Search results

If pin 3 of the *audio chip* has 1 or more volts on it, it's a telltale that the PLL loop is not locked. It also mutes outgoing audio, including the PA (pulling C232 is a hack that keeps the audio unmuted by disabling pin 3, even between channels). It's probably due to the pin voltages at the...

There was a TSB on this board that added a Zener diode in that spot as a safety limiter. That one looks pretty darn corroded to me, It should operate just fine without it. I would unsolder that wire and the diode and try to clean that area up with a little wire brush. Then see if the 8 volts...

Modification #18 in the PDF from post #43.

8 should be 8v during TX (6 and 8 should toggle, RX/TX). Pin 1 is being dragged down, it should always have 8v on it. Here is a schematic from CB tricks.org. It's for a 148, the regulator circuit is nearly identical. I chose it because it's very clear and searchable. The 1st thing I would try is...

Was going to do the controlled carrier mod after finding a failing VR8. I thought the 1K dimmer pot would be a cool spot for an adjustable carrier to use with "low drive" amps. Also noticed that the schematic drawing doesn't match the trace illustration, C102 would (still) be on the emitter the...

I have a hunch that the regulator is being bogged down by one of the grey 10v caps on the board. You've already checked the usual suspects, but even if they test "good" a recap can make everything run way smoother in the end. I use nothing less than 25v caps everywhere. See if pin 1 and pin 3 of...

I started on a TRC449 today and was looking for 858 info. This post popped up. Here's something I saved a while back. If it's not allowed let me know, I'll take it down.

I dragged the PC76 out to see if it still ticked. It looks like the channel spacing is off on the modified frequencies, If you have more than the usual 40 it might get worse... 19+10k is spot on, 40+10k is 80 high and 1+10k is 80 low. I've seen AM radios being used at 300 off, so its no big...

I know this is an older thread, but I wanted to share some of my experiment results. This was with a Uniden PC76XL, it's about the same as the Cobra 29s inside. Cut the rearmost trace on the 10.24, remove C131 and bridge the cut trace with a 22pf trimmer and the lower half of the CH9 switch...

I used one (HG2312) in a pinch to repair a side mic. 29 LTD a while back, then monkeyed around with some trial and error stuff. It seems to make easy power the way it is. A clean 23pep without tweaks. These are from my notes some add a little more oomph, or help keep things sharp and clean...

I had mentioned above that I added an "NPC" mod at an earlier point. My notes on this radio were that replacing the 560ohm R282 with a 1K with a 4148 and 220ohm in series, parallel to it, works awesome. I don't "volt" the finals, I never find much to gain in it unless it has a MOSFET driver...

Okay.... Who did this??? Ohh $#!7! It was me ...... Whoops!Yep that's backwards As soon as it was corrected, everything went smooth as butter. Thanks for not cursing me out for trying stupid mods on this radio (on my post anyhow) ...lol Here's some more pics and video.

I like my older radios, most were discarded by someone else and snatched up for parts and experimentation. Mine always end up as living breathing functioning works of love. Even after freshening up, some of my radios drift with temperature. Being in the Cleveland area, my mobiles can see...

I think I know where the problem might be, but thought it would be cool to share as I undo a few audio cap changes that I thought would "open up" the audio a little more. The issue is with the ALC and AMC adding weird distortion and oscillation that will continue without any added audio while...

That's really cool! I always thought there was some "magic formula" that calculated the 500nH value. I'm going to try this in the morning. These .5uH chokes are so common in radios, but a PITA to find. I have to go to that site to play with that calculator too. Thank you!

Thank you, very much!

Hi everyone, I smoked L39, the .47uH inductor near the finals in one of my PC409 Grants. I'm sure someone else may have been, or will be in this situation. Without any HG 2SC1969, or similar for replacements onhand, I installed the IRF520 and related components. I have a few others that...

I understand the rules and would like to enter.

I ended up swapping out a few suspect caps and put the supply back on 8v with a choke, in case the distortion was from RF bleeding to +. After I poked around with the scope in a few spots, the distortion went away, but came back after the radio sat a few hours. (time for a full recap ???). * I...

After removing the "epoxy deal" I was able to chip the back of the board clean because the builder forgot to clean up the flux. After reflowing a few spots, it was working again. I hooked it up with jumpers and was able to tune 26.965-27.405 on "C" and 27.415 to 27.855 on "D" again not touching...