Ekco A22 low volume - UK Vintage Radio Repair and Restoration Discussion Forum

5SC · 6th Dec 2019, 2:00 pm

Hi,

My A22 initially presents with low volume. Touching the EF39 cap with a screwdriver resolves the problem - until the next time I switch on.
All the capacitors are relatively new and do not seem faulty. I have also replaced valves but still have the problem.

A point in the right direction would be much appreciated !

Many thanks,

Iain

PJL · 6th Dec 2019, 5:18 pm

Have you tried another EF39? Is the metalisation in good condition? Have you cleaned the valve pins and socket?
This is the grid of the IF valve so I would be looking at IF instability or possibly the AGC resistors have gone high.

5SC · 6th Dec 2019, 5:40 pm

Thanks for your advice. Yes, I did replace the EF39 with a known quantity ie out of my other A22 but no different. Strangely, the set will run happily for hours after the “ kick start” but once switched off for a period it reverts to low volume.

Iain

cathoderay57 · 7th Dec 2019, 10:18 pm

Hi Iain, try cleaning the wavechange switch contacts and also the extension speaker switch contacts, and check the continuity at the ends of the braided speaker leads. Touching the EF39 grid can produce a thump that can temporarily override a dry joint somewhere. The other possible cause is that the EF39 is on the verge of oscillation for some reason. Re-check AGC decoupling capacitors and their chassis connections. Failing that, try to establish whether the audio stage is working normally under "low volume" fault conditions compared to normal conditions. Cheers, Jerry

PJL · 8th Dec 2019, 6:38 pm

Try measuring the AGC voltage on (trader sheet) C15 with and without the fault condition.

6th Dec 2019, 2:00 pm	#1
5SC Triode Join Date: Apr 2004 Location: Glasgow, Scotland. UK. Posts: 15	Ekco A22 low volume Hi, My A22 initially presents with low volume. Touching the EF39 cap with a screwdriver resolves the problem - until the next time I switch on. All the capacitors are relatively new and do not seem faulty. I have also replaced valves but still have the problem. A point in the right direction would be much appreciated ! Many thanks, Iain

6th Dec 2019, 5:18 pm	#2
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Ekco A22 low volume Have you tried another EF39? Is the metalisation in good condition? Have you cleaned the valve pins and socket? This is the grid of the IF valve so I would be looking at IF instability or possibly the AGC resistors have gone high.

6th Dec 2019, 5:40 pm	#3
5SC Triode Join Date: Apr 2004 Location: Glasgow, Scotland. UK. Posts: 15	Re: Ekco A22 low volume Thanks for your advice. Yes, I did replace the EF39 with a known quantity ie out of my other A22 but no different. Strangely, the set will run happily for hours after the “ kick start” but once switched off for a period it reverts to low volume. Iain

7th Dec 2019, 10:18 pm	#4
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,382	Re: Ekco A22 low volume Hi Iain, try cleaning the wavechange switch contacts and also the extension speaker switch contacts, and check the continuity at the ends of the braided speaker leads. Touching the EF39 grid can produce a thump that can temporarily override a dry joint somewhere. The other possible cause is that the EF39 is on the verge of oscillation for some reason. Re-check AGC decoupling capacitors and their chassis connections. Failing that, try to establish whether the audio stage is working normally under "low volume" fault conditions compared to normal conditions. Cheers, Jerry Last edited by cathoderay57; 7th Dec 2019 at 10:32 pm.

8th Dec 2019, 6:38 pm	#5
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Ekco A22 low volume Try measuring the AGC voltage on (trader sheet) C15 with and without the fault condition.