Ekco A274 - Project No 2 - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

DoubleWound · 30th Mar 2021, 7:16 am

Quote:

Originally Posted by Barnjet

Thanks, Frank I found C28 and C34 - see photos. I now have to research how to test these types of cap in some way without owning a High Voltage Electrolytic Capacitor Reformer.
Max

If it helps, I show how my A274 chassis turned out:-

Click image for larger version

Name: Ecko A274 Under Chassis.jpg
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Click image for larger version

Name: Ecko A274 Rear View.jpg
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Barnjet · 30th Mar 2021, 6:37 pm

Thanks Synchrodyne that discussion is quite a long way over my head! I'm still at the R = V/I and all circuits are potential dividers level, so forgive me if I don't join in.

I have a very basic question: The “Initial Checks and Test" section recommends a resistance check across the HT smoothing capacitor. There are 3 such capacitors in the set: C34, C36/C37.

Can these checks be done in situ without lifting any wires?

Thanks

Barnjet · 30th Mar 2021, 6:39 pm

Quote:

Originally Posted by DoubleWound

Quote:

Originally Posted by Barnjet

Thanks, Frank I found C28 and C34 - see photos. I now have to research how to test these types of cap in some way without owning a High Voltage Electrolytic Capacitor Reformer.
Max

If it helps, I show how my A274 chassis turned out:-

Attachment 230464

Attachment 230465

Thanks DoubleWound, those photos are very instructive!

paulsherwin · 30th Mar 2021, 7:39 pm

You can perform a resistance check on these capacitors in situ. You are really just looking for potentially catastrophic short circuits, but your lamp limiter will give you a lot of protection against these anyway.

Barnjet · 30th Mar 2021, 7:45 pm

Thanks, Paul helpful and practical advice as ever

Barnjet · 2nd Apr 2021, 5:01 pm

Having ascertained that the transformer windings are neither open or short circuit and that the HT smoothing caps all show >480k ohms, I am in the process of replacing the white paper Hunts capacitors before trying first power-up through the limiter.

There is a Hunts cap in the FM tuner (C2 heater by-pass for V, I believe) but I am unsure of the best replacement and soldering method, as it's very snug - see photo

NicktheDentist replaced it in his project and I have included his before and after photos as well, so it obviously can be done. But how would be best?

Alternatively, can I risk leaving the original Hunts cap in situ and doing the first power-up through the limiter to see what happens.

thanks

Nickthedentist · 2nd Apr 2021, 5:37 pm

Leave that one until your soldering skills are up to it.

i think I did it by shaping tbe wires then firming little loops by wrapping around a jewellers screwdriver, placing the loops over the terminals, nipping the loops so they gripped the terminals, then applying solder and the freshly tinned iron simultaneously

Barnjet · 2nd Apr 2021, 5:54 pm

Thanks Nick, my soldering skills are certainly still at beginner level. So I’ll leave that cap alone for the time being.

One other observation, many of the wires in my photo are sleeved, whereas the same ones in yours are not.

Is this the likely work of a previous owner, or would the sleeving have been embodied by the OEM, as part of a modification programme? Just curious.

Thanks

Nickthedentist · 2nd Apr 2021, 6:24 pm

The latter, I’d say.

paulsherwin · 2nd Apr 2021, 6:42 pm

Actually, when I did my A277 I never changed that cap. I normally change Mouldseals on sight, but that one was quite awkward to do as you say, and I couldn't see that a modest bit of leakage would do any harm there. The radio worked very well with the original cap in place and there were no signs of physical disintegration, so I decided to leave it alone.

Barnjet · 3rd Apr 2021, 4:03 pm

1st switch-on....exciting stuff!! No catastrophes after first few goes, so switched on for 10mins or so.

Steady glow (photo) on lamp and steady state current through the limiter of 2.7mA Of course, the voltage across the set is reduced by the lamp in series, but this current seems quite low, or is it? The set power consumption is rated at 55w

Visible glow on V5 (EL86 - output) and very faint on V4 (EABC80 - ratio detector, AF amp), but nothing visible on the others.

With volume at max, occasional faint reception of R4 or R2 but signal not stable and fading in/out.

After switch off, V1,V2,V3 and V4 only faintly warm and V5 and V6 hotter, but not burningly so.

Not sure where to go next? voltage measurements?further component replacement? by-pass the limiter? Rig external aerial? I'd much appreciate a steer, thanks.

Max

paulsherwin · 3rd Apr 2021, 4:16 pm

I think all is well, and you can safely bypass the limiter, though obviously using caution at first. You won't get much FM reception without an aerial of some sort - a length of wire in one of the aerial sockets should get you something.

Keep an eye on it for the first 10 minutes or so without the limiter, watching out for nasty smells or smoke. It should be OK though.

I can't account for your meter reading. It's obvious that more than 2.7mA is flowing. Do you have the probes plugged into the right sockets?

G8UWM-MildMartin · 3rd Apr 2021, 5:44 pm

The meter is set to measure direct current.

Barnjet · 3rd Apr 2021, 6:28 pm

Quote:

Originally Posted by G8UWM-MildMartin

The meter is set to measure direct current.

He shoots .. he scores!

Doh .... sometimes I need to be saved from myself.

Anyway, meter correctly set up and guess what? Now reads 165.2mA steady state.

paulsherwin · 3rd Apr 2021, 7:42 pm

That is certainly more plausible.

Barnjet · 5th Apr 2021, 11:28 am

Full power switch-on for 10min or more - nothing untoward. Maximum current 326mA, steady state 310mA Is this excessive?

A nominal 55w power consumption would require P =VI hence I =P/V = 55/240 = 230mA

thanks

paulsherwin · 5th Apr 2021, 11:35 am

I wouldn't worry too much about this. The 55W value is pretty rough and ready, and the overall current consumption is obviously not seriously excessive. Time to take some circuit voltage readings. Don't expect them to be spot on, but look for any that are significantly higher or lower than they should be.

Sideband · 5th Apr 2021, 2:11 pm

Quote:

Originally Posted by paulsherwin

I wouldn't worry too much about this. The 55W value is pretty rough and ready, and the overall current consumption is obviously not seriously excessive.

Yes agreed. The 55W is likely to be the maximum power the set is expected
to consume. Plug some aerials in and see how the set performs. If you want to take some voltage readings for practice, expect them to be + or - 15% of stated value (and it also depends on the meter you are using). Any you are not sure about, list them so that we can assess and advise.

Barnjet · 5th Apr 2021, 5:07 pm

Thanks, I took some voltage readings, mainly to practice and learn, starting with V2 and V3 (both EF89) which were easy to access with the test probe, and to identify pin No1. I have put the Trader values in brackets with the percentage +/-

V2
Pin 3 Cathode 0.93V (1.8V) (-50%)
Pin 7 Anode 171V (227V) (-25%)
Pin 8 Screen 92.5V (79V) (+17%)
All other pins showed negligible values

V3
Pin 3 Cathode 1.38V (1.8V) (-14%)
Pin 7 Anode 166V (227V) (-27%)
Pin 8 Screen 90V (79V) (+14%)
All other pins showed negligible values

I then went on to measure V4 (EABC80)
Pin 1 Anode b -0.17V (35V) (-100%)
Pin 2 Anode a 0.0V (35V) (-100%)
Pin 9 Anode c 47.5V (35V) (+ 35%)
All other pins showed negligible values expect Pin 8 which had -0.5V and incurred a loud hum when touched with the probe.

These don't seem right so I will now test the input/output voltages at the rectifier

Barnjet · 5th Apr 2021, 5:24 pm

V6 Rectifier (EZ80) test results

Pin 1 Anode 243VAC (253VAC)
Pin 3 Cathode 220VDC (270VDC) (-19%)
Pin 7 Anode 237VAC (253VDC)

The DC voltages at the HT smoothing caps C36 and C37 are 220V and 191V respectively. So it would seem that the HT rail is under-volts (191V) which would account for the low anode voltages at V2 and V3. Please correct me if my analysis is wrong here.

Why would this be and is it significant?

30th Mar 2021, 6:37 pm	#22
Barnjet Pentode Join Date: Mar 2021 Location: Yeovil, Somerset, UK. Posts: 130	Re: Ekco A274 - Project No 2 Thanks Synchrodyne that discussion is quite a long way over my head! I'm still at the R = V/I and all circuits are potential dividers level, so forgive me if I don't join in. I have a very basic question: The “Initial Checks and Test" section recommends a resistance check across the HT smoothing capacitor. There are 3 such capacitors in the set: C34, C36/C37. Can these checks be done in situ without lifting any wires? Thanks

30th Mar 2021, 7:39 pm	#24
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: Ekco A274 - Project No 2 You can perform a resistance check on these capacitors in situ. You are really just looking for potentially catastrophic short circuits, but your lamp limiter will give you a lot of protection against these anyway.

30th Mar 2021, 7:45 pm	#25
Barnjet Pentode Join Date: Mar 2021 Location: Yeovil, Somerset, UK. Posts: 130	Re: Ekco A274 - Project No 2 Thanks, Paul helpful and practical advice as ever

2nd Apr 2021, 5:01 pm	#26
Barnjet Pentode Join Date: Mar 2021 Location: Yeovil, Somerset, UK. Posts: 130	Re: Ekco A274 - Project No 2 Having ascertained that the transformer windings are neither open or short circuit and that the HT smoothing caps all show >480k ohms, I am in the process of replacing the white paper Hunts capacitors before trying first power-up through the limiter. There is a Hunts cap in the FM tuner (C2 heater by-pass for V, I believe) but I am unsure of the best replacement and soldering method, as it's very snug - see photo NicktheDentist replaced it in his project and I have included his before and after photos as well, so it obviously can be done. But how would be best? Alternatively, can I risk leaving the original Hunts cap in situ and doing the first power-up through the limiter to see what happens. thanks Attached Thumbnails

2nd Apr 2021, 5:37 pm	#27
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,846	Re: Ekco A274 - Project No 2 Leave that one until your soldering skills are up to it. i think I did it by shaping tbe wires then firming little loops by wrapping around a jewellers screwdriver, placing the loops over the terminals, nipping the loops so they gripped the terminals, then applying solder and the freshly tinned iron simultaneously

2nd Apr 2021, 5:54 pm	#28
Barnjet Pentode Join Date: Mar 2021 Location: Yeovil, Somerset, UK. Posts: 130	Re: Ekco A274 - Project No 2 Thanks Nick, my soldering skills are certainly still at beginner level. So I’ll leave that cap alone for the time being. One other observation, many of the wires in my photo are sleeved, whereas the same ones in yours are not. Is this the likely work of a previous owner, or would the sleeving have been embodied by the OEM, as part of a modification programme? Just curious. Thanks

2nd Apr 2021, 6:24 pm	#29
Nickthedentist Dekatron Join Date: Jan 2005 Location: Oxford, UK. Posts: 17,846	Re: Ekco A274 - Project No 2 The latter, I’d say.

2nd Apr 2021, 6:42 pm	#30
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: Ekco A274 - Project No 2 Actually, when I did my A277 I never changed that cap. I normally change Mouldseals on sight, but that one was quite awkward to do as you say, and I couldn't see that a modest bit of leakage would do any harm there. The radio worked very well with the original cap in place and there were no signs of physical disintegration, so I decided to leave it alone.

3rd Apr 2021, 4:03 pm	#31
Barnjet Pentode Join Date: Mar 2021 Location: Yeovil, Somerset, UK. Posts: 130	Re: Ekco A274 - Project No 2 1st switch-on....exciting stuff!! No catastrophes after first few goes, so switched on for 10mins or so. Steady glow (photo) on lamp and steady state current through the limiter of 2.7mA Of course, the voltage across the set is reduced by the lamp in series, but this current seems quite low, or is it? The set power consumption is rated at 55w Visible glow on V5 (EL86 - output) and very faint on V4 (EABC80 - ratio detector, AF amp), but nothing visible on the others. With volume at max, occasional faint reception of R4 or R2 but signal not stable and fading in/out. After switch off, V1,V2,V3 and V4 only faintly warm and V5 and V6 hotter, but not burningly so. Not sure where to go next? voltage measurements?further component replacement? by-pass the limiter? Rig external aerial? I'd much appreciate a steer, thanks. Max Attached Thumbnails

3rd Apr 2021, 4:16 pm	#32
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: Ekco A274 - Project No 2 I think all is well, and you can safely bypass the limiter, though obviously using caution at first. You won't get much FM reception without an aerial of some sort - a length of wire in one of the aerial sockets should get you something. Keep an eye on it for the first 10 minutes or so without the limiter, watching out for nasty smells or smoke. It should be OK though. I can't account for your meter reading. It's obvious that more than 2.7mA is flowing. Do you have the probes plugged into the right sockets?

3rd Apr 2021, 5:44 pm	#33
G8UWM-MildMartin Heptode Join Date: Jan 2004 Location: Stockport, Greater Manchester, UK. Posts: 827	Re: Ekco A274 - Project No 2 The meter is set to measure direct current.

3rd Apr 2021, 7:42 pm	#35
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: Ekco A274 - Project No 2 That is certainly more plausible.

5th Apr 2021, 11:28 am	#36
Barnjet Pentode Join Date: Mar 2021 Location: Yeovil, Somerset, UK. Posts: 130	Re: Ekco A274 - Project No 2 Full power switch-on for 10min or more - nothing untoward. Maximum current 326mA, steady state 310mA Is this excessive? A nominal 55w power consumption would require P =VI hence I =P/V = 55/240 = 230mA thanks

5th Apr 2021, 11:35 am	#37
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,947	Re: Ekco A274 - Project No 2 I wouldn't worry too much about this. The 55W value is pretty rough and ready, and the overall current consumption is obviously not seriously excessive. Time to take some circuit voltage readings. Don't expect them to be spot on, but look for any that are significantly higher or lower than they should be.

5th Apr 2021, 5:07 pm	#39
Barnjet Pentode Join Date: Mar 2021 Location: Yeovil, Somerset, UK. Posts: 130	Re: Ekco A274 - Project No 2 Thanks, I took some voltage readings, mainly to practice and learn, starting with V2 and V3 (both EF89) which were easy to access with the test probe, and to identify pin No1. I have put the Trader values in brackets with the percentage +/- V2 Pin 3 Cathode 0.93V (1.8V) (-50%) Pin 7 Anode 171V (227V) (-25%) Pin 8 Screen 92.5V (79V) (+17%) All other pins showed negligible values V3 Pin 3 Cathode 1.38V (1.8V) (-14%) Pin 7 Anode 166V (227V) (-27%) Pin 8 Screen 90V (79V) (+14%) All other pins showed negligible values I then went on to measure V4 (EABC80) Pin 1 Anode b -0.17V (35V) (-100%) Pin 2 Anode a 0.0V (35V) (-100%) Pin 9 Anode c 47.5V (35V) (+ 35%) All other pins showed negligible values expect Pin 8 which had -0.5V and incurred a loud hum when touched with the probe. These don't seem right so I will now test the input/output voltages at the rectifier

5th Apr 2021, 5:24 pm	#40
Barnjet Pentode Join Date: Mar 2021 Location: Yeovil, Somerset, UK. Posts: 130	Re: Ekco A274 - Project No 2 V6 Rectifier (EZ80) test results Pin 1 Anode 243VAC (253VAC) Pin 3 Cathode 220VDC (270VDC) (-19%) Pin 7 Anode 237VAC (253VDC) The DC voltages at the HT smoothing caps C36 and C37 are 220V and 191V respectively. So it would seem that the HT rail is under-volts (191V) which would account for the low anode voltages at V2 and V3. Please correct me if my analysis is wrong here. Why would this be and is it significant?