[NJARC] Hallicrafters SX-16

[jr6v6gt at yahoo.com]

Hi Scott,

Before I comment, one question -- have you reaplaced ALL of the filter caps, so you don't fry the power transformer again?

I just looked at the schematic on Nostalgis Air. BFO's are pretty simple -- basically, a tuneable 455 Khz osc. Basic resistance and voltage checks should find the problem fairly quickly and easily. The only thing that might "throw" you is if the BFO coil is open -- but a basic ohmmeter test will uncover that -- check that first.

We've been down this road before with your SX-16 -- this is not a 5-tube AA. It's a fairly complicated set -- what I mean is, it's probably a bit too complex to troubleshoot via email. It may need another trip to an NJARC clinic! ;-) I have learned the hard way that making troubleshooting suggestions via email is a hit-and-miss business at best....

No audio output? Check the plate voitage on the 6V6's. Also measure from plate to cathode, to ensure that the cathode resistor (235 ohms?) has not opened. Also check screen voltage. Also check plate voltage at 6R7 1st audio stage.

Looks like you've got several problems. Lack of sensitivity on the higher-freq bands could be due to a weak osc. tube, bandswitch issues, coil/cap issues, etc.

Do you have a signal tracer? Very handy gadgets -- this would be a good set to practice on.

Regards,

John

--- On Sat, 4/11/09, Scott Roberts <ng19delta at yahoo.com> wrote:

> From: Scott Roberts <ng19delta at yahoo.com>
> Subject: [NJARC] Hallicrafters SX-16
> To: "NJARC Radio Club" <njarc at mailman.qth.net>
> Date: Saturday, April 11, 2009, 8:29 PM
> Just remember 
> Reply = Poster
> Reply All = Everyone
> 
> _________________________________________________________
> 
> Hi Guys-
> Getting back to the SX-16 after waiting for the transforer
> to be rewound. Came back the other day, very nice job by TRS
> in Maine.
> 
> Anyway, it seems I still have a couple problems:
> 1 BFO still does not seem to be operating
> 2 Amplification seems missing. I do not seem to be getting
> proper amplification- If I connect anything besides
> headphones, it does not have enough power to get the speaker
> going. If I switch the crystal in, I can hear stuff through
> the headphones, without the crystal, it is minimal. Even
> with the crystal, volume is at full, with minimal sound.
> 
> And seems like nothing coming through in the top 3
> bands.(10-61 khz)
> 
> Ideas?
> 
> Thanks!
> Scott
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