The key message that Posters here keep mentioning is "Schematic" - and I agree.

I think rather than just replacing the parts by sight, you may wish to follow the schematic from stage-to-stage. This can be tedious, and laborious, but allows you to do a thorough wiring checkout and (gives me at least a lot of confidence) before applying power.

How many times have I found weird wiring differences - usually due to someone else's slap-dash, quick-fix repair job.

I learned this the hard-way.

From the photos it appears to have a fine wire lead on the terminals which is consistent with an RF choke as does the resistance measurement. I would solder it back in as you found it.

I agree with the previous poster but with one caveat: especially with Hallicrafters gear there are often significant differences between the printed schematic and the actual original wiring even if your schematic is supposed to match the run number of your receiver. Other manufacturers were also guilty of these transgressions but in my experience Hallicrafters was by far the worst. When using the schematic to restore if you find a change but the existing wiring looks original I would not change it to match the schematic because there are likely to be other associated differences and unless you find and correct all associated changes you will likely turn a working receiver into a non-working and possibly smoking unit.

Rodger WQ9E

Excellent caveat...also find these scenarios in Hickok test equip

Good to know that about Hickok. The only piece of Hickok gear I have is their version of the HP-410C meter (a 1604M) and the only thing I have done to that is calibration. So far it has never given me any problems.

I do recall reading about the Hickok copies of Tektronix scope plug-ins in Stan Griffith's book. I can't recall his exact line but his general observation was the Hickok vertical plug in he owned had variable gain pots that would not clean up properly and if he had a spare set of Tektronix wire wound pots he wouldn't waste them in a Hickok built plug-in

Happy 4'th!

Rodger WQ9E

If in fact you do find discrepancies you might want to sketch them out on separate piece of paper and attaching them to the original schematic for future reference. It would save significant frustration the next time you have to work on it.

Looks like it has thin wire wrapped around at least one end. Probably an RF choke. Check the schematic and connections, it's probably an RF choke.

Rodger.

Good tip. I wired it back in.

All I understand all that you are saying with your points on using the schematic. I have it out and am using it as best I can but I have to tell you that this set is almost beyond graduate level work for me. I'm on the edge of my capabilities just taking this one on. Frankly I cannot follow the schematic half of the time. It is so busy it makes my head hurt and in a couple of small studies I have found so many inconsistencies that it is ridiculous.

My approach may appear primitive but I think it makes sense considering the situaiton and my experience.... The set was completely origional, unmolested, and worked. To me one for one replacement of the caps of known value on a working set is almost foolproof. I checked the set to ensure it was working after soldering in every two capacitors. I'd love to be able to understand this set and radio theory the way some of you do but try though I might I'm still not there. Not even close.

As of now I have replaced all of the caps and the set works good but with weak FM as before I just finished measuring almost all of my tube voltage and they are spot on except for one. That's not too bad on a set this big. Now my voltage and function problem lies with the 6c7. I don't have any BFO. or audible xtal calibration. Have found one completely open resistor. Tacked in a semi close replacement and got the voltages to the 6c7 closer to spec. Did not fix the problem. Do you think I can find the other resistor in the circuit? It is on one of the band switches that is all I have learned from the schematic. Wish I could figure out which wafer 1a1 is...

More detective work. Thanks to all for your suggestions. They have been very helpful. Once I get this small issue fixed then off to the alignment adventure which I know is going to be a huge challenge for me.

Tom

When you typed 6C7 did you mean 6C4? The only role of the 6C4 is a crystal oscillator for the 500 Khz. calibration signal. The listed voltages for this tube will only be correct with the calibrator on.

Your BFO is likely to be an alignment issue, once you get the receiver otherwise operational follow the alignment procedure which includes setting the BFO. If it isn't fairly close you won't hear it and without the BFO you won't hear your calibrator (except as an often difficult to discern change in the background noise). The calibrator provides harmonics from the 500 Khz. crystal and these fall off in amplitude as the frequency increases so your calibrator signal will be most easily heard on band 1 and will drop in level on the higher bands.

I have yet to restore a SX-62 (or its SX-42 sibling) that did not need capacitor replacement in the FM discriminator transformer. This is one area where any leakage is going to greatly impact the function of the FM detector. The general symptom is reduced audio on FM coupled with poorly defined center spot tuning. Modern mica caps (these are the proper ones for this use) are much smaller than the originals and will fit in easily but take some good photos (or make very good notes) before removing the old capacitors. I just clip the leads of the old caps because it is very easy to damage one of the fine transformer winding wires while trying to unsolder an old cap that often has leads wrapped several times around the posts. You can remove the entire transformer from the receiver if you need to replace the capacitors but if you are careful you can just dismount the can, remove the cover, and replace the caps with the transformer still wired in place; this is how I do the SX-42/62 transformers now.

You will sometimes find bad mica caps in the IF transformers. This will become obvious during alignment if one of the transformers has no discernible peak or if the peak is very shallow and broad compared to the other IF transformers. The peak will be broader for the 10.7 Mhz. IF adjustments compared to the 455 Khz. adjustments, this is entirely normal.

For those not used to a discriminator type FM detector it takes a little getting used to because it behaves differently than the later popular ratio detector and far differently than the current crop of PLL type FM detectors. With the discriminator detector you can tune each FM signal so that audio is recovered at 3 tuning points and the center point is the correct tuning. The discriminator detector acts as a slope detector (like using a regular AM detector to receive FM) when tuned to either side of center. Until you get used to tuning on FM you will find it easiest to set the mode to AM and tune for MAXIMUM distortion (which is dead center tuning) and then switch to FM at which point you are tuned to the proper point for the discriminator.

I make good use of my digital camera when starting major restorations. I have a Canon EOS 1 series and I will take some overall shots with a wide angle lens and then a number of closeup shots of complex areas using a macro lens. One laptop sits in the service area mostly for use as a photo display device.

Rodger WQ9E

Rodger

Many many thanks for all of this great information. I will refer to it frequently. This is a great help!

I did mean 6C4. Sorry for the mixup. In my schematic it gives two voltages for the plates, one with xtal switched off and the other with it switched on. With it switched on it had slightly over 400v to the pate. I don't have the schematic I front of me right now but I think the spec voltage was someting like 135. Tacking in a resistor over the open one brought it into the 70v range. As soon as I can find the other resistor in the circuit (hidden in one of the band switches) I straighten out the reat of that issue.

The set receives well with only two faults. Band 3 tracking is way off and FM output is low and exhibiting exactly the same symptoms you mention so I will add the mica caps in the FM descriminator xformer to my list. It occurs to me that I dont really know how well the set is performing since I have never heard one before or an SX 42 for that matter. I did not really want to do a complete alignment on this as it is a good deal more complex than any other one I have done before. I suppose there is no avoiding it though if I want it to perform as it was designed especially considering the fact that I have replaced all of the capacitors and a coupe resistors. My only tools for the alignment are going to be my old eico signal generator and a small DX398 radio that I sue to ensure the signal generator output is on frequency.

Thanks for all of your assistance with this Rodger. It is most helpful.

Tom

I am have done the alignment on a SX-42 and I found that a eico 324 couldn't do it. I have no idea what model of eico signal generator you have but the FM can be a task. I ended up having to borrow a HP 8640B to get anywhere close in the alignment of a SX-42. Just my thoughts.
Lynn

Yes mine is of course a 324. Why didn't it work for you? I don't want to even start this alignment if my generator is not going to work. Anyone else find the 324 coming up short?

Tom

Some general comments on alignment of this receiver:

Start with the IF sections. If there is any question as to whether the original alignment is way off first make sure the 455 Khz. IF is aligned to 455 Khz. which gets you close but the final alignment is based upon the specific crystal used for the crystal filter which could be a couple of Khz. either side of 455 Khz. Sometimes the crystal filter element gets contaminated (often from a previous owner's careless overuse of a cleaner/lubricant) and this will cause the crystal response to be lowered and broadened. The element can be cleaned by taking apart the holder, cleaning the crystal element and holder parts with the highest proof isopropyl alcohol you can find, drying it carefully and reassemble using a clean paper towel to hold the crystal element to avoid transferring skin oil to it. The older National manuals detail this procedure. Follow the SX-62A manual procedure for alignment of the IF to the crystal frequency.

For FM alignment as long as your generator is reasonably stable at 10.7 Mhz. after warmup it should be OK. Most of the 10.7 Mhz. IF alignment is done in AM mode and it is generally simpler than the 455 Khz. alignment since there is no crystal filter in this IF. Note that you do need a meter to measure audio level during alignment and I would strongly suggest an analog display type because it is more difficult with the bar scale type "analog" display on a DMM. I leave a speaker connected during alignment and connect a voltmeter (AC or output scale) across the high impedance output terminal so you will get a reading with lower audio level. Make sure that the receiver is on for at least 15 minutes before doing the discriminator alignment because it will drift during warmup and you want it aligned to where it will be in normal operation and not where it is correct only for the first few minutes of use.

There are two major types of "tracking" errors. One is really a calibration error where the received frequency differs markedly from the indicated dial frequency. The other tracking error is when the RF and/or mixer stages don't track with the conversion oscillator causing a large variance in sensitivity/gain as you tune across a range.

Your band 3 error is likely due to the HFO (high frequency oscillator) being aligned to the wrong side. When trying to receive a 10 Mhz. signal the HFO should be at 10.455 Mhz. (the desired signal plus the IF frequency) but an HFO frequency of 9.545 (desired signal minus IF frequency) would also receive the 10 Mhz. signal. Most receivers use high side tracking (HFO=dial frequency PLUS IF frequency) but some use low side tracking (HFO=dial frequency MINUS IF frequency) on higher frequency ranges. I have a fair amount of test gear but one of my most used items during alignment is a Grundig YB-400 shortwave receiver (but any decent digital readout, pushbutton entry, BFO equipped) receiver will do. I use the receiver to set the HFO to the correct frequency and with it there is no question as to whether the HFO is set correctly. For example the calibration set points for your troublesome band 3 are 7.0 and 14.0 Mhz. So with the SX-62 dial at 14.0 (make sure the calibration reset control is centered before starting) I set the external receiver for 14.455 (in SSB mode) and adjust the high end adjustment to hear the SX-62 oscillator in my test receiver. Then tune the SX-62 to 7.0 and set your test receiver to 7.455 and adjust to again hear your SX-62 oscillator in the test receiver. Alternate back and forth until you have both ends correct.

In some cases the alignment of a given band is so far off that it will take a long time to get it close. In this case I tune the receiver to the center of the range (say 10 Mhz. in the SX-62 example) and set the oscillator trimmer cap to the center of its range and then use the coil adjustment to set the oscillator to 10.455. This gives you a reasonable starting point with a receiver that has been seriously misaligned and you can then proceed with the normal alignment procedure.

One more hint you will find useful is that in many vintage receivers alignment of the mixer (and sometimes even the RF) stages will pull the oscillator frequency slightly so to truly find the peak when aligning with a signal generator you have to keep retuning the receiver as you adjust the alignment controls which is not an easy thing to do. To get around this problem, use a broadband noise source to do the final part of these adjustments. Because the signal source is broad a slight change in the oscillator frequency doesn't matter. You almost certainly have one of these broadband noise sources nearby because even though most CFL (compact fluorescent) lamps are fairly RF quiet they all generate some RF noise; put a small wire lead from the antenna terminal near the bulb.

Rodger WQ9E

Rosger

I can't thank you enough for this information and SX62 wisdom! I greatly appreciate it. I'm going to be gone until the middle of next week and will be able to get back to work on the set then. Your alignment notes answer all of the questions I had lingering in my mind after reading the procedure many times. I especially appreciate the techniques you added.

I have some confidence that I can get this set back up to 100% again. I will keep you updated and no doubt pepper you with more questions if you are willing.

Thanks much!

Tom

Tom,

You are welcome and I will be happy to address any questions for which I have an answer

Rodger WQ9E

Locate that 180 ohm resistor to which one end of the component is attached. Can't be many with that value. It dos look like a RFC which almost never fails.

Rodger or anyone else?

I am aligning my SX-62A but have not got very far. Do any of you have a readable electronic copy of the schematic for the SX-62A? Specifically, page 10 that shows the underside of the receiver where the trimmers are for the 455 IF and others? The two copies I have from the web are unreadable.

Also, an explanation of why the manual calls for only "approximate" settings for the dial at 1000 kc and the signal generator at "approximately" 455KC. Why "approximate"?

thanks

Tom

Tom,

I MAY have an original and if so I will scan it but it will be tomorrow before I have a chance to check for it so hopefully someone else will chime in first. In the meantime all of the SX-62 series are close and I think the SX-62B on edebris is probably the best scan of the bunch so try that one. The Nostalgia air site may also have something and the IF section of the SX-42 is nearly identical as are the major front end alignment locations so a good manual for it can also be useful.

I should have a couple of originals from the SX-62 series and as soon as I have time I will make some high quality scans for the bama/edebris site.

The final alignment of the 455 Khz. IF is dependent upon the crystal frequency of the IF filter so the procedure is designed to do a rough alignment to make sure you are close and then set the signal generator to the exact crystal frequency for the final alignment. That is why great precision isn't called for at that step.

Don't be surprised if the crystal element needs cleaning, the holder style used on most of the Halli gear in that era has a little "gasket" between the two halves that cracks and if anyone has sprayed cleaner or lubricant in the area then the crystal probably has some on it. If the crystal seems to have high loss and/or no distinct peak then it probably needs to be cleaned.

While aligning the IF if a slug adjustment doesn't produce a fairly pronounced peak like the others then it is likely it has a bad mica cap in that particular transformer.

Rodger WQ9E

Thanks Rodger

If you have a readable diagram underneath showing the trimmers in the 62A that you can post or e-mail that would be great. I was able to peak the initial 455 using my analogue meter and trimmers S-1, 3, 5, 10, 12, and 14 with no problem. They were off. I'm stopped at the next step. Setting the switch to CW and trimmer S8. The only thing throwing that switch does is make the signal generator tone quieter. Adjusting S8 just changes the peak of the signal generator tone. I have no idea what a 1000 cycle note the spec calls for is.

Bottom line, throwing the set into CW just reduces the signal generator tone..

Tom

Just a coupe of questions and it is time to call it quits on this one. I am unable to bring this set to full function. It is beyond my capabilities. Condition is: set is completely recapped and working on all bands. All tubes have correct voltages except for the 6c4 which has over 400v on the plates instead of 130 with xtal calib switched on as required. Despite all voltages being good on the 6J5 it has no BFO either. The coil has continuity, I have had the shield off, all is ok there and he resistors in the circuit are also OK.

My questions are:

1. Is it possible to align this set correctly without the BFO? I was aligning and got through the initial setting of the IF thinking the next step (adjusting C8) might bring the BFO back. Nothing heard or effect throughout the full adjusting range of C8.

2. Any harm in running the set with this fault?

Thanks to all for all of your previous assistance. I guess this is the frustrating part of this hobby. I set out to recap this set to keep it going or years to come and also fix the BFO and XTAL calibrator as I enjoy it immensely and use it daily. I have been successful in my recapping efforts. the rest I cannot wrap my brain around.

Thanks!

Sorry but no luck on finding a good manual to scan.

I am at a loss as to how you could possibly have 400 volts on the 6C4 plate. The highest voltage in the set is a nominal 260 volts right at the rectifier cathode and there is a dropping resistor feeding the 6C4 which should draw current even when it isn't oscillating. Even if your line voltage is 20% high (highly unlikely since this would put it over over 130 volts AC) you still should only have about 300 volts maximum B+.

The highest DC voltage in the set is at the screen grids of the 6V6 output tubes because they come off before the filter choke which will have some drop, what do you measure there? The 6C4 is fed on the output side of the filter choke. If the 6C4 plate voltage is really that high then there is a power supply issue that MUST be addressed and the set should not be run that way. But if the voltage is OK there will be no harm running the set without a working calibrator and BFO.

Without a working BFO it will be difficult to determine if the calibrator is actually working because it depends upon the BFO to generate an audible "beat" note. This is one case where an oscilloscope is really handy because you can "see" if an oscillator is working. It is possible the BFO is oscillating but it is so far from the IF frequency that its effect cannot be heard. With the set tuned to a blank spot (no station) on one of the lower bands, carefully tune the BFO adjustment through its entire range listening for an obvious change in the back ground noise. When a working BFO is tuned through the IF frequency it will cause an obvious change in the sound of the background noise.

Rodger WQ9E