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Author Topic: DX 100 B  (Read 22040 times)
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WB4AM
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« on: July 01, 2015, 09:04:44 AM »

Hello,

Saw a DX 100B on Ebay that was selling for 499.00.  I thought it looked some what clean so I continue to read about it.
The seller said he had no way of testing it and didn't know the condition.

Since the Seller is from Jersey and I am here in Pa. I stated that I have seen these DX-100's sell from 150.00 to 300.00, and the 300.00 ones were working.  I then stated I could pick it up for 200.00.  Reluctantly the Seller agreed.

I brought it home and connected it to a Dummy Load and continue to power it up up.  It seemed maybe it was weak on the bands above 40 meter?  It may be just my inexperience of peaking the grid and dipping the plate?  

Anyway I bought it for 40 meter on down so I wasn't to concern at the moment.

This was yesterday, and so I went down in the shack this morning to try the audio output using a condenser mic.  
Well I was in my house slippers (!) and they were damp from walking outside.  I bumped the back of my right hand on the corner of the radio due to it hanging a little over the edge of the bench.  I felt a little tingle of voltage when doing so.  I then proceeding to turn it off remembering I didn't have a ground on the back of it.  I had gotten another hit of voltage again on the power switch.

Anyway I turned it off and pulled the electrical plug and then connected a secure ground to the back of the chassie.

When I plugged the transmitter back in, there was this "Pop" sound!

I unplugged it again and then continue to remove the outside casing so I could have a look underneath where I assumed I would find the issue.

Well it turned out that one of the caps across the AC line had blown.  I take it that these caps are the line filter caps.

My question is why would one of these blow after I installed a ground wire?

The plug is an old style non-grounded type and the two bladed plug is not the polarized type either.  Both blades are the same.

If I had by chance plugged it in with the blades reversed, would it HAD NOT blown the AC line filter cap?

Thank you,
Ken





* (2) Line Filter Cap.jpg (37.53 KB, 600x337 - viewed 399 times.)
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KA2DZT
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« Reply #1 on: July 01, 2015, 11:49:24 AM »

The caps were probably leaky, that's most likely why you were getting bit.  When you grounded the case and most likely plug the cord in with the hot side on the bad cap, it shorted.

Get rid of the caps on the AC line, you don't need them.  They usually cause more trouble than they're worth.  You can install a 3 wire grounding cord.  If you do make sure the black wire goes to the fuse first  It should connect to the rear terminal of the fuse holder.

Fred
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AB2EZ
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« Reply #2 on: July 01, 2015, 12:05:21 PM »

Ken

I agree with Fred about eliminating the AC line bypass caps... and converting to a 3-wire configuration. with the safety ground wire connected to the chassis.

In the original configuration, current must flow through both RF bypass capacitors (in series)... but the mid point, where the capacitors are joined, is connected to the chassis.

If only one capacitor is bad (leaky), the other capacitor will limit the flow of current (essentially none). When you connected the chassis to ground, you provided a path for current to flow from the "hot" (black) wire through one capacitor (not both capacitors in series)... and back to neutral... via the ground connection. If the bad (leaky) capacitor happened to the one that was connected to "hot", it would conduct too much AC current, heat up, and pop.

Stu
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K9DXL
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« Reply #3 on: July 01, 2015, 12:57:44 PM »

I have a DX-100 (non "B").  Absolutely agree with the above posts.  If you're still using the Heath plug with two fuses, replace the plug and cord with a three wire system.  You can save the fused plug if later someone else wants to return the rig to "original" condition.  Install a fuse holder on the chassis and put one 8A fuse in it.  The black wire is switched and fused. The white wire goes to the other transformer connection point.  The green wire goes to any convenient chassis ground point.  No more bites!

Here's a second thought:  You said you went "down" to the shack.  Is it in the basement?  Cement floor?  If so, I'd be sure to wear dry shoes with rubber soles because damp cement floors and stray voltages are not a good mix with poorly insulated feet.
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« Reply #4 on: July 01, 2015, 02:00:01 PM »

With all of the noise and "buzz" on AC Power lines these days I prefer this type of input filter:

Phil - AC0OB

* General Input Filter for Ham Rigs.pdf (32.69 KB - downloaded 246 times.)
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WB4AM
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« Reply #5 on: July 01, 2015, 02:33:18 PM »

The caps were probably leaky, that's most likely why you were getting bit.  When you grounded the case and most likely plug the cord in with the hot side on the bad cap, it shorted.

Get rid of the caps on the AC line, you don't need them.  They usually cause more trouble than they're worth.  You can install a 3 wire grounding cord.  If you do make sure the black wire goes to the fuse first  It should connect to the rear terminal of the fuse holder.

Fred

Okay, I removed the old two conductor cord and I am going to replace it with a 3 prong plug as suggested.  And of course I removed the old line filter caps.  Do I leave the existing inductance coil in tack?

There is not a lot of room in there to work.  I temporary removed the coil mount screws so I can solder in the new cord neatly and then replace.  Its going to be a bear holding onto the nut with needle nose pliers!  I will have to drill out the existing AC wire hole to fit a Strain relief for the new 3 wire cord.  The original was just tied in a knot. 

I will have to think it out carefully where to place the fuse holder.  Its really tight and I want to make it look like it is suppose to be there!

Does anyone know where to download a manual for the "B" version?

Thank you Fred, Stu, and others.

Ken






* Indictance Coils.jpg (23.58 KB, 600x337 - viewed 405 times.)
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KB2WIG
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« Reply #6 on: July 01, 2015, 03:00:32 PM »



Somewhere on the web is a reengineering of the Viking Ranger 2 coil monstrosity. I think that the redesign took up a lot less space, 2IIRC. I guess that you could try that....


klc
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KA2DZT
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« Reply #7 on: July 01, 2015, 03:22:11 PM »

Now that you removed the caps you can remove the coils.  Drill the line cord hole to size but not too big.  You'll need to file the hole to size, it's not round for a strain relief bushing.  Try to locate the fuse holder near where the AC cord enters.  Connect the black lead directly to the rear terminal of the fuse holder.  Next connection, from the fuse holder, is to the switch.  Make sure you're switching the hot lead.  Neutral lead (white) would go directly to the power xfmr via a terminal strip if there is one already on the chassis.

Most common fuse holders have a rubber washer.  The washer goes between the chassis and the holder on the front side and not on the nut side.

Fred
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K9DXL
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« Reply #8 on: July 01, 2015, 03:24:24 PM »

I found an open space to install the fuse holder.  
The black disk that looks like a capacitor is an inrush current limiter.
The diagonally mounted transformer on the right is a reversed audio output transformer that feeds the modulator tubes directly from an external audio amp. (And that, as they say, is a whole 'nother story!)  Sorry I don't have a better pic of where the power cord actually comes in.


* GEDC0255 (2).JPG (2359.2 KB, 4320x3240 - viewed 637 times.)
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KA2DZT
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« Reply #9 on: July 01, 2015, 03:29:32 PM »

OK FB, you can use that type fuse holder, much easier to install than drilling holes.

Keep up the good work.

Fred
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w8khk
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« Reply #10 on: July 01, 2015, 04:33:21 PM »

In your photograph it looks like there is a stray 6-32 x 1/4 inch nut laying between the 1625 socket and the LV can electrolytic.  Might want to remove that one.
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« Reply #11 on: July 01, 2015, 05:14:11 PM »

In your photograph it looks like there is a stray 6-32 x 1/2 inch nut laying between the 1625 socket and the LV can electrolytic.  Might want to remove that one.

Nice find!!
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K9DXL
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« Reply #12 on: July 01, 2015, 07:03:59 PM »

Yep, I got it out before I buttoned up the rig!
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« Reply #13 on: July 01, 2015, 10:56:54 PM »

Ken,

I have a DX100B on the bench, but haven't replaced the line cord yet.  I will add a 14 gauge 3-wire cord w/strain relief and chassis mount fuse holder, wired as the other guys have specified, which is what I did with my Heathkit Apache (see photo).  The white & green wires are not connected together, although it looks that way in the photo because of the angle.  I removed the stock pass-through caps and used one of the available holes for the fuse-holder.  I think I may have had to slightly enlarge the hole for the fuse holder with a round file.  I decided to replace the pass-through caps with new 1KV disc caps.

Brad


* Apache-AC-Fuse.jpg (292.88 KB, 1024x768 - viewed 409 times.)
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WB4AM
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« Reply #14 on: July 02, 2015, 01:21:51 PM »

Ken,

I have a DX100B on the bench, but haven't replaced the line cord yet.  I will add a 14 gauge 3-wire cord w/strain relief and chassis mount fuse holder, wired as the other guys have specified, which is what I did with my Heathkit Apache (see photo).  The white & green wires are not connected together, although it looks that way in the photo because of the angle.  I removed the stock pass-through caps and used one of the available holes for the fuse-holder.  I think I may have had to slightly enlarge the hole for the fuse holder with a round file.  I decided to replace the pass-through caps with new 1KV disc caps.

Brad

Hello Brad,

I will also be going with a chassie mount fuse holder as you did, I haven't done it yet, I need to buy a new cord from the hardware store.  Also I have to alternate working on the DX100B and renovating my house which feels like it is taking forever!

So you still installed the pass through caps?  Was this for line noise or just another form of line protection?

Ken
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KB2WIG
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« Reply #15 on: July 02, 2015, 01:55:47 PM »


 " I need to buy a new cord from the hardware store'

I'll carry a nice big wire cutter in the ca. When I drive down the road and see tv/computer monitor/ vacuum cleaner alongside the road, out comes the cutter. Crude but effective.

 I had lots 'o fun when the transition from CRT monitors to SS came along. Mouse cordage is fine also.


klc
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WB4AM
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« Reply #16 on: July 02, 2015, 05:37:47 PM »


I'll carry a nice big wire cutter in the ca. When I drive down the road and see tv/computer monitor/ vacuum cleaner alongside the road, out comes the cutter. Crude but effective.

 I had lots 'o fun when the transition from CRT monitors to SS came along. Mouse cordage is fine also.

klc

Actually I have several cords from extension cords to the ones that have those complex outlets.  I have a couple that has burned out with nice heavy cords.  But...they are to heavy!  The outer shells are to thick with the strain relief that I plan on using.  Plus there isn't much room to play since I will be adding a fuse holder as well.  The original hole is right up against a transformer mount.  So I have to be careful there if I want to do a nice install.

I know I have some other cords around, but I won't find them until I buy one!  Isn't that how it goes!!! 

Ken
 
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KA2DZT
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« Reply #17 on: July 02, 2015, 08:58:41 PM »

You can power that xmtr with a 16ga cord, even a 18ga cord will work FB.  The lighter cords require a smaller strain relief bushing since space for one is limited.

Fred
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K4RT
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« Reply #18 on: July 02, 2015, 11:05:32 PM »


Hello Brad,

I will also be going with a chassie mount fuse holder as you did, I haven't done it yet, I need to buy a new cord from the hardware store.  Also I have to alternate working on the DX100B and renovating my house which feels like it is taking forever!

So you still installed the pass through caps?  Was this for line noise or just another form of line protection?

Ken

Hi Ken,

I know what you mean.  Since spring, I have been working on house projects in my spare time and have neglected the DX100B.  In this unit, all the iron appears to be good.  I have replaced the electrolytic caps in the PS, and I'm replacing other caps as well as out of spec and open resistors.  There was a strange modification to the speech amp, which I have removed, and I will return the speech amp to stock configuration, perhaps changing the value of the interstage caps.  A couple of the front panel knobs are cracked or broken, so I will need to find replacements.

In the Apache, I got rid of the stock pass-through caps and installed new 1KV disc caps.  As noted above, some of the guys get rid of the caps and coils.  But after reading up on it, for me there was no compelling reason to leave the caps out.  I bought my 6 ft. AC cord at Lowe's.  It is made in U.S.A., came with the plug installed, and the black, white and green leads were tinned.  Probably a good idea to look at the copper wire ratings chart in the back of a handbook before deciding on which wire gauge to use.

Brad
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« Reply #19 on: July 04, 2015, 10:26:49 AM »

consider adding a separate fuse for the low voltage/filament xfmr ... sooner or later solid stating the supplies will come up .... please remember it is a system and should be considered as such ...73  John
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WB4AM
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« Reply #20 on: July 07, 2015, 05:46:45 PM »

Now that you removed the caps you can remove the coils.  

Fred

Hello Fred,

I finally drilled a hole for the strain relief that I also finally found!  No one seems to have any locally.  I was lucky enough to find one in storage, imagine that...

I also went with a 14 gauge wire with a ground.  I had to cut the strain relief ears off on the part that folds over the wire.  The strain relief that I had found could had been a little larger, but I managed to get it altogether and looking like it should!  Pics will follow later...  

I haven't done anymore.  The DX-100 is still sitting on it's side.  Brad K4RT had me thinking about those Caps, so I did a little research here and there, and it made me think that I should put them back in?

Can you Fred or anyone else elaborate more on the Caps?  At first I was just going to remove them because I thought "what the heck this isn't a receiver".  If the Caps are made for line noise, is it a possible that some noise can make it through to the transmit audio circuit?  I am just throwing this out there.  

Please don't get me wrong, I appreciate all the help I can get.  I just want to learn about what I am doing or not doing.  This way I will know for any future modifications and perhaps I can help someone down the road as well?

Ken


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K4RT
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« Reply #21 on: July 07, 2015, 06:19:13 PM »

Ken,

FB on installing the new AC cord and strain relief.

I reviewed everything I could find on the subject and just did not see a compelling reason not to put caps back in.  My impression is that those caps and coils were intended to address TVI issues back in the day.  But I don't think there's any significant down side to doing away with the caps and coils nowadays.  If you do away with them you'll have more room to work in that section under the chassis.

Brad
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« Reply #22 on: July 07, 2015, 07:45:32 PM »

depending on the size of the line filter caps and how they are connected, you may have problems with ground fault circuit interrupters "false tripping".....

if this gives you the 'deer in the headlights' look just ask ....
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KA2DZT
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« Reply #23 on: July 07, 2015, 09:19:39 PM »

Ken,

The caps were put there to reduce TVI which today is a thing of the past.  As far as worrying about line noise, not much line noise (if any) is going past the power xfmr.  I built many power supplies for rigs, never put any line caps.  They're just something that can short and give you problems.

Today with many products, TVs etc, there are special line filter caps that are used.  The reason, most all these products have no power xfmrs.

Fred
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WB4AM
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« Reply #24 on: July 08, 2015, 12:30:45 PM »

Hello,

Okay the install is complete all but the the Plug.  So No Smoke Test as of yet!

I think I mentioned I had found a fuse holder but I also had bought one too. (It's a Good Thing...)

The one I found was a little slimmer and shorter, so I thought I would go with the one I found.  Well the soldering tabs holes where one would insert the wire wasn't large enough to accommodate the 14 gauge wire.  So I started to drill it out and turning it from one side to the other in hopes not to have the drill bit catch and twist the fuse holder.  Well it did and the tab was toward off.  But it turned out that the new fuse holder stuck out beyond the case more getting it away from the new power cord.  So it worked out in my favor.

Also if you look at the pic with the red arrow, I am trying to point out that the once countersunk hole that held the coil connections had left a beveled edge.  This was due to not drilling the hole perfectly in the center.  I purposely did this to move the hole away from the new power cord install.

However this would leave an issue with the fuse holder nut not being able to tighten flush.  So if you look at one of the other pics with the cutter and grommet, you will see I had cut a grommet in half so to use it as a way to accommodate the offset.

Its not perfect but it worked!

I was actually thinking ahead when I was planing on placing the fuse holder in its location.  I thought about the outer case and how it might not clear the fuse holder.  I looked at the mounting holes on the chassie and assumed the fuse holder would clear.  Well we all know what the word "Assume" can do!!!  As I was drilling the holes, the drill and the file had slipped a few times revealing a couple of scratches.  I thought I could clean them up with Steel Wool.  Well I did some what but it also took off the gray like paint covering that revealed with the outer case would fit.  If I didn't use the steel wool I would had noticed up front that the fuse holder wouldn't had cleared.  That's what I get for trying to hide my mistakes!

Anyway so I had to grind and file a half circle to accommodate the new installed fuse holder.  I didn't what to do a hack job, but it looks like I did anyway.  Well live and learn, but sometimes we never do!

I want to thank everyone here who had participated in helping me to getting the is DX-100 back on line.

I may have not commented back to everyone who posted, but I did take everyone's advice in and thought about what was said.

So a Big Thank You to All.

Ken

I will have to post again to add more pics....
 



* Install Complete.jpg (4219.39 KB, 5312x2988 - viewed 328 times.)
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