Heathkit HO-10 and EMI

[w4fms]

I've recently started using a Heath HO-10 that I haven't used in years.  I recaped it in the 90's but that's about all I've done to it.

My HO-10 produces a lot of EMI type noise when near my 76A-4 receiver.  I recall reading a fix for this years ago but can't seem to find it now. 

Short of lining the inside of the case with mu metal, does anyone recall a mod for reducing this type of hash noise?

Frank, W4FMS

[W3NP]

I have several HO-10's and they all make noise. Don, K4KYV addressed this some years back. The source of the noise is the cheap wafer socket used for the CRT. It develops arcing with the subsequent carbon tracks getting worse as it arcs. I think the cure is to take it apart and clean it or replace it. Maybe Don will reply.

Dave

[w3jn]

Best fix for a HO-10 is to swing it by the line cord against a hard surface 

Seriously, with real scopes so cheap at hamfests, why mess around with these thing?  The don't have a linear sweep, they can't be used as a scope for troubleshooting, and they have all kinds of reliability issues.

Last 'fester I went to there was a decent Tek 5000-series scope with all the plugins, working, for $20.  FOr that, it's not worth your time to mess with a HO-10.  Or so it seems to me.

[w4fms]

Thanks for the comments.

I like the HO-10 because it so small and fits right on top of my GK 500.  It's just convenience.  I've got a big Tek scope over on the bench.  The HO-10 saves me some table space for transmitter, receivers, speakers and other junk.  I've got an old Tek 317 around someplace too that I'll put into service if I can quiet this guy down.

I'll take Dave's advice and start cleaning up the tube scocket and poking around a bit to see if I can find a way to eliminate the noise.

Frank

[k4kyv]

I never had a problem with my HO-10 generating noise.

Mine had severe hum problems.  I looked at the book, and they said this was normal, but the hum modulation "wouldn't detract from its usefulness as a modulation monitor scope".

I got rid of 90% of the hum by rewiring the filament line so that the chassis no longer carries one leg of the filament line and by effectively shielding the CRT.  The stock piece of tin wrapped round the neck of the tube is totally useless as a magnetic shield.  I found a real magnetic shield that fit the shape of the CRT in some old piece of surplus gear, and was able to shoe-horn it into the HO-10. That made a tremendous difference.

I don't use the built-in vertical amplifier, but feed the rf directly to the deflection plates of the CRT, so I pulled out that tube.  I pulled out the two-tone oscillator tube too. Pulling those tubes lightens the load on the power transformer, which is prone to crap-out.  Mine burnt out, but I found a basket case HO-10 for $5 at a hamfest, that had apparently been dropped, and salvaged the transformer for it.

[WQ9E]

Last 'fester I went to there was a decent Tek 5000-series scope with all the plugins, working, for $20.  FOr that, it's not worth your time to mess with a HO-10.  Or so it seems to me.

JN,

Surely not a 5000 series!?!  You need a real vintage Tek scope to go with vintage gear, like my Type 555 that stays in the corner near my Desk KW.  The 555 is a true "manly" scope with true dual beam operation, dual vertical plug-ins, dual plug-in time bases, a separate power supply, and of course a scopemobile to hold it all.  It probably uses as much power on average as the Desk and like the Johnson has dual cooling fans.

Seriously, you are right about the low cost for quality scopes.  I have a pair of Tektronix 7854 scopes for the bench and the total for both of these 80's era 400 Mhz. analog/digitizing scopes with their keyboards and a dozen plug-ins including spectrum analyzer and TDR was $600.  The 7603 that was sold in quantity to the military is readily available and dirt cheap.

I have a couple of HO-10's and a pair of SB-610's that are paired with the matching Heathkit stations and they are somewhat useful but you could buy a couple of 7603's with plug-ins for the price of an SB-610 and end up with a nice lab grade triggered sweep scope. 

Rodger WQ9E

[Steve - WB3HUZ]

And you can get smaller sized ones for minimal bux too. Even some of the Tek portable ones (465, etc) are going cheap now. I just bought a two-channel, 40 MHz B&K for on-air monitoring for $40. It's not much larger than the HO-HO 10. It comes competete with no hum modulation, linear sweep, vertical amps that actually work, triggering and no EMI.   

[Todd, KA1KAQ]

It comes competete with no hum modulation, linear sweep, vertical amps that actually work, triggering and no EMI.   

I remember fondly when you and Johnny were over last year for the BBQ and we were hauling crap out of the garage. There was a HO-HO-10 sitting there and I mentioned that not only did it work, but that I was planning t use it. To which Johhny replied "what the hell for?? Get a REAL scope, they're cheap enough!". Still makes me laugh thinking about it! 

Seems it should be easy enough to gussy up any smaller scope by making a rack panel or installing it in an old BA cabinet and adding period ka-nobs. When you think about it, that's really all those 'desirable' Millen 'scopes are. My HO-HO will eventually be set up with the matching Griefkit station gear and only used with that. I do have the predecessor to Rodger's BA scope, the 545, complete with cart and plug ins. 32mhz, huge for the day! But something more manageable will be dressed up for the main station.

What about those little surplus Navy OS-* scopes? About the size of a shoebox, sloping round screen, certainly period-accurate. Think I have a coupla those kicking around too. Perfect for desk top operation.

[w3jn]

Rodger, that 555 is tits on a Ritz!  Definitely fits the theme.

I have a 7603 with the freq counter plug in for the station monitor at home.  One channel displays the IF out from the RX and the other channel is an off the air tap.  WHole thing was <100 bux, and I use it regularly in the shack as a scope, too.

At my lake QTH I have a Gould (made by Philips, IIRC) 100 MHz scope with freq counter internal as well.  Was $30 or 40 - had been dropped on one corner so there's a bit of a dent but works FB.

Only you have to decide whether the HO-10 is worth the work required to obtain an acceptable result.  At the end of the day the HO10 is better than no scope at all.  Todd, a cool mil scope would be a TS-34 (the one you need to peer into a porthole to view the magnified CRT)

[k4kyv]

Speaking of vintage scopes, I have one of those little National jobs from the 1930's, about the size of a HO-10, with the 1" round screen, black wrinkle cabinet.

The problem is, it doesn't have a real horizontal sweep circuit.  It uses 60~ a.c., with no retrace blanking.  So you get two images, superimposed on each other, moving in opposite directions.  Basically the same thing as the homebrew scope described in some of the 50's era ARRL handbook.  Good enough for monitoring percentage of modulation, but difficult to tell much of anything about the waveform of the envelope.

I once built one of those, and used a little trick with a resistor and capacitor, that blanked the image on retrace, so at least I had only one image, but the sweep was still non-linear - expanded in the middle and crowded together at each end - since it was half a sine wave, not a sawtooth wave.

[WQ9E]

JN,

That 555 was free, it had been sitting unused for a number of years.  It needed a couple of black beauty caps replaced in the power supply and calibration and it was back in spec.  It still had the special roll of silver bearing solder (used for the ceramic strips) still tucked inside the case.  It does fit well with the vintage gear.

I have several of the old 500 series scopes around.  My father was a civilian attached to the Air Force at Keesler in Biloxi, MS and was in the precision measurements section.  I learned how to calibrate the old scopes when I was around 10 or 12 years old and have acquired a few over the years including the 514AD that was my father's personal scope.

The 7603 is a great scope for monitoring and general use, fairly small and very reliable.

[Todd, KA1KAQ]

Todd, a cool mil scope would be a TS-34 (the one you need to peer into a porthole to view the magnified CRT)

Is that the flat one with the eyepiece hood? Seen a few of those for sale. I wouldn't mind reconfiguring one of those little OS-1 scopes into a cabinet or rack panel as needed.

Knowing some of the other old gear and projects you have there Rodger, the 555 mobile rig came as no surprise at all.

[KD3CN]

That's it John.  The only way I'd enter a room with you and an HO-10 or an HR-10 is wearing a football helmet.   

73, Karl

Worst.  Receiver.  Ever.

Best thing to do is swing it by the line cord against the wall, then set fire to the remains so you're never tempted to put it back together.

Best fix for a HO-10 is to swing it by the line cord against a hard surface 

[WQ9E]

Todd,

The 555 is the perfect complement to my HP-524C frequency counter which weighs 118 pounds without plug-ins.  I was in TN several years ago to pick up a Super Pro 210LX and I also took the counter and a couple of plug-ins to save them from the dumpster.  Rather than leave all of this gear in the back of the pickup I unloaded it in the hotel room while my wife and I spent a few days in the Smokies.  I am sure the hotel maid was quite curious what was up.

A few years ago I found a manual for the counter at a hamfest, the price was free as long as I also took another free 524C.  So now I have 2 very heavy counters that work but are rather impractical.  But I can't bring myself to toss them or part them out so they get to occupy some storage space in the climate controlled part of the barn.  I know this is a disease....

Rodger WQ9E

[w3jn]

That's it John.  The only way I'd enter a room with you and an HO-10 or an HR-10 is wearing a football helmet.   

73, Karl

Ah, ya busted me Carl! 

Heathkit did make some Fine Business stuff.  The HOHO-10 and HR-10 are NOT among them.

[Todd, KA1KAQ]

Upon hearing that I still had the HoHo-10 and had not heeded his advice, the HO-10 Master tech arrived here for some personal instruction.

First, grip the power cord firmly. Next, grimmace appropriately. Best for the uninitiated to take shelter at this point. 

[w3jn]

 

Fixed 'er but good!!

Stopped by casa de Todd's last nite on my way back from Atlanta.  Todd has a super place out in rural N Cackilacky, had a great albiet all too brief time there.

TNX for the hospitality and any time you need a HO-10 fixed, gimme a call 

[Opcom]

those who don't like HO-10's are welcome to ship them to me for disposal..

[k4kyv]

A lot of scopes use the same type CRT as the HO-10.  Last time I  looked on one of the tube vendor sites, the only replacement available was made in China, and they wanted $46.00 for it.  So, before slinging the HO-10 by the line cord to a hard surface, please remove the scope tube.  If you can't think of a better use for it, just send it to me.

[Todd, KA1KAQ]

No no, send it to me! Oh, wait - it's already mine.

Just to reassure the board and keep the PC Radio police from showing up at the door, No HOs were harmed in the filming of this adventure. It will eventually be used with my Griefkit Injun station. There's even a can of matching paint waiting for the cabinet, courtesy of WA2PJP.

We basically did it to frighten Karl more, and to further establish 'JN's legend as the HO Master. 

[KD6VXI]

No no, send it to me! Oh, wait - it's already mine.

Just to reassure the board and keep the PC Radio police from showing up at the door, No HOs were harmed in the filming of this adventure. It will eventually be used with my Griefkit Injun station. There's even a can of matching paint waiting for the cabinet, courtesy of WA2PJP.

We basically did it to frighten Karl more, and to further establish 'JN's legend as the HO Master. 

Does this mean that all parts during a restoration will be contained in individual hobags?

--Shane

[Opcom]

Also consider substitutions of other CRTS when something like the HO-10 goes dim. It's too not hard to sub a CRT and the manuals have the voltages, in case any changes (bias or focus voltage etc) are needed. Many that specify higher maximum voltages will happily run on the 1800V of the HO-10. The main issues are length and socket/pinout. I've made sockets before from molex female contacts, cardboard, and hot glue (.don't laugh too much..)