Hi folks,
I've just acquired stereo console Kuba Serenade, Made in West Germany (by Telefunken?). There is no model on the case, but I believe it's 609a or 611a, according to radiomuseum.org. I think it's 1962-1963 year range. It consist of stereo receiver, auto-changer turntable and 4 speakers (bass front-firing and trebles side-firing).
Any body familiar with the console? I'd really appreciate if I can find at least similar schematic for it. The console is 9/10 cosmetically and AM works, so does the amp, but right channel is very weak, so it needs TLC.
Unfortunately - the only electrolytic caps I can see are the power-rail ones (3 x 50uF/380V), it does have discrete Graetz bridge rectifier by Siemens, everything else seems to be non-electrolytic - is it possible?
I can post detailed photos if needed.
Appreciate in advance all the help I can get!
😎
Thanks.
Old Hush
I've just acquired stereo console Kuba Serenade, Made in West Germany (by Telefunken?). There is no model on the case, but I believe it's 609a or 611a, according to radiomuseum.org. I think it's 1962-1963 year range. It consist of stereo receiver, auto-changer turntable and 4 speakers (bass front-firing and trebles side-firing).
Any body familiar with the console? I'd really appreciate if I can find at least similar schematic for it. The console is 9/10 cosmetically and AM works, so does the amp, but right channel is very weak, so it needs TLC.
Unfortunately - the only electrolytic caps I can see are the power-rail ones (3 x 50uF/380V), it does have discrete Graetz bridge rectifier by Siemens, everything else seems to be non-electrolytic - is it possible?
I can post detailed photos if needed.
Appreciate in advance all the help I can get!
😎
Thanks.
Old Hush
Yes, that's what I am looking for, Eli... unfortunately even in RadioMuseum they don't have it...
Try to trace the audio section out. The TT rates to use a piezoelectric cart. and belongs in a landfill. The FM tuner requires, among other things, a sweep alignment. Many DIYers lack the equipment needed.
Work up a complete list of the tubes present.
Definitely take those detailed photos and post them. Do shoot the TT, arm, and cartridge. An outside chance exists that those items are worth saving.
Work up a complete list of the tubes present.
Definitely take those detailed photos and post them. Do shoot the TT, arm, and cartridge. An outside chance exists that those items are worth saving.
I have a couple of Kubas....pics of the unit will help narrow things down perhaps...the Germans were notorious for using the same PTs and OPTs in everything from Normendes, Loewe-Optas, Telefunkens, Grundigs etc. etc. pics are really not optional in a quest such as yours.
BTW many german sets like the Kubas used a breathtakingly wide combination of mica, wax, foil and PIO caps.
BTW many german sets like the Kubas used a breathtakingly wide combination of mica, wax, foil and PIO caps.
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OK, the details - first,I am attaching first the general front/back Console View’s photos here...
Attachments
... and now the receiver's photo with the details.
Also- here it is the list of tubes:
1, 2. Stereo amp – 2 x 6BM8 (Sylvania)
3. One unknown (in irremovable metal shield, no labels)
3. EABC 80 (Valvo)
4. EF 85 (Valvo)
5. ECH ?? (Valvo) – the number is erased...
6. ECC 85 (Lorenz)
7 EM 84 (Lorenz)
I have created one photo with tubes' position for easy illustration.
Basically I have the following issues with this unit:
1. One of the amp's channel works (almost) fine - just some overpower at max volume. But the other channel is very week to non-existent. Changing the tubes doesn't make a difference, so the two amp tubes are fine. The balance works and makes the difference on the working channel. Bass and treble setup works fine.
2. On AM I can find one station only and it's very, very low volume. Clear, though.
3. On FM and MW - nothing. Tuning Level Tube (EM 84) is lit, but doesn't make a difference when rotating the dial.
4. Turntable moves, but I guess is irrelevant as it's sapphire - it'll be replaced with "new" vintage one anyways.
5. With one channel working and on internal speakers, when connected to CD player - the sound is full, rich, clear and powerful.
Questions:
1. Am I right about the only two electrolytic caps at the left? Anybody see others?
2. Any chance to have a similar schematic?
3. I can run a test signal and trace with a scope the signal to workout the missing amp channel, but have no idea how to approach FM and MW troubleshooting. I started my electronics degree around 25 years ago, when the tubes are out of the alumni already, so no tube troubleshooting experience, so be patient with the newbie... 🙄
Thanks in advance!😀
Also- here it is the list of tubes:
1, 2. Stereo amp – 2 x 6BM8 (Sylvania)
3. One unknown (in irremovable metal shield, no labels)
3. EABC 80 (Valvo)
4. EF 85 (Valvo)
5. ECH ?? (Valvo) – the number is erased...
6. ECC 85 (Lorenz)
7 EM 84 (Lorenz)
I have created one photo with tubes' position for easy illustration.
Basically I have the following issues with this unit:
1. One of the amp's channel works (almost) fine - just some overpower at max volume. But the other channel is very week to non-existent. Changing the tubes doesn't make a difference, so the two amp tubes are fine. The balance works and makes the difference on the working channel. Bass and treble setup works fine.
2. On AM I can find one station only and it's very, very low volume. Clear, though.
3. On FM and MW - nothing. Tuning Level Tube (EM 84) is lit, but doesn't make a difference when rotating the dial.
4. Turntable moves, but I guess is irrelevant as it's sapphire - it'll be replaced with "new" vintage one anyways.
5. With one channel working and on internal speakers, when connected to CD player - the sound is full, rich, clear and powerful.
Questions:
1. Am I right about the only two electrolytic caps at the left? Anybody see others?
2. Any chance to have a similar schematic?
3. I can run a test signal and trace with a scope the signal to workout the missing amp channel, but have no idea how to approach FM and MW troubleshooting. I started my electronics degree around 25 years ago, when the tubes are out of the alumni already, so no tube troubleshooting experience, so be patient with the newbie... 🙄
Thanks in advance!😀
Attachments
2X 6BM8s tell us you have about 2 WPC of SE pentode power.
The reason FM doesn't work is that it requires an external unit. As is, it's AM only, for radio. The tuning cap. is 2 sections, with many plates. That's a dead giveaway. You also have the DIN connector on the back panel.
The Benjamin/Miracord record changer will not damage the center holes of records. The arm is the $64 question. Can a decent mag. cart. be mounted in it, along with holding the tracking force down at a reasonable level? The cart. in situ is definitely a piezoelectric POS, which actually destroys records.
The reason FM doesn't work is that it requires an external unit. As is, it's AM only, for radio. The tuning cap. is 2 sections, with many plates. That's a dead giveaway. You also have the DIN connector on the back panel.
The Benjamin/Miracord record changer will not damage the center holes of records. The arm is the $64 question. Can a decent mag. cart. be mounted in it, along with holding the tracking force down at a reasonable level? The cart. in situ is definitely a piezoelectric POS, which actually destroys records.
No. Permeability tuning for FM was common in Europe at this time. I think the photos show a piece of dial cord heading for the FM tuner. The presence of an ECC85 is a dead giveaway - this was the standard FM front-end valve and almost never used for any other purpose in domestic equipment.Eli Duttman said:
My view is that it is almost impossible to do 'remote debugging' of RF circuits unless the local person already has some knowledge, experience and test equipment. Audio is simple by comparison.
Kuba used chassis of some of the major German radio manufacturers for their furniture.
In 1958 however, they took over the "Continental Radio" company. Their brand was Imperial.
After that Kuba made their own chassis and changed the company name to Kuba Imperial.
Your console is likely to be of that era.
My Dad who was a radio repairman in those days always said that Kuba Imperial made really nice furniture with not so nice radios.
There are several versions of the Serenade with different chassis. The chassis numbers are in the range of six hundred something. Does your set have a number in that ballpark?
Elektrotanya has a schematic for the Imperial J611. Definetely not your set, but it might be a start. ElektroTanya | Service manuals and repair tips for electronics experts
search for Imperial J611.
The tubes in your list are standard in many German FM radios around 1960. Most radios will have a more powerful amplifier with an EL84 instead of the ECL82, though.
You could try to find out how these tubes were used in other brand´s radios. Compare working points and reverse engineer what you have.
With the ECC85 you are certain to have an FM tuner on board. FM was widely used in Germany at that time. I would bet FM Stereo is not possible with that radio. It was common for those consoles to have a stereo turntable, amp and speakers but no stereo decoder for FM.
And as for debugging the FM circuit: There is one question I like to ask first. Does it give static?
Or is it aboslutely mute when switched to FM?
In 1958 however, they took over the "Continental Radio" company. Their brand was Imperial.
After that Kuba made their own chassis and changed the company name to Kuba Imperial.
Your console is likely to be of that era.
My Dad who was a radio repairman in those days always said that Kuba Imperial made really nice furniture with not so nice radios.
There are several versions of the Serenade with different chassis. The chassis numbers are in the range of six hundred something. Does your set have a number in that ballpark?
Elektrotanya has a schematic for the Imperial J611. Definetely not your set, but it might be a start. ElektroTanya | Service manuals and repair tips for electronics experts
search for Imperial J611.
The tubes in your list are standard in many German FM radios around 1960. Most radios will have a more powerful amplifier with an EL84 instead of the ECL82, though.
You could try to find out how these tubes were used in other brand´s radios. Compare working points and reverse engineer what you have.
With the ECC85 you are certain to have an FM tuner on board. FM was widely used in Germany at that time. I would bet FM Stereo is not possible with that radio. It was common for those consoles to have a stereo turntable, amp and speakers but no stereo decoder for FM.
And as for debugging the FM circuit: There is one question I like to ask first. Does it give static?
Or is it aboslutely mute when switched to FM?
The unknown valves will be ECH81 and, probably, EZ81. I am surprised that the EZ81 has a metal shield - this may be to aid cooling.
You probably have a standard AM/FM mono receiver with a stereo amplifier replacing the normal mono audio section. The circuit will be fairly standard so if you can't find a specific service sheet you can get a rough idea by looking at anything else from the same era.
You probably have a standard AM/FM mono receiver with a stereo amplifier replacing the normal mono audio section. The circuit will be fairly standard so if you can't find a specific service sheet you can get a rough idea by looking at anything else from the same era.
DF96: in the photo with the two big electrolytics you can see a flatpack rectifier. So probably not an EZ81.
The tube in the shield seems to be of smaller diameter than the EABC80 and ECL82. That makes me guess it is an E ninety something. It does not need an EAA91 as it has the EABC80.
The tube in the shield seems to be of smaller diameter than the EABC80 and ECL82. That makes me guess it is an E ninety something. It does not need an EAA91 as it has the EABC80.
Thanks for the replies, guys!
Eli, my previous console I made a separate receiver unit with box had 1 WPC, it works excellent with my Bose 301 speakers, so no issues with that. The DIN connector I am used to- I am originally from Eastern Europe where that was the only connector and I even have some with me.
About the TT – I have one used, but working JVC arm with cartridge I can use as a start. Funny, but my biggest problem with TT is... how it operates – I’ve never touched automatic TT like this – any manuals which may show me how it should operate correctly – I will fix the possible mechanical issues then...?
Grommeteer, unfortunately I didn’t have any luck with the link – it’s Hungarian site, change to English doesn’t work, there is no login page for new customers, neither has search filed... Google gave me nothing for “Imperial J611”... can you point me to easier link or more popular schematic?
About the FM tuner, I understand it’s mono, not stereo, as the console is made before broadcasting stereo ages (assume – 1962 or 1963, am I correct?). And YES, it has very low static.
I am newbie on tubes, but otherwise I am electronics engineer and can do debugging. Also I have scope and can make a signal generator from the PC nearby, so I can try debug the FM if I have at least similar schematic/service manual...
DF96, can you point me to a similar device – I don’t have so much experience with tube consoles (yet), so if you point me to popular similar device – I’d appreciate it!
One last question – nobody saw any electrolytic caps, right (beside the two big “bottles” at left), right?...
Eli, my previous console I made a separate receiver unit with box had 1 WPC, it works excellent with my Bose 301 speakers, so no issues with that. The DIN connector I am used to- I am originally from Eastern Europe where that was the only connector and I even have some with me.
About the TT – I have one used, but working JVC arm with cartridge I can use as a start. Funny, but my biggest problem with TT is... how it operates – I’ve never touched automatic TT like this – any manuals which may show me how it should operate correctly – I will fix the possible mechanical issues then...?
Grommeteer, unfortunately I didn’t have any luck with the link – it’s Hungarian site, change to English doesn’t work, there is no login page for new customers, neither has search filed... Google gave me nothing for “Imperial J611”... can you point me to easier link or more popular schematic?
About the FM tuner, I understand it’s mono, not stereo, as the console is made before broadcasting stereo ages (assume – 1962 or 1963, am I correct?). And YES, it has very low static.
I am newbie on tubes, but otherwise I am electronics engineer and can do debugging. Also I have scope and can make a signal generator from the PC nearby, so I can try debug the FM if I have at least similar schematic/service manual...
DF96, can you point me to a similar device – I don’t have so much experience with tube consoles (yet), so if you point me to popular similar device – I’d appreciate it!
One last question – nobody saw any electrolytic caps, right (beside the two big “bottles” at left), right?...
OK. Yes it seems to be a B7G. Two pins are unused, so with two for the heater that only leaves three for the circuit. It appears to be connected to the volume control. Need to take the shield off.
I'll try to remove the shield, it has to be cut off with Dremel or something - it's too tight and seamless...🙄
You said it may control the volume... of the amp part or something with RF? And what the next step would be with this tube?, how it'll help?
You said it may control the volume... of the amp part or something with RF? And what the next step would be with this tube?, how it'll help?
grommeteer, excellent, thanks a lot!
Do you have by any chance schematic of an ECL82 (6BM8) amp, the above schematic has ECL86 which I guess is basically the same (different gain?), but for sure it has different pinout on the tubes...
Do you have by any chance schematic of an ECL82 (6BM8) amp, the above schematic has ECL86 which I guess is basically the same (different gain?), but for sure it has different pinout on the tubes...
The B7G is probably an EC92 (same as half an ECC81). See Mamba Ch= 609a Radio Kuba Imperial; Wolfenbüttel, build which looks similar.
Unclear what this does. The triode in the EABC80 is different (that is more like half a 5751), although similar mu. I suppose they could be used as a stereo pair, but an EBC90 would be a better match to the EABC80 triode.
Unclear what this does. The triode in the EABC80 is different (that is more like half a 5751), although similar mu. I suppose they could be used as a stereo pair, but an EBC90 would be a better match to the EABC80 triode.
DF, you are the vintage radio detective!
Look here, and see what the Kubans do with those triodes.Imperial 609a
Look here, and see what the Kubans do with those triodes.Imperial 609a
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