President Richard stock mic substitute

[freecell]

NZ8N posted:

" increase the release speed and decrease the "hold time" of the circuit."

otherwise known as attack and delay times. i prefer the fast attack when the transmitter is activated and slow decay after the transmitter is de-activated. before that happens the slower decay time also helps support maximum talk power levels between words, especially with short pauses in speech. rc circuits composed of a resistor and a capacitor (rc circuit) control both attack and delay times based of the values of the devices. both parameters can also be designed to be adjustable to compensate for noisy environments and other factors instead of using fixed values.

 

[Eldorado828]

The mod is what @NZ8N was talking about - but one thing we all missed...

Recognize this...schematically...
View attachment 35589
The Red circled item is the "lag resistor"

The Richard has something similar...​

View attachment 35588

It's located here...
Blue Arrow...
View attachment 35592
​

It was a throwback to the old days - in the Grant and 148's there was a 1Meg resistor used in the Limiter circuit that helped (if that is the word) keep the Limiter from staying on all the time. But it worked In a coupling stage area that was NPN to PNP - so you really just couldn't tailor R127 to meet the needs of how Hot or Cold the limiter was...R131 is what others usually took out to affect on AM side, R127 affected both SSB and AM limiter actions.

R339 is a 1Meg, a 105 on the chip itself...that is the main one you have to change to obtain better gain and AMC action.

The problems are

D300 - you can't remove it, but NZ8N's dropping resistor - is needed right where it stands - but - you have the power flow arriving from the Stage just ahead of the Limiter - which can put a lot of current thru the part and with the shunt installed at the limiter - it can fail and you may or may not be able to talk again because the limiter got cooked at the same time. That was one of the main quirks about the repair - we have had only one return but the Boss kept us in the loop and warned us about the Q313 Solder Blob problem as he called it.

So to reduce that current - if you use the 1K - it will not hold up well - but if you use TWO of them - it will - you use the 1K (just one) at NZ8N mod spot, and place 1K over the top of the 1 Meg resistor (105 R339) just line it right up top of the 1 Meg and tack solder both sides. You don't anything else. You've brought the limiter action down and you even have some limiter action still but allows you to attain 80+ watts (as shown on MFJ meter in Smokin Joe's shop...) if the thing can really attain it.

The D300 is a fail-safe device - one-way valve - but the Q313 and EDIT (308) Q312 (Limiter) clamp so hard - its' for that reason so it (the Fail safe) doesn't engage that fail-safe mode, the radio can go into that mode if it gets too hot or shutdown - but you didn't hear this from me ok? I get yelled at otherwise...

I've got my magnifier and tiny tips for my iron and going to give this mod a run. I've been studying the circuit and walking out the traces because these components are so small I can't afford to screw this up.

So @Handy Andy in order to avoid the "blobs" I might be better off trying to keep my soldering distances as far apart as I can. I'm thinking of scraping mask on the foil on the ground side of these joints because I'm using through hole resistors.

If I'm understanding correctly, from the junction of d300(cathode side), r354 and q313 to ground with 1k. At the junction of q308, c323 and r339 it will be another 1k to ground.

For me, it may be easier to scape pcb mask and go straight to the foil on the ground side because the close proximity of those surface mount components.

I just wanted to make sure I'm getting the right picture.

 

[Handy Andy]

I'm glad to know you're stopping by to keep us posted.

Yes, I still recommend the "two part" approach. You will need to cut down the signal before the LIMITER amp (AVC) and then at the LIMITER itself.

Please continue.

Best to stick with 1K to divide - then the loading between the two sections is FAR less.

Remember too, the @NZ8N location - this part divides down the signal by 50% - it's a divider, which will still knock down the MIC Input - not the response control the the section further towards the RF side, that is at R339 - that is your 2nd part - this 2nd part can absorb more power from the ALC/AMC further back.

The one you need to install correctly is NZ8N's - you have more area to work with - but you need two parts installed CORRECTLY to reduce the AMC (R339) and AVC Added Resistor - both being a 1K will work, just remember one will not accomplish as much as the two will.

And I'll have cash on hand if I owe you a radio...

 

[Slowmover]

As dentist specs get attached:

“Drum roll, please . . . . “

 

[Eldorado828]

I'm glad to know you're stopping by to keep us posted.

Yes, I still recommend the "two part" approach. You will need to cut down the signal before the LIMITER amp (AVC) and then at the LIMITER itself.

Please continue.

Best to stick with 1K to divide - then the loading between the two sections is FAR less.

Remember too, the @NZ8N location - this part divides down the signal by 50% - it's a divider, which will still knock down the MIC Input - not the response control the the section further towards the RF side, that is at R339 - that is your 2nd part - this 2nd part can absorb more power from the ALC/AMC further back.

The one you need to install correctly is NZ8N's - you have more area to work with - but you need two parts installed CORRECTLY to reduce the AMC (R339) and AVC Added Resistor - both being a 1K will work, just remember one will not accomplish as much as the two will.

And I'll have cash on hand if I owe you a radio...

Thank you sir for confirming, planning on getting to the bench this afternoon and will definitely be reporting back.

One of those risks I'm willing to take for the sake of education. I sure appreciate your guidance and patience.

As dentist specs get attached:

“Drum roll, please . . . . “

Already nervous and somewhat intimidated by this microscopic surgery, the drum roll raises the anticipated level another notch haha

 

[Eldorado828]

Reporting back,
Resistors in place as pictured below, checked double checked and triple checked for stray solder and to make sure of no unwanted bridges.

Powered up and no magic smoke so that was a good indicator. Went into the service menu to turn down am modulation just to be on the low side of things for start up. Also lowered carrier power again to be safe and start low.

With the stock electret microphone it's made an incredible difference in swing from low carrier and you definitely don't see the hard clamping affect of the limiter. Tried the telex 56, 636l and sra198, all vary when set to dynamic settings as they are much less effective as the stock mic.

Quickly going through the difference functions of the radio to see if anything else has been affected by the mod and all seems to be OK other than talkback. Talkback now sounds terrible but only with the stock mic, with the telex 56 it seems to not be an issue. That's one of those quirks that would matter to the guy that uses talkback of course.

I didn't have time to go through it thoroughly as family necessities need my attention so will be getting back this when time is a friend.

@Handy Andy my friend it's definitely made a huge difference and I'm very thankful to you for your knowledge and guidance. This isn't a finished project though, we'll be back!

The soldering is not easy on this tiny stuff, not for the average tinkerer, I had to wait for the morning coffee to wear off in order to have a hand steady enough haha.

Please give me some grace on my soldering!

 

[NightThumper]

Nice soldering! Definitely not done at Bell’s CB!

 

[Crawdad]

I had to wait for the morning coffee to wear off in order to have a hand steady enough haha.

I feel your pain with the shaky hand syndrome and the morning joe.

Well done sir.

73

 

[Handy Andy]

Don't forget to thank @NZ8N for his guidance as well!

 

[Handy Andy]

Already nervous and somewhat intimidated by this microscopic surgery, the drum roll raises the anticipated level another notch haha

It wasn't all that bad, you did great...

The reference to Striker is a good one!

Bought back memories - thanks!

 

[Eldorado828]

Andy, you are correct!

@NZ8N thank you sir for your contribution on this modification. I'm sorry that when coming back to research this thread I didn't go back far enough to see that you had initially suggested half of the modification. Your help is greatly appreciated.

Next step is to try some different values at the Q313 location to see what works best and full functionality checks to see what or if anything has been negatively affected. I will keep you fellas updated on findings as time permits.

Full credit to NZ8N and Handy Andy as I only listened, studied and soldered.

@Handy Andy I felt like striker trying to land that plane and you folks were the Leslie Nielsens haha

 

[Handy Andy]

"...and stop calling me Shirley!"

He will be missed...

 

[Eldorado828]

So just checking around for radio stuff but nothing specific I bumped into this piece of information pointing to a possible suitable sub for the president and anytone radios. Not sure as to how verifiable this may be but worth looking into.

Anyone here across the pond familiar with this animal mentioned in the attached picture?

Is it simply a superstar 452 in another shell?

 

[Eldorado828]

A big thank you to @Handy Andy & @NZ8N for guiding me through the mentioned modifications. Because of that the Richard has been given a second chance in the truck. I owned one before and tried to use it in another truck but it just didn't talk like the radios I'm used to running. I really wanted to like the radio but it was just a turd... Today it replaced the C 29 that sat in that overhead for the last year with the Richard to see how it does in the real world. So far it's done much better than expected with several conversations to which all have asked what radio was being used. Night and day difference from the stock Richard and plays well with the 636L. Several steps up from the just ok radio it started as.

P.s. @Slowmover I know it isn't a side mic!

So far so good so we'll see how it does in the long term.

Gentlemen, I appreciate it very very much

 

[Slowmover]

A big thank you to @Handy Andy & @NZ8N for guiding me through the mentioned modifications. Because of that the Richard has been given a second chance in the truck. I owned one before and tried to use it in another truck but it just didn't talk like the radios I'm used to running. I really wanted to like the radio but it was just a turd... Today it replaced the C 29 that sat in that overhead for the last year with the Richard to see how it does in the real world. So far it's done much better than expected with several conversations to which all have asked what radio was being used. Night and day difference from the stock Richard and plays well with the 636L. Several steps up from the just ok radio it started as.

P.s. @Slowmover I know it isn't a side mic!

So far so good so we'll see how it does in the long term.

Gentlemen, I appreciate it very very much
View attachment 47758

PRESIDENT has a sound of its own. Unique. Just hang a little Frenchie beret on it and practice speaking like Pepe Le Pew.

Seriously, am glad you are making it work. Was bummed at end of trial run when you yanked it.

At least you didn’t launch it at the skeet range like a couple a mokes around here might’ve.

.