The AM Forum

Well I got the receiver back together again after replacing a screw in the gear train and realigned all the cams and set off to testing it. All was working well, I had good reception now on both ends of each band. I was trying to tune in some guys on 160 when all of a sudden the audio went away. I checked the B+ fuse and it  was blown.

So I checked the wiring at the fuse. It's reading about 17 meg ohms back into the supply so that's OK. I checked from the other side of the fuse which is the B+ buss and it reads a low 217 ohms. That's my problem, what could cause this low resistance?

Any ideas would help. It hard to find a straight through schematic of the receiver to look for the obvious. I remember reading something about the alignment of a certain wafer switch. I'll try turning the MC dial and see if the short goes away. 

Several years ago I had a similar problem after removing the front panel of an R390A. It turned out that I had pinched a wire between the panel and chassis when I reinstalled it panel.

Ed

You may have a point, sometime you only need to look back at the last major thing that was done. Maybe later tonight, I'll loosen it up while watching the ohm meter.

Unplug the connectors to each module one at a time.  That;ll narrow it down to the module, if you don't find a pinched wire on the front panel.

  Yup...

Posted by: Edward Cain
Insert Quote
Several years ago I had a similar problem after removing the front panel of an R390A. It turned out that I had pinched a wire between the panel and chassis when I reinstalled it panel.

Ed


Me too..

/Dan

It turned out to be the plug in filter capacitors. does anyone know a supplier?
 

Hayseed hamfest

http://www.hayseedhamfest.com/

Those caps look great! Thanks. There is room to put caps under the chassis but I think they would run cooler on top. I think by the time I purchased all the caps it would be close to the total they want for the cans.

If that R-390/A still has old caps, better leave it unplugged. All the electrolytic caps by this time are kaput and the BBOD's are crap.

33uf @ 350V    140-XRL350V33
Xicon
The above will fit inside C603

47uf @ 350V    140-XRL350V47
Xicon
The above will fit inside C606; all of the above can be ordered from Mouser. Then there is the cap, C609, that rots the audio board, it is full of sulfuric acid. Plus the electrolytic bath tub cap C103 on the back panel will need attention also.

73's
Craig

Thanks Craig, I'll look at your suggestions tomorrow. Me going to bed :P :P

WOW crapola caps overnight.
I replaced mine for the helluvit a year ago and it was like a new radio. It just seemed like performance took a huge jump.
You can get the type with AXIAL leads and stuff underneath the audio chassis. And leave the cans intact. There's not that much heat under there to be concerned.

Fred

Where would I find them at a reasonable price?

Try justradios.com.

JustRadios, is the place to buy, speaking of buying there is an R-389 on Epay now. Never heard of one of those. Must be a bear on LF.