Heathkit SG-8 Signal Generator
 

Hello everone I just bought on fleabay a Heathkit SG-8 Signal Generator that I intend to use to help me realign the radio that I restore, the unit itseld is in near mint condition, but the unit doesn't have its original probes with it anymore and it doesn't have its manuals anymore either.

I was wondering how hard it would be to source some probes for this unit or to make some, and if I could get a manual for this thing online somewhere?
Would also like to know how to use one of these with radio alignment.

Any help would be appreciated.

There is a little thing called "Google". You ought to try it sometime.
http://pdf.textfiles.com/manuals/SCA...thkit-SG-8.pdf

The connector used on that unit are what was known as microphone connectors. The end that goes onto the cable end can be found but a better solution is to replace the connectors on the generator with BNC jacks. There are even pre-made cables with BNC plugs made. I believe that the stock cables were coax with alligator clips on the other end.
There are a number of sources for general instructions on AM radio alignment. Usually the service data for each radio gives further details.
Most of the time you can connect the generator cable clips to a small coil of wire (4-6 inch diameter) with something like 8-10 turns. This coil sends a signal to the radios antenna loop. Some radios don't have antenna loops and the coupling is done another way. Sometimes the signal is injected into the radios IF circuits various ways.
I recommend a book like this one.
https://www.amazon.com/Old-Time-Radi...s=books&sr=1-1

This is the type of BNC jack you could replace the microphone connectors with.
https://www.mouser.com/ProductDetail...zdb4bk0FGlA%3D

Yeah, I ended up finding the manual after someone on the Philco Phorum told me about it, (I wrote this thread before I saw the reply on the Philco Phorum).

Anyways I also bought a Radio City Products Model 705A Signal Generator that also needs test leads and a manual.

Although I'm kind of regretting asking about those signal generators on the Philco Phorum because the person who replied to my thread on there is trying to make me feel bad about my purchases by telling me that they are going to be crappy and telling me that I should of instead bought a Hewlett-Packard one instead (even though I could never afford to buy one).

Well the Heathkit doesn't have a very nice sine wave output but it usually does not matter. The SG-8 like many generators used for radio-tv repair are what is known as "service grade" as opposed to "lab grade". A sinewave that doesn't have the right shape has harmonic distortion. That means that a 1Mhz output also could contain 2MHz, 3MHz, 4MHz, 5MHz, etc. Many times just the odd harmonics. However the tuned circuits in a radio-tv reject the harmonics for the most part, so they don't really matter in practice.
Also the service grade generators do not keep the signal amplitude the same as you change the frequency. However you can monitor the amplitude if you need to and adjust the amplitude as you change frequency. Maybe not as convenient, but you can make it work. Most of the time you don't change the frequency that much anyway.
The frequency dials on service grade generators are not as accurate so if you must have the frequency exact a frequency counter is a good addition to the set-up.

That's what I thought. The guy on the Philco Phorum basically said the same thing. But the thing is, I'm just repairing old tube radios and stereo receivers so lab quality gear like the Hewlett-Packard units are not what I need.

I just need something to get me close enough to make the radios work again as intended, it's not like I'm designing new radio circuits where you would need something like a lab grade unit for.

Most of the units I'm repairing are units that are already working circuits but just need to be touched up, so a regular bench grade unit is more than enough for the work I'm doing.

I've gotten working 70s HP gear for under $10 before. It is all a matter of being in the right place at the right time.

Some many service generators are inaccurate enough on frequency that if you don't have a frequency counter to check them they can sometimes mess up alignment. Some frequency counters will get confused if the carrier is not sinusoidal enough. My old lab grade generators lack modulation capability (which is important for some alignment work) so I calibrate my service grade generator by dialing the lab gen to the right frequency on the counter, connecting the lab gen to my scope, counting the time divisions with 1-3 cycles on screen, then connecting the service gen and dialing it for the same number of time divisions.
If you haunt enough big ham radio swapmeets you'll eventually have enough decent budget equipment.

Well the problem is, there are no swap meets near me, and trust me, I've already checked, the closest ones to me are in Indianapolis, and Chicago, and I don't want to drive to those areas because they are horrible to drive around.

The cheapest Hewlett-Packard signal generators on eBay are $150 and $50 shipping, there's no way I can afford that on my meager budget.

Fort Wayne?

http://fortwaynehamfest.com

jr

That's another city I'd rather not drive around in because traffic is terrible there and my mom doesn't want me to drive around there unless someone is with me for the reasons I mentioned.

Plus activities like that are canceled until further notice because of the corona virus.

It is great that HP equipment is more affordable now. I have some myself and I don't usually spend a whole lot on things. That being said, you have to keep in mind that a piece of HP test equipment built in the 1950's will require re-capping just as a radio or TV from that era. HP used very high quality parts so they hold up better than others, but there are limits on how well anything lasts. Solid state test equipment made more recently are less likely to need restoration before they can be used. Repair shops in the 40's through the 70's seldom had HP equipment.
There are brands that fall between HP and say Heathkit in precision. Heathkit items are very easy to work on since they were intended for assembly from scratch. There are service grade brands with better performance that are factory built but are simpler than HP. B&K, RCA, EICO, Sencor, Leader and Tektronix, etc.
Here is my modified SG-8. My B&K 2005A RF generator and HP 5382A frequency counter. Also my Leader LAG-27 audio generator, a home-built 455KHz generator and my RF coupling loop. I think I found the SG-8 locally on Craig's list. The others were very carefully selected form ebay. The B&K RF generator had some broken front panel pieces (poor packing) that I was able to glue back together. Except for the SG-8 the equipment shown is solid state, but I think I replaced the electrolytics in all of them.

OK, thanks for the info.
I'm just curious, how do you hook up a frequency counter to a signal generator if I got one?

Good question. That points out a bit of a problem normally. The output of a typical RF generator is very small. It only takes something like 10 uV ( 10 one millionth of a volt) of signal at the radio antenna for the radio to receive it. The problem is many frequency counters need something like at least 100 mV for them to work. One thing to do is turn the generator output up to max to read the frequency and then turn the output down before connecting to the radio. Another thing that sometimes works is to modify the generator and bring out the signal before it goes into the output attenuator to a separate connector. The B&K 2005A has this already done. It has the normal output connector that the amplitude can be varied and a frequency monitoring output connector. Some people have bought small frequency counter modules and install them in the generator if there is room. I don't think the modules have a very precise timebase oscillator in them however.

It the counter is microcontroller based and has a crystal osc it can be very precise.

Depends on how good the crystal oscillator is more than anything. You get what you pay for.

Unfortunately I can't seem to find any frequency counters on ebay that are under $100 except for the cheap Chineseum kits, but they don't have a case and they require a 9V battery to operate and use a WiFi Antenna style input plug, and they don't seem to have any sort of adjustments on them like the factory built ones that are going for over $100 and as much as $25,000 for a Hewlett-Packard Agilent model from the 1970s...:sigh:

Oh my. You need to sharpen your ebay skills.
Search on "frequency counter", select "pre-owned" and something like a max of $ 50. I saw at least half a dozen decent ones, even a HP or two. Out of those you have to look at the shipping costs and add that to find a total below $100. Some of the remaining have technical factors like a minimum of 20 MHz that disqualifies them. That might only bring it down to one or two or so. But if none look right you may have to try again in a couple of days.
You want to get one that covers the frequency range you will be working with, for broadcast AM maybe 10Hz to 2 MHz, Shortwave 10Hz to 25MHz, FM 10Hz to 120 MHz or TV 10Hz to 250 MHz. BNC input connector. You may have to do some research, you definitely want one with a crystal timebase oscillator, usually 10MHz. Hopefully you will have the time to run it past the forum for opinions.

Well I don't use eBay on a regular basis which is why I'm a little rusty with my eBay skills.

I'll search again using the tips you suggested and see what I come up with.

Thanks so much for your help.

The units linked below are some units I have found that are in my price range that seem like decent units.

https://www.ebay.com/itm/Heathkit-IM...temCondition=4

https://www.ebay.com/itm/Elenco-F-10...temCondition=4

What do you think?
I'm leaning heavily towards the Heathkit unit, as its cheaper and it does cover the basics as far as all the frequencies I would be using in radio and TV repair goes.

Those two are about equivalent. The Heathkit has a upper frequency limit of 30 MHz. I found a manual online.
The Elenco has all those switches so that might be a source of problems (cleaning etc.). I could not find a manual after a quick search.
So if 30 MHz is OK ( for AM Broadcast and SW radios I think it would be), then if I had to choose between the two I would go with the Heathkit. You wouldn't be able to check the frequency of a generator that is producing a signal for a FM radio (88-108MHz) for instance.

There were a couple of multifunction frequency counters that tested upto 250 Mhz or something like that that were Hewlett-Packard branded ones that were under $40 but they were listed as "as-is" untested condition.

https://www.ebay.com/itm/Victor-VC31...temCondition=4

https://www.ebay.com/itm/BK-Precisio...temCondition=4

https://www.ebay.com/itm/HP-5382A-SI...temCondition=4

Here's 3 frequency counters I have found including a Hewlett-Packard 225 MHz unit that is only 29.99 but the shipping is $64, which is twice the price that the unit itself costs! :thumbsdn:

OK, something very important here. You want to get something that you can find service data on. Units like the Elenco that you can find nothing about (except if they have a manual with them that has the service data) are not a good choice. If something goes wrong with them, no one is going to be able to help. That was a good thing about the Heathkit.
The Heathkit counter would be a good companion piece to the SG-8. The SG-8 upper band (E) doesn't work well on my unit. The amplitude is very low if it works at all. The next lower band ends at 25 MHz which matches that counter. Unless you are sure you need more frequency range, that would do.
The HP is gone now. You don't have a lot of time with ebay to decide.

I got the Heathkit Signal Generator today and it looks like its not going to need a lot of work done to it, in fact it looks like it was hardly ever used, it does have modern film caps and modern electrolytics in it which makes me think that it may have been recapped already.

pictures below are of the inside of the unit.

You'll see how clean it is inside and you'll see what I mean by having modern components inside.

I think that someone did it already for you! Unless there was a wiring error, you should be good to go.

That's what I was thinking.

All I need to do is just change out the jacks for modern BNC jacks and get some probes for it and I'll be all set! :yes: :thmbsp:

Does the name David Hamm sound familiar to you guys? He's the guy I got it from, he out in Marion, Iowa which I believe is Eastern Iowa.

He packed it really well it was packed in several layers of thick foam packing and then wrapped in a couple of plastic bags to protect it.
It arrived in one piece with the only thing that happened to it in shipping was that the front of the case popped out of the back cover but easily popped back into place without any damage. :thmbsp:

You know I thought you already had the SG-8.
Great that it has been re-capped. I'm not sure the selenium rectifier was replaced correctly.
Are you going to get the Heathkit IM-4100 ?
The manual I was able to find on the counter seems to be missing some pages at the front, but the service data is all there. There are also some videos about the counter.
Just so you know, a couple of years ago it was easier to find good info on Heathkit units. A company bought the rights to the info, I believe, and now charges for the manuals. There are still some copies still left here and there on the internet.

No, I had just bought it on ebay at the time but it hadn't been delivered until today.

As for the frequency counter I do need one that can do the FM Bandspread because I do Work on AM/FM Stereo Receivers as well.
So I will need a frequency generator that can do at least up to 200 MHz.

What do you mean the selenium rectifier wasn't replaced correctly? I think its original to the unit, which I'm thinking of replacing it with a 1N4007 Diode.

https://www.ebay.com/itm/Victor-VC31...temCondition=4

https://www.ebay.com/itm/Heathkit-Mo...temCondition=4

https://www.ebay.com/itm/B-K-Model-1...temCondition=4

Here's 3 more I've found that look promising, neither of them have a power cord though, specifically the last two, which uses the old style computer plug.

what do you think? Which one would be the best out of these 3 units?

I don't know anything about the Victor brand.
The Heathkit is older because Nixie tubes were used before LED displays were used. Also the corrosion on the BNC is not a good sign,
My first counter was similar to that B&K. The display on mine became unreliable, I believe because of a connector issue. My model didn't go very high in frequency so I decided to trade up.
Note that both the Heathkit and the B&K used a power cord connector with
round pins, unlike the common power cords now which have flat blades.
I not wild about any of those three.

Apparently some restorers connect a Si rectifier diode across the selenium one without disconnecting the selenium. I even saw that in a book about radio restoration. It isn't a good idea because the old rectifier can leak reverse current.Since your generator had been re-capped I thought that might be the case.

Well that Hewlett-Packard one that that I previously Posted about that's like yours is still available, I'm just not too keen on having to pay over $60 for shipping on an item that's only $30, I'm not even quite sure why that the shipping on that is over $60 when other frequency counters that are similar in size and traveling a similar distance to get to me have only $10-$15 shipping costs.

In some cases that is the difference between packing it to survive shipping abuse, and just throwing it in box loosely or in the case of a friend who bought a used BT modulator off eBay throwing it in a plastic bag with a shipping label pasted on....but then again some sellers try to profit off the shipping if they can't get the margin they want on the item it's self...

It has no silicone diode going across the selenium in this unit, its just the selenium rectifier.

I agree about packing things well so that it doesn't get damaged but that doesn't require a $60 shipping charge though, my Heathkit signal generator had a $20 shipping charge and it was well packed and survived the trip undamaged, and the packing job that was done on that didn't require no $60 shipping charge, I think that person is just trying to cover his butt because he probably isn't going to pack it well.

Isn't there a way that you could change the power cord plug-in on the back of the B & K unit so that it fits a modern PC Style plug in? If so then I would think that the B & K unit would be a fine alternative to the Hewlett-Packard one that has the rediculous shipping charges.

https://www.ebay.com/itm/Heathkit-Di...temCondition=4

I just found a Heathkit SM-2420 512 Mhz Frequency Counter on ebay buy it now price of $24.99 and $27.99 shipping costs, and it has a hardwired cord rather than an old school style computer cord.

OK, so I just figured out that by reading the manual for the Radio City Products Signal Generator I'll be getting, that it actually has a hookup on it that can be used to hook up a frequency counter and monitor the frequency.

So the RCP unit might actually be a better unit than the Heathkit one in this case. :thmbsp::yes:

There are three different in compatible old style 'computer' power cord receptacles in old test equipment (somewhere here I posted a picture of them). They range from somewhat common to 'OMG this is the only cord for this I have ever seen' my Heathkit Nixie DMM had the later and I needed the cord for a much rarer Sony Badged Setchell Carlson monitor so I converted it the DMM to use a modern computer power receptacle(IIRC pirated off a dead PC PSU)... I had to enlarge the case opening with a file but it was easy enough to do....I could have converted it to a hard wired cord too but I wanted it detachable for convenience.

There's always a way to power something with a weird 120v power receptacle...I keep a cord with insulated alligator clips around specifically for portable TVs with weird proprietary jacks for Missing power cords....

That's all I needed to know, I might just go for the B & K unit then because its will only come out to a little over $40 including shipping and taxes.