Hamarlund HX50 crystal Oscilator Question
 

During the alignment procedure I have found the crystal oscillators dead or
off frequency (as in unable to adjust to spec with in 1khz). The crystals
have a 1962 dates stamp on them. After disassembly, checking, replacing out
of tolerance components and cleaning all of the associated 6AW8 passive
components, I got most of the crystals back to oscillate. Only two would
achieve spec frequency.

1- Is this common with old crystals? (Typical aging is 50ppm/yr. so 44
years times 50 ppm times 33.88mhz takes these crystals to where I am
experiencing trouble.)
2- Should I expect to be replacing these to obtain accurate frequency and
oscillation on the dead ones (10b and 10c meter bands)?
3- What crystal companies would you suggest I contact for reasonably priced
third harmonic crystals?

Alignment/schematic at http://bama.edebris.com/manuals/hammarlu/hx50/.
Manual page number 31 (32 djvu). Step 7-6.

Am I tripping over rat turds here (except for the dead crystals)? What do
you think?

Thanks,
Paul.

Hamarlund HX50 crystal Oscilator Question
 

"Paul P" wrote in message
news:veMHf.2180$Fe.1311@trndny06...
During the alignment procedure I have found the crystal oscillators dead
or
off frequency (as in unable to adjust to spec with in 1khz). The crystals
have a 1962 dates stamp on them. After disassembly, checking, replacing
out
of tolerance components and cleaning all of the associated 6AW8 passive
components, I got most of the crystals back to oscillate. Only two would
achieve spec frequency.

1- Is this common with old crystals? (Typical aging is 50ppm/yr. so 44
years times 50 ppm times 33.88mhz takes these crystals to where I am
experiencing trouble.)
2- Should I expect to be replacing these to obtain accurate frequency and
oscillation on the dead ones (10b and 10c meter bands)?
3- What crystal companies would you suggest I contact for reasonably
priced
third harmonic crystals?



Band hetrodyne xtals for a sideband transmitter? If the transmitter doesn't
have
a companion receiver that it can slave to for transceive operation, a 1 kHz
error
is something I wouldn't worry about. Can the dial scale resolve a 1 kHz
difference?
If not, don't sweat it.

You could probably add a few trimmer caps to allow some pulling to get them
closer to spec.

BTW, International Cyrstal Manufacturing in OK City, OK is usually the
vendor
of choice for crystals.

Pete

Hamarlund HX50 crystal Oscilator Question
 

Paul P wrote:
During the alignment procedure I have found the crystal oscillators dead or
off frequency (as in unable to adjust to spec with in 1khz). The crystals
have a 1962 dates stamp on them. After disassembly, checking, replacing out
of tolerance components and cleaning all of the associated 6AW8 passive
components, I got most of the crystals back to oscillate. Only two would
achieve spec frequency.

Hi,

I wouldn't worry much about the band setting crystals,
you only have a string dial with that rig, so you need
to spot with an accurate receiver if you get near the band edges anyway.

The important crystals are the USB and LSB carrier oscillator
crystals. If they are off frequency, your voice will either
sound thin or bassy.

There is an easy mod to almost elliminate the resting current
of the 6DQ5 during HX-50 standby periods.
The mod appeared in an early-sixties CQ magazine,
and is very worthwhile to reduce heat in the cabinet.

If you'd like, I'll send the info to you directly.

73,
Ed Knobloch

Hamarlund HX50 crystal Oscilator Question
 

Edward Knobloch wrote:


The important crystals are the USB and LSB carrier oscillator
crystals. If they are off frequency, your voice will either
sound thin or bassy.

I might add to this. My rig, and mind you the xmtr was only about ten
years old at the time, had suffered from some drift in the filter. I
understand this was a common issue.

If memory serves the upper and lower filter frequencies are stamped on
the filter itself and thats what you need to match the carrier
oscillators to, not the actual crystal frequency. I believe manual
explains how to do this and place the oscillators correctly on the skirt
of the filter. Its pretty easy to do to get them matched to the
filter...and if need be give them a tiny tweak while listening to the
transmitted audio.

-Bill

Hamarlund HX50 crystal Oscilator Question
 

I wouldn't worry much about the band setting crystals,
you only have a string dial with that rig, so you need
to spot with an accurate receiver if you get near the band edges anyway.

The important crystals are the USB and LSB carrier oscillator
crystals. If they are off frequency, your voice will either
sound thin or bassy.

There is an easy mod to almost elliminate the resting current
of the 6DQ5 during HX-50 standby periods.
The mod appeared in an early-sixties CQ magazine,
and is very worthwhile to reduce heat in the cabinet.

If you'd like, I'll send the info to you directly.

73,
Ed Knobloch

Ed,

Please send me the mod. I found some modifications had been done to the
bias circuit. It would be great to verify them.

THANKS!
Paul

paulREMOVE at REMOVEppinyot dot REMOVEcom