Heathkit GR-54 audio hum fix

[Ed Van Krevelen]

I would like to correct an error I made in my previous message.  The
statement “So it would seem that the circuit design used in the HW-16 is
superior to the original one used in the GR-64.”  I meant to say GR-54 not
GR-64.

The audio output circuits are similar in both the GR-54 and HW-16.

I did cover all the basics first with replacing power supply electrolytics,
replace every component, one at a time, in the original GR-54 circuit and
attached a separate external speaker.    All had no effect on the hum level.
 However, I would say that the tube that came with the radio was less noisy
when it would operarate when physically tapped.

The two replacement tubes (6HF8) I purchase may have been noisier than the
original.   I can only assume at this point that the HW-16 circuit design
could be more tolerant of noisy 6HF8 tubes.  Also in switching to the HW-16
circuit design in the GR-54, I kept the feedback loop capacitor C56.  I only
changed to the component values found in the HW-16 and added the capacitor
C87(HW-16).

-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.aspx?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html