Grundig 80U

[Terry]

If you've got the set handy, try taking it out and see what happens!

However you earlier posted a different Grundig schematic on another forum. It isn't easy to see but appears to follow the same arrangement as in the 80U. It the other case it is C53 that provides the DC block.

You mention a clearer version of the schematic - if you have it, perhaps we can all have a look?

[pwdrive]

If you've got the set handy, try taking it out and see what happens!

However you earlier posted a different Grundig schematic on another forum. It isn't easy to see but appears to follow the same arrangement as in the 80U. It the other case it is C53 that provides the DC block.

You mention a clearer version of the schematic - if you have it, perhaps we can all have a look?

I don't have any radios anymore.

No, definitely not....If you look at the schematic you refer to there's a dc circuit between the anode and cathode of the AM detector.....Anode>Last AM IFT sec>R37>R38>Function switch contacts 9k&9l>R28>Cathode.....

No direct link to the clearer schematic that was mentioned on the other forum, however, click on the link below and scroll down to HF35 to open the PDF (safe site so far as I know, been using it for ages):

https://www.vintageshifi.com/repertoire-...ndig-4.php

Lawrence.

[Amie]

Hi guys.

Must admit that you lost me about a page ago.

C1 (2n2) has been replaced, I was putting in the tidy up work and having read the replies I cut a lead through on R9 (300K). There wasn't a bit of difference to the sound. Edit...on medium wave of course!

Amie

[Amie]

One final note

If R5 (2M) is cut, that goes from the AGC diode anode to the junction of the last AM IF and 50K resistor, the sound dies away to nearly nothing, but the IF signal at the anode of the EBF80 stays the same.....

Amie.

[Terry]

Hi guys.

Must admit that you lost me about a page ago.

Having spent some time last night with the considerably more complex circuit that Lawrence pointed me to, I must admit to feeling a bit lost myself!

If R5 (2M) is cut, that goes from the AGC diode anode to the junction of the last AM IF and 50K resistor, the sound dies away to nearly nothing

Amie, you are a genius! I think you might have found the answer! However, mistakes on schematics do happen though, thankfully, they are very rare, so I was going to ask you a question: could you carry out the following cold check?

Simply do a resistance check from the junction of R5/R8/C16 to earth. If you get a reading it would suggest that there is another resistor there, which will please Lawrence no end. If not then, as I said, you must have already found the answer.

[Amie]

Terry.

I'll look and do that test.

Ami

[Amie]

I'm back!

In its present working condition I did the suggested test

There's no epiphany (is that the right word?) Measured with a dmm its O/C, with the Avo it reads @400k.

Remove the 300k (R9) and both tests show O/C.

Sorry 

Amie.

[Terry]

No need to apologise!

You've:
- proved that there isn't an error in the schematic
- resolved the answer to Lawrence's question (even if you did prove me wrong in the process!)

Give yourself a gold star!

(Do they still do things like that in schools today? In my primary school you got red stars but if you really excelled you might get a gold one!)

Of course, all that nonsense stopped when you got to secondary school.

[pwdrive]

So which is the AM detector load resistor, still not quite with it...

Lawrence.

[Amie]

So which is the AM detector load resistor, still not quite with it...

Lawrence.

Nor I.

I Think, (you said), the FM discriminator is the DC return, but the set works on MW without the diodes there, provided R6 (2M) is in place. I've tried the set with the discriminator working and connected, but without R6 and it doesn't work very well (low distorted audio).

Why? Or what that is telling me I just dont know.

Thanks,
Amie.