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Hi All,
Does anyone have any experience of working on this radio, its the small Grundig with a leather case designed by F.A. Porsche.
I have recently repaired one with corroded battery contacts which had obviously not worked for many years.
Its now working perfectly on FM, but MW and SW1 and SW2 have no reception, just noise.
If I leave the radio connected to a 5v power supply for many hours it does actually get some reception on AM, but its not consistent. I'm thinking the fault is somewhere in the 'front end', oscillator stage perhaps.
I have checked the AM coils and wave selector switch are OK and everything is visually in excellent condition. 
Reading various reviews on this radio confirms they were sold very cheaply in the USA and many customers have complained there is little or no sensitivity on AM, whilst others say it works perfectly. This makes me wonder if there is a common fault on these which someone may know, before I start with my test equipment to try to find the problem...

Any advice would be much appreciated!  
 

Sziasztok! Ezen készülékhez keresek CD egység rajzot és mechanikai beállítási utasítást, vagy tapasztalati tanácsot. Üdv.:Ckó

This one had been sitting in a barn for years. Powered it up and the large power transistors on the heat sink would get hot
after a time....and the heat sink would also get quite hot. Speakers sounded like they had some DC on them....with a loud thump

Found the manual on Hi-Fi engine,
[ http://www.mediafire.com/file/b8mlsu7q3pz0bvf/hfe_nad_3140_service.pdf/file ]
and saw a video on youtube saying lots of capacitors dry out
due to their locations near resistors that get very hot, I guess sorta a poor
design. Went in and recapped almost the entire
product save for the (4) large 50V PS caps which appear to check ok.None of
the high power or driver transistors
mounted to the main heat sink were shorted..

Powered on but no audio, and noticed the fuses to Bridge D805 were melted open.
I believe they were ok before.
Replaced them and they started to light up like fiilaments, so shut down,
removed the bridge D805, then checked it, its ok.

There is about a 16 ohm short on the + / - lands where the bridge was. It
seems like something I did maybe is causing this,
like a capacitor in backwards, which I am doing alot of lately for some
reason.

Turns out, yep I put C805 (470/ 63) In backwards ! Capacitor still checks
ok, so will re-use it.

Short is still there though Im guessing R803 is adding in 5.6 ohms or so,
that means theres a 10 ohm short someplace. Q801, 802 arent reading short,
and looks like this becomes a +43V ps feed.

Any ideas out there on what to check next? I am guessing this cap in
backwards caused the voltage applied to a component to be
reverse and its shorted. Or would this be normal with a reversed cap installed,
and putting it in right would be how to fix it?

Steve Hearns
Technotronic Dimensions [USA]
WWW.TECHNOTRONIC-DIMENSIONS.COM
 

Ave Tanyalakók! Hozzám került egy ilyen szörnyeteg! Sajnos már előttem "javították+" ezt a masinát. Mivel semmi baja sem volt, össze forrasztottak benne mindent, hátha meglesz a baja. Nem lett meg... Ekkor ugyan ez történt a másik felével is! Ezért ki tudja hányadik "hozzáértő" után került hozzám... A probléma a következő: van a hűtőborda aljrára ragasztva egy termisztor, csak az a baj, hogy nem tudom, hogy milyen értékű. Sajnos mindkét oldalon le vannak törve a lábai. Számolgatni, próbálgatni nem akarok, mert erre sem időm, sem energiám de, ha más megoldás nem lesz, akkor muszály... Valaki nem rendelkezik ilyen erősítővel, hogy meg tudná mérni az értékét. Mivel emiatt nem "szól" De egy rajz is nagyon sokat segítene! Köszönet előre mindenkinek! "KISO PXA700 végfok alkatrész probléma" Szerinted ez jó így? Esetleg: "KISO PXA700 végfok termisztor azonosítása". Nézetem szerint jobban tükrözi a topik tartalmát!