The AM Forum

Last evening, in order to keep up with the Joneses, I drug out my ancient Bell & Howell (Heathkit) Oh Scope in order to monitor my modulation.

All went well until I turned it on.  Talk about sacred, stinky smoke!  It worked just fine 15 years ago.

I'm not going to work on it.  It was a (working) mess when I bought it for $5.00 in 1990 (price tag is still afixed).

I have an SB-614, but I'll be darned if I can figure out how to view a trapazoid pattern on it.

What would be a good (cheap) 'scope to use for trapazoid monitoring?  I'd prefer a large tube (5") but will settle for less.

73, Barrie, W7ALW

Heathkit SB-610 is one ....It is designed as a monitor...just rf in and rf out .....Regular or trapezoid pattern your choice.....

Barrie,

With the conventional O scope some type/style of RF pick-up is needed for the waveform pattern. To get trapazoid pattern another bit of work must be done. A capacitor is added to the output of mudulation tranny secondary; from this cap to a voltage divider circuit and on to the scope. Equations for the cap value & resistance can be found in the older 50's handbooks. Not hard to do, I've got an old Eico 460 on the Junkston "500" and a little project box to view either the waveform or trapz. The RF pick-up goes directly to the vertical deflection plates, bypassing the vertical amp. Cap & voltage divider goes to the external Horz input. Works well, last long time for the older 5MHz scopes.

Just about the same JS for the Desk KW, only the scope is a Tek 2336YA. Cap & voltage divider goes to one of the vertical inputs and the X-Y method is used for the trapz.

Never had my hands on a SB-610, but the ops with low powered AM rigs followed with a leenayr like them for the trapz pattern.

Craig,

I prefer a regular scope and regular pattern.  SB-610s, HO-10s, etc., are really pretty crummy and you can use a regular scope for troubleshooting as well.  If you're married to the trapezoid pattern you can use the X-Y function in the scope and feed in the modulator/RF appropriately, I guess.

You should be able to score a decent 50 MHz scope (or better) at a hamfest for $50 or less.  RF pickup for a regular scope can be nothing more elaborate than a BNC coax terminated with a couple turns of wire wrapped around your transmitter feedline.

Barrie,

Your SB-614, like the earlier HO-10 and SB-610, can be set up to display a trapezoid pattern.  If you are using an AM exciter with an external linear amplifier then the RF out from the exciter goes to one of the exciter terminals (RCA jack) on the 614 and then the other exciter jack goes to the amp RF in connector.  The RF out from the amp goes to one of the antenna terminals on the 614 and the antenna goes on the other.

For displaying a trapezoidal pattern for a high level modulated transmitter then you need to tap off a source of modulator voltage in the transmitter and feed that to the horizontal input of the SB-614.  The rated maximum voltage for the horizontal input was 200 volts on the earlier scopes but it is probably lower on the SB-614.  The RF output of the transmitter is then connected to one of the antenna terminals.

I have matching monitor scopes with some of my setups but I use "real" scopes for most off-the-air monitoring.  There is a truly vintage Tektronix Type 555 dual beam scope on a scopemobile near my main floor AM station and some later 7000 series Tek scopes in the basement area.  There are lots of good hamfest choices and the military dumped a ton of Tektronix 7603 series scopes which are a cheap and reliable good quality scope.

Rodger WQ9E

I have 2 SB-610's and the issue with them is 1) the brightness tends to diminish over time, (mine is pretty bad. I need to place a shade of the 'shade). 2) The HV transformers tend to go out regularly. They are a funky voltage that is doubled for the HV. I don't know if the HO-10 suffers the same fate.

Oooops. I changed the model. 8)

The HO-10 and SB-610 were all tube designs. The SB-614 was all solid-state. The SB-614 manual covers all types of connections you can make with the SB-614 and the manual also includes lots of pattern illustrations.

When I had an r390a, it had a scope output, a buffered IF output that worked really well, on RX you get to look at peoples modulation, on TX, the gain seemed to adjust so that the display of my transmitted signal was close to what I had on RX, which was REAL nice.
That is one flaw in the homebrew receivers I built, no matter what I tried, the output was way too high on TX, even after installing a micro relay to short the mixer input.

If you have an r390 and dont put a scope on it, you are missing out!

Brett

I run a scope off of the IF output on my R-390A as well.  I run it in break in though.  I use a capacitive pickoff (BNC connector with a length of wire gimmic cap) built into the HB antenna switch to provide a signal to the other channel of the scope for Transmit envelope viewing. That is also T'd off to the frequency counter.

No provisions for the trapazoid view yet, but it'll be a built in "feature" on the HB rig (BNC connectors of the back of the decks).

Right now I drive an amp on AM, a pair of 3-500zg.  I use a SB610 for the trapezoid and a Tek 475 to see the mod. envelope.  For RF from the amp to the 475 I simply ran coax to an unused jack on an antenna switch that switches the amp to antennas, and dummy load.   For triggering I took an old CB swr meter, the type with an RF pickup connected to a diode and meter set pot and added a 3rd jack, BNC, to tap the diode off the meter pot.  This is on the exciter output and gives some audio voltage to trigger on.  I can use the meter set pot to zero the v. if I want to.   

I wuz talking to a very well known hamboner who told me that it took 750 watts to drive the vertical plates directly to get a pattern. Can this be true?

No way!! I have used a small pick-up in the coax and fed it directly to the vertical deflection plates of a Eico 460, transmitters used DX-40, DX-100B, & a Junkston "500". All worked fine for a waveform pattern. The reason for going straight to the deflection plates is the old 5MHz oh scopes would have some problems with the higher freqs. Being able to vary the vertical height of the waveform requires a little more JS.

No problems with newer faster multiple trace scopes.

73's
wd8kdg
Craig

Barrie,

Is your scope this one?
Heath Model # 100-203-31, Bell & Howell # Model 9560-1
It's the only one I know of that is Bell&Howell.

If so, the manual is online here:
http://www.bunkerofdoom.com/lit/bellandhowell/index.html

It could be worthwhile to see if the magic smoke is from the power transformer or not. I have 2 of these scopes and they do not work, but the pwr xfmrs are OK. I had one working, and the deflection amp transistors decided to short out.

They are good candidates for mod scopes because the 5DEP1 CRT is rated for 2750V (as was used with 3KV in the Friden EC-130) and can be made decently bright. The HV is about 1200-1400V in the scope. The HV is made by a doubler, so it could be changed to a quadrupler. The tube needs about 60V per inch deflection for one set of plates and 35V for the other.

So 300V peak to peak/100V RMS would be the max needed to fill the CRT screen. 200W PEP rig's RF would do that.

In case the scope is to be junked, the 5DEP1 CRT has value to collectors of the Friden EC-130 electronic calculator which uses the CRT as the display and they often have burns. Quite rare calculators. The transformer is worth keeping too, for the HV winding.

well hope that is the right model, otherwise I wasted space.

I prefer to run the vertical plates directly off the rf and bypass the vertical amplifier altogether.  That way I know any nonlinearity is in the transmitter, not in the vertical amplifier of the scope.  A lab grade scope might be different, but I use a HO-10 and I don't trust the linearity of the vert amp.  I have used other scopes, even military ones in the past, and have always directly coupled RF to the CRT.  To save on power supply drain and wear and tear on the transformer, I pulled out the vertical amplifier tube and the one that runs the built-in two-tone slopbucket test oscillator.

The stock Heathkit HO-10 coupling system is crummy IMO. It requires that you route your main antenna transmission line through the scope, and the rf sample is taken through a couple of small ceramic coupling capacitors.  I use a toroidal pick-up coil in the feedline to get my rf sample remotely, and couple it to the scope with a short run of scrap coax (RG-58 or 59; forget which).  I use a little tuned circuit next to the scope to transform the rf voltage sample high enough to get a good deflection on the scope display.  I do have to re-tune the circuit when I QSY or change bands, but don't find that a  problem.  It works as low as 40w with my little 6146 10m rig.

I modified my HO-10 and made a pretty decent monitor scope out of it.  The biggest problems I found with it involve 60~ hum and focus issues.  I corrected the hum by re-routing part of the filament line and installing a real magnetic shield, salvaged from some piece of surplus gear, to replace that rolled up piece of thin sheet metal that Heapshit had the builder slip over the neck of the tube.  There was a Z-axis hum problem as well; the display would brighten and dim at a 60~ rate.  I corrected that by beefing up the HV ripple filtering.  Changing out some resistors got the focus to work right.

I don't want to tie up my good test scope as a modulation monitor.

I love what the Heapshit manual says about the hum problem; to paraphrase, "Expect some hum pick-up due to the design of the scope circuitry. This is completely normal but the scope should still be satisfactory for modulation monitoring purposes".  It was so easy to correct the problem that the design engineers must have just plain been too lazy to bother.  A good quality magnetic shield undoubtedly would have added to the cost, but other amateur monitor scopes such as the one made by Millen used a real one.

I have accumulated a couple of spare power transformers, since they have a reputation for crap-out.  My first one did.  I have managed to find a couple of basket cases at hamfests for spare parts.  One had been dropped and the case was completely mangled, but the tube and transformer were still good; got it for $5.

Scope tubes have become expensive and hard to find.  Like everything else these days, apparently they don't make them in the USA any more.  Last time I checked for a 3" CRT of any type, all I could find were made in China and cost $40-$50 each.  But I have some spares.

Tubes are  rarely an issue with a bench test scope used in a ham shack since you would unlikely run it for hours every day unless you do repair work on the side.  But a modulation monitor may get many hours of use per month if you are active on the air, so it wouldn't hurt to stock up on spare CRTs.

Unfortunately, monitor scopes are no longer part of the equipment line used by appliance operators.  Yaecomwood used to offer monitor scopes that matched their transceivers and leen-yars, but I haven't seen one listed in the ads in years. This no doubt accounts for some of the cruddy signals heard on the air, but I'm sure a lot of hammy hambone types would never be able to figure out how to use a monitor scope.

To me, transmitting without a monitor scope is like driving on a country road at night with the headlights turned off.

And yet more OH-SCOPE here....

I have a Heathkit 10-4350 here that appears to work... at least I get a trace. However, it's missing the entire CRT bezel/lense/graticule assembly. Can someone tell me the size of the grid on the graticule so I can try to fabricate one (unless someone has one in their junkbox they can send me).

I also have the 85-1521-1 calibration board, but no docs. It appears to run on 6.3v AC or DC. Does anyone know what the output level on these pins are?

I have many 5" CRT pull from old HP or TEK scopes, without burns. Most of those can take high voltages like 8-10KV (maybe more..) - they can be built around by downloading the manual and making the necessary voltages. Most are avail for around $20. This isn't intended to be an ad, but to show that tubes need not be costly and that some of the better, brighter ones can be used without having to have the huge old scope there.

Take the 154-0758-00 (T51, T54, T65) 5" round tube from the 545 for example. That is a really bright scope. The voltages used are:

Ultor anode: +8650V
Geometry anode +325V
2nd anode adjustable geometry voltage +225 to 350V
G2&4 -astigmatism adjustment +225 to 500V
G3 - focus -1170 to -800V Focus
G1 - some value -1300 to -1400V for brightness control, enough to cut off the tube.
Cathode -1300V

deflection plates DC levels:
swing from 100 to 350V, your mileage may vary.

The simple circuits from the ARRL handboks using a large voltage divider of many megohms do work and can be adapted to different designs. Usually 1mA is a good level for tubes up to 3-4KV, but a little more might be good for the better more modern 8-15KV scope CRTs because of somewhat higher beam currents.

So, just saying, a cheap 'pull' tube can go a long ways in the shack. Manual is from bama.edebris.com mirror, so that's where the voltages came from. I've played alot with different CRTs. The next question will be "where will I get 8600V?". maybe from an old black and white portable TV set chassis.. And there is no need to have the cathode negative so much. It can be grounded and the HV raised. All on a sliding scale. The most important thing is the ratios of the voltages. Next is to be sure to blank the undeflected high-intensity beam.

One interesting thought - if the TX is big enough, a voltage multiplier with a 1-second time constant on the output filter, hooked to the modulator output, might work to make the 10KV or so, only when modulation is present, otherwise feeding only the rig's unmodulated HV DC to the tube at 1-3KV resulting in a rather dim spot? I have not tried that yet but it is interesting. I think someone already did it (only a doubler because they used a smaller 2-3KV CRT) and it was published in a ham rag. The idea was to eliminate the need to make a separate xfmr-powered CRT anode supply.




Mr. Boogie, those age of scopes are usually set to 1cm square grids. Very old scopes will go by the inch, but one that new would be centimeters. 5" use 8x10, or 4x8, or the like. You will find that the scope graticule is one of the most interchangeable parts there is. The attaching holes might not quite line up but they can be filed or reamed a little, equally, and then it will usually work. The entity that claims to own the heathkit manuals, he's pretty much run them off of the web wherever he finds them I think.

Nobody mentioned the yaesu YO-100 and YO-101s.  They can be had cheap.  RF in and RF out.  I have run 2KW SSB through them and 500 watts AM. Never a problem.  They have a nice clean picture, Have Trap Built in, That also have tone built in for 1000 and 1600 HZ. 

I have mine setup here measuring mod when I am transmitting and either AF on the scope or IF for the recieve. Its real nice to see signals across the scope.

The 100 is an all tube model and the 101 is a later model with transistors. Both work well for tuning, monitoring your station.

Clark

And the Wawasee Catalyzer! with large scale 3-range power meter, deluxe 60Hz sweep, and 3" CRT

HAHAHA...  I have three of those in the stack of Gear in the store room.  ALL three are broken.

Clark

Broken Catalyzers? what killed them? The item I see broken on mine is the electromagnet that pulls the beam off to the side when there is no RF. It just does not work. Does not affect the operation though.

One I got a long time ago.. It never worked.. The Freq counter does not and the meter does not.. But he scope does.  The older model units both failed. I used them in my CB days. One of them I used for years and one day smoke rolled out of it just sitting there.  Some device that I could never identify smoked. I believe this might have been a black beuty cap but it was Torched.. No schematic.  Its in great shape..  Maybe one Day I will try to fix it. 

Do these things actualy work on other frequencys?   I know they where strictly a CB Scope meter..  I actualy liked the Scope picture.. It was very nice and clear and the att allowed you to get the scope calibrated. Doubt I will ever use them again.  I use a Bird 43 and a Real O scope with a Tap. Or a Yaesu Yo-100 which I really like.


C

The Bell&Howell 9560-1 is an enhanced Heathkit IO-102 with triggered sweep.
The Heathkit IO-102: http://www.heathkit.nu/IO-102.jpg (http://www.heathkit.nu/IO-102.jpg)

That's a nice site. If you want to see the rest of the site use: http://www.heathkit.nu/ (http://www.heathkit.nu/)

I have one I'll find and send (The schematic to the catalyzer).  I've fixed a few of them in the past, Dennis O. was always a good source of parts (he didn't design, but signed off on almost anything Demco, Dosy (which only copied) and Blackcat (who Dosy copied.  Dosy WORKED for Blackcat, and then screwed him over and went into business for himself, spreading his crap through the kentucky connection until any idiot that wanted a 4kw pep reading meter could afford it, regardless of accuracy).

The catalyzer will work on nearly any frequency for monitoring modulation.  It really only reads the audio frequencies.  The freq counters are accurate to (IIRC) 45 mhz or so (I remember when I found the mod on the RCI 2950/70 to go from 20-40, the catalyzer I had at the time would read the entire range).

As I said, SOMEWHERE I have a schematic of the thing.  And yes, those are black beauties in there.  About the biggest expense in them! :)

--Shane

Get a real scope like my Tektronix 555  ;)

It is the perfect scope for a vintage station with a total of 111 tubes in the power supply and mainframe plus another 40 or so tubes depending upon which vertical plug-ins are mounted.  It is a true dual beam scope with separate CRT "guns" along with dual plug in time bases and vertical amps for each beam and probably weighs about as much as a Globe King when sitting on its scopemobile.

This scope is retired to monitoring service although it is a pretty decent lab type scope with stable triggering and a rated bandwidth of 33 mhz.  With separate fans for the mainframe and power supply it is anything but quiet and it definitely isn't green from the energy consumption standpoint.  But the price was right, free.  It needed a few replacement caps and calibration and it has been chugging along for several years without a problem.  I also have a slightly smaller Type 556 dual beam rack mounted in another radio room.  It is a hybrid design that goes to 50 Mhz.

Rodger WQ9E

LOL.. What a Boat anchor!   I ripped the tubes out of one of those recently and smashed the thing into a dumpster..


C

Before I knew any better I salvaged one of those too. I still have the power transformer, and all the tubes and parts I could pull out.

I thought the Ceramic terminal strips with silver solder construction was the cats meow though.

Rodger, I had a beautiful 555 with matching power supply and cart.  I made the mistake of loaning it back in the early 80s, unfortunately it never found its way back home.  The dual beam is so much nicer than chopped or alternate sweep.  Before acquiring the 555, I had visions of building a low-freq dual beam storage scope using the CRT from an F4 Phantom radar display; with the 555 I never needed to do it.  I would love to find another 555 in decent or restorable condition.  If you ever get tired of yours.......

Rick,

I will keep an eye out for one; I saw one at a hamfest earlier this year and apparently the FAA owned a number of them so they are out there if you can catch them before they get parted.  The twin vertical sections are usually full of the "Bugle Boy" tubes so they often get scavenged with the rest of the scope being parted out or trashed.

My father was a civilian attached to Keesler Air Force Base in Biloxi and was in the precision measurements area.  I was 12 (back in 1972) when he taught me how to align my first Tektronix scope.  I will never forget going through the L/C delay line multiple times until I had it to his satisfaction-those later coaxial delay lines take all of the fun out of scope alignment.

Rodger WQ9E

I had a 555 with the cart.
Not a bit of trouble with it for many years.

I still think it had the sharpest brightest trace of any scope I ever had.

A friends father worked at a place that went out of business, but before they did, they did not pay the employees for a few weeks, and all the equipment walked off with the workers.
he had it in the crawl space under the house, but it worked fine.

I think I sold it at a fest a long time ago.
A power hog by todays standards...

Mine had the spool of silver solder inside...

Brett

Thanks for the offer, Rodger!  I have not yet seen any 555s at fests, and last year I made it to 13 fests up and down the east coast.  Lots of 53x and 54x, and even more 45x scopes, but no 555s.  I have sufficient vertical plug-ins, but would need horizontal plug-ins if we find a 555.  I have a cart, so I just need the 555, and ps with cable.  I get up to Mich at least once a year, so it would be no problem to schedule an eyeball qso either up or back.  Or maybe we could hook en route to Dayton! 

Interesting the ancillary value the military electronics programs provide!   I was in the AF from 66 6o 70, working on F4 Phantom weapons release computer system / radar, as well as comm nav.  The last 1.5 years I spent maintaining and calibrating the specialized test equipment used to manage the radar system and sparrow launch computers.  In the lab I had a Tek 454, Fluke 803B, HP 5245 with 500mhz plug-in, lab bench power supplies, etc.  I was in hog heaven!  In the last few years I have managed to duplicate most of the test equipment I drooled over during my stay at Davis Monthan!

Yes, Brett, it is a power hog, but only in the summer.  In the winter, it is 100 percent efficient at heating that cold shack!  Much more class than those cheap electric heaters that buzz if you knock them over.

They work pretty well on any HF frequency Really a decently thought out one appropriate for the low cost end of things. Here is one schematic for it. Might be other versions. note the inductor there as if the circuit is a carrier-keying relay. That is the electromagnet that pulls the beam off to the side when there is no RF. Really does well for having only 1800V acceleration.

It could use a dynamic focus circuit though. If you turn the focus control, you can get either the middle or ends of the sweep perfect, but not the entire sweep. No different from other cheap modualtion scopes.

It has to do with the rather short CRT length meaning a short gun as well, and the front glass not being equidistant from the cathode at all points. Older design. The longer tubes minimize this to some degree and the radius of the faceplate has to do with it.

DF is not difficult especially with that HV power transformer there as long as the voltage error is the 'right' polarity.

I have not studied the modern flat faceplate professional scope diagrams too much to see what they may have done, but the tubes were longer, custom made, and a lot better designed. I will never go to an LCD for a mod scope. It will just suck and suck and suck. No presentation!

Hmm.. Maybe I will have to drag one out and get it going.  I bet if i take pics of the part that smoked, you guys could tell me what it is.

C

Check your email, I sent you the manual and schematic for it.  It also has the schematic (separate) for the frequency counter:  It's the same exact counter as other wawassee products, just in the same case.  NOT integrated into the rest of the unit you have.

Anyway, they are nice, for what they where.....  BUT, finding a working model is becoming an excersize in futility.  You have 3 and a schematic now, let us know how it turns out :)

--Shane

I think I have that schematic.  Its the one for the unit that has the watt meter, Counter and scope.  I need the schematic for the older unit that has just the watt meter and scope.  I will compare yours with mine to make sure. THe boards are totaly different. This one says "built by JB 1976" inside :) 

I did not get an email yet..


CLark

It sent.  I think we went through this before.

The one I sent you has the schematic for both.  The freq counter is a SEPERATE schematic and module.  It specifically states on the front for BOTH models.

I've rebuilt a couple.  It IS a HV cap, and very typically blows. Unfortunately, it's been half a decade since I did my last one, and can't remember what it was / is...  Whoa, my son just celebrated his 6th bday. Guess it's been a decade :/

--Shane

Ok.. I got it.. Thanks shane.  I will pull the thing out and compare it to the file next week.    Thanks

C