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Old 15th Apr 2021, 1:14 am   #1
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Default Ekco CR152/N car radio

I got this Ekco radio — the dial arrangement is unique and puts a smile on the face of anyone interested in design. Could have been a B&O or Brionvega from the 70s.

It came with no power supply so, after cleaning, I started it using a solid state Chinese inverter. I set it to 245V to be safe. As it is, it has garbage sound, squeals and so forth. But that does not bother me too much since MW radio here in the US is either political talk shows, sports narration or weather! And there has never been LW broadcasts. But I will get to it one day.

I then seperated the radio signal from the high side of the volume potentiometer and connected a line level input. After warming up it worked well, sound was loud and clear and the line level (0.7V ?) input was fully adequate.

10 minutes into it some troubles started up — 1) some up and down modulating hiss, 2) Distortion, sounded more in the higher registers, and 3) the pentode was hot enough to iron a doll’s outfit. I turned it off. Later I checked again and pentode filament was exactly at 6.3V and the whole radio was drawing 1.8A.

What should be my best new step...look for a substitute EL42 to test? Swap out the electrolytics? Change all caps?

I will turn off power to RF tubes or remove them for the time being (of course I need a solution for V4 where the heater is paired with V3).

Many, many thanks
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Old 15th Apr 2021, 10:25 am   #2
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Default Re: Ekco CR152/N car radio

Is it possible to measure the voltage at the control grid of V5 when the receiver been on for a few minutes?

If it is positive with respect to the chassis then I'd strongly suspect the 0.01 uF inter-stage coupling capacitor is electrically leaky, so causing V5 to draw too much current and overheat.

Last edited by SteveCG; 15th Apr 2021 at 10:27 am. Reason: extra info
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Old 15th Apr 2021, 4:27 pm   #3
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Default Re: Ekco CR152/N car radio

Quote:
Originally Posted by SteveCG View Post
Is it possible to measure the voltage at the control grid of V5 when the receiver been on for a few minutes?

If it is positive with respect to the chassis then I'd strongly suspect the 0.01 uF inter-stage coupling capacitor is electrically leaky, so causing V5 to draw too much current and overheat.
Thank you so much. I can and will measure it. But I should first probably take care of this electrolytic which has made a watery mess underneath! Smells very old time electric-y.
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Old 15th Apr 2021, 5:12 pm   #4
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Default Re: Ekco CR152/N car radio

2 posts edited and one deleted already.

Please be mindful of the following when discussing this radio.

https://www.vintage-radio.net/forum/...d.php?t=177297

Cheers

Mike T
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Old 15th Apr 2021, 5:23 pm   #5
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Default Re: Ekco CR152/N car radio

OK, apologies for mentioning the vehicle in question.

Attached is a page from a garage manual for 1952-59 which indicates this radio is rather earlier than the 1970s - probably pre 1955. It contains full service information for this radio.

Suggest you pm me if you want further details.

Chris K
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Old 17th Apr 2021, 10:30 pm   #6
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Default Re: Ekco CR152/N car radio

Quote:
Originally Posted by SteveCG View Post
Is it possible to measure the voltage at the control grid of V5 when the receiver been on for a few minutes?

If it is positive with respect to the chassis then I'd strongly suspect the 0.01 uF inter-stage coupling capacitor is electrically leaky, so causing V5 to draw too much current and overheat.
I replaced the two electrolytics and the interstage cap (as you suggested). It works great now. I put new caps in heat shrink to make them look less out of place.

I guess these electrolytics are cathode bypass capacitors. They were originally 12mF ones but according to a formula I found, they should be larger, 50 for the triode, 100 for the pentode. I used 47 for both.

According to the schematic, the pentode anode gets 275V and the last screen 245V. Right now I am running them both at 245V. Info on the web is a bit confusing as to whether they should be the same, a bit lower or higher.
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Old 18th Apr 2021, 12:16 pm   #7
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Default Re: Ekco CR152/N car radio

Hi,

A friend of mine had one of these in the 1960s in his van.

The power supply had completely rotted away under the bonnet and I replaced it for him with a dynamotor. It worked fine, but needed mounting on a thick rubber pad to quieten it!

Kind regards, Dave
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Old 18th Apr 2021, 4:12 pm   #8
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Default Re: Ekco CR152/N car radio

Quote:
Originally Posted by Dave757 View Post
Hi,

A friend of mine had one of these in the 1960s in his van.

The power supply had completely rotted away under the bonnet and I replaced it for him with a dynamotor. It worked fine, but needed mounting on a thick rubber pad to quieten it!

Kind regards, Dave
Yes, as I mentioned, I am running this off a SMPS I bought, as mine never came with its power pack. I actually have a similar CR181 model and that too was missing the PS.

I do have a Dynamotor. Thanks for reminding me of it — never tried it, I should, if just out of interest.
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Old 9th May 2021, 10:23 pm   #9
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Default Re: Ekco CR152/N car radio

Hi, I continued to work on this radio. The volume potentiometer was crackly, so I replaced it with a new 500K one (I was unable to find one with the correct shaft so I epoxied part of the old shaft to the new one).

I also installed a 3.5mm AUX input jack, which cuts off the signal coming from the radio, when a jack is inserted and instead injects that AUX signal to the AF stage, right at the high end of the volume potentiometer.

My question: this works well and the radio is silent when the volume knob is at the low or high ends of its range, but anywhere in between there is a slight crackle. Is that because in the middle of the range, V4 is seeing too high an impedance, say 250K, whereas at the extremes it is either zero or whatever the output impedance of my iPhone is? Should I try adding a lower value resistor somewhere?

Many thanks!
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Old 12th Jul 2021, 3:56 pm   #10
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Default Re: Ekco CR152/N car radio

This weekend I replaced all suspect capacitors in this radio. Still, just makes a bunch of noise (MW and LW) but no reception.

The only caps I did not swap were small value "silver mica" ones -- about 10 of them -- which I had read never fail. Is that so? I also read that in some UK caps, the silver manages to grow "fingers" through porous mica and shorts.

I would appreciate any advice as some of these small value caps are inside tunable coil enclosures, I do not even know how to access them, I fear I may damage the coils inside if I try.
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Old 12th Jul 2021, 4:18 pm   #11
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Default Re: Ekco CR152/N car radio

Quote:
Originally Posted by Dave757 View Post
Hi,

A friend of mine had one of these in the 1960s in his van.

The power supply had completely rotted away under the bonnet and I replaced it for him with a dynamotor. It worked fine, but needed mounting on a thick rubber pad to quieten it!

Kind regards, Dave
I also fixed the power supply over the weekend. I installed a solid state vibrator, it now seems to run at too high a voltage. The orange thing in the back is a solid state diode to replace the triode rectifier with. When I install that, voltage climbs another 30V. I will have to change the resistors once all done.
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Old 12th Jul 2021, 4:21 pm   #12
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Default Re: Ekco CR152/N car radio

In post #6 you said it was working great. When did it stop working?
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Old 12th Jul 2021, 6:24 pm   #13
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Default Re: Ekco CR152/N car radio

Sorry, I must have misspoken -- the audio section, the last two tubes, work great. I actually installed a 3.5mm jack to input outside signals. But the receiver, the radio itself, had not been working. Recapping, this weekend, was my first effort to revive the radio. As I said, that has so far not been successful.

I am waiting on some small value caps and I will replace those too, to the extent I can reach them.

If that does not work, there are only 12 resistors, I may replace those too. Beyond that, I am not sure. I guess I need to take out the oscilloscope and poke around?

Many thanks
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Old 12th Jul 2021, 7:13 pm   #14
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Default Re: Ekco CR152/N car radio

Resistors can be checked in circuit using a meter on an appropriate resistance range. A rule of thumb is to replace any which are more than 20% off value.
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Old 12th Jul 2021, 8:38 pm   #15
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Default Re: Ekco CR152/N car radio

Thank you. Here is the recapping that I did. There are a few low value ones, for which I had to order more.

Some of the “silver mica” ones look a bit suspect (second picture).
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Old 12th Jul 2021, 8:46 pm   #16
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Default Re: Ekco CR152/N car radio

Personally the last thing I'd do is replace low value capacitors in RF and IF stages. They're generally reliable and replacing them will upset the set's alignment.

You'd be better off taking voltage readings from the valves and comparing them with the service sheet. The higher voltage quoted is the anode and the lower one the screen grid.
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Old 13th Jul 2021, 12:12 am   #17
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Default Re: Ekco CR152/N car radio

Thank you. Like these underneath the schmatic?
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Old 13th Jul 2021, 9:36 am   #18
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Default Re: Ekco CR152/N car radio

That's correct.
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Old 17th Jul 2021, 4:39 pm   #19
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Default Re: Ekco CR152/N car radio

I checked all the A and G2 voltages. They are as specififed within +/- 10%.

The resistor values all seem to be too high by 20 to 50%. I will start replacing them but I do not know if they would affect reception this completely, I guess we shall see. Otherwise I am completely stumped concerning where to look next.

This radio had arrived in very rough shape, especially the PS which I believe was mounted under the bonnet. I cleaned off all the rust, the old paint, dents and powder coated it. I just need to make it work now!
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Old 18th Jul 2021, 6:28 am   #20
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Default Re: Ekco CR152/N car radio

This is now done. Turns out the problem was I was using a SMPS to power the radio, until I got the original PS sorted out. I believe the high frequency from the SMPS was causing all the problems. It works great with its own PS.
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