Grundig 4198 tube radio restoration - Part 4. Close look at the Audio stage.

Grundig 4198 tube radio restoration - Part 4.
The audio stage of this radio is really interesting, so a close look at how it works was warranted.
I must warn you ... this video may be a serious test of your alertness level. Don't drive or operate heavy machinery while watching this.

Full info on this radio at:

You can see the playlist for this series restoration at:

See a series of 'Restoration Building Blocks' videos on detailed steps in the restoration process:

See also playlists on some other completed restoration projects.

PHILIPS BX750A:

TELEFUNKEN OPUS 2114:

SABA UW-175-Z 3D:

GRUNDIG 1070:

SCHAUB-LORENZ GOLDY 58 type 3020:

BUSH VHF64:

GRUNDIG 3060A:

TELEFUNKEN OPERETTE 8:

GRAETZ SUPER 171W:

LOEWE-OPTA MAGNET 3737W:

BRAUN ATELIER 3:

LOEWE-OPTA TRUXA STEREO 4741W:

GRAETZ COMEDIA 616:

SABA FREIBURG W2:

GRAETZ MUSICA 4R417:

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CAPACITOR LEAKAGE TESTER:

[arongooch]

Very well explained and a very smart and interesting design.

[abeleballestri]

Very interesting description of the whole regulation of the various tone controls of this radio. It is just beautifully described and planned from Siemens.

[jassenjj]

Just wow! The most complicated signal processing imaginable for this mixed SE and PP mode and that EM84 in one of the channels and the asymmetric electrostatic tweeter... I wonder if they tried to compare the frequency response of the 2 channels at the design stage.

[saeedjahangiri]

Hi
Its very amazing and not boring at all.
It’s interesting for me to know that if the external speakers connected to the amp and an stereo phono input played, the sound quality would be as like as surround system of a home theater
The big oval speaker can play the role of a sub woofer, midranges like left and right channel speakers.
For that era its an innovative idea to have a stereo single end and crossover together with a push pull mono in single chassis.
The mixing of lower frequency range with opposite input signal could reduce the stereo effect, is it so ?
At the end the art of presentation of you is quite remarkable, really it was interesting and not boring at all
Thanks

[Groove]

Excellent video!
this circuit is just amazing.
i never seen filtering using transformers and caps this way on the last amp stage.
really cleaver, it make a 3.1 system using only 2 output tubes.
i hope it's going to fully work really soon.
it will have a really great sound.

[zorka]

Surprisingly, I did not fall asleep! ;-> Actually, as I am theory-weak, I found this rather enlightening and added value to what I have learned from you and others over the past few years of watching.

[Rush-gzsx]

Manuel. Brilliant description. I'm still not competent around pentodes triode etc but even I managed to keep up with this. Awesome video

[Mikexception]

I must say this was the most clear story about one of most interesting tube audio circuits. Admire the work you've done to describe amazing technology - sensational :). I would be delighted to listen to it.

I've had experience with another interesting solutions of such idea build in ERRES radio model 618A Which is less advanced due to use of widerange speakers instead of separated super . high tone and low tone speakers and with use of two ECL82. Bad headache to understand idea - in Erres they used two differently sized transformers winded in opposite phases to gain for TA stereo in left and right in class A and secure mono and semi stereo for mono programs which in this case are amplified with 1x PP. Later Erres was purchased by Philips and their model BX look somehow like continuation of Erres. Anyway solution in Model 618 A (up to my knowledge) was not replicated .

[abeleballestri]

Very tutorial lesson on how to read and understand such a complex circuitry on audio signal level fro the pick up socket of the radio.i had to follow in a very concentrated way and you succeeded perfectly, to my understanding by this very easy way of explaining.I think you were an electronic teacher some time in your life..?thanks for the interesting video.

[rogeriozambotto]

Thanks...interesting circuit, so I am glad to got your excellent explanation...great teacher! Waiting for more videos!

[rotwang]

Nice analysis of the circuit! I went through it some days ago, it took me some time to understand how they operate the eye tube as indicator since the internal triode is already used as phase inverter. The phase inverter is known from Philips datasheets as "see-saw"-inverter. I think WUN stands for Wunschklang which means custom tone setting.

[martintelfer]

It's a nice set with some clever circuitry. The downside is that those ELL80s are $75+ to replace if they fail....

[EsotericArctos]

It looks like Grundig used that same audio stage in a few of their Stereo radios from the late50's and early 60's. The seem to go to completely separate channels in the mid 60's though. I quite like the way it is done is the sets of this era.

[lyntonprescott]

Who on earth works all this out? Very clever engineers. Way beyond my understanding!

[bluesonkel]

hi greetings from germany!

The button WUN means Wunschklang. (the name of the radio) in engl.: wish-sound
if you press this, you have not only adjust the bass and the hights, also you can adjust now the upper bass and the lower hights.

in "WUN" you have the full control over the 4-band equalizer


i hob you understand my bad english :D

Wondering what program / software you used to get these colored lines?

[andygozzo]

i've seen a similar but less complicated output stage used in some ferguson stereo radiograms,

[fishyrider]

This is great. Pleas keep them going. I tried to understand and i had problems. This is added value. Verry few on the net. Thx. This i would support. How can i help u keep this going?