Hello Everyone,

I picked up the above radio at a garage sale for a quarter.
It has low sensitivity on AM and it does not work on FM.
Does anyone has a schematics by chance?
Here are some pictures of the radio:

Thanks, Peter

Hey Peter,

Very possible you have electrolytic cap failure(s) which is common with older transistor sets...

And noticed the Sanyo speaker---wonder if it is a "re-badged" Sanyo product ? If so, there may be other sets that use the same chassis which might have an available schematic... Can you see any other info on components or PCB that might verify this ? Maybe a chassis number which you can Google...

Good luck...

John

I don't have a schematic, but I would replace the 5 electrolytic caps with the closest current equivalents and I bet it works.

Brett

I spy six Brett...

OOPS, missed that little guy to the north of that transistor. Nonetheless, hardly need a schematic as long as you pay attention to the polarity.

Brett

p.s. BTW, I haven't done a lot with classic Grundigs and no portables yet, but I am blown away by my two Grundig solid-state table radios (RF-121 and RF-95). MUCH better sound than I expected, particularly the RF-95, and filthy cheap (one free, one $20). Makes me want to go find some more of them. Easy to work on, too. bwb

A quarter is a lot of money, but if it came with the battery...

Agree about changing the six caps, and AM should come thundering in.

If FM still doesn't, however, the first things to check are the connection to the telescoping antenna, and the AM/FM switch.

Thanks for everyone for the valuable comments!
Well, the radio did not come with the battery, so it was not quite the deal (-;
I also have a somewhat similar radio to this one with the schematics.

Some progress. I did check all the electrolytic caps with my ESR meter, I replaced one capacitor. Was not really that bad, just the new one was a lot better. There is altogether seven elcos in the radio (the seventh is behind the big cap on the left of the speaker).
I think I know why the sensitivity on AM is down, the modulator coil on the ferrite was not in its original position, I could see it from the trace of the beeswax. I moved the coil back, but have not tested it.
I have not checked the FM yet.

On another note, my ESR meter is starting to crap out. It is the 99c meter, an 555 based circuit used with a scope. The signal disappears after about a minute of operation, and after a couple of minutes of rest it comes back again. It is not the battery. My guess would be a crappy 555 chip that expires when warms up. I will have to fix that as that is one of the most useful test equipment that I have!

Peter

[quote="orbanp"]
...
On another note, my ESR meter is starting to crap out. It is the 99c meter, an 555 based circuit used with a scope. The signal disappears after about a minute of operation, and after a couple of minutes of rest it comes back again. It is not the battery. My guess would be a crappy 555 chip that expires when warms up. I will have to fix that as that is one of the most useful test equipment that I have!
[/quote]

As it turns out, it was the battery. I used an alkaline (not Duracell) battery that unloaded had about 9.6V! Under load (10mA) it went down to about 3V. The used up Duracell batteries have about 7.5V unloaded.

Peter