Grundig R1000

Hello,

Often only the switches and potentiometers in the signal path are oxidized and for this they should be operated about 50 times.
This loosens any oxidation that may be present on the contacts.

Otherwise there is a real defect. For this purpose, however, the error can be in the preamplifier or also in the power amplifier.
Measurements should be taken for this, because with remote diagnosis it is rather difficult to say.
Is it at every line-in?

Hallo camuscamus,

ist das Verhalten bei allen Quellen (UKW Tuner, MW oder LW, TB und Phono) gleich?

Welche Messmittel hast du? (z. B. Multimeter, Oszilloskop)


Hello camuscamus,

ist the effect the same for all sources (FM tuner, AM tuner (MW or LW), TB and phono)?

Which measurement equipment do you have? (e.g. multimeter, oscilloskope)

Zuerst muss ich sagen, VIELEN DANK, dass Sie überhaupt geantwortet haben. Ich habe keine Antwort erwartet, weil ich dachte, ich hätte Leute beleidigt, die auf Englisch schreiben. Das ist großartig. Ich fühle mich willkommen. DANKE!

Ich habe ein Multimeter. Wenn jemand einen Blick auf den Schaltplan werfen kann und mir sagen kann, wo und was ich wie überprüfen muss, habe ich das Gefühl, dass das Problem bereits gelöst ist. Ich danke Ihnen!

Ja, der Effekt ist der gleiche, unabhängig vom Eingang: TAPE, PHONO, TUNER, ETC

Übersetzt mit www.DeepL.com/Translator (kostenlose Version)


First, I must say, THANK YOU VERY MUCH, for responding at all. I did not expect a response, thinking I have insulted people writing in English. This is great. I feel welcomed. THANK YOU!

I have a multi meter. If someone can look at the schematic and tell me where and what to check, and how, I feel already, this is solved. Thank you!

Yes, the effect is the same, no matter the input; TAPE, PHONO, TUNER, ETC

Zuerst muss ich sagen, VIELEN DANK, dass Sie überhaupt geantwortet haben. Ich habe keine Antwort erwartet, weil ich dachte, ich hätte Leute beleidigt, die auf Englisch schreiben. Das ist großartig. Ich fühle mich willkommen. DANKE!

Ja, der Effekt ist der gleiche, unabhängig vom Eingang: TAPE, PHONO, TUNER, ETC

Wenn Sie sich bitte den Schaltplan ansehen und mir sagen, was ich wie überprüfen soll, werde ich das sofort tun.

Übersetzt mit www.DeepL.com/Translator (kostenlose Version)

First, I must say, THANK YOU VERY MUCH, for responding at all. I did not expect a response, thinking I have insulted people writing in English. This is great. I feel welcomed. THANK YOU!

Yes, the effect is the same, no matter the input; TAPE, PHONO, TUNER, ETC

If you please look at the schematic and tell me what to check and how, I will do it right away.

Danke!

Berlin

Hello camuscamus,

did you operate all switches and potentiometers several times, as proposed from Rabia_sorda?

This test will detect contact problems in the appropriate control element.


If a control element contact is not the cause:
The error can be in the preamplifier or also in the power amplifier, as Rabia_sorda has already noted.

I recommend to measure the DC voltages of the base potentials of T34 and T35 against ground (volume potentiometer set to minimum). These base nodes are the inputs of the left and right power amplifiers.

Both voltages shall be in the range 0...60 mV. If yes, connect both base nodes. This connection enforces mono mode.
If one of the base voltages is outside of this range, do not connect the nodes to prevent damage of the other power amplifier.

With connected base nodes increase the volume:
If both speaker outputs are now working, the failure is in the left preamplifier part.
If the left speaker output is still not working, the failure is in the left power amplifier part.

Then you should measure the three voltages of all transistors in the appropriate amplifier part (volume potentiometer set to minimum).

Hello

Thank you very much for your help and contributions.

I have been busy on this.

I have done what Rabia_sorda proposed. I have moved the switches and potentiometers more than 50 times.

I bought a can of contact cleaner. That did something, the cracks when you move the switches and potentiometers are gone. But the problem of the channel is there.

I found the the base potentials of T34 and T35. Perhaps because I did not make the correct selection on my multimeter, the readings were either 0 or very high on both.


I have shared the pictures of the the base potentials of T34 and T35. And my multimeter.

Please when you reply, say what selection on my multimeter I must make, and also how I must make the measurements on the base potentials of T34 and T35.

I am very grateful and happy for your support. Thank you! Danke! Danke!

To measure DC Voltage turn the knob into the position of 20 V =. The black cord to ground and the red to the base of the transistor. When the reading is below 2 V turn the knob into the position 2 V =. Then you get a more accurate value of the voltage. Be carefull don´t make a short. And before you use this multimeter on the Grundig try to test something else before. Never use the section with the "A" unless you know what you are doing. Otherwise you make a short.

Dear Ingor,

Thank you very much.

I put the dial to 20, the 20 to the left of the multimeter, which is the 20 V =. I put the black probe of the multimeter to the body of the amplifier and used the red probe to the base of the transistor. I got nothing.

I then turned the knob on the multimeter to 2. Here are the results:

Both T35 and T34 transistors have 3 pins each.

On T35
Pin C = -.002
Pin E = 0 (no change in the meter display which at default was .000)
Pin B = -.002

On T34
Pin C = -.002
Pin E = 0 (no change in the meter display which at default was .000)
Pin B = -.001

Before the test, the multimeter was tested on a AAA battery. And it tested well on the 2 V.

Thank you very much. Now, what's the next step? I feel like we've made some progress, but I rely on you, the experts, to confirm.