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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 16th Jan 2021, 8:20 pm   #1
Kidmorris
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Default Kuba-Imperial radiogram.

Hi there.
I recently bought the jmperial kuba radiogram. I understand it was bought from a London department store in the mid 60s. All writing is in German on unit. Does anyone know anymore info on these units as I’m struggling to find more history on them and maybe even a manual?
All was working great on it until the other night and it started to crackle and ‘bang’ occasionally seeming to get worse when warm. I originally thought it was a record we where playing and then started to do it on the fm radio too. It did blow a fuse a little while ago changed it thought nothing of it maybe not linked but maybe a valve has gone? Could anyone point me in a direction?
Thankyou in advance Laurence.
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Old 16th Jan 2021, 8:24 pm   #2
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Default Re: Jmperial kuba radiogram

You can find models from this manufacturer here.
https://www.radiomuseum.org/m/kuba_d_en_1.html

Cheers

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Old 16th Jan 2021, 9:33 pm   #3
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Default Re: Jmperial kuba radiogram

Further to my earlier post welcome to UKVRRR

It's possible that there are some parts in the power supply parts are failing valves do fail but unless abused are remarkably robust.

To help some pictures of the inside of the set would be helpful along with the valve types used. Our German cousins were very fond of using valves such as the ELL80 and these do have something of a reputation.

Please don't feel offended if you already know this but make sure its unplugged when removing the back

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Old 16th Jan 2021, 10:09 pm   #4
roffe
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Default Re: Jmperial kuba radiogram

Looks like a Serenade 63.
https://www.radiomuseum.org/r/kuba_serenade_63_1.html
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Old 17th Jan 2021, 9:43 am   #5
Edward Huggins
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Default Re: Kuba-Imperial radiogram.

These use a contact-cooled bridge rectifier and this may now be breaking down. We do not know what skills the OP has in troubleshooting valved vintage kit?
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Old 17th Jan 2021, 6:05 pm   #6
Michael Maurice
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Default Re: Kuba-Imperial radiogram.

I doubt if its the rectifier, they either work or they dont, More likely is coupling caps. From his post, I think the O/P hasn't much if any experience.

There are no circuits for this so you are effectively working blind. If you are experienced enough you can reverse engineer it using the valve data that is available.

I would suggest that it isn't used until it has been properly looked at.
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Old 17th Jan 2021, 9:30 pm   #7
Kidmorris
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Default Re: Kuba-Imperial radiogram.

Thankyou for all your replies.
I’m pleased I now know what model it is.
I’m not experienced with these kind of things at all. But have always had a love for them and took me a while to get one in good condition.
Could anyone suggest where I start? I have good mechanical knowledge but not helpful on this. I have the back off and can’t see anything untoward other then one of the bands that holds the antenna is broken. Also when powered up and looking I noticed all the valves have a slight glow apart from one. I swapped this with another same valve it then glowed in the place that the other didn’t and I presume the non working valve didn’t glow in the other place. The gram did not like it this way round at all so shut it down quick.
Sorry for my lack of knowledge but I’d love to learn.
Thankyou.
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Old 18th Jan 2021, 11:19 am   #8
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Default Re: Kuba-Imperial radiogram.

You cannot just swap valves around, it could do an incredible amount of damage.

I will send you a PM.
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Old 18th Jan 2021, 12:48 pm   #9
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Default Re: Kuba-Imperial radiogram.

There is information on repair and restoration at this link if you want to sort it yourself. Suggest read it first before doing anything else to the radiogram that could cause damage. After reading you may decide to have the repair done professionally.
https://www.vintage-radio.com/repair...ion/index.html
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Old 21st Jan 2021, 8:25 am   #10
Richardgr
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Default Re: Kuba-Imperial radiogram.

'A crackle and a bang' sounds like something physically breaking down, like a switch, loose joint, loose valve pin. The music playing in the unit could trigger the noise due to vibration.

Did you notice a smell at the same time? Chemical, burning?

Does it contnue to work, but still has the same symptoms?

It is one channel or both channels?

When you replaced the fuse, where was it and how did you select the right replacement?

If it is both channels, that is the best result, because the wiring under the chassis of those console units is not for the faint hearted, if you were locating a channel-specific issue!
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Old 21st Jan 2021, 9:43 pm   #11
Kidmorris
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Default Re: Kuba-Imperial radiogram.

Thankyou for all your replies. I only swapped a valve with the same number valve so I saw no harm in that. I had the radiogram on for over two hours this evening. I had it playing the radio and records with very little interference kinda noise and only every now and then. I had a look in the back to see if I could see anything going on on. The only thing I managed to pin point was on the rear of the unit there is a knob that would accept a flat blade screwdriver to adjust. If I very gently tap this or even around the area with the rear of a screwdriver I can make it make the offending noise. If I also attempt to put a screw driver on it also makes the noise. I did not adjust anything. I’m not sure what this does if I’m honest, hopefully attached a pic of this. Almost seem strange how it played so well this eve compared to the other day. Sorry for I’m sure the silly questions.
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Old 22nd Jan 2021, 10:10 am   #12
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Default Re: Kuba-Imperial radiogram.

That's a potentiometer (pot) or variable resistor, I don't know what its function is.

The chances are it's gone noisy. Carefully note the position of the slot and then turn the shaft from one end stop to the other several times before returning it to its original position. It that doesn't cure the noise squirt some Servisol 10 contact cleaner into the pot and repeat the treatment.

The only two valves of the same type in this radiogram are the ECL86 output valves. I assume it was these you swopped over? are they both lighting up now?
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Old 22nd Jan 2021, 10:56 am   #13
Edward Huggins
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Default Re: Kuba-Imperial radiogram.

I think this may well be a rear panel "Balance" control that adjusts the output level between the LH and RH speakers. It's very important that this is fully cleaned as it can introduce much highly irritating noise. Adjust it so there's an equal volume level from each side.
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