Yep. I'll be the first to admit, this radio started out just as bad as Curt Reed said it was.
But, I kept tweaking it, because it was something that my brother found at a swap meet and gave to me as a gift. Well, that and the fact that it was the radio I really wanted to get back in the day, not the GR-64 AA5 that I ended up putting together at age 13.

And after awhile I start to pull in some stations that are pretty well hidden in the weeds. Hummm, says I, it's got some sensitivity in it after all. It still has some issues, but not as rough as it was a few months ago. I was surprised to find that quite a few of the resistors have changed in value about 150% or better. So, out they go. I'm sure there are a few more to replace. After a good tune up it's starting to hum along. I mean that litterally. The audio output transformer isn't the original, but a generic sub from some time in it's long ago past. Even so, there is an intolerable audio hum from the no-volume level to about 40%. And it isn't the speaker picking up something from the transformer. Removed that to no avail.
I've most likely read all the comments on the 'Net that there are and have the "Heathkit Manual" downloaded (well, except for the 40 missing pages or so).

What would really be helpful is if anyone has any type of voltage chart on this beast. The smaller GR-64 put em right on the schematic. That worked out well. Here, not so much. If anyone has such a critter please let me know. It would be most helpful. Thanks!!

There is a manual here:

http://tubularelectronics.com/Heath_Man ... /GW-54.pdf

But it doesn't show voltages. There is a resistance chart for the bandswitch wafers.

Tony

Thanks, Tony. I appreciate the feed back.

I've seen 2 variations of the abreviated manual, this one and one other in which the schematic
is broken up: page 1=last half of the schematic, last page=first 1/2 of the schematic. Goofy scanning arrangement, I guess.

But I still haven't seen anything with voltages on the tube pinouts or at other circuit locations.
The product detector works but really cuts down the output on USB and LSB signals. Quieter signals go away all together. And the Audio out almost sounds like it has a feedback component of some kind. Sounds very much like hum till just below 1/2 volume, then it clears up wonderfully. Replaced pot = same issue.

Question for all you guys with Heathkit experience: Have you picked up some of their older gear and had issues with resistor and cap values drifting?

Hi There OtherKennyG,

I am a BIG GR-54 Fan! Lots of things I can share about it because I fixed one up that was in sad condition and it kept me busy for some time!

Yes, the resistors drift badly. I replaced almost ALL of them in my set! They were so far out of tolerance it was a miracle that the set worked at all when I found It!

There are a number of modifications for the GR-54 and I've done almost all of them to my set. No regrets! I particularly recommend changing the RF Amp and 1st IF Amp tubes with 6DK6's. Note that you must first change resistors R15 and R19 before making the tube substitutions. See this page:

http://forums.qrz.com/showthread.php?49 ... -receivers

Audible hum is a very real problem with the GR-54. After trying every suggestion I could find, I discovered a recommendation by a College Professor in Arizona who modified the GR-54 audio circuit so that it is the same as in the Heathkit HW-16. After making this modification I was amazed at the reduction in hum. Still not perfect but very much improved!

If you have other GR-54 related concerns, I'll be watching this Post.

--Daniel

Hey, Daniel. Good site for information. Thanks.

I've determined there must have been at least 2 runs of the GR-54: an early run with no caps on the power line input/primary side of the transformer, and the 2nd run with those caps in place. I've seen schematics both ways. Mine had them, but I've moved the terminating location of one of them.

I'm looking at isolating the line going into the audio section and running it into the phono input of my National NC-173 to see if that doesn't squash the hum. The mod to match the audio section on the HW-16 might be the ticket. I did find that all the hardware securing the 2 pc boards to the chassis had loosened up quite a bit, and that tightening them down and re-doing all ground connections did have a positive impact. I do have the schematics of several mods, one of which is the 6DK6 change-over. I don't know yet if I want to go quite that far with it. It's sensitivity seems to be quite good, now. I've found that the broadcast band works much better (without pops and whistles) without an antenna, other than the ferrite bar already on the set. Lifting a lead on the load resistors on the lower 2 bands helped them pull signals in with less interference, too.

Hey OtherKennyG,

The GR-54 Circuit boards easily develop faulty grounds to the metal chassis and it varies a great deal depending on who did the original assembly and what kind of soldering skill they had. So tighten up those PC to ground connections!

There were changes in production with the GR-54 and GR-64 models. I saw photos of one version with all of the shielded band coils on an above chassis circuit board (youch!) and I'm pretty certain it was the 1st production run of the GR-64. The GR-54 has a sufficient number of issues to resolve - I don't want to think about what the even cheaper GR-64 must be like to live with!

You do understand that the design of the GR-54 audio drives the final as hard as possible and the AF and RF gain controls are "coupled" in such a way that even a slight increase in RF gain forces ever more gain into the audio circuit! It's like having two volume controls to restrain a wild horse of an audio circuit! No wonder the hum is so strong! Heathkit was clearly trying to make barely usable RF signals audible. This is another sensible reason to change to 6DK6 tubes so that you are amplifying something beside RF and IF noise.

Hey, Daniel. Your thoughts about the GR-64 4-tuber really plucked my heart strings. I built one at age 13 (yeah, that WAS a long time ago!! ) and then proceeded to run right out and get my novice ticket, 'cause I thought I finally had a ham rig. Couple that with the Conar 400 transmitter and you've got a beginner's station, right? Not so much. Gave up trying to figure out if anybody was coming back to me, as I tried to copy code from one end of the band to the other. Heavy sigh! As far as code goes, I must have a tin ear.

That same GR-64 is sitting downstairs right now. It gets fired up every once in a while. Still works, has only one non-original tube in it, and a couple thousand hours of listening time on it. Can't believe it still works as well as it does. Need to re-cap the 'lytics and align the IFs. I'd admit it's a little overdue..... Together we've made some fond memories.

I'm hoping to get to play with the GR-54's audio soon. I did find a schematic where the gent did an extreme makeover of the filtering and biasing of the audio output section. I'm considering going there.

Regarding the GR-54 Audio modifications, the schematic for the GR-54 reads left to right from 1st stage audio to the loudspeaker. The HW-16 however reads the opposite direction, from right to left. Realizing that this difference was a prescription for making a mistake, I made a hand drawn schematic which shows the modified GR-54 audio section using the same component values as those found in the HW-16.

Note that the audio output goes directly to the headphone jack. I removed the side mounted speaker and the original space wasting speaker bracket on my set and sent the audio straight to the headphone jack. I now use an external speaker which sounds so much better!

Daniel, you're right. That schematic is quite close to the existing GR-64 audio section, except for a few variations.
I'm starting to get the feeling I'm gonna have to give that a try......