[Hammarlund] HQ-170A info/help

[Mitch]

All,
    I am still trying to sort out my HQ-170A. I have read all the archives back to 2003, and plan on reading the rest as time permits. However, I have not been able to locate the specific information I need. I have been conduction various test on the receiver and have come to some interesting conclusions. I will try and list them briefly. 

The receiver still drifts. Not as much as it did before I replaced the 6C4. I will be replacing the first mixer as soon as the tubes arrive.

I have been making an attempt to measure the amount of drift on each of the bands. I have a very stable (PLL) Bontoon 103D Signal generator. I can set the frequency with a fair amount of accuracy, and it will stay where it is set. So I have been setting the frequency to mid band and tuning the receiver for a zero beat on the signal. I then let it stabilize for approx 15 minutes then adjust the output of the signal generator for zero beat with the receiver. I note the new frequency and come up with a drift number. Here are the preliminary results.

1.9 mhz- No discernable drift
3.8mhz-approx 500hz increase in frequency
7.150 mhz- approx 300hz decrease in frequency
21.1mhz and up, the frequency drifts up and down in frequency by about 400hz. Not possible to get a stable reading.

I've also discovered that the receiver will drift in frequency if the line voltage changes. I do not have the cleanest power where I live. It is mostly stable, but it does vary as much as 10 volts throughout the day.

I know these receivers are known for  drifting, but I am sure that someone has found a "fix" to eliminate or at least reduce the drift of these receivers. I have been studying the schematic trying to sort this issue out. Any help that you guys can give will be greatly appreciated. 

I almost forgot, I have not unplugged the receiver in over two weeks. So the VFO has had plenty of time to heat up. I still gave it one hour turned on before conducting these tests.

thanks
Mitch KJ7JA

P.S. I love this Radio. It's way cool!