper knobs on this unlike the Cossor.

Alf Fisher · 12th Jun 2016, 8:29 am

Hi Bill,
Last evening I had another look at the scope and took out the CRT to see it is a DP7-5 and there are five EF91 valves.
The timebase operation was a bit crazy as the sweep speeds didn't behave as you would expect on switching up the ranges. I assumed these strange effects were caused by dubious Hunts caps so replaced all the timing caps and then it behaved correctly. I didn’t get as far as tracing the circuit but in all, I replaced 8 Hunts capacitors, one 47k resistor that measured 69k and soldered a 10k resistor in the Y amp that had never been soldered when it was manufactured. Now the scope works quite well.

Still hoping that someone will come up with a circuit diagram but if all else fails, I might resort to tracing it myself.

Alf

David Simpson · 12th Jun 2016, 1:53 pm

Alf, Sounds as though you've done a great job on your EMI scope. You've put me to shame, as mine is still in bits. Heaps of gardening, & my son's knackered septic tank's soak-pit have taken up a fair bit of time.
My impression is that EMI made nice compact scopes for everyday use.

Regards, David

WME_bill · 12th Jun 2016, 10:15 pm

Sonatronic / EMI 2300.
Thinking aloud, with 5 valves and that DG7-5 tube, for which the X axis has to be driven symmetrically and needs a lot of volts. DP7-5 =GM=P7 medium long phosphor, DG7-5 = P1=GJ. both yellow-green.
So unlikely to be a 3 valve Puckle timebase. I'd expect a single transitron (phantastron) TB and the X amplifier in paraphase. The Y amplifer probably a single EF91, but could just be a paraphase pair, as the EMI-WM1. That will be worth checking: two valves, with equal anode resistors, each driving a Y plate. Three valves counted now, so one extra as sync polarity, and one around the TB as sync amplifier or hold off feed. We are back to something like the CT52 arrangement already posted.
I am much intrigued, and waiting for a circuit to turn up or for your researches to produce a bit more information. wme_Bill

3rd Jun 2016, 6:17 pm	#1
Alf Fisher Hexode Join Date: Sep 2005 Location: Potton, Bedfordshire, UK. Posts: 293	EMI scope model 2300 Hi folks, Does anyone have a circuit diagram for the little EMI scope model 2300. This is the only place I have found it mentioned. http://www.thevalvepage.com/testeq/emi/2300/2300.htm Alf

5th Jun 2016, 6:51 pm	#2
WME_bill Octode Join Date: Oct 2007 Location: Exeter, Devon, UK. Posts: 1,554	Re: EMI scope model 2300 No, I do not have the circuit, and would like one also. It is not a very sophisticated machine, so it would not be too difficult to trace out the wiring. Made in 1956, by Industrial Electronics, East Sheen, Surrey, SW14, and marketed as Sonatronic for £39.10.0. EMI then badge engineered it, and sold it as EMI 2300. Uses Mullard DG7-5 3" tube, with 3 EF91 valves. Y performance was 7cm/V (140V/cm) to 100khz, and 0.7cm/V (1.4v/cm) 20Hz to 2.5Mhz. X Amp 5cm/V to 100khz. Fine for Television servicing in those far off black and white 405 line days. wme_bill m0wpn.

6th Jun 2016, 10:58 am	#3
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,856	Re: EMI scope model 2300 Hello Alf, If you scroll down to page 2, you'll see that I have an EMI WM1 scope of similar vintage. https://www.vintage-radio.net/forum/...d.php?t=111781 Take away the voltmeter, and it may well have similar circuitry & CRT. I'll look out the Manual pdf. Regards, David

6th Jun 2016, 3:59 pm	#4
Alf Fisher Hexode Join Date: Sep 2005 Location: Potton, Bedfordshire, UK. Posts: 293	Re: EMI scope model 2300 Thank you Bill for the data and thanks David for the link to the WM1 scope. I picked up this little scope up at the Luton rally a couple of years ago and it has been sitting in the roundtuit pile ever since. I'll have a look and see how the circuits compare. Cheers, Alf

7th Jun 2016, 6:29 pm	#6
Alf Fisher Hexode Join Date: Sep 2005 Location: Potton, Bedfordshire, UK. Posts: 293	Re: EMI scope model 2300 Hello Bill, I realise the circuit of the WM1 will be nothing like the 2300 but I like to study these things. I had a look inside the EMI 2300 last evening and found 5 valves all mounted horizontally. There are 2 above the CRT and 3 below which are impossible to get out. They all look like Z77 (EF91) but can't be sure about the lower ones until I can get them out to check. Power supplies are a bit simple using a HW tubular selenium rectifier for HT and similar but a longer and thinner one for the EHT. Its all a bit tightly packed. I daresay I will need to replace some capacitors. I checked a few resistors that are easy to get at and they hadn't gone as high as some of similar age in other equipments. I will have another look at it in the coming days and let you know what the other valves are and what type of CRT is in it. Alf

7th Jun 2016, 7:48 pm	#7
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: EMI scope model 2300 It would be useful if a circuit turns up. Someone gave me a 2300 on Sunday, looks mint, just plugged it in and it worked. Prefer the proper knobs on this unlike the Cossor.

12th Jun 2016, 8:29 am	#8
Alf Fisher Hexode Join Date: Sep 2005 Location: Potton, Bedfordshire, UK. Posts: 293	Re: EMI scope model 2300 Hi Bill, Last evening I had another look at the scope and took out the CRT to see it is a DP7-5 and there are five EF91 valves. The timebase operation was a bit crazy as the sweep speeds didn't behave as you would expect on switching up the ranges. I assumed these strange effects were caused by dubious Hunts caps so replaced all the timing caps and then it behaved correctly. I didn’t get as far as tracing the circuit but in all, I replaced 8 Hunts capacitors, one 47k resistor that measured 69k and soldered a 10k resistor in the Y amp that had never been soldered when it was manufactured. Now the scope works quite well. Still hoping that someone will come up with a circuit diagram but if all else fails, I might resort to tracing it myself. Alf

12th Jun 2016, 1:53 pm	#9
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,856	Re: EMI scope model 2300 Alf, Sounds as though you've done a great job on your EMI scope. You've put me to shame, as mine is still in bits. Heaps of gardening, & my son's knackered septic tank's soak-pit have taken up a fair bit of time. My impression is that EMI made nice compact scopes for everyday use. Regards, David

12th Jun 2016, 10:15 pm	#10
WME_bill Octode Join Date: Oct 2007 Location: Exeter, Devon, UK. Posts: 1,554	Re: EMI scope model 2300 Sonatronic / EMI 2300. Thinking aloud, with 5 valves and that DG7-5 tube, for which the X axis has to be driven symmetrically and needs a lot of volts. DP7-5 =GM=P7 medium long phosphor, DG7-5 = P1=GJ. both yellow-green. So unlikely to be a 3 valve Puckle timebase. I'd expect a single transitron (phantastron) TB and the X amplifier in paraphase. The Y amplifer probably a single EF91, but could just be a paraphase pair, as the EMI-WM1. That will be worth checking: two valves, with equal anode resistors, each driving a Y plate. Three valves counted now, so one extra as sync polarity, and one around the TB as sync amplifier or hold off feed. We are back to something like the CT52 arrangement already posted. I am much intrigued, and waiting for a circuit to turn up or for your researches to produce a bit more information. wme_Bill