• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Heathkit W4 AM Integrated?

marloubow

marloubow

Best Day Ever
Hi all!

I've been asked to restore this mono block amp.
It seems to be a integrated version of a Heathkit W4AM amp.
Unfortunately, most of the info label is gone. So an exact model number is unavailable.

Anyone have info on this particular model or know where I can pick up a service manual?

thanks
Martin






Photo of Heathkit W4AM
 
Register to hide this ad
I've never seen one of those.Are you sure it's a oem Heathkit?I wonder if another company made that amp,starting with a 4AM,like some companies started with a Dynaco Mark IV ans Mark III to rebrand and modify for their own use.It might even be homebrew(from a w4am)as the brown caps and resistors appear to be a different source than the rest.
Someone also added the can cap below the chassis.
 
Last edited:
Pre 1954. I have a couple of other reference manuals pre-54. Let me see if I can find this particuliar model. The RF style input connector for the tuner does not show up in any of the 10 heathkit catalogs I have reviewed.
 
Actually the RF style connector was common up into about 1960 on PA amps for the microphone.

It does appear judging by some of the components, it may have been recapped in the mid 1960's. They may have added the other controls for convenience at that time as well.
 
Gentlemen,
Thank you...all excellent input.
The unit was pulled from a pretty far gone, home built, open back cabinet that at one time had had a single driver.
So, my guess was an attempt at a guitar amp or portable PA unit.

The lettering on the controls is silk screened, so I don't think it was a one time build. Someone made a number of these from stock Heathkits, at least enough to justify the cost of silk screening.

Here's a photo of what's left of the label.
Interesting that there is a gain control on this W-4M, but not on a W-4AM.

All input is welcome

Thanks


 
It's a W4am with added input and volume control. It's a mono amp so you need 2 for stereo. With a total strip down and a repaint it could be very nice.
 
It definitely started life as a Heathkit W-4M -- and does not appear to be the AM version, as no "tweeter saver" (Heath's term) network appears to be present in this model.

What are the numbers of the two shielded tubes added to it?

Dave
 
dcgillespie said:
What are the numbers of the two shielded tubes added to it?

Dave
Click to expand...


Dave,
That is one of my unknowns.
The tube ID'er was of the "printed", not "etched" variety.
Those numbers, like most of the important info is gone.
They are GE Mullards, code 188-5. However the shield's do have
"EF86 6267" hand written in pencil on them. FWIW

Finding a schematic for this unit would take a great deal of luck. Supposing that one actually does exist.

I would at least feel some encouragement if the unit was actually producing sound.

This one feels like a time trap.


Thanks

Martin
 
Personally I'd strip out the two extra tubes, extra controls and all passive components (resistors, capacitors) - then rebuild per the original W4 manual as if it were a fresh kit.

With a little bit of creative cosmetic treatment to hide the extra holes etc it should be a very nice amp.

- Gary
 
Gary Kaufman said:
Personally I'd strip out the two extra tubes, extra controls and all passive components (resistors, capacitors) - then rebuild per the original W4 manual as if it were a fresh kit.

With a little bit of creative cosmetic treatment to hide the extra holes etc it should be a very nice amp.

- Gary
Click to expand...



Gary,
I'm inclined to agree with you.
From what I've been reading, these units are definitely worth restoring.
I think I'll try and talk the owner into finding a second and restore them at the same time...minus added controls.

Is there any valid reason for keeping the added controls if "stereo" is the goal?

I could see a nice face plate covering the front. Not so sure about the vacated sockets yet.

Any other input?

Thanks
Martin
 
Trio said:
Actually the RF style connector was common up into about 1960 on PA amps for the microphone.

It does appear judging by some of the components, it may have been recapped in the mid 1960's. They may have added the other controls for convenience at that time as well.
Click to expand...

Heathkit also had factory installed 1/4" microphone jacks in the 1960's as evidenced in my AA-181:

http://www.heathkit-museum.com/hifi/hvmaa-181.shtml

Hard to see it in the tiny picture, but it's the small speck to the right side of the three RCA inputs, half way between the RCA's and the edge of the chassis.

There's a slightly better picture (with incorrect knobs and mismatched tubes) here:

http://www.nostalgickitscentral.com/heath/products/heathkit_audio.html

Just ignore the tube compliment info in the text file as it has some of the tubes incorrectly identified?!?
 
I have scans that include part of the assembly manual for W4AM and W4B, pm me if it would be helpful.

I'd ditch the extra controls, and convert back to the original circuit.

I'd also make sure the transformers are good before you get too far into the project. Although you can un-pot and replace transformers - if I had a bad transformer on that amp I'd just part it out.

You can epoxy a piece of sheet metal to the backside of the holes, then use auto body filler to hide the holes from the top. With a bit of careful sanding it will look perfect. Heathkit used a variety of paint colors/textures over the years. I'd use one of the hammer-tone types on the chassis before re-assembly.

- Gary
 
What Gary says, if you restore it back to original, change out old resistors and caps and do a Bricktop or DC mod and the transformers are OK you will find you have a very musical amp on your hands.
 
Tom_r said:
Heathkit also had factory installed 1/4" microphone jacks in the 1960's as evidenced in my AA-181:

http://www.heathkit-museum.com/hifi/hvmaa-181.shtml

Hard to see it in the tiny picture, but it's the small speck to the right side of the three RCA inputs, half way between the RCA's and the edge of the chassis.

There's a slightly better picture (with incorrect knobs and mismatched tubes) here:

http://www.nostalgickitscentral.com/heath/products/heathkit_audio.html

Just ignore the tube compliment info in the text file as it has some of the tubes incorrectly identified?!?
Click to expand...

I did not mean to imply they did not have 1/4 inch jacks, just that a number of kits intended for PA use and commercail made units also had that RF type of connector. Which if clip the end/center terminal off the connector still used on CB and other HF radios (I forget at the moment the correct designator), it will fit that old style end- a useful tidbit for those looking to make their VTVM's functional again. I picked up a Knight 3235 that had 1 of each.

However, the EF86 is a 6267 basing 9BJ, and the data I have indicates type A resistance coupled voltage amplifier. So likely similar to a 6U8/6GH8. But the 9 pin socket gives you the ability toadd 12AX7's or 12AT7's depending on your preference.

They could be used for an on board preamp for vinyl. Most FDA approved MP3 players need some extra gain as well.
:banana:
As far as the controls go, I would leave them. They would add some versatility in spite of not being original, they could at least help obviate the need for a sepearate control unit.
 
Trio said:
I did not mean to imply they did not have 1/4 inch jacks, just that a number of kits intended for PA use and commercail made units also had that RF type of connector. Which if clip the end/center terminal off the connector still used on CB and other HF radios (I forget at the moment the correct designator), it will fit that old style end- a useful tidbit for those looking to make their VTVM's functional again. I picked up a Knight 3235 that had 1 of each.

...
Click to expand...

No problem ... I only posted it as an FYI. You never know when someone might want to use an audio amp for a guitar!
 
Hello, 1st post to this terrific site. Please forgive me if this is not the correct thread, just latest one on W4 AM that i could find. I am a former motorcycle racer who cant throw a leg over a bike anymore, so adopted a new hobby later in life. Ive recently found a Heathkit W4 AM at flea market for 20 bucks. Looked all over the country for its match at a reasonable price and located one. Want to recap, but im at a standstill due to all of the information i have found on the interwebs. I understand there are improvements that can be made on the original design and ive read much theory on the topic. But being a newb, it would be great if there was an actual list of new improved cap values, tube improvements with schematics or photos (better yet) for someone like myself. I am fairly competent with a soldering iron, have science backround and degree, and have many car, boat and motorcycle restorations under my belt. Can anyone give me advise or better yet, step by step instructions with crayon drawings? Thanks in advance. Love this website!
 
m611ott,
Welcome and congrats on your find.
This thread was my first experience with Heathkit, so my hands on with this model is limited.

However, these amps were sold as kits to be built from the ground up.
I have rebuilt a similar amp, a pair of Eico HF-22's using the supplied assembly manual.

http://audiokarma.org/forums/showthread.php?t=405199


The assembly manual for the Heathkit W-4 AM can be found in the AK database.
http://akdatabase.com/AKview/albums/userpics/10007/Heathkit W4-AM Assembly Manual.pdf.

That's about the best I can do for you. Starting a separate thread might bring more help.

Hope things go well with you restore.

Martin
 
You must log in or register to reply here.
Back
Top Bottom