The AM Forum

eBay purchase last week, 525 mile round trip last weekend to get it home.
The receiver worked all bands Saturday at his QTH.
The receiver worked all bands Sunday my QTH.

Turn it on monday....
No reception, no gain, no static on top two bands Monday (7.85 & 15.35).
Not even the calibrator can be heard on top two bands.

The unit appears untouched and unmolested since leaving the factory.
The unit was a daily driver the past 12 years.

I have some modest (and sometimes successful !) building and repairing experience beginning late 70s.
I have a sig gen, scope, freq counter, tracer, etc.

Besides fiddling with the bandswitch, what tubes (stages) would you focus on ?
I don't completely understand Hammarlund's 2 / 3 stage conversion in this set.
Annoyed that it worked one day but not the next.

For starters, I would check or replace the 1st converter tube (V3) 6BE6. I would also check or replace the H.F. Oscillator tube (V12) 6C4. Sometimes a mere juggling of the tubes in their sockets will bring it back to life. (contaminants, sitting around for a long time, etc.) It probably would be a good idea to check all the tubes in the receiver with a good quality tube tester. The fact that it worked and then stopped working on the upper bands could also indicate an intermittent connection or actual component failure. There is a crystal, 2.580 MHz, that's used with V3 for upper frequency operation.

It's almost certainly the 6C4 LO tube.  You might have to try several to find one that works.  Pete has outlined some other possibilities.  Get at it with a scope and see if the 6C4 oscillator is running.  If so, focus on the first converter and see if that's oscillating.

This is a very common problem with HQs.

Ditto the comment on the 6C4.   I recently ordered 5 NOS 6C4's from Antique Electronic Supply.   I tried all of them in the HQ180A and although they all worked, there was a definite difference among them.  I left the best one in there.   The date code on the "best" 6C4 was from 1945!!!

73
Ted  W8IXY

Additionally, the fact that a 6C4 tests good in a tester does not seem to mean that it'll oscillate in a receiver.  I don't know what it is about 6C4s but I've gone through, at times, a dozen NOS 6C4s to find ONE that will oscillate.   One tip, don't even bother trying a Raytheon, I was never able to get a Raytheon 6C4 to work.

Id start with some DeOxit, a partial drop into each socket pin and insert the tube several times.

Then if needed do it on the oscillator section of the bandswitch. I use a toothpick or awl to get that tiny drop (as compared to a big drop) on to the rotors and then run it thru the bands several times before turning on.

A 6C4 usually acts up on the lower end of the top 2 bands. Ive found the mil 6C4WA and the 6100 to be the most repeatable and reliable.

The 6BE6 may very well be the culprit but its less probable as a mixer (as in V-3)compared to a converter.

Carl