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 Post subject: Heathkit W4-Am Restoration
PostPosted: Nov Mon 06, 2017 4:24 am 
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Joined: Nov Mon 06, 2017 3:56 am
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So, I may have bitten off more than I can chew, but as a determined gal with a fairly high aptitude for gadgets, electronics and mechanics and a background in audio engineering, Ive decided to restore a pair of Heathkit tube amps that were gifted to me along with a preamp, turn table and 4 massive speakers...but I'll get to all those others later. 8)
First off, these things are filthy after being stored unprotected in a filthy garage for who know's how many years.
Does anyone have any advice on cleaning the chassis and tubes, etc? Am I correct in assuming I need to drain the filter caps before doing anything? With that last question, I suppose I've given away the fact that I'm a total newbie at this. I have just enough knowledge to be dangerous (to myself) ...lol.
Seriously though, I want to do this safely and with no damage to the amps.
For cleaning supplies I'm thinking, amonia, q tips, naval jelly incase of rust and Deoxit.
Anyone have any other suggestions??? Help would much appreciated.
Thanks!

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Carol


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Mon 06, 2017 1:17 pm 
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Location: Utica, NY 13502 (USA)
Welcome to the forum! You will find lots of good advice here. I also have a pair of W4-AM's awaiting restoration.

The capacitors used in these units do not need to be drained but will need to be replaced. You have probably heard the term "leaky caps". A capacitor normally will pass AC voltage and but is supposed to block DC voltage. With age, many types of capacitors begin to pass DC voltage which alters the operation of the circuit design and can even cause damage to other components. When this happens, a capacitor is said to be electrically leaky because some of the DC voltage applied to it "leaks" through. However, sometimes (but not very often) a leaky cap will also show leakage of the internal chemicals used. In this case, a capacitor can be both electrically and physically leaky.

Dave


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Mon 06, 2017 2:39 pm 
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Joined: Nov Wed 07, 2007 12:44 am
Posts: 1781
Location: Hawthorne, Ca
I own 2 W4's that I restored years ago. They are simple amps to restore, but I do recommend obtaining the service information before starting any restoration work. I used regular automotive cleaner/ wax to clean up the chassis on mine as that is what I had in the garage. All of the parts for the electrical restoration are readily available and not expensive. If you can't obtain the service info locally, I have the original construction manual that I can scan and send to you. Harry


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Tue 07, 2017 6:26 am 
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Location: New Port Richey, FL, USA
If you are new to this, don't go working on them just yet. You need to make sure you understand a few things to keep from hurting yourself or the amps.

If you don't have the manual for the amp, then visit this page: http://www.vintage-radio.info/heathkit/

Scroll down and you will see the W4-AM link. That is the manual that came with the kit to tell how to put it together, and how it works. But look at the parts list and the schematic for the electrolytic capacitors. Not just the filter caps, but there are others. Don't question if they are good or bad - they are bad. If you want to verify that, give them the clunk test. What you do is remove the cap and throw it in the trash can. If it made a clunk sound, it was bad. If it didn't, then your trash can needs to be emptied, and the cap is bad. Obviously you also want to look for any other parts that appear to be damaged, etc.

As far as cleaning, start with a vacuum and a small paintbrush. What that doesn't get, try alcohol. Don't go at it with too harsh of chemicals. But one big word of caution. DON'T try to clean the tubes with anything wet. The tube numbers will wipe off very easily. Even with a dry cloth, take it easy around the tube numbers.

Ultimately, once you get this thing to where you are confident it will work, don't just plug it right into the wall. Either use a variac or a dim bulb tester. Do a search on this site for both of those, and there are plenty of YouTube videos. But both are meant to protect the amp if it has a short yo don't know about. And when it's powered up, don't touch anything under the chassis. You have 300-400 volts under there. And yes, the filter caps would need to be discharged, but we're talking the new ones. As Dave mentioned, the ones in there now are not going to hold anything.

And the last most important thing about working on a tube amp, NEVER run it without a load on the output. In other words, if you don't have a speaker connected, then you have to have a resistor across the speaker terminals. But if you don't have an oscilloscope to view the signal, then, make sure you have the speaker connected.

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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Tue 07, 2017 1:48 pm 
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Excellent advice, Michael and spot on.

Please keep us posted and pictures are always appreciated!

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Don


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Tue 07, 2017 2:37 pm 
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Can't thank you guys enough for the excellent advice. Michael, your clunk test had me laughing at 7:00 A.M. No easy task. 8)
I do have the orginal manual and a scope. I've even got an old tone generotor that's older than dirt! ( HP 200 CD)
I'll definitely be doing some research before I dive into these beauties. Thank you guys for not giving me the proverbial "nice try, kid" pat on the head and sending me down the road. lol
I've been a pest to the guy who works on my guitar amps and figured he could use a breather.


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Tue 07, 2017 2:49 pm 
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Location: New Port Richey, FL, USA
GeerGirl wrote:
I've even got an old tone generotor that's older than dirt! ( HP 200 CD)


I had to look that one up. Looks like it's form the 50's. There's a lot of folks on here with test equipment form that time frame. Look at it this way - that's new and modern compared to some of the radios being worked on.

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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Tue 07, 2017 4:57 pm 
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:lol:
Too funny! Yes, it's from the 50's. Came out of a studio where I used to work.

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Carol


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Tue 07, 2017 10:43 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Boston, MA USA
The HP 200CD was the standard for audio measurement for many years. Every broadcast and recording studio had one. HP may have introduced it in the mid-1950s but they continued selling it well into the 1970s.

-David


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Wed 08, 2017 12:01 am 
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Joined: Nov Wed 07, 2007 12:44 am
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Location: Hawthorne, Ca
If you are planning on doing the restoration work yourself, please keep in mind that you are working with high voltage which if you aren't careful can be deadly. Don't be afraid to do the restoration yourself as most likely your amps were built someone that had little or no knowledge of electronics, but was handy with a screwdriver and soldering iron. If you run into problems, there is always someone here at ARF that will be willing to help you solve the problems, just ask. Harry


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Wed 08, 2017 5:15 am 
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Thank you for that , Harry. I'll keep that in mind. Hopefully I'll learn something by taking on this project.

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Carol


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Sat 11, 2017 1:43 am 
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Joined: Jul Sun 19, 2009 3:51 am
Posts: 27
Location: Flin Flon, Manitoba
Carol

If your doing any live testing it's wise to keep one hand behind your back so you don't get a loop through your heart. I wear good rubber gloves with leather ones over them in case I slip though!

Another thing to do is take many detailed & close up pictures before you proceed and check the resistors for high ones as that's the usual way they go. Cleaning tube sockets and checking tension is also good to do & they can be re-tensioned with dental picks etc.

There is a thread over at audiokarma where the Williamson circuit (wasn't the best back in the day for stability etc.) has a few caps & resistors, & output tubes changed for a nice sonic improvement. It may be something you may want to try after getting it working. Dave Gillespie is the engineer behind this if you want to try it. Easy to reverse with the P2P wiring.

I hope I don't offend anyone by posting a link!

http://audiokarma.org/forums/index.php?threads/gillespie-triode-williamson-build.795322/

(NFB phase advance cap is cut off in the image above - should be 24pF for Chicago output transformer)

All the best on that rebuild!

Randy


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Sat 11, 2017 3:34 am 
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Randy,
I greatly appreciate your advice. I've been studying up on safety and have taken note of the one hand in a pocket technique and also using a wooden chopstick or other tool made of nonconductive material.
Thanks for sharing the link. I'm still researching and learning before I dive into this.
I'm sure you all are thinking "this chick has no idea what she's doing and she's crazy" . You're right..ha!

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Carol


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Sat 11, 2017 2:43 pm 
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Joined: Nov Wed 07, 2007 12:44 am
Posts: 1781
Location: Hawthorne, Ca
Many of us learned how to service electronic by getting in and doing it. The W4 circuit isn't complicated and as stated earlier, there are circuit mods that can be made if you want to do them. I recommend getting the amps working in a stock condition before doing any mods that may or may not be a sonic improvement. If you take your time, work carefully and safely and when in doubt, ask questions before proceeding as you don't want to hurt yourself or damage an expensive transformer. Parts to rebuild the amps are available at places such as Antique Electronic Supply. Mouser, Digikey, Just Radios and Sal's capacitor corner who is a contributor at ARF. Harry


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Sat 11, 2017 5:34 pm 
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Joined: Jul Sun 19, 2009 3:51 am
Posts: 27
Location: Flin Flon, Manitoba
We all start the same as we have the interest & enthusiasm to do it (so your not crazy) and learn as we go along and I'm still learning!

Anyway great amps to start with as they are easy to work on and have great sonic potential!

Randy


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 Post subject: Re: Heathkit W4-Am Restoration
PostPosted: Nov Sat 11, 2017 9:11 pm 
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Joined: Jul Sun 19, 2009 3:51 am
Posts: 27
Location: Flin Flon, Manitoba
An earlier thread on the mods!

http://audiokarma.org/forums/index.php?threads/heathkit-w4-am-modifications.459630/


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