Hello All,
My "ebay-INOP" TR-7 is mostly working. The problems were mostly in the connectors. The remaining problem is
occasional loss of lock. It happens at random times, a few times a day. A quick poke on the "RCV FIX" button fixes it. An appropriately named button!
I still haven't cleaned the connectors on the cards under the shield panel that is under the DR-7 display board. Maybe that will fix it up.
Also planning to do a full alignment, starting with the 10V - which I suspect is now 9V. At least, that's what's reaching the fan, from a pair of homebrew-added wires departing into the guts of the radio. Preparatory
to that, I discovered I needed a frequency counter. And it had to be reasonably sensitive. So I ordered - and
received about an hour ago - an HP 5385A. Supposed to be good down to 15mV RMS. Not wanting to pull out serious
instruments to check it out, I grabbed my Millen grid dip oscillator off the shelf, wound a clip lead around the coil and patched it up to a BNC. Yup, it's plenty sensitive. It measured the RF on my clip lead with the loop about an inch away from the GDO coil. And the Millen is well calibrated....for a GDO.
Another item that the manual says I need to do an alignment is a VTVM. Don't have one of those. Well, I'm
pretty sure there's an HP410B hiding in the junk somewhere, but darned if I can find it. Pretty sure I can
manage with an oscilloscope. But just for yuks, I ordered a Heathkit V7B on Ebay.
I replaced the trim pots on the power supply board with 10-turn units. The original pots had their pins in a triangular pattern; the 10-turn ones in my junkbox had the three pins all in a row. No problem - bend these that way a bit, and bend the middle one the other way, and they plug right in, tilted up a bit for easy tweaking. But the pots are sort of in mid-air hanging off their pins. And when you fuss with it - plugging the board in & out - they get bent out of position. Then you put them back, but you don't get to do that too many times before the pin breaks off - especially the leftmost pot. Reinforcement? I cut a strip of phenolic perfboard to a size just right to lay across the sides of
all the pots. Applied accelerant to the pots, cyanoacrylate cement to the perfboard and glued it to the pots. Now they're still hanging in midair, but in order to push one out of line, you have to push all of them, and it's a lot stronger.
I obtained a 450Hz CW filter from Noble Radio and installed it. Now we have viable CW! I decided to also get a 2.7 kHz SSB filter for better intelligibility. Also got a patch card and extender cards.
I'm planning to build an AUX7 card. There is ample information on the Web and in the TR7 service manual to do that. It will get me full WARC band coverage without cutting the "transmit anywhere" trace. Ebay yielded up
three baggies of 4-pin female Molex connectors ( P/N 09-62-3041 ). These are higher quality connectors than what Drake used - they have selective gold plating on the connection. More than I need, but I always get spares.
Also got some Augat machine sockets to connect & make the individual band modules. Plan to wire it up with 30gauge Kynar "wire wrap" wire, of which I have a good supply.
I did the mod to control the SSB power with the carrier level pot. Seems to work. I still can't use it with
my linear though; Need to figure a way to get band data out of the transceiver, OR - modify the linear to have its own bandswitch. I have resisted doing that because the LDMOS device is expensive and would be a genuine
PITA to replace. But it is protected; the linear has two tandem matches, one before its LPF, the other after.
- Jerry, KF6VB
