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C18 helps keep the 8v line for the limiter and part of the mic line steady, sometimes the original value cant handle the switching of the transistors in that area, causing clicking or squealing noise. Ive read somewhere that bumping it up to a 330uf to 1000uf fixes all kinds of mic issues. I had...

The 1137 should be fine, The AM regulator can be upgraded to handle more amperage, the same way a 148GTL would be. I don't remember the "popular TIP" part numbers offhand but I think one or two of mine have a "D44H11" In the a.m. regulator spot. It's just a 10 amp transistor, to allow a little...

I had 2 that did this. On one I noticed that dropping the bias on the driver helped a little, but made sideband crunchy. It was TR41, changing the AM regulator fixed it. On the other it ended up being the driver itself I used an HG branded 2166, use the scope and your ears to set the bias on...

On a PC66, VR4 will be VR5, L14 will be L10. I think the 68 is the same.

To add to my last post: Setting the deadkey through the amp into a scope to get 100 to 125% growth (after amp) is what I found to be the sweet spot between "Loud Enough" and "Kazoo". It will be way more from the bare radio, swinging 18 watts from 0.5 will distort the receiving radio, but...

For a clean swing, remove R44, then solder the anode of a 1N4148 or 1N400(#) to JV17 and the cathode (stripe side) to the positive side of a 10uf (25v+) electrolytic cap, ground the negitive side. Install 1 of the bottom legs of a 1k (102) VR into the R44 hole closest to C49 and the top leg to...

I almost did the same thing, until I looked at the posts date.

I got all exited when I saw the extra output. I'm going to play with it another day, it's a really cool little radio. We're going to see if a mosfet is better tolerated in there.

Thanks for the response, I should have known beter. I played with it for a while, it cleans up under 5w deadkey with under 20pep. But... After adjusting it back to max again the 2312 went into a no return meltdown along with D10 until I pulled the plug. It held on as long as it could. Thats...

Check this out, I've seen this before on another old am radio, but an alignment of the band pass area straightened it out. Is anyone familiar with this, what could be causing it? It was worse, shaped like 2 halves of two different measurements put together. This was a scrap/parts radio that I...

I understand the rules, and wish to enter the contest.

Nothing in the radios Mod meter, only in my external monitor meter. Thanks for the responses. I needed to hear that someone else has the same result. I think we're hearing what the modulator (AN612) rejects.

I've added talk back to a Grant classic (almost identical inside to the Grant DX), using the modulation meter switch to bypass the diode in front of the audio chip. I use a small amount of reverb sometimes and thought it would be cool to monitor at the radio. In SSB it sounds terrible (with or...

Ya, I noticed the missing LED a while back... Haven't noticed the other issues yet. Thanks for the heads up!

Audio chip is the 10 pin next to the regulator on the same sidewall. We want to check VCO voltage before we continue. Find Test point 9 it should be it should be somewhere to the left of center towards the front half, to the left of L21. Put the radio on channel 40 AM Hook your meter to the...

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...