Thoughts on Heathkit Equipment?

[David G4EBT]

There's very little to the AF oscillator section, which uses few components and the triode section of V2 - ECF80.

I've attached the relevant parts of the circuit.

The one that was subject to my BVWS Bulletin Article has since gone to another forum member. The audio frequency of that one was 308 Hz.

I do have two others, one on which I've just made a few small improvements which I'll refer to in a new thread. If I get chance tomorrow, I'll check the audio frequency of both of those just out of interest. I took the last two pictures today as I'd been doing some work on my 'scope and fixing a fault on my Robin Frequency Counter, designed by the late Mike Rowe of 'Sussex' valve tester fame. (Shocked when I took the lid off it to see that I made it back in Feb 1995. 26 years gone in a flash!).

I think someone said in post that they weren't too impressed with the modulated waveform of the RF1U. It looks OK to me.

[wd40addict]

Trigger the scope from the 300Hz and feed the modulated RF into the scope and slow the timebase until you see the modulation envelope.

Attached are three traces for comparison:
1) Heathkit RF-1u
2) AVO HF135 (modified)
3) HP8648B

[Radio Wrangler]

Those are just running 30% mod. Life gets more difficult when you want 80% to check receiver distortion. That's the difference when you want a sig gen good enough to test that a serious receiver is working to spec. Any of the three will do for a functional test and finding where a signal chain is broken.

David

[OldTechFan96]

Here is the output of my generator. A lopsided sine wave and a funny looking modulation envelope.

If the sine wave is not right I imagine that will have a knock on effect on the modulation?

The sine wave from David G4EBT does look quite good.

[wd40addict]

In 1970 Heathkit issued a change note to change R8 from 100k to 330k, this would reduce the depth of modulation. My apparently 1969 unit doesn't have this change. My unit also has a 3 core mains cable with a decent compression grommet.

Looking at the spectral outputs of the 3 generators from #42 is quite a surprise, the AVO has the most unbalanced sidebands!

1) Heathkit RF-1u
2) AVO HF135 (modified)
3) HP8648B

[David G4EBT]

To answer couple of comments:

firstly, post #39 re the frequency altering when switched from internal to external modulation. I've checked mine today and it doesn't change.
See first pic below showing the counter frequency with the switch in internal & external external positions.

Secondly, regarding the modulation envelope referred to in posts #42 and #44, please see the second picture. It looks OK to me, and it's not something I've ever bothered to check before. My test gear needs are modest, as befits my limited technical knowledge. My scope is an old Hameg 203-7 which I bought from a fellow forum member for under £20 with some minor faults as a back-up for one I bought on eBay some years ago.

My frequency counter is the PW Robin which I built in Feb 1995 and give sterling service.

This particular Heathkit RF1U is one that I bought at Barnsley radio rally in 1989 for £7.00, which I guess equates to about £20.00 today. It meets all my needs for aligning domestic radios. I enjoy making little bits of homebrew test gear and though I don't make a virtue of eschewing expensive and complex 'famous name' test gear, nether do I hanker after it as I have no need for it. It's not because I'm stingy or strapped for cash - its just that the cost/benefit doesn't stack up.

I guess I'm a product of my time. My formative years was a life based on mottos, sternly dispensed by our 'elders and betters' - 'cut your suit according to your cloth, make do and mend, waste not want not, 'I want' doesn't get, a fool and his money are soon parted, don't make a rod for your own back' and so on, ad infinitum. As a kid, you think it goes in one ear and out of the other, but it doesn't - it lodges in the deep recesses of your mind.

The downside is that it creates a mindset which may lead to me spend a fruitless morning to strip down a faulty 20 year old toaster which I could replace for under £20 from Tesco. Then when I conclude that it's irreparable, saving the screws and the flex 'in case they'll come in useful, (like the elastic bands that the postmen drop on the pavements).

As to the original question of whether Heathkit is of a laboratory standard, I've no idea if Heathkit made such exaggerated claims at the time, but realistically, a kit of parts which can be put together on a kitchen table by someone with little or no technical expertise, simply with the aid of a copiously illustrated detailed assembly manual, is clearly aimed at the hobbyist market, into which I fit fair and square.

I have another unloved RF1-U in need of attention, to keep me occupied.

[Boulevardier]

Following from posts# 41 &44, these are waveform from my RF-1U at 465 kc/s. The frequency of modulation is about 720 c/s sine. Something up with my phone - very poor focus on these, but hope they're good enough.

Mike

[vidjoman]

In their day these were affordable by an enthusiastic amateur. They were as good as most other similar parts on the market, in fact the range of equipment available from them was much larger than anywhere else. As a ‘kit’ they were also free of purchase tax. I had several audio items and they worked very well.

[ms660]

Originally Posted by Radio Wrangler

Those are just running 30% mod. Life gets more difficult when you want 80% to check receiver distortion. That's the difference when you want a sig gen good enough to test that a serious receiver is working to spec. Any of the three will do for a functional test and finding where a signal chain is broken.

With my basic signal generator I just used the external modulation facility....

Lawrence.

[wd40addict]

I think David G4EBT wins the prize for nicest envelope. Is your R8 100k or 330k?

[David G4EBT]

I both the one I've posted about in this thread, and one that I restored and sold to another forum member, R8 was 100K, as it is in one that I have which needs restoration. I've done little to the one that I've posted about - just checked the resistors, which apart from two were in tolerance and it still has it's original Sentercel C2D selenium rectifier which gives the required 160V DC output. However, on the one I restored the rectifier needed replacement and several resistors which were out of tolerance, notably:

R33 (33k): was 41.2K (+24%)
R4 (10K): was 12.6K (+26%)
R11 (330R): was 460R (+40%).

They may not have had much of an adverse impact on performance, but it was no hardship to replace them.

There are some other things I could say about RF1Us on the rectifier replacement and other small improvements, so given that this thread is not just about the RF1U, but about the wider aspects of the Heathkit range, which we know was quite vast over the many years of the company's existence, I'll start another thread about the RF1U.

[wd40addict]

To go back to the wider range I have the following in regular use:

AG-9u - Audio generator
AV-3u - AC millivolt meter
C-3u - RC Bridge
IM-13u - Valve Voltmeter
IM-48 - Audio Analyser
IM-102 - Nixie DVM

And make use of the following less frequently:
IM-58u - THD Meter
IP-20u - Power Supply
MM-1u - Multimeter
MSP-1 - HT power supply

None of it is Lab quality (although when it was new the IM-102 might've just qualified), but for hobbyists like us it's still good useful equipment. Easy to fix and modify to improve performance / usability.

[HECTOR63]

https://www.schematicsunlimited.com/h/heathkit

I Came across an old thread this morning which I think was posted a while ago possibly by David about a site that had an amazing list of Free schematics so I looked up Heath kit and thought this might help on this thread, plus its a fabulous source of others info's aswell

[David G4EBT]

Closer to home, the Heathkit Data Archive on this forum, recently updated, can be found at this link:

https://www.vintage-radio.net/forum/...d.php?t=174460

[Ted Kendall]

There seems to be a lot of hindsight here. Heathkit was good stuff in its day - Dad built a lot of it - the IG-18 audio generator, the IG-37 stereo generator, the AR-2000 receiver to name but three. Granted, the stereo generator wouldn't accept external mod, the audio genny was greatly improved by buffering the meter circuit, and the 2000 wasn't the last word in compactness, but they were nicely presented and effective bits of kit when properly assembled. I built the FET voltmeter and the Severn transistor radio, both of which worked well.

[avocollector]

I have a large amount of Heathkit test equipment that I started collecting about 10 years ago as they were appearing on local auction sites very cheaply and I found them appealing. I think the most 'shocking' one was the small signal tracer with the magic eye and speaker which had a innocent looking 'noise' switch on the case. Turn it on and 90v+ve appeared at the tip of your hand held probe!! Of course with no instructions (long gone) it would have been a bit of a surprise BUT fortunately the one on my tracer was dicky and did not work. I still have one of their unbuilt kits for a VTVM I must make up some time.

[mole42uk]

I have a CO-1015 Engine Ignition Analyser which I built from an un-touched kit about ten years ago. It is very temperamental, sometimes it works but many times it doesn't. It locks to the mains 50Hz and uses that to time the display on a CRT but there is a fault on the trigger circuit (ISTR, it's been a few years since I touched it) which is both persistent and intermittent.....

High quality components throughout, the usual superb assembly instructions, but I suspect there might be an issue with converting the 60Hz prototype to a 50Hz model.

[wd40addict]

Avocollector, I have an unbuilt IT-12 signal tracer. One day I will build it and reduce its value to 10% of what it is at the moment!

[Andrew2]

Originally Posted by David G4EBT

The downside is that it creates a mindset which may lead to me spend a fruitless morning to strip down a faulty 20 year old toaster which I could replace for under £20 from Tesco. Then when I conclude that it's irreparable, saving the screws and the flex 'in case they'll come in useful, (like the elastic bands that the postmen drop on the pavements).

Oh what a relief, it's not just me! Yes to the above plus a drawer full of misc bits of metal, brackets, grommets and spacers, plastic 'things' which I'm sure will one day be very useful for something. Cardboard tubes, especially the super-sturdy ones that come with Bacofoil on them. Must keep, you never know...

[Boulevardier]

Originally Posted by Andrew2

Oh what a relief, it's not just me! Yes to the above plus a drawer full of misc bits of metal, brackets, grommets and spacers, plastic 'things' which I'm sure will one day be very useful for something. Cardboard tubes, especially the super-sturdy ones that come with Bacofoil on them. Must keep, you never know...

Me too! A shedful of things that it would be criminal to throw away, but that will almost certainly never get used.

When I read David's comment about elastic bands on the pavement, I also thought "it's not just me then!". When I pick them up I always look over my shoulder to make sure no one's looking, but I haven't bought, or lacked, an elastic band for many years!

Mike