Let’s Build A Heathkit Stereo Pro-Series Preamplifier • P2

In this video we begin assembly of our 40-year-old, NOS, unbuilt Heathkit preamplifier. In part one I told you about the history of Heathkit’s pro-series components, we unboxed the kit, and tested many of its components. In this multipart series, we’ll build, fully-test and demonstrate the preamplifier. Also tips on how to solder, and how to remove flux rosin with TechSpray Solder Remover pen and MG Chemicals Safety Wash.
#electronicsrepair #stereo #stereorepair #preamplifier

[@cdavidhord]

19 minutes and 6 seconds-OK-give us the real amount of time spent for the sub assemblies and video editing. I want to give you the full appreciation you deserve!

[@FluxCondenser]

Dave, just the fact that you wrote that tells me you appreciate the time put into making these videos. As always, thanks for being a great supporter of the channel.

[@fabieneldridge3414]

LooksGreat ! Can’t wait to hear!

[@mdd47]

This thing should be incredible. Independent left/right tone controls with variable turnovers.....cartridge matching....variable loudness.....variable high and low filters.....two attentuation settings. This is like a tweaker's dream, I gotta get my hands on one of these things now.

[@FluxCondenser]

It really is quite a preamp. Looking forward to getting it built and testing its performance on the bench. I'll be doing some listening tests with an excellent MC cartridge as well. Stay tuned.

[@rogersellers493]

I have four, Heathkit AP-1800 preamplifiers and all of them have a three position switch for the tape monitor. The parts packer must have just made a mistake in packing this kit. I enjoyed watching your build of a NOS AP-1800. I miss those days of getting the new Heathkit catalog and wondering what new kits would be offered. I have a complete Heathkit Pro-Series rack system. Every piece pictured in the two catalog pages you show, in addition to the AD-1309, white and pink noise generator, the AD-1308 spectrum analyzer, an ADC, Accutrac 4000 turntable (Heathkit offered the same turntable under a private label agreement with ADC, but I don't have the Heathkit version), a pair of the AE-1705 equipment racks, plus a pair of AA-1600 and a pair of AA-1800 amps and even a copy of the Heathkit catalog you picture. All that equipment is attached to a pair of Heathkit AS-101 speakers. Every piece is still fully functional and I enjoy it all on an almost daily basis. I also have an unbuilt AD-1308 spectrum analyzer kit and an unbuilt AR-1650 AM-FM, stereo receiver kit. I have been struggling to decide whether to build these kits or continue to save them. At least so far, they are still unbuilt. I was also lucky enough to purchase one of the original prototype AA-1800 amplifiers from a person in Benton Harbor, Michigan. It had belonged to a person who went to school with a former employee and kit designer at Heathkit back in Benton Harbor. I also have lots of other Heathkit audio equipment going back to the A-7 and A-9C tube amps offered in the mid to late 1950's. Lots of Heathkit test equipment as well. Ah......... the good old days!

[@FluxCondenser]

Roger, thanks so much for visiting and sharing your incredible experience with the Heathkit Pro Series components and others. What a treat it must have been to build that system and what a treat it must remain to be able to still listen to it today. Even a pair of AS-101 speakers! I was a young teenager when the Pro Series components were introduced, so I largely missed the Heathkit-building experience due both to my age and the expense. So now when I come across these unbuilt kits, it’s hard to fight the urge to not build them! I have a lot of vintage equipment to choose from, but lately I’ve been listening a lot to the AP1800 with a McIntosh MC2105 amp I restored and B&W Series 3 802 speakers. When I listen, I have no regrets that I didn’t keep the kit as a bunch of parts in a box.

[@PrimeHiFi]

Fantastic build series. Thanks so much for sharing. Looking forward to part 3! PS: I also use Cardas Quad Eutectic solder. Best I have used by far!

[@FluxCondenser]

Thanks for watching and taking the time to comment. Glad to hear people are enjoying the series. Yeah, that Cardas solder just makes soldering so pleasant. I tried, really tried, to make lead-free solder work for me (in one of my earlier videos I said there was no reason to not use lead-free and told holdouts to “get over it”). It did work fine, I suppose, but it’s harder to work with, never looks as good, and I didn’t have the faith it would hold up as well and not lead to cold-solder issues down the road. I’m a sucker for perfect-looking, shiny-happy solder joints.

[@PrimeHiFi]

@@FluxCondenser Couldn't have said it better myself. I have never had luck with lead-free and I don't think I ever will. It's just the name of the game.

[@jimdavis6833]

I was hoping to watch you actually build it. Speeding through it was slightly disappointing to me. BTW, if someone hasn't already told you, the little red thingy is a nut starter. The manual will tell you that. I've built several Heathkits including a GR900 and GR2001 TV W/Programmer and remote plus clock. Also a couple of scopes and the IT-28 as well as the IT-21 Tube tester. I loved doing them. My 1st encounter with Heathkits was in an Amateur radio club in the late 50s. We built a SSB transceiver but all these years later I don't remember the model. Keep up the good work.

[@FluxCondenser]

Thanks, Jim. Yes the nut starter tool was addressed in subsequent videos in the series. Sorry you were hoping to see this built in real-time, but that’s just not practical within the constraints of KZbin, at least as far as I’m concerned. Thanks for sharing your experience with Heathkit. I always enjoy hearing those stories. Good stuff!

[@1834RestorationHouse]

Denatured alcohol and a brush is a fast way to clean the PCB.

[@sguttag]

Very enjoyable! I'm an old Heathkit builder myself. I must admit, I don't recall getting much in the way of mystery parts or missing parts (not saying it never happened but it was VERY rare). One thing to watch out for is that Heathkit would add addendums/updates to kits and would often print (well, Xerox) the alteration and one was to staple/tape the change to the existing manual. The last 2 digits in the part for the manual was normally the revision number. You are on Rev 06 on the book. You're Illustration Booklet should having a matching part number (upper-right corner of the front page). Furthermore, the Schematic should also have the SAME part number. This can give you a clue as to if your kit was somehow altered and also if you are seeing some prior revision parts (they didn't always remove older parts if there was a revision but merely had you use the newer parts. I have some kits were I built multiples (clocks and TVs) and due to the time span between them, had different revisions of the manuals and circuits. I never had/built the AP-1800 but strongly considered it, back in the day. In the end, a Yamaha C-4 won the day but you can see many similarities in the two. I did build (and still have) the Graphic Output Indicator (AD-1701...don't recall the "A" suffix) because you can't have enough meters! Thanks for posting and enjoy the build. I do miss them a bit.

[@FluxCondenser]

Sguttag, always great to hear from those that built Heathkits “back in the day.” Thanks for sharing your experiences. I’ve built several over the years and I do run into missing/extra parts issues from time to time. I had checked the parts bags and literature thoroughly and no mention of a change to the switch was mentioned. All versions of the preamp had just three positions, I believe, for the tape monitor so this wouldn’t be a revision issue. Looks like they just dropped the wrong switch in the bag (understandable since the 2, 3, and 4 position switches look identical other than the part number. This is an old kit, though, and although it certainly appeared that I was the first one to open the box, I suppose it’s possible (although unlikely) that someone robbed the box of the 3-position switch and replaced it with the 4-position.

[@sguttag]

I was mostly referring to the extra resistors you showed. I'm sure the switch issue was indeed a mistake. I'm wondering if the 4-position switch couldn't have a mechanical stopper put in to prevent it from turning too far. Oh well, it looks like your solution will be more than sufficient, however.

[@FluxCondenser]

I knew somebody would pose the question about whether a stopper could be added at some point, so you win the prize! It’s a good idea, and I’m sure it’s possible, but as these switches are probably hard to come by I decided right away to not even try to open or modify the switch. I just couldn’t take the chance that I’d botch something and ruin the thing. You may be right that the extra resistors are to be used later in the build. When I was briefly reading the circuit description for phono stage, I think I recall some mention of adjusting the impedance by swapping resistors, so we’ll see if those extras will be useful coming up.

[@petenamlook18]

I find that a toothbrush + acetone is excellent for cleaning boards of flux.

[@BobbyS1981]

Awesome build video! By the way, where did you buy the PCB holder? I'm interested in purchasing one.

[@FluxCondenser]

Thanks, Robert. The PC board holder is available from Amazon and elsewhere. See the attached link. Stay tuned for the next episode where I’ll make some modifications to the holder. www.amazon.com/Aven-17010-Adjustable-Circuit-Holder/dp/B00Q2TTQEE/ref=sr_1_2?dchild=1&keywords=Pc+board+holder&qid=1597805946&sr=8-2

[@BobbyS1981]

@@FluxCondenser Thanks for the link. Payday is coming up, might just have to order one. I work on all kinds of antique and vintage electronics in what little spare time I have. This will be great for old transistor radios. I came across your channel on the Vintage Audio Collectors and Technicians group.

[@FluxCondenser]

You’re very welcome. I think the holder will make a nice addition to your bench. Thanks for watching and taking the time to comment.

[@bigfoot4000]

Mine has a three position tape monitor switch.

[@FluxCondenser]

Thanks for letting me know. Much appreciated.

[@natgarrison7616]

I also have a three position tape monitor switch. I built mine back in 1982.

[@raccoon874]

*JUST LICK THAT FLUX LIKE ICE CREAM*

[@hmbpnz]

Replacing Nichicons with Spragues? Are those Spragues newer?

[@FluxCondenser]

The original electrolytics were tested in part one of this series and I explained the reasons for any replacements: kzbin.info/www/bejne/qKaqqZh9pqycf80

[@hmbpnz]

@@FluxCondenser Understood. I was questioning the vintage of the Spragues. Are those new?

[@FAKECARL]

Hope I win the raffle

[@tookitogo]

That’s a really odd way to clean boards. Use a brush to do the scrubbing, and dab off the flux-laden solvent with lint-free tissues (kimwipes, etc) - microfiber is not antistatic. I used to do a lot more flushing with solvent, but in the end, doing a few passes with solvent-moistened tissue works better and consumes far less solvent.

[@len9518]

Forgive me for being critical, but I think you should heat the joint, before you add the solder. You obviously know what you're doing, and can get away with it, but it's not good practice, and may cause problems for those who follow you.

[@FluxCondenser]

No, that’s absolutely incorrect. Add the solder to the tip first, then apply heat, then solder from behind to flow.

[@tookitogo]

You’re both right, but FluxCondenser needs to explain what he’s doing in much more detail: the small amount of solder added to the tip isn’t intended to form the joint itself, but rather to act as a thermal bridge to allow the joint to heat quickly. Then solder wire is applied to the hot workpiece (not the tip!) to make the joint.

[@bertjetolberg103]

For a moment i thought this was a Nice making/building channel but i soon find out that its just another talking and fingerwatching channel😢