Thinking Heathkit SB series...

[AE1PT]

At the Rochester Hamfest, I picked up a couple working SB-610 station monitors for cheap. A couple weeks ago I started to get around to putting the 'new' LK-500ZB amp on the operating desk--and pulled out the SB-200 amp that was there.

I set the 200 next to the spare 610 (one is already inline with the Icom) and got to looking at them together. Suddenly the whole station line began to look like a very appealing boatanchor addition to the shack. I am thinking about picking up the SB-301/401 twins, the station timer, and a speaker...

Anyone here fond of or using these rigs? The major complaint that I have seen involves the PTO drive mechanism. My primary use would be SSB--as I have the Valiant/National NC-300 combo for AM/CW, and the IC-751A for digital modes. Whaddya think?

[wa6mhz]

Get a SB-301 & SB-401. Except no WARC bands, it works great!

[W3WN]

The 301/401 'twins' are readily available at most hamfests, as are the 101 & 102 transceivers. Depending on condition, you should be able to find the twins for $100 and up each, the transceivers for $250 and up each. (And don't forget the power supplies for the transmitter or transceiver)

The rigs are easy to maintain, and most of the electronic (non-mechanical) components are readily available. So if some TLC is needed, you shouldn't have much problem performing it.

I had an SB-301 paired with an HT-37 for many years. Fantastic little receiver. Then I got a TS-430S, and the pair fell into disuse. I got talked into loaning the 301 to a friend; when it was returned to me, it looked like someone had carelessly tossed it into the trunk of a car & bounced it around for a few weeks; heartbreaking. Of course, no one involved would take responsibility for the damage... but that's another story.

[W8XLR]

I have the SB-301/401/610/220/speaker here. I use them all the time - love 'em! Soon I hope to aquire an SB-620 panadapter, and the station console to round out the set. As you go shopping, one thing you should look for in a '401 is one that has all its crystals, so you can work split. Alot of SB-401's dont have thier rocks, as they cost extra back in the day and to many were considerd not needed when mated with the SB-301 receiver.

[WØTKX]

I really, REALLY, like the green. But I prefer the performance of other radios.

Mind you, I'm quite nostalgic for Heathkit. Would enjoy an HW-101.

Got a couple of meters, two SB-200's, and a 201. Grid dip meter too.

[KB3LAZ]

I have the SB-301/401/610/220/speaker here. I use them all the time - love 'em! Soon I hope to aquire an SB-620 panadapter, and the station console to round out the set. As you go shopping, one thing you should look for in a '401 is one that has all its crystals, so you can work split. Alot of SB-401's dont have thier rocks, as they cost extra back in the day and to many were considerd not needed when mated with the SB-301 receiver.

Having a look at your shack, you have an interesting mix. I see the SB line, a drake 4 line, a Viking II(?), an NC 183(?), some Hallicrafters that I cant identify off the top of my head, an FT-950, An FT-450, an FT-7800, what I think is an Ten tec 544, and some Misc.

A little bit of everything I see. =)

[AE1PT]

I do have to admit that I am suffering from a bit of nostalgia. This was a coveted thing back in either 70 or 71. I remember liking the Drake stuff as well. Seems that Lafayette Electronics had a visually similar knockoff for the Drakes. In any event I could never scrum up enough cash to do either. I did manage to bargain a 32V-3 without a case for $20, and resurrect an HQ-129X salvaged from the dump...

Once I get this sort of thing in my head it is usually a done deal. As I am to understand it, the PS for the 401 will be found in the speaker enclosure? The trick here is going to be finding all of the interconnects so that building new ones is not a requirement!

Pat, you use yours on a fairly regular basis too, don't you?

[N8YX]

You also need an SB-620 (panadapter), SB-500 (transverter) and an SB-310 (SWBC version of the ham-bands receiver). More thoughts on all of this a bit later today.

[W8XLR]

Having a look at your shack, you have an interesting mix. I see the SB line, a drake 4 line, a Viking II(?), an NC 183(?), some Hallicrafters that I cant identify off the top of my head, an FT-950, An FT-450, an FT-7800, what I think is an Ten tec 544, and some Misc.

A little bit of everything I see. =)

Yes, the Hallicrafters units are the HT-32/SX-101a... I enjoy all types of gear, ancient and factory fresh. It makes me well rounded (not just my beltline!) There's also a national HRO-5RA behind the Halli's. Ive had it since I was kid... Its very special to me 'cause I learned about high voltage the hard way with it!

[KB3LAZ]

Yes, the Hallicrafters units are the HT-32/SX-101a... I enjoy all types of gear, ancient and factory fresh. It makes me well rounded (not just my beltline!) There's also a national HRO-5RA behind the Halli's. Ive had it since I was kid... Its very special to me 'cause I learned about high voltage the hard way with it!

I like free for all shacks with such variants. My eyes dont get drawn to one or two things, they continue to examine. :)

[W8XLR]

I do have to admit that I am suffering from a bit of nostalgia. This was a coveted thing back in either 70 or 71. I remember liking the Drake stuff as well. Seems that Lafayette Electronics had a visually similar knockoff for the Drakes. In any event I could never scrum up enough cash to do either. I did manage to bargain a 32V-3 without a case for $20, and resurrect an HQ-129X salvaged from the dump...

Once I get this sort of thing in my head it is usually a done deal. As I am to understand it, the PS for the 401 will be found in the speaker enclosure? The trick here is going to be finding all of the interconnects so that building new ones is not a requirement!

Pat, you use yours on a fairly regular basis too, don't you?

Power supply is built into the '401, interconnects are specific lengths of RG-62...

[wa6mhz]

I brought my 301 and 401 up to field day one year, but the headphones didn't work, so I used the spare SB-101 I had brought. That worked fine. I found the 301 doesn't like modern headphones. I thought I fixed that, and brought it up the 2nd year. This time the headphones worked fine, but the 301 wouldn't MUTE during transmit for some reason. I was unable to figure it out and used the SB-101 again. Finally I score a Hallicrafters SR-400 and have been using that ever since. Never did figure out the story on the 301/401. They got put in the Museum pile where they have sat ever since.

[AE1PT]

I brought my 301 and 401 up to field day one year, but the headphones didn't work, so I used the spare SB-101 I had brought. That worked fine. I found the 301 doesn't like modern headphones. I thought I fixed that, and brought it up the 2nd year. This time the headphones worked fine, but the 301 wouldn't MUTE during transmit for some reason. I was unable to figure it out and used the SB-101 again. Finally I score a Hallicrafters SR-400 and have been using that ever since. Never did figure out the story on the 301/401. They got put in the Museum pile where they have sat ever since.

I thought you had put some Heathkit stuff to work on your OP and was working SSB with it. Or do I have my wires totally crossed? :ashamed:

[W8XLR]

I brought my 301 and 401 up to field day one year, but the headphones didn't work, so I used the spare SB-101 I had brought. That worked fine. I found the 301 doesn't like modern headphones. I thought I fixed that, and brought it up the 2nd year. This time the headphones worked fine, but the 301 wouldn't MUTE during transmit for some reason. I was unable to figure it out and used the SB-101 again. Finally I score a Hallicrafters SR-400 and have been using that ever since. Never did figure out the story on the 301/401. They got put in the Museum pile where they have sat ever since.

Right about the phones, Pat. I think 600 ohm are called for. As far as muting, I had to replace the T/R relay in the '401 to fix that

[wa6mhz]

That must be what was wrong. I put in a 600 ohm to 8 ohm transformer to get them to work.

I had a Heathkit SS-9000 in the station, but it was occasionally intermittent and kinda clunky, so I replaced it with a nearly equally clunky Yaesu FT-107M. The SS-9000 is now in Museum service. I think the 107M has a better receiver and works all the time. You can't have a "Sometimes it works" radio when you are in DX Hunting. Need MAXIUMUM peformance and reliablity. If I had the room, I would have the SB-301/401/200 set up as a dedicated ragchew rig, maybe for 40 and 75. But my station is over packed now with not even any VERTICAL room to stash stuff. We have radios all the way to the Ceiling!

[AE1PT]

I remember what I was thinking now! It was the SB-200.

[WØTKX]

You can't have a "Sometimes it works" radio when you are in DX Hunting. Need MAXIUMUM peformance and reliablity. If I had the room, I would have the SB-301/401/200 set up as a dedicated ragchew rig, maybe for 40 and 75.

I couldn't agree more. If I were a serious boat anchor dude, I'd probably fly Drake, and maybe Collins. Some of my opinion is because of time spent with Yaesu, Drake, Swan, Heathkit, Hammarlund and Hallicrafters in my younger days. I always care more about the RX than the TX side anyway. For some reason. ;)

Mind you, I was spoiled forever as a young hamster with a modded Hammarlund SP 600. Mainly a home brew Q multiplier and a tunable (early design) FET preamp. Of course it was fantastic for AM and CW, a little fussy to make it listenable on SSB... but decent.

While I have heart tugs for Heathkit, the one older boat anchor I have is a hybrid, the FT-902DM. It does not transmit (got it that way) and I have not bothered to fix it yet... but I've listen to it a lot, and it's pretty damn nice. The most listenable older Yaesu I've ever played with. These decisions are interesting and fascinating. However, the discriminating ham enthusiast (much like audio enthusiasts) could use a little more information than anecdotes by the admittedly opinionated ham community. ;)

That's why i am a fan of Sherwood Engineering's Receiver Test Data (http://www.sherweng.com/table.html)

My first ever purchase of a brand new radio about two years ago was influenced by this information. Picked the Flex 3000 over the Ten Tec Eagle. It was a difficult decision, that I wish upon all of you. Moar Radios!

The Sherwood list is a ranked group of 107 tested rigs and receivers, many with mods as noted. They are sorted by Dynamic Range Narrow Spacing... which is considered to be 2Khz for this list.

You can copy paste it into a spreadsheet to sort it differently if you want. Here's some that I find interesting because I have spent time with them OR I know people that use them...

Elecraft KX3 #1
Yaesu FTdx-5000D #2
Ten Tec Orion II #6
Flex 3000 #9
Ten Tec Eagle #10
Icom R9500 #13
Drake R4C #14
Icom IC-765 #16
Kenwood TS-830 #18
Ten Tec Omni VII #19
Icom 7800 #20
Yaesu FT-901DM #23
Yaesu FT-950 #24
Collins R-390A #25
Ten Tec Corsair #26
Kenwood TS-820 #30
Heath SB-104 #40
Ten Tec Omni B #43
Icom 781 #47
Yaesu FT-1000 MP MKV Field #55
Icom 756 Pro #56
Drake R8 #57
Yaesu FT-100 MP #69
Signal One CX-11A #71
Kenwood TS-520 #90
Collins 75-S3 Wing #92
AOR 5000 #107

[W3WN]

When I was a college freshman, K3CR's shack had two HF stations... an S-Line, and a 301/401. The S-Line was primarily used on phone, the Heath's on CW.

Eventually the 2nd station became a TS-520, later an 820. The Kenwoods eventually became the primary station, the S-Line secondary (it got pretty well used but not so well maintained, which I know now but didn't know then), and the Heath's sat collecting dust. They eventually got sold to a club member, (then) WB3DCJ & went West with him after he graduated and took a job in CA. (He also took with him a Regency HR-2B that he bought from me -- I got it new from AES for a pretty penny, back in the day, including all the crystals for the local repeaters -- which helped finance my purchase of an HW-2036, which I still have)

I lost touch with Rick over the years; he's back in the area now, but I've had no luck reconnecting with him. Don't know if he still has the gear after all the years, or if it went into other's hands. For all I know, it could now be in Pat's famed museum collection!

[N8YX]

Nostalgia to me is something with a purely analog (VFO/crystal premix oscillator) signal chain, analog readout and preferably solid-state PA. Analog readout being desirable because it's a lot easier to convert one of these to the WARC bands than it is to reprogram someone's preloaded counter design.

For that reason I recently got hold of an FT-301 lineup. It doesn't do FM on 10...but the "C" and "D" ranges are going to get converted to other bands, as are the "AUX" and "WWV" slots.

No matching amplifier, and Yaesu didn't make an "FT-621" (6M) to go along with the radio as they did the FT-221, and the YO-301 scope doesn't incorporate a panadapter function like its cousin the YO-901.

But the receiver is nice. Very pleasant to listen to, and the thing sounds great on AM. You can insert the low-level PA into the scope's 'Exciter' input then take the output of the PA (via the radio's SO-239 connector) and run it through the RF Monitor connections. Voila! Trapezoidal display. I've not seen another rig that allows you to do this, or for that matter to feed the low-level (10w) RF amp to, say, a 4CX1500 in grid-driven configuration. That could make a killer AM lashup.

[AE1PT]

Some things are solved easier than others. The Elmira Fester this morning took care of the SB line main acquisition...

http://ae1pt.com/photos/imh/fresh-in.jpg

I had been wandering around since 6:30AM looking for someone setting out a table to put some of this gear out. By 10:30, I was pretty well at an end to it--tired feet and nothing to show for my time but a 1957 ARRL Handbook, and the antenna analyzer I was supposed to have picked up Thursday. There was an SX-28 that was looking good outside, but a little rough inside for $60, an SX-100 for $140 that I was sure could be had for $120--they were weighing on me. But noting Heathkit except a bunch of lunchboxes, HW series, and phone patches...

One final tour up and down each aisle. It was only the second row and there they were. SB-303/401 pair, SB-650 digital display, all of the crystals, all of the correct interconnects, the original manuals for each, and a full complement of NOS replacements for all of the tubes in the 401. I was dealing with the original owner & builder, also...

$325 later, you see them sitting on my bench. :omg:

Condition excellent, will clean up nicely--and from a non-smoker. Now I gots to find a speaker, the station ID box--and it will make a nice spread for sideband ragchew on the new station desk when done.

[N8YX]

Jolly good score! :clap:

[PA5COR]

Impressive listing...
I can only boast the Heathkit SB-1000 i rebuild and with new tune 3-500 ZG has a new life for the next umpteeen years.

[W8XLR]

Congratulations on the SWEET score... lots of boat anchor fun is at hand!

[NQ6U]

Boat anchors are a ton o' fun. Besides, just knowing the correct way to tune up a tube rig sets you slightly apart from the rest of the ham pack these days.

[AE1PT]

Congratulations on the SWEET score... lots of boat anchor fun is at hand!

I sometimes wonder if over half the fun is not the bench part... :yum:

As usual with fester goods--everything is not exactly as it ought to be. Before I bought it I had noticed that the 15.895Mhz (40M) crystal was missing from the 401. The seller acted a bit surprised. No big deal.

Pulling the 303 apart at home was a bit more surprising. There I found that that 4 crystals had been unsoldered from the oscillator board. No 40M there either. What totally baffles me is that in transceiver mode, the LMO & HFO signals are derived from the receiver--so I am not getting how these worked either as a discrete pair or together. It also explained why I got completely off the wall frequency readings on the SB-650 for four different bands/sections... :twisted:

As to be expected the axial electrolytic caps in the 303 are nearing their useful life (cracking bubbles on the end). I have already cleaned it inside and out, cleaned and readjusted the PTO/dial mechanism, cleaned and lubricated all trimmers, switches, pots, and shafts--and touched up the alignment. That took robbing the remainder of the missing crystals from the 401. HV & B+ on that rig are good--a bit of ripple though. Caps, caps, and more caps. The bias supply rectifier is open--transformer windings good. Probably one of the caps gone bad there as well. A good project as things get a bit colder outside, and the nights longer.

By the time I am done getting the full complement of crystals and new caps, it will probably be another $150 or so. So $500 by the time it's done for a 2.1Khz sideband ragchew station. But lots of fun getting there. I could say that there is something wrong with this, but it's cheaper than crack, leaves something tangible to show for it, and does not create nearly the marital issues... :cool2:

[N8YX]

I'm sure the other Pat will be along shortly to chime in about gear purchases and marital issues. :lol:

[AE1PT]

I'm sure the other Pat will be along shortly to chime in about gear purchases and marital issues. :lol:

He could smoke quite a bit of crack for what he spends on acquiring whatever he is stockpiling. If it were me with all that stuff, I would now opt for the crack.

[wa6mhz]

Those crystals are readily available on Ebay. In fact, a SB-303 was just listed today missing only the dial. Lotsa 303s get into the Ebay CHOP SHOP mill.

[AE1PT]

Those crystals are readily available on Ebay. In fact, a SB-303 was just listed today missing only the dial. Lotsa 303s get into the Ebay CHOP SHOP mill.

It seems that way...

My bet is that the basket case 303 will top out at least $140-150 before shipping. The eBay chop shop solved my issue--I just bought a crystal board with the switch and all 8 crystals for $75 (shipped). I only need 4 of them, and already have the other 4 and switch/board sold for $40! Such a deal... But it's sad to to think that people are scarfing up nice stuff reasonably and then stripping it down for sale to the last nut and bolt.

But hey, I got mine now. Thinning the herd just makes it all worth more! :dance:

I don't know why I am worrying about it. The crystals pack could be taken out of the 401 and put into the 303--as they are not necessary in transceiver mode. In five years I have never run split even once--not even listened to pileup humpers chasing split. BUT--because the rig can do it, that's the way I have to restore it. I'm funny about shit like that... :nuts:

[wa6mhz]

U need split to work the DXpeditions!

U should see what a good SB dial goes for!!! They are very prone to cracking (I have a whole box full of Cracked dials!) so install the dial with the VERY Gentlest of installation. Any pressure WHATSOEVER will crack the dial. They are more brittle than ICE Sheets! If the crack doesn't go all the way to the edge, you can still use it but you may feel a bump when you pass over the crack in the spiral as you turn the dial. Probably 90% or more SB dials have cracks out there. A Perfect one is like a 5 leaf clover!

[W8XLR]

My SB-401 was a "labor of love" rig also. It worked fine when I put it away and went QRT for 15 years, but it didnt age well over all that time in the closet. Upon re-activation the rig needed a complete power supply rebuild (including transformer), parasitic choke, and T/R relay (which was a real BONER to change - may yours last forever!) While at it, I fully re-tubed and re-capped just because. The rig still has a minor intermittent with the meter switch, but not annoying enough to change out yet.

The SB-301 required very little to resume service. A good band switch & pots cleaning, a fresh tube lineup and minor tweaks to the alignment was all. I could use a fresh 20 meter crystal, as it has aged and drifted slightly.

Since re-activating "The Heath Twins", they have operated FB for over two years now. I try to work them at least a couple hours a week to keep them healthy... old men need proper exercise! Neither of my dials are cracked, but do have minor crazing. Im not going to touch them, I think it ads character to the veteran units.

Interestingly, I have the original manuals complete with the builders notes. My rigs were built circa 1969 (I Think), by Bill Petlowany/W8KZH (now K6NO). A Google search of Bill's call reveals an intriguing VHF antenna design that he came up with. It looks just like an old style electric stove burner. Bill did fine work on these kits... soldering was perfect!

Just want to ad, I picked up the twins back in '95 at the Portage County hamfester for a budget bustin' $100 bucks... the seller even helped me heft them the 1/2 mile to the parking lot, and also gave me his name & phone # in case of trouble. I had NO trouble!

My, how times have changed!

[N8YX]

For that reason I recently got hold of an FT-301 lineup. It doesn't do FM on 10...but the "C" and "D" ranges are going to get converted to other bands, as are the "AUX" and "WWV" slots.
About that '301: It's a darn shame that Yaesu didn't make a matching receiver for the transceiver. Something along the lines of a Drake R-7 or Kenwood R-820 that would allow the various crystal filters to be selected independently of mode. Something that incorporates an IF width or IF shift control as well as an IF notch. Maybe an all-mode squelch control...and the ability to act as a remote VFO for a companion FT-301.

Well...as luck (!) would have it I won a beat-slightly-to-hell FT-301 on eBay. The front panel could definitely stand a repaint and it supposedly doesn't transmit...the case top is a handmade aluminum job. The rig was acquired for spares - and the hope that an AM filter might be lurking on its filter board.

Nyet.

All of those usable parts...workable VFO and other subassemblies must be good for something, right? That's when it dawned on me: An FT-901's IF strip is very close to the '301's (8.9875 vs 9.000MHz), the FT-901 incorporates an IF Width control (as well as a switchable Rejection Tuning feature) and has an accessory FM board with companion squelch.

Studying the two IF boards - which incidentally are the same form factor; an 18-contact dual-sided card - one sees that the unit of the '301 contains a number of transmit as well as receive circuits. On the other hand, the '901's has control lines for IF Width and Rejection Tuning, squelch and other interference fighting features but no TX-path circuits. It also has an IF scheme that's all wrong: 8.9875 MHz input; mixed with a 19.7475MHz VXO then applied to a 10.76MHz 2-pole filter. That signal is then mixed with the VXO output to convert back to 8.9875MHz and is applied to a 2-pole, 20KHz B/W crystal filter before being converted to AF.

Well. There seems to be a lack of 9.000MHz filters on the open market but there are a bunch of 10.7MHz parts to be had - and Inrad has several 9.000MHz D-I-Y filter kits which could be pulled to 6-8KHz B/W. Subbing a 10.7MHz unit for the OEM filter on the '901 IF board, subbing a 19.700MHz crystal for the VXO rock and installing a homebrew 4-pole 9MHz filter in the post-mixer filter spot ought to net me a usable IF Width control.

More on this project as it develops.

[KB3LAZ]

U need split to work the DXpeditions!

U should see what a good SB dial goes for!!! They are very prone to cracking (I have a whole box full of Cracked dials!) so install the dial with the VERY Gentlest of installation. Any pressure WHATSOEVER will crack the dial. They are more brittle than ICE Sheets! If the crack doesn't go all the way to the edge, you can still use it but you may feel a bump when you pass over the crack in the spiral as you turn the dial. Probably 90% or more SB dials have cracks out there. A Perfect one is like a 5 leaf clover!

I have never used split outside of 2m/70cm, ever.

If DX wants me, it finds me. :P

[AE1PT]

Just ran the Digi-Key order for all of the caps to be replaced in both rigs. Another $75 including shipping...

Each time I do this, it becomes more of a challenge to find component values at or near the originals. As to power supply caps I always go larger and usually higher voltage--but axial lead caps are not so much in distributor inventories. For RF/IF and certain other circuits getting as close to the original capacitance is a necessity as the circuits are designed around the values. Sigh...

This time I am going to do something different. For whatever reason I plan on gutting the existing 3 cans in the 401 and stuffing them with radial lead replacement caps. Then seal the things back up and put them back on the chassis. Just for fun I guess, because I don't really put too much care into "preservation" of everything original in a piece of gear.

I have this SB-650 display thingy which is wicked 70s retro with its little nixie tubes and all--but I am also seeing fools line up on eBay and paying $230-275 for working examples. So the thought of dumping this "Rare and Mint" vintage thing and pocketing $200 bucks is looking pretty appealing. That would cover all of the new component/crystal costs, and even buy one of these puppies:

http://www.aade.com/dfd2.htm

There are some pics around where one can see the display inside of the 1-5 slide rule indicator. Then I would have a completely updated and aligned 303/401 pair for the inclusive original $325 price. Plus all of the fun I have been having getting all of this stuff together and the project that is going to emerge once all the parts are in. That part I can't put a price on--there is nothing else like it!!! Pretty nice to me... :cool2:


I have never used split outside of 2m/70cm, ever. If DX wants me, it finds me. :P

Yup, I feel pretty much the same way about it. The nice thing is that there is something for everyone in this hobby. Chasing DXpeditions is not one of them for me...

[N8YX]

Pat,

I have a metric shit-ton of electrolytics kicking around the shack. Far more than I'll ever use. Let me know some values and types you need and if they're in the stash, they're yours for postage.

[AE1PT]

What I need right now is an LMO...

The one that is in the 303 is all over the place. Starts out right at about 4.9mhz and tracks pretty well to 5.2. Then it drops back to 4.9. A little further up the dial--after this little plateau, and it will erratically climb up to about 5.3, then back to 5.1--where it stays for the other half of the dial.

I spent about an hour taking the damned thing apart. Cleaned the contacts to the rotor. Checked for debris or anything in the stator. Nothing. Reversing the bias for SSB makes no change in the frequency either. TOAST... Not that unusual I find out.

I guess that it's a stupid dust collector for a while now. A google search turned up nothing in the way of any replacements for sale or fix-it deals. Where to start with this?

[N8YX]

I did a quick check on the net for info and found an article by the Zookster. An excerpt:


"Then, check the “stops” on the main tuning shaft. These rotate as the dial is tuned with each stopping at one full turn of the shaft after the last one stopped. Over the years, these “stops” start sticking to each other and the shaft may not be able to be turned through the slightly over 5 revolutions to tune the 500 kHz frequency range (with a few kHz over at each end). Spray WD-40 on these and make sure that the shaft easily turns the 5+ revolutions. Watch the main tuning capacitor to make sure that it mostly opens and mostly closes. The “stops” actually prevent the capacitor from going completely from open to closed.

Putting a knob on the tuning shaft makes turning it MUCH easier! If the shaft cannot be turned the full 5 revolutions, then use a small screwdriver to separate the ones that are sticking. Spray a little more WD-40 on the “stops”. You may have to force the shaft in the direction which the full 5 revolutions would normally be made. Work the shaft “back and forth” until the “stops” break free. Then, run the shaft back and forth several times the full 5 revolutions. If the shaft is still hard to turn, put a little WD-40 on the “worm gear” at the rear of the shaft which activates the gear which rotates the variable capacitor."
If those stops index each 100KHz segment... :chin:

[AE1PT]

I have full rotation across all 5Khz of the LMO--the rotor plates do a full 180 degree circuit through the stator plates. On the off chance that something might have moved radically, I loosened the collar on the shaft and rotated the thing a full 360 around to see if there was a difference in performance. No joy, and set the cam again from low to high. There are spots where the oscillator is pretty stable--although not really what I would want to see in output. Here is the LMO pulled out and fed with a 10VDC supply:

http://ae1pt.com/photos/imh/stable.jpg

Less than a one-eighth turn of the shaft finds one of the crap zones and drops by nearly 500Kc. The frequency begins wandering about erratically +/-10-15Kc, and look at the trace:

http://ae1pt.com/photos/imh/unstable.jpg

[AE1PT]

Persistence pays off. I ended up replacing the 2N706 oscillator with a 123A, and a dipped .001uf cap with a tantalum one. Results? Rock solid and perfectly linear coverage from 4.995Mc to 5.510...

http://ae1pt.com/photos/imh/final.jpg

[W1GUH]

The SB-series is [almost] great. The reason for the "almost" has to do with the solid state LMO's, something to be avoided. AFAIK, the tube LMOs are just fine.

The solid state LMO's have two problems. First, they regularly develop the problem of the rotor on the variable cap losing good contact to the frame. Fixable, I think, but that's a total PITA. Second, the later SS LMO's, the ones that aren't stamped as made by TRW have horrible tracking.

So steer clear of an SB-102 or the SB-303. OTOH, the '303 has a great reputation, so maybe that makes it worth the LMO problems? Dunno -- never had one.

Now for the good news. Some who have put them up against S-Line for electrical performance claim they equal or surpass the Collins, and make a freakin' GREAT rig to operate. Had a '102 and (apart from the LMO problem) I really loved it. Also had a '401 in the early 90's and it, too, was a great transmitter.

You're right about the dial drive mechanism, it can be superb or lousy, depending on how it's been adjusted. That's pretty easy to get right, so that's not a real deterrent. I have heard, tho', that the plastic parts can crack, then you're SOL til you get a replacement. Never had that problem, so I don't know the current state of this issue.

All in all, if it's got a tube LMO & the dial drive seems to be functioning, that'd be a good radio. Hope you find a nice set!

P.S. No time here to read all through the thread, so I hope this wasn't too tediously repetitious!

[WØTKX]

Awesome job fixing that skanky LMO! :clap:

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