MOHAWK RECEIVER MODS?

[K7NCR]

  I've seen referances to a series of article in electric radio mag for mods to the infamous Heath Mohawk receiver. Since I had good luck with the Apache, I thought I'd dig into the receiver half of the twins. Anybody have a copy they could scan or snail-mail me? I would pay postage if needed. I think I have a line on one on e-bay this week, we'll see. Thanks for the help, and am listening for you guys up here in Montana, but conditions have not been great lately. Too bad they were so crapy for the Classic exchange weekend. I really like joining in on those.
Norm Palin K7NCR

[Pete, WA2CWA]

Back issues of Electric Radio are available.
Contact Electric Radio:
http://www.ermag.com/index.cfm?v_link=product_detail&v_key=239
You need Issues 103, 104, and 105

[K7NCR]

  I got the back issues, thanks for the info. And the Mohawk is due Friday, 10/26. I'm looking forward to diggin' in to this one! Wish me luck!!
Norm K7NCR

[K7NCR]

  Here we go! Great series of articles in Electric Radio magazine about improvments for the mohawk. But since this was written about 10 years ago, does anyone have a good source for the temp compansating caps in this upgrade? I will do the whole boatload of mods, as the Mohawk already had the PS solid stated. Any info would be appreciated! By the way, it arrived today in fine shape, the UPS store did a good job of packing it. Some mild rust on the cabinet, but the radio seems pretty clean.
Norm

[WU2D]

Norm,

Before you go chopping away!

Do you have the Heath manual? Before you try to upgrade it, it may be a better idea to clean it up and lube everything and get it working stock. This is not a bad receiver - it is a lot better than many!

Start by pulling all of the tubes and testing them. Then squirt some deoxit into the sockets.

Swab the deck with q-tips and cotton balls for cobwebs using something that will clean it like basic green or even Windex (careful Windex can take old lettering off). I use an old pair of tube pullers with rubber tips with cotton balls. Dont forget to pull out the lamps and clean the dial glass.

While you are doing this, look for scorchs or burned up parts, brittle wires, previous mods. Check all of the hardware and ground lugs. 

Hit all of the pots, trimmers, variable contacts, relay contacts and switches with deoxit and move everything back and forth.
Lubricate all of the bearings with grease and oil as appropriate. Check the dial string and pulleys. Then remove the knobs and buff them so you can see yourself and clean the front panel and retighten all of the hardware and replace the knobs.

Check the fused plug - take it apart - this thing is a great design but it can be a bad thing if frayed wires are loose or corriosion is present.

The main power electrolytics will be suspect - you can try to reform them by putting only the rectifier tube in its socket and bringing the voltage up slow using a small fused variac. Observe the voltages and look for heating on the cans.

Replace all of the (tested) tubes and bring the radio up per the Heath manual. There will be a couple bad caps no doubt, but now you can use the receiver for a week or two. Only then would I start the mods.

Good luck!
Mike WU2D

[w3jn]

Problems with the Mo-hack

1)  Very drifty
2)  Numerous sources of distortion - both AM detector and product detector, not to mention audio amp
3)  LO injection too low IIRC
4)  Multiple AVC design problems
5)  10 times more complex than it needs to be

Only way to correct these issues is with lotsa work.  Cleaning pots, etc., ain't gonna do it.

It is a very pretty receiver though.

[K7NCR]

  I agree that the pair look awsome! The mods I did to the Apache made all the diffirence. I of course will do all the basic restoration items before I tackle any mods. The 3 part series in ER magazine address AGC, S meter calibration, detector distortion products, audio chain fidelity issues, and drifting. I need a sourse for the temp compansating capacitors so I can make the RF chain mods that address the drift problem. The types listes were N80, N150, N220, N330, N470, N750, and 1, 20pf N2400.  These others in assorted values, plus some NPO values to make the total values needed for each band coil in the band switching assy. This is by far the most involved of the mods listed. I will do the others first, and play with the radio alonf the way. Nothing like a naked multi-tube rig lit up on the bench, warming up the room!
Norm K7NCR

[K7NCR]

  O, I forgot to mention. The power cable is not the fused one I expected. It looks like the original 2 wire cord, with a (broken) chassis mount fuse holder. Someone's better idea?
Norm

[WU2D]

My elmer had the Marauder, Warrior and Mohawk setup - nice looking setup for the late 60's. He was a SSB net man.

This was supposed to be Heaths premium big receiver design - like the Marauder was the premium big SSB transmitter. After that pretty much everybody switched to SSB and the smaller Collins form factor and put the power supply external.

If somebody mounted a fuse holder, I would go ahead and and install a conventional grounded line cord.

Mike WU2D