1953 EAR Microgram - or is it ? - UK Vintage Radio Repair and Restoration Discussion Forum

TechProp · 20th Feb 2024, 5:03 pm

Dear all,

I have recently acquired an EAR Microgram, which I've been led to believe is from 1953 (as it was the sellers mothers 21st birthday present), and has a Collaro RC 531 deck in it .

However, I've been unable to find *any* reference to it whatsoever (and I've looked for a many years).

The circuit has 2 valves, an EZ80 and an EL34 and this is where the mystery begins. Those of you 'in the know' will now tell me that :

"It cant be from 1953 as the EZ80 was released in 1954 and the EL34 in 1955."

So, my questions to you are :-

1) What year was it likely to have been made ?
2) Where can I get a circuit diagram ?
3) What advice can you give on attempting restoration as the case is very mouldy plywood.

Thanks in advance

Perplexed Pete...

Robert Gribnau · 20th Feb 2024, 5:52 pm

Are you sure there is actually an EL34 inside your record player?

The EZ80 was introduced in 1952 and can be found in UK made equipment from 1953 going. See:

https://www.radiomuseum.org/tubes/tube_ez80.html

Edward Huggins · 20th Feb 2024, 6:31 pm

This is a very early EAR Microgram and looks to be completely original. But is it really an EL34 - say, in a single stage configuration? - and that would be very strange if it is. An EL84 was normally used by EAR, but valve this was introduced until late 1954./55.

paulsherwin · 20th Feb 2024, 6:53 pm

I agree with the others. You almost certainly have an EL84 and have simply misread the number. An EL34 is a much bigger valve and extremely unlikely in this sort of equipment (though it's not completely impossible I guess).

I think it was introduced in 1955, not 1953. A 1953 model would probably have used B8A valves (EZ41/EL41).

Robert Gribnau · 20th Feb 2024, 6:56 pm

The EL84 was introduced in 1953 and can be found in UK made equipment from 1953 going. See:

https://www.radiomuseum.org/tubes/tu...oogle_vignette

TechProp · 20th Feb 2024, 7:57 pm

Dear all,

Yes, you're absolutely right !
Upon much closer inspection, it is an EL84, thank you.

Now to find a circuit diagram.

I suppose its not out of the question for me to draw out what I see there and present it to you all, but I'd rather have what EAR designed, rather than my amateur identification !

Where do i begin to find one ?

TIA

Pete...

ben · 20th Feb 2024, 10:40 pm

Is it just me or is that arm mounted too far forward?

Analogue man · 20th Feb 2024, 11:17 pm

Ben,

The arm is in the same place on my 3RC531 which was made in 1953, I suspect if the whole thing was much newer than 53 then it would have had a RC54 deck. As an aside my 3RC531 still works perfectly along with it's original Collaro Studio crystal cartridge.

Edward Huggins · 21st Feb 2024, 9:22 am

Quote:

Originally Posted by TechProp

Yes, you're absolutely right! Upon much closer inspection, it is an EL84, thank you.

This circuit is very easy to draw out. You may need to ensure if the mains transformer is isolated or just a valve heater (filament) type.

TechProp · 22nd Feb 2024, 1:29 pm

Thanks Edward

I've made a start on drawing it out

, but how can I tell if the mains transformer is isolated ? I've attached a photo of it and the condenser 'can'.
Is the latter 3 capacitors ? (8uF , 8uF & 32uF 350v DC) or just two (8uF & 32uF 350v DC)
Are these in series, parallel or mixture of

?

Also, if the can needs replacing, I can source (from Farnell) 8uf 600V at a reasonable cost, but the 32uF ones appear to be rather pricey

- is there a better option.

As always, thanks in advance.

Pete...

Station X · 22nd Feb 2024, 2:53 pm

How many transformers are there in the player? Is the amplifier fed power from a tap on the motor winding?

Analogue man · 22nd Feb 2024, 5:33 pm

Quote:

Originally Posted by Station X

How many transformers are there in the player? Is the amplifier fed power from a tap on the motor winding?

I'm not sure Collaro motors could do that, I've certainly never seen one that could.

Edward Huggins · 22nd Feb 2024, 5:33 pm

Quote:

Originally Posted by TechProp

Thanks Edward

I've made a start on drawing it out

, but how can I tell if the mains transformer is isolated ? I've attached a photo of it and the condenser 'can'.
Is the latter 3 capacitors ? (8uF , 8uF & 32uF 350v DC) or just two (8uF & 32uF 350v DC)
Are these in series, parallel or mixture of

?

Also, if the can needs replacing, I can source (from Farnell) 8uf 600V at a reasonable cost, but the 32uF ones appear to be rather pricey

- is there a better option.

As always, thanks in advance.

Pete...

If it's a filament transformer there will be just 2 wires coming in from the mains to 2 wires going to the valves to power the heaters at 6.3V. If it's mains isolated, there will be more wires going to the amplifier for the HT supply. The capacitors should be replaced with 3 seperate ones at 350V rating. The speaker looks damaged by damp, check the cone from the front side.

TechProp · 28th Feb 2024, 11:27 am

Quote:

How many transformers are there in the player?

There are two: one is attached to the speaker, the other one appears to be attached to the valve heaters.

Quote:

The speaker looks damaged by damp, check the cone from the front side.

Sadly, it is BER and needs to be re-coned

- does anyone know of who / where that can help ?

Quote:

The capacitors should be replaced with 3 separate ones at 350V rating.

Looking at Cricklewood Electronics (heard they sell quality components), I can source Axial 8uf @450v capacitors but there is only an Axial 33uf @450v will this suffice ?
Or do I have to purchase the 'Dual cans' (ie 32+32) and only use one side ?

I have attached 3 photos, so you have a clearer idea (valves have been removed EZ80 on top and EL84 on the bottom.)

As always, thanks in advance.

Pete...

Station X · 28th Feb 2024, 5:37 pm

There were no pictures attached to your post.

Edward Huggins · 28th Feb 2024, 6:07 pm

That speaker is not worth the time and expense of re-coning. It look like a standard 6.5" ( or 8",so ever better) 3 ohm unit. There are so many Woodies that use these, a Forum Member out there is most liable to have one.

TechProp · 29th Feb 2024, 12:55 pm

Quote:

Originally Posted by Station X

There were no pictures attached to your post.

Apologies, finger issues

Quote:

That speaker is not worth the time and expense of re-coning. It look like a standard 6.5" ( or 8",so ever better) 3 ohm unit. There are so many Woodies that use these, a Forum Member out there is most liable to have one.

Ah, Thanks for the advice. Does anyone have one they would like to part with ?

Also, will the Axial 33uf @450v in place of the 32uf suffice ?

Thanks in advance

Pete...

Station X · 29th Feb 2024, 1:57 pm

You'll need to post your request for a speaker in this section:-

https://www.vintage-radio.net/forum/...splay.php?f=28

Please state the diameter and impedance needed.

TechProp · 29th Feb 2024, 3:48 pm

Quote:

Originally Posted by Station X

You'll need to post your request for a speaker in this section:-

https://www.vintage-radio.net/forum/...splay.php?f=28

Please state the diameter and impedance needed.

Thanks, I'll get on to it soon.

In the meantime, I feel that I should apologise to all those experienced at reading correctly drawn thermionic valve based electronic circuits, rather than what I now present as my first attempt at 'Reverse Engineering' the circuit.

Not all of the values of the components are known as some have their markings missing. So, if you see a component in the wrong place, wrong value etc, please let me know and I'll make an amendment.

Thanks in advance

Pete...

TonyDuell · 29th Feb 2024, 4:04 pm

I am assuming the 'earrth' symbol means 'connected to chassis'. This is a live-chassis unit, the mains transformer (top centre of your diagram) is for the heaters only.

I think you'rs missing a couple of earth symbols :

Mains Neutral/end of VR2 should go to chassis

Pin 4 on the EL84, likewise

I would also check that you've correctly identified the 3 capacitors in the can. Why are there 2 'C1's?

20th Feb 2024, 5:03 pm	#1
TechProp Triode Join Date: Oct 2018 Location: Bournemouth,Dorset, UK. Posts: 28	1953 EAR Microgram - or is it ? Dear all, I have recently acquired an EAR Microgram, which I've been led to believe is from 1953 (as it was the sellers mothers 21st birthday present), and has a Collaro RC 531 deck in it . However, I've been unable to find any reference to it whatsoever (and I've looked for a many years). The circuit has 2 valves, an EZ80 and an EL34 and this is where the mystery begins. Those of you 'in the know' will now tell me that : "It cant be from 1953 as the EZ80 was released in 1954 and the EL34 in 1955." So, my questions to you are :- 1) What year was it likely to have been made ? 2) Where can I get a circuit diagram ? 3) What advice can you give on attempting restoration as the case is very mouldy plywood. Thanks in advance Perplexed Pete... Attached Thumbnails

20th Feb 2024, 5:52 pm	#2
Robert Gribnau Banned Join Date: May 2017 Location: Konongo, Ghana Posts: 516	Re: 1953 EAR Microgram - or is it ? Are you sure there is actually an EL34 inside your record player? The EZ80 was introduced in 1952 and can be found in UK made equipment from 1953 going. See: https://www.radiomuseum.org/tubes/tube_ez80.html

20th Feb 2024, 6:31 pm	#3
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,345	Re: 1953 EAR Microgram - or is it ? This is a very early EAR Microgram and looks to be completely original. But is it really an EL34 - say, in a single stage configuration? - and that would be very strange if it is. An EL84 was normally used by EAR, but valve this was introduced until late 1954./55. __________________ Edward.

20th Feb 2024, 6:53 pm	#4
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 28,012	Re: 1953 EAR Microgram - or is it ? I agree with the others. You almost certainly have an EL84 and have simply misread the number. An EL34 is a much bigger valve and extremely unlikely in this sort of equipment (though it's not completely impossible I guess). I think it was introduced in 1955, not 1953. A 1953 model would probably have used B8A valves (EZ41/EL41).

20th Feb 2024, 6:56 pm	#5
Robert Gribnau Banned Join Date: May 2017 Location: Konongo, Ghana Posts: 516	Re: 1953 EAR Microgram - or is it ? The EL84 was introduced in 1953 and can be found in UK made equipment from 1953 going. See: https://www.radiomuseum.org/tubes/tu...oogle_vignette

20th Feb 2024, 7:57 pm	#6
TechProp Triode Join Date: Oct 2018 Location: Bournemouth,Dorset, UK. Posts: 28	Re: 1953 EAR Microgram - or is it ? Dear all, Yes, you're absolutely right ! Upon much closer inspection, it is an EL84, thank you. Now to find a circuit diagram. I suppose its not out of the question for me to draw out what I see there and present it to you all, but I'd rather have what EAR designed, rather than my amateur identification ! Where do i begin to find one ? TIA Pete...

20th Feb 2024, 10:40 pm	#7
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,500	Re: 1953 EAR Microgram - or is it ? Is it just me or is that arm mounted too far forward? __________________ Regards, Ben.

20th Feb 2024, 11:17 pm	#8
Analogue man Hexode Join Date: Dec 2020 Location: Raunds, Northamptonshire, UK. Posts: 360	Re: 1953 EAR Microgram - or is it ? Ben, The arm is in the same place on my 3RC531 which was made in 1953, I suspect if the whole thing was much newer than 53 then it would have had a RC54 deck. As an aside my 3RC531 still works perfectly along with it's original Collaro Studio crystal cartridge. __________________ Graham

22nd Feb 2024, 1:29 pm	#10
TechProp Triode Join Date: Oct 2018 Location: Bournemouth,Dorset, UK. Posts: 28	Re: 1953 EAR Microgram - or is it ? Thanks Edward I've made a start on drawing it out , but how can I tell if the mains transformer is isolated ? I've attached a photo of it and the condenser 'can'. Is the latter 3 capacitors ? (8uF , 8uF & 32uF 350v DC) or just two (8uF & 32uF 350v DC) Are these in series, parallel or mixture of ? Also, if the can needs replacing, I can source (from Farnell) 8uf 600V at a reasonable cost, but the 32uF ones appear to be rather pricey - is there a better option. As always, thanks in advance. Pete... Attached Thumbnails

22nd Feb 2024, 2:53 pm	#11
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,290	Re: 1953 EAR Microgram - or is it ? How many transformers are there in the player? Is the amplifier fed power from a tap on the motor winding? __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

28th Feb 2024, 5:37 pm	#15
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,290	Re: 1953 EAR Microgram - or is it ? There were no pictures attached to your post. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

28th Feb 2024, 6:07 pm	#16
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 8,345	Re: 1953 EAR Microgram - or is it ? That speaker is not worth the time and expense of re-coning. It look like a standard 6.5" ( or 8",so ever better) 3 ohm unit. There are so many Woodies that use these, a Forum Member out there is most liable to have one. __________________ Edward.

29th Feb 2024, 1:57 pm	#18
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,290	Re: 1953 EAR Microgram - or is it ? You'll need to post your request for a speaker in this section:- https://www.vintage-radio.net/forum/...splay.php?f=28 Please state the diameter and impedance needed. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

29th Feb 2024, 4:04 pm	#20
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,228	Re: 1953 EAR Microgram - or is it ? I am assuming the 'earrth' symbol means 'connected to chassis'. This is a live-chassis unit, the mains transformer (top centre of your diagram) is for the heaters only. I think you'rs missing a couple of earth symbols : Mains Neutral/end of VR2 should go to chassis Pin 4 on the EL84, likewise I would also check that you've correctly identified the 3 capacitors in the can. Why are there 2 'C1's?