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The DY-88 Power Supply is a marvelous design... for the 1940's.  It could take 3 different DC input voltages (6v, 12v or 24v) and output the 2 different filament voltages (1.5v, 6.3v), plus the low and high B+ voltages (105v, 585v).  It was designed to be as efficient as possible when the radio wasn't in SEND mode (receiver only) by employing a mechanical vibrator and transformer to power the low B+ 105v at about 1 amp current (when running off a 12v input).  

Prior to the DY-88, I'd restored a 1960's Heathkit HP-13, which was a mobile DC to DC power supply.  It employed a multi-tap transformer and 2 transistors to create the needed low and high B+ voltages for Heathkit radios.  in the case of the HP-13, the two transistors worked in tandem to collapse the magnetic field in the transformer to create high voltage DC, which was rectified and filtered for the radio.

Prior to the DY-88, I'd never heard of, or encountered a mechanical vibrator used in power supplies; so it's been an interesting learning experience for me.   Vibrators were very common up until transistor revolution, for use in mobile applications where 12v needed to be transformed into much higher B+ voltages needed by hollow state equipment.

In oversimplified terms: the vibrator makes DC look like a square wave version of AC which can then be used by a transformer to raise the voltage required by the circuit, then rectified back to DC.  Low voltage DC enters the Vibrator, which contains a relay that makes and breaks contact rapidly, chopping up the DC.  It occurs so fast that the unit "vibrates" or buzzes.

The contacts eventually, become worn and pit making the vibrator less reliable.  Additionally, military vibrators (maybe others) used a rubberized insulator that broke down over time inside the vibrator, releasing a corrosive gas that would further affect the components and essentially, "stick" the contacts on the relay together, making it difficult to get started or completely non-operational.  Depending on how it the contacts "stick" the vibrator can act as a short and unpleasantness ensues.

The vibrators were intended to be disposable devices but they aren't being made anymore.  What to do?

In the case of my DY-88, when I received it the vibrator power supply refused to start but eventually, after a bit of percussive maintenance (banging) and reapplying power it started.  Over the past couple of weeks it usually will start, but there are still occasions where power has to be switched off and on repeatedly to get it to start.  It is obviously entering failure mode.

There is a procedure using an AC light bulb in series with the contacts to attempt to freshen a stubborn one up, but the procedure is hard on the contacts and generally only restores it for a while.  It needs to be replaced, and vibrator power supplies have not been manufactured for many decades.  The NOS vibrators are generally not good due to the breakdown of the materials inside over the decades rendering them bad even if they've never been used.

The solution is to replace the mechanical operation of the vibrator power supply with a solid state equivalent.  

Entering the age of the Jetsons, we have these nifty things called transistors that are excellent and making and breaking contact of DC voltages rapidly and reliably.  I found a number of articles describing a solid state circuit I could build but most did not offer much in the way of circuit protection if a component upstream failed, or if the circuit itself failed.  There are a lot of difficult or un-obtainable components in that DY-88 that I'd rather not have to replace due to the failure of the Vibrator Power Supply.

I read an article by a GRC-9 enthusiast from 2004 (NC6AV) on using a commercial circuit that was designed for this very purpose to replace mechanical vibrators in vintage automobile radios https://www.radionerds.com/images/c/cd/Wire_VBN-1.pdf.  In the article describes the procedure for using a solid state replacement.

I purchased my solid state module from http://dodgem37.com/vibrator-conversion-module/ and ordered some high voltage diodes from antique radio supply to use in the conversion.  I cut apart a non-functional vibrator module to use the phenolic 7-pin base for the VBN-1 module.

The instructions for soldering the VBN-1 module are great with one exception.  From the instructions: 

If you are looking at the base of the vibrator there are 2 large diameter pins.  The instructions say count them from the pin on the right.  That pin will be different if the large diameter pins are at the bottom rather than the top, when looking at the base.  Turn the base such that the two large diameter pins are facing you and located at the top (12 o'clock position).  Now the instructions will be correct.   This may seem minor, but when I first read the instructions I was looking at the two large diameter pins situated in the 6 o'clock position and all the pins were off-by one.

The replacement circuit works a treat, except that I can't hear the faint humming from the DY-88 now when the radio is in Receive mode.  Of course that is immediately obliterated as I turn the radio to SEND and the Dynamotor leaps to noisy life.

Next step would be to JB-weld the can back to the base to restore the look, but I'm debating whether to do that.  I kinda like the look of the modern mixed with vintage vibe (vibe, get it?).

That's all for now,  keeping my heavyweight QRP GRC-9 rig on the air, one repair at a time.

Lower your power and raise your expectations, 

AA4OO

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One of the most enjoyable operating events of the year is fast approaching -- the Novice Rig Roundup or 'NRR'. This year, the activity is dedicated to NRR founder and long-time participant, Bry, AF4K, who sadly became a silent-key last year. 

 

Bry - AF4K

Technically, the NRR is a contest, but I have the feeling that most participants think of it as just a lot of fun and a nice opportunity to hear and work some of the great old 'classics' of the past -- rigs that were used when they were teenage Novices or rigs that they could only drool about owning, back in those formative years when they each discovered the magic of radio.


Once again the bands will be alive with the sounds of Heath AT-1s, DX-20s, DX-35s, DX-40s and DX-60s, Johnson Adventurers, Eico 720s, Drake 2NTs, Knight T-50s and T-60s, Ameco AC-1s and of course, an endless variety of lovingly-constructed homebrew delights and ... a full week plus two weekends to celebrate the 'good old radio days' of their teen years, as many of us remember them.

The dates to remember are 0000 UTC March 6 to 2359 UTC March 14 and this multi-day opportunity is, for me, what makes the NRR so enjoyable. With a nice diversion from the usual 'contest frenzy' associated with standard weekend operating events, the NRR can be enjoyed throughout the week, whenever you choose to participate. If last year's operating patterns continue, you should find activity at any time of the day ... and even more as sunset arrives.

With the early growth of Cycle 25, we will likely be treated to some transcon opportunities on 15m or even 10m, as many 15m transcon contacts were made during last year's event thanks to some well-timed solar activity! 

 

If you operate during the daylight hours, please get on 15m or 10m and give it a shot ... and be sure to announce your activity on the NRR's sked and chat page here, so that others will know where to find you, especially if you are rock bound in true Novice fashion. With our present spotty conditions, we need all the help we can get and the sked page proved a very valuable asset during last year's affair.

Although technically not required, if you plan to participate it's best to obtain your own NRR number, which is an easy 30-second process.

Additionally, there is an online logger where participants can post their daily log. The nifty logger also keeps track and figures out your score as it goes and no 'after contest' log needs to be submitted. If you plan on submitting a log, the logger is a requirement. The logger will also require you to set up a 'log-in' and once again, a simple 30-second process will take care of that from here. If you used the logger last year, you will have to set it up again for this year as the old system has been changed.



Stations may run either crystal-control or VFO or can switch between either method ... the online logger will keep track and score things appropriately.


All of the rules and information can be found on the NRR's excellent website. As well, the soapbox comments and station pictures from last year's NRR may provide the inspiration that you need to spark-up your own activity in this year's event ... from what I can tell, this year will be bigger and busier than ever!


There is also a dedicated NRR Group, often the source of much valuable discussion but there is a now HUGE group of great NRR chat and activity now on Facebook's NRR Group here. I avoided Facebook for many years and have now discovered that it is an excellent forum for real time chat and information exchange ... one can still choose to maintain a very low profile and avoid unwanted interaction if set up correctly.


If you have access to the web while operating, be sure to bookmark and check into the NRR's realtime chat page. Many ops that are crystal controlled will announce their operating frequencies, making it easier for you to find them ... sometimes way up or down from the normal NRR watering holes of ~  3550 - 3650 kHz,  7100 -7125 kHz, 21.100 - 21.150 MHz and 28.114, 28.120 MHz ... and don't forget to check the colorburst crystal frequency of 3579!

'CQ'ers should always remember to tune up and down the watering hole for replies from other NRR stations that may be crystal controlled and not able to answer you on your own frequency!! This is extremely important and a real reminder of what was common practice back in the Novice days.

courtesy: Harry - VE7AIJ

Harry's homebrew 6AQ5 crystal oscillator (Feb '55 Popular Electronics) and Hallicrafters S-53, pictured above, allowed him to work the world back in the amazing radio days of Cycle 19. Let's relive some of that excitement in the early days of Cycle 25 ... in the NRR!


You still have time to get that old clunker on the air but if that's not possible, you can join the fun with your modern rig as well ... all are welcome to jump in and have a great week of radio-fun. I think you will be surprised, just as I was last year, how good some of these old classics can sound ... and you'll hear some great bug-fists as well.




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The NRR once again provided many notable highlights over the nine day event.

Almost topping the list was just experiencing the variety of old classics and hearing how well almost all of them sounded. Numerous Knight T-60s, Drake 2NTs, Heath DX-40s, Johnson Adventurers and Eico 720s, along with a nice variety of homebrew MOPAs and one-tube power oscillators graced the nightly airwaves. These oft-forgotten shelf-queens always seem to develop super-powers, far beyond their expectations, when the NRR rolls around!

I was really surprised to work so many T-60s, a small and inexpensive 60 watt transmitter kit from 1962 using a popular 6DQ6 television  sweep tube ... one never expected to achieve such RF greatness! I was very impressed with every one that I heard.


What radio-struck pre-Novice teen, dreaming about getting on the air, could resist a clever ad like this.


Scott, KA9P's 80m T-60 signal sounded as sweet as it looks in his NRR setup, paired with his Heathkit HR-10B inhaler.

KA9P  NRR station with RAF Vulcan bomber Type 51 hand pump

Right up there with the plethora of T-60s was the Drake 2NT, another great sounding radio and also my choice for this year's event. My summer refurbishing project, described here, proved a worthy companion, although my much-treasured VF-1 VFO's short term drift probably had my 2NT getting red in the face whenever I took her off of crystal control to scurry around the band, seeking out the CQ'ers. I've had a love-hate relationship with the VF-1 ever since buying my first one back in '63!

VE7SL  NRR with 2NT, VF-1 and my Original '63 Vibroplex

Yet another 2NT packed a powerful punch from West Virginia, keyed by Dave, W3NP, when we exchanged 579 reports on 40m, 45 minutes before sunset.

W3NP -  NRR setup

K2YWE's Globe Scout and Adventurer were worked on all three bands!

My NRR exchanges with George, N3GJ (KA3JWJ) in Pennsylvania, truly demonstrated just how well the low bands were performing. More than an hour before my local sunset, I responded to his 569 40m 'CQ NRR' only to learn that his signal, now reaching a solid 579, was coming from an original Ameco AC-1! This one-tube crystal-controlled power oscillator has, over the years, reached Holy Grail status among many amateurs. Originals are guarded like precious jewels and handed down from father to son ... or in George's case, from uncle to nephew!

N3GJ and his all powerful original AC-1

I was astounded at the strength of George's signal and before exchanging '73's added 'CUL on 80', not really thinking how low the chances of that might really be. Two hours later, his even stronger 'CQ NRR' was heard on 80m, as his 579 signal flirted with reaching S8 ... all emanating from just a low hanging inverted-V.  It's nights like this that remind me how I was bitten by the radio bug so many years ago and to have them coincide with the NRR was an added bonus. I've rated my contacts with George's AC-1 the highlight of this year's NRR for me!

Heathkits were plentiful too, with the DX-60 seeming to be the rig of choice, often paired with the matching HG-10 VFO. Both Mark, VA7MM and Gary, W8PU, packed a wallop with these fine examples.

VA7MM - NRR

W8PU -  NRR set-up

But it wasn't just DX-60s representing Benton Harbor engineering in the NRR. All of these neat old Heaths made it out to the west coast, sometimes on both 40 and 80. KN8RHM's (Rick) HW-16 made it here on 40m with a solid signal almost every night, while KE4OH (Steve) sported a modernized DX-20 in the form of Heath's HX-11. Steve even received the highly-treasured 'OO' report for his NRR chirp ... good job!

KN8RHM - HW-16 NRR set-up

KE4OH - HX-11 NRR station

Not to be forgotten was the ubiquitous DX-40, used by several, including this proud old warhorse, lovingly keyed by Doug, N3PDT.

N3PDT - DX-40 NRR transmitter

Rich, WN7NRR / AG5M operating in nearby Washington state put some of his 44 crystals to work with his HW-16 ... that's some collection!

WN7NRR - HW-16 NTT set-up

 

It seems that many NRRers are as adept with a soldering iron as they are with a hand key, as several homebrew transmitters were worked from here as well.

Howie, WB2AWQ in Reno, was using his homebrew pair of 807s, driven with a Millen 90700 swing-arm VFO from 1945. Most shacks worldwide, including the Novices, found plenty of use for the 807 as they were dirt-cheap in the post war surplus market. The filament has a beautiful illumination and if a bit gassy as most are by now, emit a wonderous blue glow with each press of the key.

WB2AWQ - 807s

KD7JG (Joe) in Oregon, sported a 12 volt version of the 807, a 1625, in his home brew rock-crusher. With 25 watts into his ladderline-fed 160m inverted-V, his 599 signal up here was hard to miss on both 40 and 80m.

KD7JG's 1625 NRR mainstay

 

K4IBZ down in Florida also utilized the magical 6DQ6 sweep tube in his homebrew rig for 80 and 40m. Bill was worked on both bands from here with his 10 watts receiving a 569 on both contacts.

K4IBZ's 10 watter

 

AA8V, Greg in Maryland, used an LM-13 war surplus frequency meter to drive a popular Novice pairing of the 6AG7 / 6146 at 90W input ... good enough for a 579 report on 40m, 30 minutes before my sunset.

AA8V's homebrew NRR stack

VE3BDV / VE3AWA - 50C5 Bare - Essentials power oscillator

As indicated on the NRR website, this is "more of an EVENT than just a typical contest ... once again taking our OLD ham radios off the shelf and putting them to use again! "

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