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Old 29th Jul 2020, 2:30 am   #21
usradcoll1
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

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Inside pix - set 2. The 0.05uF is my doing: the one that was there was actually melted into the socket and would have been an eventual surprise for a future owner at some point.

I have a source of these caps in surprising NOS bulk.
Is that the white porceline capacitor shown? If so, get rid of that one right away. Those things are paper and are extremely leaky, as well as 60 years old.
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Old 29th Jul 2020, 8:30 pm   #22
mrrstrat
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

We actually have loads of these NOS beauties. This was a NOS cap (new in box).
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Old 30th Jul 2020, 9:10 pm   #23
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

This evening I tested all the valves on the CT160 and they all tested as as if they were new. Not something I expected in a 76 year old set.
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Old 31st Jul 2020, 12:40 am   #24
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

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We actually have loads of these NOS beauties. This was a NOS cap (new in box).
It doesn't make any difference. They're Japanese sourced many years ago. They were sold under the Olson or Calrad name. From experience!
I bought a load of Sprague caps at an estate sale, which I always considered the best. I checked all of them for leakage and many were extremely leaky. The later issue were very good.
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Old 31st Jul 2020, 2:25 am   #25
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

Avo CT-160? Nice - I never seen one before. I have a TV-7 in my shop and from what I can tell both the TV-7 and CT-160 pretty close in performance.



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This evening I tested all the valves on the CT160 and they all tested as as if they were new. Not something I expected in a 76 year old set.
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Old 31st Jul 2020, 7:29 pm   #26
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

Hallicrafters is well known for bad IFT's.
I am aware of "silver mica disease" and also the insulation on the IFT's failing.
I had 15+ of them in my collection, and think I have 2 models left. S 38B & one mil. model.
Just got tired of the IFT problems, and repairing or replacing the IFT's in them.
I'd suggest checking the IFT's before progressing.
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Old 31st Jul 2020, 8:29 pm   #27
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

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Hallicrafters is well known for bad IFT's.
I am aware of "silver mica disease" and also the insulation on the IFT's failing.
I had 15+ of them in my collection, and think I have 2 models left. S 38B & one mil. model.
Just got tired of the IFT problems, and repairing or replacing the IFT's in them.
I'd suggest checking the IFT's before progressing.
That early model SX24 doesn't use the type of IFT you're referring to.
the IFT's used in that set have compression trimmer resonant caps used.
This is from a collector who has over 50 pieces of Hallicrafter models.
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Old 31st Jul 2020, 9:43 pm   #28
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

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That early model SX24 doesn't use the type of IFT you're referring to. The IFT's used in that set have compression trimmer resonant caps.
You're absolutely right about the trimmers Dave. If I find any faulty IFT's I'll just regard it as a challenge.
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Old 4th Aug 2020, 6:35 pm   #29
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

A quick question to mrrstrat assuming he's still following this thread.

Is the aluminium (aluminum) can capacitor in your set a triple? I believe it contains C28 30uF, C29 10uF and C32 10uF.

In my set this can has been replaced with a double can, which might explain why I can't find C32. A wire from R34 which looks as if it might once have gone to the can has been snipped off.

Thanks.
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Old 4th Aug 2020, 6:52 pm   #30
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

I am still here

The cap can in the set I have looks to be maybe a 60s or 70s replacement(?).

Do you need to see where these go inside? This set is well maintained and appears to be modified here and there modestly. I am not sure how much is stock - many of the other sets I have are in original and unchanged condition. The SX-24 I have here is not one of them, but it works fantastically!
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Old 4th Aug 2020, 6:56 pm   #31
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

That's a quadruple can! I don't recollect ever seeing one before.

I'll tie it up with the under chassis views and work out what's going on.

Many thanks.
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Old 4th Aug 2020, 6:59 pm   #32
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

Just noticed it has C28, C29, C32 and C20 penciled on the can. That explains everything.

My set has a separate replacement cap for C20. I'll do the same for C32.
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Old 4th Aug 2020, 7:06 pm   #33
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

I guess someone was nice enough to jot this down for us to use many decades later

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Just noticed it has C28, C29, C32 and C20 penciled on the can. That explains everything.

My set has a separate replacement cap for C20. I'll do the same for C32.
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Old 7th Aug 2020, 1:16 pm   #34
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

I don't get to spend much time on this set, so replacement of the waxies is proceeding slowly.

I have a couple of queries for mrrstrat.

The first one concerns the capacitor outlined in red on the attached picture. My set has a cap in this position connected to chassis via the tag strip, but it doesn't go anywhere. The other lead is floating in the breeze! I assume this is C38 0.05uF 400V and should be terminated on the S Meter zeroing control. Could you confirm that the cap is connected here please.

The second query relates to a 0.25uF capacitor connected between wiper and track of the RF Gain Control. My set has cap here, but the schematic doesn't show a cap in this position. Does your set have a cap here?

Many thanks.
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Old 7th Aug 2020, 6:26 pm   #35
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

You might have seen this (ignore this post if you have):

https://stationvm.wixsite.com/statio...s-sx-24-re-cap

A left click towards the left hand side of the receiver photo gives a rotating carousel arrangement of photos, the capacitor outlined in red in your photo can be seen in one of those photo's, it does look as though it's connected to the meter set zero pot at one end of the track together with a resistor....that does seem to tally up with the circuit.

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Old 8th Aug 2020, 11:59 am   #36
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

Thanks Lawrence.

The S Meter has been removed from the set and the wiring to it messed with, something I still have to sort out. For the moment I've soldered a new cap to the tag strip and left the top end floating.
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Old 8th Aug 2020, 12:20 pm   #37
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

Good luck with the fix, I have a soft spot for some of the Hallicrafters receivers, a couple I had performed very well.

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Old 8th Aug 2020, 5:49 pm   #38
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

I removed all the modifications from the output stage, ie four capacitors, two resistors and a tag strip. What the mods were intended to do I have no idea and I'll never know now.

I then then rebuilt the output stage to the original spec, but at present there's no output transformer, that's in the pipeline along with a high impedance speaker. Having rebuilt the output stage I went round all the tags on the 6F6 valve holder accounting for every component and wire on every pin. ie type, value, where it goes to and where it comes from. I didn't find any faults, which should make things easier at the testing stage.

All the waxies were then replaced along with any out of spec resistors connected to the same tags. I found missing capacitors, capacitors which shouldn't be there, documentation errors and wiring errors, all of which were corrected. I'll document the various errors later to assist any future restorers of these sets.

I removed some tape bombs and created some new temporary ones of my own to prevent snipped leads shorting to all and sundry.

The resistance across the HT supply rails was then checked, the reading settled down at 35 kohms which is the resistance of the potential divider used to derive the screen grid supply. With all valves removed an external PSU was used to supply 350V of HT and the current settled down at 13mA. 10mA of this was going into the potential divider and 3mA leakage through the smoothers seems reasonable.

Next step will be to check out the resistors followed by the S Meter wiring. There's a long way to go yet, but i feel I've reached a significant milestone in the repair process.
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Old 12th Aug 2020, 11:39 pm   #39
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

Keep plodding on your SX24. I have an SX25, same but with 2 RF stages. It sits next to
a beautiful all-to-spec SX88 and gives it a real run for the money as far as
actual reception goes ... even SSB. If you get the alignment right you'll be delighted.
The RF and xtal filter are not easy!
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Old 16th Aug 2020, 9:25 pm   #40
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Default Re: Hallicrafters Skyrider Defiant SX24 Receiver

IT'S WORKING. I feel quite pleased with myself.

All the usual suspects are coming in on Medium Wave or perhaps I should say AM Band as this is set was made in the USA. I know for a fact that this set hasn't worked during this century and I suspect it may have been out of use for 40 or 50 years following unsuccessful repairs and modifications by a previous owner.

I still have quite a bit of work to do to get this set into a tidy electrical state and I'll have to sort out an S Meter. Then there's the chassis and cabinet work..........

Full report to follow.
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