Found. A new/old Hammarlund. It's now working great.

[Curt Reed]

OK, but I am getting totally lost here. The filaments do not have DC voltage on them, they run of AC.
Curt
_________________
Curt, N7AH
(Connoisseur of the cold 807) CW forever!

[KC4VWU]

Cathode and one side of the filamet are tied togeather. Measure DC from there and chassis ground. I would probably unsolder the lead from rectifier cathode to the input choke and measure it again if it reads low the first time around. Also, measure B+ at the output of the last filter choke and see what you have there.

Phil

[badrestorer]

Rectifier voltages. Seeing is believing. The schematic calls for a 5U4G, but it's been substituted with a 5R4GY.

Pin 2 (one end of filament), 5.20vac:


Pin 8 (opposite end of filament), .10vac:


DC voltage on the filament. Pin 2...12.60vdc:


DC voltage on the filament (opposite end of filament). Pin 8...12.95vdc


Power transformer secondary. Center tap to pin 4...299vac:


Power transformer secondary. Center tap to pin 6...298vac:


Across pins 4 & 6...596vac

_________________
Regards,
John

They don't know the power of the radio side.

[Curt Reed]

Then I would say the rectifer tube has lost its emission.
Curt
_________________
Curt, N7AH
(Connoisseur of the cold 807) CW forever!

[Burnt Fingers]

Pull the tube and use a couple of SS diodes. Since the AC on the plates is fine, the tube isnt turning red and the transformer isnt groaning then there isnt much left.

Meanwhile PM me an address and I'll send a good 5U4 on Monday.

The diodes will let you at least work on the radio, alignment, etc. while waiting for the tube. Or you can just leave them there.

WAIT a minute, I just reread your post and Im getting confused....nothing new. You cant measure the DC between the filament pins as there is no ground reference. It has to be measured from Pin 8 to chassis ground.

Also check your meter to be sure its still working on DC.

Carl

[badrestorer]

Burnt Fingers wrote:

[Burnt Fingers]

That is a 9.1V zener diode, no good for this.

Go to Rat Shack and buy four 1N4007's. You will wire two in series as two sepearte pairs. The banded end is the cathode and the other the anode. Wire the cathode of one to the anode of the other. Connect one pair with the anode to Pin 4 and cathode to Pin 8 and the other pair with anode to Pin 6 and anode to Pin 8. Leave the tube out.

Carl

[badrestorer]

Carl,
Of course they're zener diodes. I hate brain-farts. But I'm still confused. Do the cathodes of both sets of diodes get hooked to pin 8? Doesn't something have to be hooked to pin 2?
Also, won't two diodes do the job/ I do have two on hand.

[Burnt Fingers]

Nothing goes to pin 2 and both cathodes go directly to the filter cap and choke via Pin 8. Its a standard full wave rectifier circuit.

One 1N4007 in each leg is cutting it close but should work. Just keep a close watch on them while working on the set.

Carl

[badrestorer]

Thanks again, Carl. Too pooped to do it tonight. I'd make a mistake. Tomorrow morning it'll get the works. I sure hope this solves the problem.
_________________
Regards,
John

They don't know the power of the radio side.

[badrestorer]

And here it is, folks. Many thanks to Carl for the diode idea and installation guidance. He was right on:



Two questions: To get reception, I have to keep the sensitivity maxed out. Is that normal for this unit?
Also, the antenna compensation adjustment (located below the S-meter window) works fine, but it spins it round and round. Shouldn't it have a stop tab or something?
_________________
Regards,
John

They don't know the power of the radio side.

[Dave Doughty]

With the AVC on, you would usually set the sensitivity control at maximum. The antenna trimmer capacitor has no stops and will go around and around.

Glad you got the set working!

Dave

[gvel]

Nice!

What are you using for a speaker? It's sounds great, in your video.
_________________
There's always next year!
WD8PHW

[Uffda]

Nice work John. You sure are getting your moneys worth out of that camera.


-Phil

[badrestorer]

[badrestorer]

[Ross Hochstrasser]

HURRAY!! Congrats !! I had a feeling it wasn't a big problem. Keep going with it, you'll really like thei radio. If you need a NOS JAN 5U4 I have a few extras. Good Luck!! Ross
_________________
"If you throw it through the window,you have to fix the window too!"
Cats are living proof that God has a sense of humor!

[Curt Reed]

It isn't often a rectifier tube looses all its emission like that without the filament opening up. The 5R4 is a tube that is rated at higher voltages, but less current than the 5U4 tube is. But still the HQ-129X would not draw enough current to harm the tube. I suspect that the tube was well used in something else before it was plugged into this set.

Curt
_________________
Curt, N7AH
(Connoisseur of the cold 807) CW forever!

[KC4VWU]

Could the rectifier tubes have been so depleted that a really leaky filter cap or some heavy draw down line wouldn't make the tube run into meltdown mode? I've never ran into that but it sounds feasible? Especially at the DC output voltages he's getting there. I need some wisdom here to figure that one out.

Phil

[Burnt Fingers]

Glad thats fixed John Ive been outside all day cutting trees and clearing brush.

Whats with the crystal filter switch?

Carl