[RodB]

I'm having trouble locating the cause of garbled short wave reception on a Zenith R600. I was doing an alignment on the broadcast band and it comes in great. When I tried the SW bands, all the stations came in garbled or distorted. I didn't want to start turning rf coil slugs because it is happening on all sw bands. I swapped out the 1L6(it's a used one) with no change.The 25 and 31 meter bands have a squeal and no stations. Any help is appreciated.

Rod

[OZ4]

Rod
I would start with the squeal. The squeal indicates that something is oscillating that shouldn't. Is it missing any tube shields? You can try laying on of hands to help locate which tube is oscillating. Also Look for bad caps in the grid bias line/ AVC . It might even be an open IF transformer.
Chris

[OZ4]

After thinking about it some if the broadcast band sounds good then the IF, Detector and Audio section is good. Look to the RF front end section for the suspect items. The parts that switch in for SW.

[David]

If you have a 1R5 you can sub for the 1L6 the, broadcast band will be fine the SW bands will have poor performance but you can give it a try without spending lots of money for a 1L6 you might not need. Yes I am cheap!!!!

[Phlogiston]

Is the 1L6 getting 1.5V to the heater? A bad selenium rectifier can cause this voltage to drop below 1.2V. Then to osc. will stop.

[RodB]

So, here's what resolved the problem. The filament voltage of the 1L6 was 1.2 volts so I brought it up to 1.43 volts. This helped but not totally. I also went back in to the band switches with cleaner and got better reception. And lastly, I replaced the RF amp tube. The original must have been on the edge(aren't we all?).

Thanks for the suggestions. They got me back to re-checking my work. Rod