Adding a tuning indicator to a Pye 15A - UK Vintage Radio Repair and Restoration Discussion Forum

Neil Purling · 13th Jan 2010, 8:43 am

This would not be defiling a restored radio, just modifying an orphan Pye 15A chassis.
You can get a Russian equivalent to a EM80.
I thought it might be a interesting project after I have got the Pye 15A going & settled down.

Alf · 13th Jan 2010, 6:05 pm

I'd have used an octal based tuning indicator in line with the rest of the valves. I know EM34s are expensive, a 1629 is cheaper but would need a voltage doubler building for the heater or a separate 12.6v supply.

Neil Purling · 13th Jan 2010, 9:43 pm

It's just a matter of what's easily available & I saw the EM80's first. There are Russian EM34 equivalents too.
Can anyone suggest a good model to look at & i'll cull the data from my BVWS 'Trader' CD's.

G8UWM-MildMartin · 14th Jan 2010, 1:43 am

Possibly Philips 170A for where to connect it and a Russian 6e5s / 6e5c for the magic eye (octal, different pinout from EM34, only single sector, but inexpensive).
Best regards,
Martin.

Neil Purling · 14th Jan 2010, 8:28 am

I looked through Forum posts on the EM34. The Phillips 170A was mentioned, so I went to the relevant Trader sheet. There aren't as many components involved as I thought.

I thought that somehow the eye would tap onto the AGC line, but on the Phillips it is connected to the bottom of the last IFT's secondary winding.

Past Times Radio does the Russian EM34's.
I would certainly consider that source, unless I found another.

G8UWM-MildMartin · 15th Jan 2010, 1:34 am

Erm, well, yes, sort of...
It uses the DC component on the detector diode for the tuning indicator, whereas the AVC/AGC diode is driven by the capacitor from the IFT's primary. Typically Philips...
Just the first set that sprang to mind as using an EBL31 plus magic eye.
On reflection, not the most straightforward scheme for me to have recommended. Sorry!

Just driving its grid straight from the AVC/AGC line is more normal, so I'd give that a try first.

Re: the Russian magic eyes, for one guaranteed good one, yes, buying from a reputable UK seller is best, though it's great fun to buy batches cheaply from the Ukraine and sort the good ones out...

Martin.

G8KBG Tony · 15th Jan 2010, 1:55 am

Quote:

Originally Posted by Neil Purling

I looked through Forum posts on the EM34. The Phillips 170A was mentioned, so I went to the relevant Trader sheet. There aren't as many components involved as I thought.

If you are modifying a Pye 15A, then I would think looking at a contemporary Pye model would be better than modifying a Philips circuit. In your first post you were going to use a EM80. What circuit were you going to use?

Leon Crampin · 15th Jan 2010, 7:58 pm

If you drive a tuning indicator from the AGC line you will get no indication below the AGC (voltage) delay, so no movement on weak signals. This is why on good sets with delayed AGC, the eye is always driven from the DC produced by the detector diode.

A dual sensitivity eye such as the EM34 (or a later all-glass eye with a variable mu amplifier triode) will give a useful indication over the whole range of signal strengths when so wired - as in the Philips 170A.

Leon.

Neil Purling · 15th Jan 2010, 11:45 pm

At first I had no particular circuit in mind. Using a Pye circuit to adapt to mine sounds sensible. The first eyes I saw on ebay were the Russian EM80, but in batches.
I note that Past Times Radio does the EM80 and EM84 in addition to the EM34 equivalent.
I don't really know which would look best: The EM34 clone (6E5S) isn't quite the same as a genuine Mullard original, having only one shadow apparently. The base wires are different to pins 4 & 5. I a original EM34 pin #4 is the grid & #5 is the target. The Russian eye has pin #5 as the grid & no indication of the target's pin.

13th Jan 2010, 8:43 am	#1
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,087	Adding a tuning indicator to a Pye 15A This would not be defiling a restored radio, just modifying an orphan Pye 15A chassis. You can get a Russian equivalent to a EM80. I thought it might be a interesting project after I have got the Pye 15A going & settled down.

13th Jan 2010, 6:05 pm	#2
Alf Hexode Join Date: May 2005 Location: Wigan, Greater Manchester, UK. Posts: 479	Re: Adding a tuning indicator to a Pye 15A I'd have used an octal based tuning indicator in line with the rest of the valves. I know EM34s are expensive, a 1629 is cheaper but would need a voltage doubler building for the heater or a separate 12.6v supply.

13th Jan 2010, 9:43 pm	#3
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,087	Re: Adding a tuning indicator to a Pye 15A It's just a matter of what's easily available & I saw the EM80's first. There are Russian EM34 equivalents too. Can anyone suggest a good model to look at & i'll cull the data from my BVWS 'Trader' CD's.

15th Jan 2010, 1:34 am	#6
G8UWM-MildMartin Heptode Join Date: Jan 2004 Location: Stockport, Greater Manchester, UK. Posts: 827	Re: Adding a tuning indicator to a Pye 15A Erm, well, yes, sort of... It uses the DC component on the detector diode for the tuning indicator, whereas the AVC/AGC diode is driven by the capacitor from the IFT's primary. Typically Philips... Just the first set that sprang to mind as using an EBL31 plus magic eye. On reflection, not the most straightforward scheme for me to have recommended. Sorry! Just driving its grid straight from the AVC/AGC line is more normal, so I'd give that a try first. Re: the Russian magic eyes, for one guaranteed good one, yes, buying from a reputable UK seller is best, though it's great fun to buy batches cheaply from the Ukraine and sort the good ones out... Martin.

15th Jan 2010, 7:58 pm	#8
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Adding a tuning indicator to a Pye 15A If you drive a tuning indicator from the AGC line you will get no indication below the AGC (voltage) delay, so no movement on weak signals. This is why on good sets with delayed AGC, the eye is always driven from the DC produced by the detector diode. A dual sensitivity eye such as the EM34 (or a later all-glass eye with a variable mu amplifier triode) will give a useful indication over the whole range of signal strengths when so wired - as in the Philips 170A. Leon.

14th Jan 2010, 1:43 am	#4
G8UWM-MildMartin Heptode Join Date: Jan 2004 Location: Stockport, Greater Manchester, UK. Posts: 827	Re: Adding a tuning indicator to a Pye 15A Possibly Philips 170A for where to connect it and a Russian 6e5s / 6e5c for the magic eye (octal, different pinout from EM34, only single sector, but inexpensive). Best regards, Martin.

14th Jan 2010, 8:28 am	#5
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,087	Re: Adding a tuning indicator to a Pye 15A I looked through Forum posts on the EM34. The Phillips 170A was mentioned, so I went to the relevant Trader sheet. There aren't as many components involved as I thought. I thought that somehow the eye would tap onto the AGC line, but on the Phillips it is connected to the bottom of the last IFT's secondary winding. Past Times Radio does the Russian EM34's. I would certainly consider that source, unless I found another.

15th Jan 2010, 11:45 pm	#9
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,087	Re: Adding a tuning indicator to a Pye 15A At first I had no particular circuit in mind. Using a Pye circuit to adapt to mine sounds sensible. The first eyes I saw on ebay were the Russian EM80, but in batches. I note that Past Times Radio does the EM80 and EM84 in addition to the EM34 equivalent. I don't really know which would look best: The EM34 clone (6E5S) isn't quite the same as a genuine Mullard original, having only one shadow apparently. The base wires are different to pins 4 & 5. I a original EM34 pin #4 is the grid & #5 is the target. The Russian eye has pin #5 as the grid & no indication of the target's pin.