[Heathkit] HW-16 Warble

[Mark K3MSB]

Hi Guys

I’m restoring an HW-16 and HG-10B for a buddy.  I stripped the chassis and
cleaned it, replaced the electrolytic capacitors and associated resistors
(using the kits from Hayseed Hamfest – nice stuff),  checked voltages,
resistances etc.   Got rid of bad solder joints, got rid of some rust
lurking under solder lugs etc.

The units look sweet and play sweet….except…..for an intermittent warble on
the TX and RX signal.   Sometimes only on the TX signal, sometimes only the
RX signal, sometimes both.  My buddy used a standalone receiver and says he
heard the warble on the HG-10B Spot signal.

I’ve used the radio on 40M and the stations I talk to say the warble is
there.   They all say it’s not bad, and don’t mention it until I ask.  But,
I want to get it cleaned up.

 I’ve been pulling my hair out trying to find it.       I need some help.

Here’s a short audio clip for the warble received on 40M:

www.k3msb.com/temp/HW16_Warble.mp3

I have more clips if needed.

This problem usually happens about 45 minutes to an hour after I turn the
radio on, and is most predominant on 40M,  but happens on 80 also.    Sometimes
it happened immediately after I turn the radio on.

Here’s what I’ve done so far:

Replaced tubes.

Taping tubes, IF cans etc,  to try to create the warble and to try to
resolve it when it's happening.

Freeze spray on components.

Monitoring power supply voltages.  They look reasonable (see below).

BFO and HFO outputs look good on scope.

IF Looks good; I’m feeding in a test signal (10 mV PP) at 7.050 into a
divider network to give me 1 uV PP into the HW-16.

Thoroughly checked (and rechecked)  all solder connections & cleaned up
suspect ones.

All switches cleaned (and recleaned….)

Air variable caps cleaned (and recleaned….)



With the signal generator input, I find I can get it to happen when I
increase the volume, using a set of cans and also with a 3.2 ohm
Hallicrafters speaker.  It will occur with the RF Gain at max and mid-way.

Here are the power supply voltages measured with a DMM (Expected / HW16 /
HW16+HG10B):

A:  175 / 161 /158
B:  310 / 298 / 290
C:  320 / 307 / 298
D:  700 / 658 / 646
E:  -150 / -143 / -143

Power output is about 50W on 40M and 80M;  don’t recall 15M but it was
lower.



I’m thinking power supply issue, but most everything in the power supply
area has been replaced.



Ideas solicited and welcomed!



73 Mark K3MSB