#218 

Well, I am sorry you didn't get the job. I have an electrical engineering degree, but I don't have the expertise, talent or skills you have demonstrated in these videos. Thank you for sharing them! I am learning a great deal from you!

That method of installing a tube socket and mounting the caps on a plug is an elegant solution that I never thought of using. Thanks.

Nice work, we will be at Knowledge Fest Thank you for the content

another great video Buddy

That's REAL HP equipment! I'm not at all surprised that even at 67 years old, after just a little bit of TLC, it will still work exactly the way it was designed to. Their innovative use of a "pilot light" as a thermistor in a negative feedback circuit stabilises the oscillator amplitude, and minimises distortion - and this almost certainly helped the 200 series to become a great financial success for the company.

Nice work! I've probably repaired 2 dozen older pieces of hp test gear in my career, and 98% of the time, you just replace the power supply caps and all the bumblebee and black beauty caps and the thing will fire right up.

I like the old test equipment that's easy to work on as long as it's accurate. Please keep up the good work and glad to hear things at work are slowing down for you.

GREAT JOB, looks brand new. thanks. W4GSM

I just tidied up a 202C last week. Came out of a TV repair shop in Athlone. They are a lovely bit of kit, that variable capacitor is a work of art!

Looks like it works correctly. Note: when changing the frequency you see a transient change in the amplitude, not a distortion. The gain of the system is being changed, as frequency is altered by the action of the Lamp. The lamp is not a protection circuit, but rather a clever way of causing the oscillator to have a loop gain of 1 exactly. The tungsten filament of the lamp is in a feed back loop with a bridge circuit. The time it takes the filament to manage the circuit gain when frequency is changed is seen as that slow amplitude change of the envelope as it eventually gets back to the amplitude set point. This was an HP innovation.

Thanks, Buddy, for another great video. I have had this same generator for about 20 years and it is probably about time that I did the same restoration. I appreciate that you went thru it first. It looks to be a very straight forward job. Thanks again for your excellent work! 73 & all the best. Chris, N9WHH.

The HP signal generators are great devices. I have both the new and old chassis. I really enjoy showing young people the radio waves are very high frequency sound you can't hear. Except for my dad he can't hear above 5,500hz which is apparently the frequency my mom talks at.

Nice one👍

What a great job. Loved the idea of using a tube base for the filter capacitors, that looks really neat.

I'm with you, don't like top handles and for that very same reason. You do an amazing job and are a true craftsman! This device turned out real nice. Bummer about the job but also understand about more free personal time! Will contact you sometime in Sept in regards in shipping my next item. 73's my friend! ~Jack, VEG

I love vintage radios and the test equipment to compliment them. Good show. Would like to see more of these.

Nice work Buddy wish I was that talented, thanks for the warning about the volume in the headphones!! 😀

Hello Buddy ! That project turned out to be a nice older HP audio oscillator!! The older HP stuff was built like a tank physically, and they were designed electrically really well too!!

Another fine restoration by Buddy! Great job!

Very clever cap substitution, nice video

Glad your working situation still suits you fine. Looking forward to many more videos as you get the chance.

Thanks nice job love the brown wrinkle finish and that tube plug cap idea is fantastic and clean and neat.

Ahh the 200ab brings back memories. I used to work with the 200cd mostly. Both are good work horses and quick and easy to calibrate or repair

Beautiful restoration of that quality equipment. I enjoy your videos even though I basically know nothing about electronics.

From Corning NY, “you’re amazing!”

Another excellent video Buddy. Good job in the old HP osc. I like your tip with the "sawed-off toothbrush" to scrub the really bad smudges. Thanks for sharing it with us. 73 DE K7RMJ Frank

Enjoyed it, Buddy. Glad you’re happy at work. I hope your “old” job remains secure as the new people come in. I’d hate to see you shortchanged there. Looking forward to more frequent videos. I like your practical approach. I just bought an Apache/Mohawk pair that I think are unmolested originals. I’ve already reviewed your related videos. Thanks for all you do.

That is a great audio generator, you did a great job on it Buddy

Great job Buddy. When you replace those banana jacks it will look almost new. You train the new boss and all will go well.

Glad to see that your situation at business went into the right direction - yes the world is crazy today in many respects. And I´m happy to see your new videos!

Sorry you didn't get the promotion Buddy, Glad we'll be seeing more of you on here though! Great restoration video!

The lamp in the cathode of the first vacuum tube is to regulate the amplitude of the oscillator. As the amplitude increases, the filament resistance increases as it begins to heat, reducing tube gain, and keeping the amplitude reasonably constant.

Great in depth video. I restored my 200 CD some years ago, tho I didn't go to the lengths you did. My fine adjustment assy was frozen. Once I got it freed up, I was amazed that the spring loaded bakelite knob was machined perfectly to engage and fine tune the back of the smooth metal dial with no other gripping material, rubber, cork etc. That's when things were built to last! My current issue is the sealed 2 gang output pot is crappy and intermittant. I'd like to get that fixed someday if I can find a suitable replacement. Probably should re-cap it as well, but it is still working great.

A new video from the Radio Shop. Cool! As usual, your approach to getting this unit back on-line is super. I am wrestling with an EICO audio generator and can't seem to get good looking signals. Next stop is to replace a few resistors in my unit. I also noticed an HP 200AB on eBay right now and have placed a bid. Here's hoping. Thank you for sharing your systematic process for restoration.

Well Buddy ....a very nice vid. as usual we learned a lot watching you. thanks for the show.

Beautiful restore work Buddy. I've learned much from you and I thank you. HP quality shows through the entire generator. Glad the job situation is working out. Hopefully, you will have more time to "play" in The Radio Shop.

I feel for you because the same thing happen to me at work. After the new guy got the job I was told to do his work for him to make him look good. I think you know my answer. I made his boss do his work. Any way glad to see you doing what you like to do.

This answered so many questions for me, i just purchased my first test equipment ascillator, i assume its going to be relatively dirty and need a little bit of work

I have the same oscillator great video

Well done, looks and works great. I had one for years. But, too large for my workbench so went with a smaller solid state unit. 73.

Nice job. 👍 HP quality shines through again. I believe the 200AB is dates from 1952. I have an HP 202C (from c1959) in my queue. I have already replaced the leather handle. I take your point about stack-ability of instruments but I don't like to stack anything on top of tube equipment because of the heat.

Sorry you didn’t get the job Buddy but it might be for the best. I had a similar situation happen toward the end of my working career (I’m retired now) but in my case I got the job. It turned out to be the worst experience of my entire 29 years with that particular company. Looking back now I wish I hadn’t gotten the damn job. But enough about that. I want you to know I really enjoy your vids and admire your skill and pride of work. I’m looking forward to seeing what’s ahead now that you’ll have more time to entertain and educate us. Keep ‘em coming!

If you look at en.m.wikipedia.org/wiki/Wien_bridge_oscillator you'll see that the bulb is used to stabilise the amplitude. It takes a bit of time to work, hence the amplitude variations when changing frequency but it soon stabilises.

Nice work Buddy. It was my impression that the last 20uf you replaced was meant to be a non-polar cap. A few HP 200cd that I repaired in the past I used a non-polar cap in that part of the circuit. I guess I could have gotten away with a regular electrolytic.

I've got one of those, from my father in law.

Good for another 65 years Buddy. Well done and still a very useful piece of gear today. I wonder if you put the old can caps on the leakage tester. I would be curious as to just how good they were. 73 Doug.

@24:00 nice solution for the cap.

Nice old unit. lots of room under the hood.

The layout is certainly cleaner than in my Eico 377. The 377 uses a 6SJ7/6SK7 as the oscillator. Interesting that it has a push-pull output.

Sounds like the job situation worked out for the best for you. Glad you are happy with it. I just hope you don't wind up doing your new bosses job for him, but I don't think that will happen.

Good to see you back, Buddy! Happy to hear you're happy with the work situation, and looking very much forward to new episodes and electronic adventures. I was getting withdrawal symptoms already! Tried to email you (both addresses) but I think your email is swamped, or I inadvertently ended up in the bit bucket. I had some questions about acquiring equipment. Have a great day and take care!

Hey Buddy, as always very nice, W4GSM Dave.

I guess you would need a frequency counter to use this signal generator to set it to 27.185 for example. To see where your at exactly. I have a frequency counter that I need to fix its a BK I have never opened it. Was wondering what it needs capacitors probably. Thanks for this interesting teaching video.

Great repair and restoration Buddy. How flat is the signal amplitude across the ranges?

Great job Buddy.. Hey.. Looks like you could do with a Sonic Scrubber like mine 👍 LOL 😃 Cheers friend John

Nice repair there Buddy, do you recommend spraying the dial with any coating to preserve it or will the ali dial be OK as it is?

Great job Buddy! That HP dial "sound" as it turns is to typical, sounds just like the dial on the HP distortion analyzer I picked up lately. 73 - Dino KL0S

Hi Sir, thank you for all your great videos really enjoy watching them. Couldn’t help but notice the low frequencies amplitude modulation at around 34m 7s mark. I recently restored an Eico 377 tube audio generator and suffers from the same amplitude modulation up until 180Hz and after that the amplitude is nice and stable. It is worst at just above and below 60Hz but very stable right at 60Hz. Do you happen to know if this is normal or what causes it? Also, glad to hear your job situation will get better and hope you don’t stay up until 2am finishing up a video. My hat off to you, you’re a hard working man. Sorry for the long post.

good unit i owned one

Great job on the restoration The old HP audio generator looks Great !! Keep the video comming Tks KM4KYA

Outsourcing - I can tell you some stories. 5.5 years in college and university, only to schlep bananas and cabbage at Walmart. Who says life is fair.

Nice Resto Buddy. Great Video as always. 73 KN4IFI

You mention at 6:58 that the lamp is there to protect the oscillator. As Hector Pascal mentioned, the lamp acts as a thermistor to stablize the amplitude of the signal. It adjusts the gain of the oscillator so it operates linearly without clipping. This gives a very low distortion signal (much lower than you'll get from the function generator visible in the background). There's more information about this design on Wikipedia: en.wikipedia.org/wiki/Wien_bridge_oscillator

Hope that's on a future give away.....hint...hint...

i wood make that into music

Great video. Would like to have watched you do a calibration to round out the restoration. I have one with three of the rotating plates on the main tuning capacitor slightly bent, throwing off the outputs. Looks like someone reached in and squeezed the end plates together on two sections. Is there a way to accurately readjust the plate seperation? After 50+ years in the work force with no college, you tend to see the good, bad and the ugly side of management. Glad to see you survived the ordeal and happy with the outcome.