my 142 GTL - CAUTION! - graphic images

[space cowboy]

The story begins HERE
I can't say it arrived DOA, but if you've come as close I'd love to hear it. after pulling it out of the box and letting it sit for a few hours to warm up I hooked it up, and called for a radio check.
"I got you radio check, you're there, but you've got almost no mod."
I keyed up to thank him for the comeback, and the light faded away to a dead LED display.

Oh well, I wanted a project radio, that's why it was so cheap.
I ordered the cap kit from Klondike Mike here on site and replaced the power supply caps.
It Lives!!!
What a bright beautiful display, even with a burned out segment.
I connect it to the antenna and get receive, a good sign, but no transmit.
I think the problem is not enough dust on it, time to let it sit for a few months.
Nope, that wasn't it.
I'm slowly working my way through. All the .47 uF caps are done, along with 6 others. I've un-soldered 3 incorrect components so far.
After about 6 caps I tested it on a dummy load and had 3 watts swinging something way up there according to the radios meters, both of which work fine.
I was disappointed when I stuck it on the antenna though. Turning the dynamike just one mark above nothing and it gives off a very high pitched, full mod oscillation you can hear.
Take it back to the dummy load, no squeal.
20 more caps to go.
Then I start on fixing the chop chop.
The limiter is cut, along with things I haven't bothered to ID yet. I believe the red wire coming over the edge of the board to the audio chip is the NPC? mod, I don't know if it's done correctly but I plan to undo it. One of the other pins on the audio chip is cut, I have no idea why yet. The clarifier looks to be unlocked. That I'll probably leave.


Hoping I'll get it done by spring. for now, I'm thinking some more dust couldn't hurt.

 

[Sideways]

I have a similar project goin on myself, lots of fun huh
That ic looks like your 8v regulator. It has 8 pins correct? See if you have 8v at pin 1, some of the problems you describe go along with a bad regulator. I believe it was common in those radios.
The red wire at pin 1 may be for the opened clarifier. The pin that is cut is supposed to be, at least it is in my washington.
Don't let the dust get too thick

 

[ExitThirteen]

Fix the diode that's cut next to TR32, and fix TR32, and that should restore your modulation to original, and SHOULD fix your "squeal" issue. That red wire if it goes to your clarifier control, needs to go to pin 3 of the MB3756 voltage regulator IC, not pin 1. Hope you get it going, those are great radios!

~Cheers~

 

[mechanic]

Good radio! Pretty much a Washington with single conversion chassis....

73 mechanic

 

[space cowboy]

thanks for the info guys.

I'm glad you put that face next to the fun sideways, or I'd have thought you were losing it. it does help pass the time though.

Fix the diode that's cut next to TR32, and fix TR32, and that should restore your modulation to original, and SHOULD fix your "squeal" issue. That red wire if it goes to your clarifier control, needs to go to pin 3 of the MB3756 voltage regulator IC, not pin 1. Hope you get it going, those are great radios!
~Cheers~

I tried a quick fix, soldering the broken components together, with the same results.

SQWEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE

found out then I have no ssb audio either.

however I did find out my personal mod is good when I dragged the hot soldering iron across my knuckles.

 

[space cowboy]

so I started to replace a few more caps, when I noticed some connections on the underside of the board that aren't soldered...

these are all VRs, 8, 9, 10. they don't look like they've ever been soldered...
should they be?
there's only 2 connections on each VR, so why put them in at all?

 

[Sideways]

You only use two legs of the variable resistor. The one leg that's by itself, and only one of the two on the other side. If they were all three soldered in to the same circuit, say you have a 20k pot, turning clockwise your resistance would start at 20k, at the halfway point would be 0, all the way clockwise would go back to 20k. Instead of going from 20k-0 with one full turn.

 

[mechanic]

Three pin potentiometers with one pin not used is a variable resistor, with all pins in circuit the pot becomes a true potentiometer in that it can reference a signal to ground or divide power or signal between two stages.
Your pics show a variable resistor application, usually for setting the gain of a signal or voltage level. Unless these are damaged there is no need to adjust these. Any adjustment is set according to tables with a scope or meter.

73 mechanic

 

[space cowboy]

ok, thanks. I didn't realize it was a pot with a third connection point underneath.

hopefully this new purchase will help me with my confusion.

 

[space cowboy]

ok, finally got some time to fiddle with it, and the squeal was from a short in the mic cord. trimmed off an inch and reconnected the end, and all is well.
sort of.

I've got this weird thing where channel 1 is channel 1, but channel 2 is broadcasting/receiving on channel 3, and channel 3 is still channel 3. channel 18 and 19 are both channel 19...
good reports though.

 

[btu44]

I like these find of threads...subscribed.