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Author Topic: Vibroplex Brass Racer EK-1 problems  (Read 412 times)

AC0AE

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Vibroplex Brass Racer EK-1 problems
« on: February 04, 2022, 08:16:49 PM »

I am helping a disabled ham friend who recently purchased a used Vibroplex Brass Racer EK-1 but it has a problem. 

When the battery is installed, there is a constant short between the positive and negative sides of the 1/4" plug.  When I disconnect the battery, there is a 465 ohm resistance between the positive and negative contacts on the plug.  Below is what I have checked:

Shorts - I have checked the soldering points on the plug to ensure there are no shorts.  Also the circuit board has been removed to ensure that the insulation plate between the circuit board the the bottom of the brass plate is protecting against possible shorts.

Tests - The circuit board has been removed from the wooden base and the brass, but the short persists.

Circuit board checked - I have checked to ensure there is no foreign matter which could cause a short, but non has been found

So I am at a loss.  My speculation is that there may be a component which has failed on the circuit board.  I am limited to a VOM for test equipment.

I would appreciate direction as to what to look for as a possible failure point.

Thank you.

73
Bret C
AC0AE
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KF4ZGZ

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #1 on: February 05, 2022, 03:10:37 AM »

The keyer board board may be shot. IIRC, it's a Curtic Keyer chip design that's not available anymore and last used in 1998.

From the Vibroplex website and pdf instruction sheet.

If constant keying occurs try these three steps for correction:
Step 1. Remove wooden base. Check to make sure the black wire and shield are
separated, then the white wire should not be touching the brass base.

Step 2. Check to see that the plug wires are not touching.

Step 3. If consistency is still occurring try reversing the white and black wires

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Matt

AC0AE

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #2 on: February 05, 2022, 04:06:36 AM »

Thank you Matt, I appreciate your help.

I also saw these points on the Vibroplex web site.  In the spirit of the amateur radio, I am curious which component on the board causes it to fail? 

I am willing to dig deeper to help this ham out.

Thank you.

Bret C
AC0AE
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W9IQ

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #3 on: February 05, 2022, 04:42:22 AM »

Bret,

The keyer uses the venerable Curtis 8044 chip. Double check that your battery is at 7.5 volts when powering the circuit.

Hopefully the chip itself is still good. You could try lifting R6 (1k) from pin 14 on the chip and connect your voltmeter to pin 14 while operating the keyer to see if the output of the chip is still functional.

If that checks out, there is a good chance that one of the two output keying transistors, a 2N3904 and an MJE-350 needs replacing. If so, also check out the reverse polarity protection diode, D5, on the output

I emailed a schematic to your QRZ email address.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

AC0AE

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #4 on: February 05, 2022, 04:57:16 AM »

Glenn:

Thank you so much for your help!

I have received he schematic that you emailed to me. 

Also I especially appreciate the tips on diagnosing the problem.  I will proceed with your tips.

73

Bret C
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AC0AE

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #5 on: February 06, 2022, 05:27:41 AM »

Glenn

I wanted to report my findings per your suggested diagnostics. 
  • The D5 Diode checks out good
  • Leg #14 of the 8044 chip has voltage of 4.75 volts
  • Transistor 2N3904 failed testing
  • Transistor MJE-350 also failed testing

Glenn, do you find it strange that both transistors are bad?

Do you know if this is a common problem with the EK-1 board?

The reason I ask is because, if the board and components are prone to failure, it may be best to abandon attempting to repair it and change the wiring so that the keyer will utilize the electronic keying system in the radio, although my friend would prefer to keep the keyer original.

Thank you for your help, Glenn.

Bret C / AC0AE
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N3KQN

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #6 on: March 15, 2022, 06:06:19 AM »

Bret
I am an original owner of an EK1 and have never had an issue with it.

Rich
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KI8DU

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #7 on: March 15, 2022, 07:02:02 AM »

If the OM has a keyer in his rig it would be a no brainer. I have a Brass Racer too, but it didn't have a keyer board in it. I had never seen a Brass Racer as such untill I friend picked one up at a Hamfest. My thinking was that someone had done a Mod. I don't know why but he removed the board and elimnated it. So what was the end result ?

73

KI8DU
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W3WN

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #8 on: March 20, 2022, 06:58:27 PM »

If the OM has a keyer in his rig it would be a no brainer. I have a Brass Racer too, but it didn't have a keyer board in it. I had never seen a Brass Racer as such untill I friend picked one up at a Hamfest. My thinking was that someone had done a Mod. I don't know why but he removed the board and elimnated it. So what was the end result ?

73

KI8DU
The original Vibroplex Brass Racer came in two flavors.. the Iambic, which was only the paddles, and the EK-1, which had the built in keyer.  So yours was most likely the Iambic.

At the time it was put on the market, early 1980’s, most rigs didn’t have a built in keyer.  Thus the option.

The paddles themselves are amongst the best ever made, and they will last.  I’ve had mine a long, long time, and they’re still as good as new (well, OK, I may have to polish the brass a little...)
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W9AC

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #9 on: April 02, 2022, 06:24:01 AM »

Was the EK-1 available with a choice of either the 8044 or 8044B IC, the B suffix meaning Curtis mode B?  To date, I've only seen the 8044 mode A version of the EK-1.

Paul, W9AC
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W9IQ

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #10 on: April 02, 2022, 07:32:31 AM »

Was the EK-1 available with a choice of either the 8044 or 8044B IC, the B suffix meaning Curtis mode B?  To date, I've only seen the 8044 mode A version of the EK-1.

Paul, W9AC

Paul,

I have only seen the 8044 version but then I am not an avid collector. If you have an 8044B chip, you should be able to substitute if that is your goal.

- Glenn W9IQ
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

W9AC

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #11 on: April 02, 2022, 08:13:49 AM »

Glenn,

I recently acquired a Curtis K5 "Lil' Bugger" keyer with the 16-pin 8044 IC.  Since I'm a mode B kind of guy, the thought was to extract an 8044B from an EK-1 and swap out IC chips.  The 8044B seems the rarest of the bunch, probably because the 8044ABM came about shortly after the 8044B's production in 1981.

Another alternative is to find an 18-pin 8044BM which is also scarce.  Get this: in a pinch, John Curtis suggested that the 8044AM and 8044BM can replace the 8044 and 8044B by simply letting the two extra IC pins hang off the 16-pin IC socket!  The extra pins are used for the speed meter circuit.  The pinout between the 16 and 18-pin versions is otherwise the same. 

I'm also on the search for an ancient MFJ Econo Keyer I model which uses the 8044B.  Strange, but it too is rather scarce.  However, its progeny (the model II and III models) are plentiful but don't use the 8044B. 

Although I could redesign the K5 using any one of several PIC chips (PK series, TiCK, K12, etc.), I would really like to preserve its originality and hence the reason for my 8044B search.

Paul, W9AC
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W9IQ

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #12 on: April 02, 2022, 08:59:16 AM »

Another alternative is to find an 18-pin 8044BM which is also scarce.  Get this: in a pinch, John Curtis suggested that the 8044AM and 8044BM can replace the 8044 and 8044B by simply letting the two extra IC pins hang off the 16-pin IC socket!  The extra pins are used for the speed meter circuit.  The pinout between the 16 and 18-pin versions is otherwise the same. 

I always admired the forward thinking of that version change. The two overhanging pins are only for the analog speed meter. He even suggested you could upgrade an old keyer by soldering the meter circuit onto the two overhanging pins! Great stuff.

Didn't the "B" version of iambic keying come about as the result of a design error in some other popular discrete component keyer like a Heathkit? Then there is the Ultimatic mode which wasn't supported in the 8044 series of chips.

Anyway, good luck with your search. You might be able to canabolize a different keyer to get your B series chip. I will let you know if I come across one.

- Glenn W9IQ
« Last Edit: April 02, 2022, 09:04:44 AM by W9IQ »
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- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

W9AC

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #13 on: April 02, 2022, 09:25:13 AM »

Didn't the "B" version of iambic keying come about as the result of a design error in some other popular discrete component keyer like a Heathkit?

I've heard the same through the years. One source told me that mode B came about due to a design flaw in the ca. 1974 HAL iambic keyer.  Whether by design or luck, this article seems to point to the WB4VVF design for the extra keyed element.  He even goes on to say the following: "...I think it is fair to call the Accukeyer's dot/dash-memory logic a major design flaw." Ouch!  That's quite a heavy-handed statement.   

http://cq-cq.eu/DJ5IL_rt007.pdf

By the mid 1970s, Heath designed the HD-1410 with Mode B keying as did other manufacturers.  I built mine in 1977.  So, it seems odd that John Curtis waited until 1981 to introduce the 8044B IC. 

Quote

Then there is the Ultimatic mode which wasn't supported in the 8044 series of chips.

Strange mode.  It's also discussed by DJ5IL.  It predated iambic squeeze keying.  It appears to be a better mode for QRQ alhtough there's a contingent of ops who swear that single-paddle operation results in the best error-free CW because dit and dah insertions need not occur within a defined window of time as does iambic keying.     

Quote
Anyway, good luck with your search. You might be able to canabolize a different keyer to get your B series chip.

If anyone conclusively knows of any other commercial keyer that used the 16-pin 8044B version, I would like to hear about it.

Paul, W9AC
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KH6AQ

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Re: Vibroplex Brass Racer EK-1 problems
« Reply #14 on: April 02, 2022, 11:34:05 AM »

Vibroplex Brass Racer schematic    https://www.radiomuseum.org/r/vibroplex_brass_racer_ek1.html

Your measurements
The D5 Diode checks out good
Leg #14 of the 8044 chip has voltage of 4.75 volts
Transistor 2N3904 failed testing
Transistor MJE-350 also failed testing

The 8044 pin 14 outputting 4.75V may be the problem. When it goes high it turns on Q1 which turns on Q2.

Because Q2 switches this shows that Q2 is probably good. Are you measuring this with the ohmmeter (+) lead to the cathode of D5?

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