Heathkit IG-102 diagnostic

Fortunately, my IG-102 came with the assembly manual.   The IG-102 is roomy enough inside that it’s pretty easy to get in and probe around checking things.

Things I’ve found so far:

  • Audio frequency (AF) output, which the manual says should be 400 Hz, is around 260 Hz.  With the AF dial turned all the way up, the AF waveform measures about 20Vpp.
  • I can reliably get RF output when the Coarse Atten switch is at the Hi position and the Fine Atten dial is all the way clockwise.
  • Setting the Coarse Atten switch from Hi to the middle position drops the frequency by about a factor of 10 (according to my M3 frequency counter).
  • Setting the Coarse Atten switch to the Lo position makes the RF output drop out.
  • Turning the Fine Atten dial counter-clockwise ends up changing the frequency (unexpected) instead of changing the signal level.
  • The band select dial is kind of fiddly.  Sometimes when I switch to a different band, RF output drops out.  Switching back and forth will usually bring the RF output back.
  • Band A (100 – 300 kHz) is the most accurate.
  • Bands B (310 – 1100 kHz) and C (1 MHz – 3.2 MHz) are about 50 kHz low.
  • Band D (3.1 – 11 MHz) is low by 0.5 – 0.7 MHz.
  • Band E doesn’t work.
  • Band F (32 – 110 MHz) is reasonably accurate up to 50 MHz, but maxes out around 75 MHz.

V1 12AT7 pin voltages

PinSpecMeasured
16562
2-4-5
300
46.3 VAC7 VAC
56.3 VAC7VAC
66259.6
7-0.75-0.38
800
900

V2 6AN8 pin voltages

PinSpecMeasured
17062.8
2-0.2-0.5
31.51.57
46.3 VAC7 VAC
500
6125127
7130130.9
800
92.52.64
IG-102 AF signal
IG-102 AF signal around 260 Hz

The RF signal sampled at pin 2 of the 12AT7 tube looks decent enough.

IG-102 RF signal
IG-102 RF signal around 370-ish kHz

Need to do some more poking around with the oscilloscope to check the RF waveform at other places along the output path to see what’s happening before I try to figure out what bits I might need to replace.

Back on the bench: Heathkit IG-102

Back on the workbench is the Heathkit IG-102 signal generator I acquired a few years ago.

Heathkit IG-102 signal generator
Heathkit IG-102 signal generator

The last time the signal generator was on the bench was to have a new power cord and BNC connectors installed.

This time, I’ll replace that big orange capacitor with something newer (along with any other components that look like they need replacing).  The signal generator doesn’t seem to be putting anything out at the BNC connectors anymore, so that will be another thing I’ll check.

Heathkit IG-102 20 uF capacitor
Heathkit IG-102 20 uF capacitor

2017 ARRL Auction time

Bidding for the 2017 ARRL Auction opened up yesterday. Didn’t see anything that made me go “I NEED THIS“, but there were still a few items that I thought were interesting enough to put bids on.

Seems like there’s a fair bit of bidding activity going on in the auction already after just a day. The ARRL Mystery Junque boxes are back (only 4 of them this year). One of them is already up to $155. Hope it’s got something good in it.

So far, the items I’ve decided to chase are a copy of Introduction to RF Design, a reproduction 1st edition ARRL handbook, and one of the Vibroplex keys. Nice things to add to the bookshelf and collection, but nothing that I’ll be disappointed over if I don’t win.

I always enjoy watching the activity in the ARRL auction. It’s interesting to see what items end up going for.

The new Top Bands

US amateur radio operators will soon have access to small slivers of the 630 m and 2200 m bands as secondary users. The 630 meter allocation goes from 472-479 kHz (a little bit below the US AM broadcast band, 530 – 1700 kHz) while the 2200 meter allocation goes from 135.7-137.8 kHz (not a heck of a lot).

Although the new allocation was announced several months ago, now access to the bands is only a form submission and 30 days away.

Before being allowed to operate, hams will be required to notify the Utilities Technology Council. Notification can be done online, and involves submitting name, contact info, call sign, lat/long of your antenna location(s) and the bands you’re planning on operating on. If you don’t hear anything back within 30 days, you’re supposedly good to go.

Even if you have no immediate plans to operate on the new bands, you might still want to notify the UTC in case you decide to operate there later. If there’s no objection to your notification, and a utility later wants to deploy or modify a PLC system near you, they’ll have to use a frequency range other than one you’ve indicated on your notification.

If an electric utility seeks to deploy a new or modified PLC system on a transmission line that is within one kilometer of a previously coordinated amateur station, the electric utility must employ a frequency in the 9-490 kHz range that has not been included in the amateur station’s notification, as ARRL suggests.  If the previously coordinated amateur station no longer operates in the band, the electric utility may deploy a PLC system in that band.

Now, how to build an antenna for 2200 m…

Power supply: Updated schematic

I’ve updated the schematic for the power supply. Made a few corrections and rearranged a few things.

Still haven’t figured out why the outputs are behaving like they’re shorted out. Putting a my DMM across the output terminals gives me about 148Ω, which seemed on the low side to me.

Power supply schematic 20170716
Power supply schematic 20170716

A quick check of the SCR shows that it seems to be ok. I think I’ll check the pass transistors next. Looks like they should be easy enough to remove for a quick test. I should probably check the big filter caps too, although I wouldn’t expect those to be bad.

In the process of troubleshooting, I’ve removed the 6 pin connector and large capacitor (1.4 mF) associated with it. I’m planning on replacing them with Powerpole connectors. Three of them will fit nicely in the space occupied by the 6 pin connector. Just need to figure out how to secure them in place.