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DX-60 - Are Bypass Caps Necessary




 
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Author Topic: DX-60 - Are Bypass Caps Necessary  (Read 821 times)
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WE1X
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« on: August 02, 2017, 10:43:36 AM »

I'm in the middle of fixing up a DX-60 that I acquired a couple of months ago. It appears to be in decent shape although a couple of mods need to be understood. While I plan on replacing the original AC cord with a 3-wire cord and a 3A fuse, I was wondering whether replacement bypass caps are necessary. I'm assuming the existing tubular bypass caps are shot and would be replaced with .01 1kv ceramics if replacements are required.  Advice?

thanks...Harry
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KB2WIG
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« Reply #1 on: August 02, 2017, 11:05:22 AM »



Watt bypass caps? A litle bit more info would help.

Klc
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WE1X
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« Reply #2 on: August 02, 2017, 11:26:21 AM »

AC cord to PS
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KA2DZT
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« Reply #3 on: August 02, 2017, 11:52:52 AM »

Get rid of the old ones.  You don't need any by-pass caps on the AC line.  If you want to use them the .01 1KV ceramics are FB.
.

Fred
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Pete, WA2CWA
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« Reply #4 on: August 02, 2017, 12:33:12 PM »

Over the years, any of my old rigs that had them, I just got rid of them. I didn't need the AC tickle  Cheesy
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Carl WA1KPD
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« Reply #5 on: August 02, 2017, 01:59:40 PM »

Harry,

As much respect  that I have for Fred and Pete, you should consider the following when entering in to the exalted brotherhood of AM

The AC bypass caps serve a critical function and must be replaced ONLY with NOS devices that came from Heath.
These caps are critical for your AM signal to be hum free.
Why? Because net DC in windings can make a transformer saturate on alternate half-cycles. That can cause acoustic hum from the transformer, and can create nasty magnetic field pulses at 60 Hz. Stacked-lamination transformers are more prone to mag field leakage, especially at the lamination stackup transitions.and tend to saturate easier and have low impedance resulting in significant primary current pulses at 60 Hz, which can themselves cause mag fields from wiring or other things like AC line filters. Low-level circuits can then pick up the mag fields. These capacitors result in the
The capacitors will result in the phase being symmetric, thus  the transformer will leak less  field!!! A review of the ARRL Handbook page 89, 43-45 will explain this in detail

Although the rig will seemingly operate without them discerning AM stations WILL notice the difference. You may gain a watt or 2 more output without them but the journey is as much about the quality as well as the quantity of the signal. Absent them, to the trained ear you will sound more like PSK-31 than audio.

Next time feel free to call your brother in law directly before posting. That is what I am here for
73
Carl
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K4RT
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« Reply #6 on: August 02, 2017, 02:42:03 PM »

and would be replaced with .01 1kv ceramics if replacements are required.  Advice?

Harry - I used .01 1KV ceramic disc caps for this purpose in my Heath Apache.

Carl - Did you get your SX-28 from Frostfest going?
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Brad K4RT
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« Reply #7 on: August 02, 2017, 03:01:21 PM »

Hi Brad,
I did get it going, even did the full replacement of ALL wax caps hidden under the BS.  Paired up with the HT-9 now.  Saw Al up in Maine several weeks ago and will be having dinner with him up there when the XYL and I go up in Sept.

Those .01's are a known producer of smoke odor in the Apache...  

Now you coming up to Nearfest?


73
Carl
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K4RT
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« Reply #8 on: August 02, 2017, 07:42:29 PM »


Those .01's are a known producer of smoke odor in the Apache...  


Hi Carl,

I'll bet your SX-28 & HT-9 make a nice station.

When the Apache warms up it's got that wholesome campfire aroma!  If you think of it tell Al I have really enjoyed using the Apache on AM.

Nearfest is on my list but it won't be this year.

73,
Brad
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Brad K4RT
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« Reply #9 on: August 02, 2017, 10:04:13 PM »



Carl,

Why only NOS from Heathkit?  Mouser and others have appropriately rated AC rated accros the line caps - the X2 and Y2 types.  Watt am I missing (cap savvyness wise)Huh

KLC
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Carl WA1KPD
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« Reply #10 on: August 03, 2017, 02:58:16 AM »

Heathkit Engineers labored extensively to find capacitors with the critical characteristics that would afford the DX-60 its rich and deep screen audio. Scrimping at this point with any "off the shelf caps" in the process effectively eliminates this effort and the resulting tonal qualities are flat with no sense of presence. The impact of the resulting low level 60 cyl waves on the transformer and down stream  circuits are discussed above


The premier Heathkit RFI caps provide the DX 60  with an almost magical touch to the audio. They are usually from the late  sixties and  are famous for their use in 68 and 69 In fact some some say that they are primarily responsible for the magical tone of this rig.

These caps tend to dampen some high-end, making the tone softer, smoother, warmer or sweeter. The bass frequencies are also smoothed out, providing familiar sounds from recordings of that era. These caps can be found at NOS or used on eBay. The only replicas I know of are from LUXE, but keep in mind that these replicas will sound different. If you want to use the vintage caps, make sure that you switch to vintage cloth wire inside your supply section, otherwise you will not fully experience the tones from these caps.
Hope that helps.

73
Carl
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wa1knx
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« Reply #11 on: August 03, 2017, 04:02:18 AM »

     Speaking of real hum, heath and others tended to use chassis as a common return of filament voltage. Often folks
would return grid leak resistors to a ground lug, and the cathode of same tube to another ground lug.  Moving returns to the
cathode pin eliminated chassis ac currents from the picture.  Point to point filament wiring helped to.  Spending 1/2 of my
ham life in damp cellars, I'm with Pete, I ditched the bypass caps.   Some guitar amps had a polarity switch to take the
ac bite off!  Ampeg as I remember had this feature as well as a hum balance pot across the filament string to chassis
ground.
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KA2DZT
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« Reply #12 on: August 03, 2017, 08:28:39 AM »

The ine caps only added more AC voltage onto the chassis. Still think you don't need them.  I've built many power supplies and never used AC line caps.

Heath and others used those caps to reduce RF on the line cord.  Carl mentioned something about the caps having something to do with hum from the xfmr laminations.  Not sue how much affect a .01ufd cap is going to have at 60hz.  I'll have to read those few pages in the Handbook that Carl mentioned.

Fred
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Carl WA1KPD
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« Reply #13 on: August 03, 2017, 08:48:47 AM »

Hi Fred,
I'll save you the trip to the Hanbook. My answers are complete B'S  Smiley.
The original poster is my brother in law. He had called yesterday morning and I told him with a therefore cord, I thought he would be OK w/o the caps  but he might want to post the question here, and I took advantage of the situation by plagerizing statements from some audiophile sites.
Guess I came across to pompously knowledgeable
73
Carl
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WE1X
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« Reply #14 on: August 03, 2017, 09:21:56 AM »

Gentlemen....and Carl....thanks for the advice.  And Carl, the entertainment was well, entertaining. The best part was the audio sounding like PSK31 to the AM purist. Given the average age and hearing of today's op I suspect an inverted voice signal sounds perfectly fine to many. Anyway, on to tracking down the mods.

BTW, you sister says you should stop playing radio, reading message boards and start fixing up the house.

Thanks again...Harry
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KA2DZT
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« Reply #15 on: August 03, 2017, 12:31:05 PM »

Thanks Carl.

I thought your comments seemed a little far out.  I especially like the part about Heath using some type a very special caps.  Most of the manufacturers of the 50s and 60s used whatever surplus parts they could get their hands on.

Fred
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KC4VWU
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« Reply #16 on: August 03, 2017, 12:48:31 PM »

Carl,
       The first post was was just about there and by the second it was way over the top. I got here just a little too late to ask if you'd gone full-out audiophool on us! Good marketing description though!
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Pete, WA2CWA
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« Reply #17 on: August 03, 2017, 02:49:42 PM »

Thanks Carl.

I thought your comments seemed a little far out.  I especially like the part about Heath using some type a very special caps.  Most of the manufacturers of the 50s and 60s used whatever surplus parts they could get their hands on.

Fred

I don't think it's that farr-out. I switched all the wire in my audio circuits of the Apache, Ranger, Valiant, etc. to oxygen enriched Teflon sealed solid silver wire to further enrich the highly tonal mellow sounds for AM audio. Combined with the use of only Solen capacitors,  https://solen.ca/product-category/capacitors/ (cost unimportant) makes my audio sound as smooth as butter.
Don't need any of those hi-tech Class E widget boards to have great audio. Great wire and caps and you're riding in the high clouds of audio smoothness.
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wa1knx
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« Reply #18 on: August 04, 2017, 04:45:42 AM »

  I can't remember were you in marketing at ESP?  should have been Wink
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Carl WA1KPD
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« Reply #19 on: August 04, 2017, 05:06:12 AM »

  I can't remember were you in marketing at ESP?  should have been Wink

Why yes, for about 5 years. How dcould you tell? Smiley
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