Antique radios, Old Time Radios

telefunken: 8; Opus

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Forum » Radios and other type of sets (Physics) etc. » RADIO MODELS DISPLAYED » telefunken: 8; Opus
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Edward Cancio

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14.Aug.06 18:22

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telefunken: 8; Opus

I own a Telefunken Opus 8 that not only looks as new, but plays as new also.....peace.....edward cancio. I will send photographs as soon as I figure out putting them into the computer.

This article was edited 28.Aug.06 01:20 by Edward Cancio .

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Omer Suleimanagich

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15.Aug.06 05:29

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Put a fuse on the B+ current and enjoy!!!

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Paul Pinyot

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31.May.07 20:08

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Alignment Instructions.

Gentlemen,

I am restoring an Opus 8. Quit an impressive radio. I have the schematics from this site. Would some one be so kind as to post or send me alignment instructions? If none is available I will use the Grundig alignments I have and attempt a close approximation.

I would prefer to complete a proper and accurate alignment.

Additionally, there is a 50uf 4vac (alternating current) on the secondary of the audio output transformer (mid range speakers). Can that AC cap be replaced with two 50 uf 8 volt DC caps in wired in series with opposing polarities?

Thanks in advance,

Paul Pinyot.

This article was edited 31.May.07 23:43 by Paul Pinyot .

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Omer Suleimanagich

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01.Jun.07 17:49

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Paul,

If I'm not mistaken, this is where a "bi-polar" electrolytic capacitor is useful.

As for all electrolytics, going up voltage specs is OK, but going below isn't.

BTW Look at the Opus 6 schematics on this site for alignment instructions.

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Paul Pinyot

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01.Jun.07 21:22

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Thanks Omer,

I ordered the non polar capacitor from Mouser today. http://www.mouser.com/catalog/630/595.pdf. I do not care to "Mickey Mouse" a restoration. Thanks for the tip on the Opus 6 Sams documentation.

Does the Opus 6 have the long wave band below 530 khz as does the Opus 8? And is is nice to have english schematic. It saves me the time to have my Dad's Girl Friend to interpret technical data.

Thanks again,

Paul

This article was edited 01.Jun.07 21:33 by Paul Pinyot .

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Omer Suleimanagich

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02.Jun.07 02:30

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They all have long wave.

I believe this radio is supposed to be identical to the Opus 7, just a different cabinet (slightly cheaper in build quality). To me, these radios were Telefunkens best, since they use two EL84s.

As for the 50 mfd capacitor, I understand that it originally was a bi-polar, like in all other speaker cross over circuits that are still used today. The later Telefunken cross over capacitors from '59 and up are distinctly marked as bi polar ones (red). No "Mickey Mouse" here, but factory design!

The ultimate Opus radio, is supposed to be, model 2004, from the mid sixties. It has connections for stereo reception. By this time, interest in expensive German table radios was waning in the North American market.

This article was edited 02.Jun.07 02:40 by Omer Suleimanagich .

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Jeffrey Angus

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02.Jun.07 05:32

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Paul wrote: Can the AC capacitor bereplaced with a pair of 50 uF 8 Volt electrolytics?

Well, yes. If you use 100 uf caps. Two equal capacitors in series equals 1/2 the value.

Jeff

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Dennis Daly

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02.Jun.07 18:03

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Greetings, all.

Since this discussion has been addressed in the past and elsewhere, I have done some small amount of studying of the topic.
It has been written by multiple credible (to me) resources, that "bi-polar" or "non-polar" electrolytic capacitors are essentially two conventional polarized electrolytic capacitors connected in series, but in opposite directions for polarity, within a single package.

What is somewhat different between the aluminum polarized and non-polarized types is the method of winding the active elements and insulation layers, the varying properties of the aluminum used for the elements and assuring the low ESR rating for the non- (bi-) polarized unit.

Since there is little to no D.C. component while serving in a simple typical speaker crossover circuit as that under discussion, one would think it should be allowable to utilize two conventional polarized units in series and of opposite polarity, however the rate of dielectric absorbtion in a non-polar capacitor is higher than would be in the series polarized types, given the same _effective_ capacitance.
So, without any D.C. component in the circuit, the forming and maintainance of the dielectric throughout the normal service life of a polarized aluminum electro cap would be adversly affected

"Non-polar aluminum electrolytics of 50 and 100-volt ratings are often used in passive crossovers for commercial and consumer loudspeakers, where the signals contain medium ac voltage components (around 30 volts peak) with little or no dc voltage content. Frequency response and vibration resistance of these capacitors are the most important criteria. Electrolytic capacitors have a positive voltage coefficient of capacitance, and this leads to some harmonic distortion." (Quoted from electrochemistry)

I thought two conventional polarized units might serve this simple consumer-grade crossover task as well... and possibly they would--for some time period, anyway...Until I read more about it. Non-polar Panasonic electros from Digikey are low cost enough for me to now stock the more common values.

Regards,
Dennis Daly

This article was edited 04.Jun.07 15:04 by Dennis Daly .

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Paul Pinyot

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15.Jun.07 05:36

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Gentlemen,

Again thanks for all the help with this Opus 8. I have restored the radio and it sounds great. This link provides some of what I experienced with the radio. The electrostatic speakers in particular.

http://www.ppinyot.com/T/telefunken.htm

Please enjoy and get your electrostatic speakers tweeting again.

Paul.

This article was edited 02.Aug.08 17:21 by Paul Pinyot .

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Omer Suleimanagich

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15.Jun.07 07:00

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Paul,

Did you change the capacitor for the de-emphasis on FM (UKW), so that it is adjusted for the 75uS North American standard.

The Opus you restored is the European model.

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Paul Pinyot

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16.Jun.07 00:03

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No I did not. Which one is it and what should the value be?

Paul.

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Omer Suleimanagich

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16.Jun.07 08:57

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Paul,

I believe you have a choice here, add 330pF parallel to C207 (330pF) as what Telefunken did in the 7, or bump it up closer to 75uS, by adding 470pF parallel to C207.

Omer

Attachments:

Opus_8_D (66 kb)
Opus_8_D (66 kb)
Opus _8_US (74 kb)

This article was edited 16.Jun.07 08:59 by Omer Suleimanagich .

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