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Grant Clarifier (Center?)

LeapFrog

Wielding Hanlon's Razor
Feb 15, 2016
1,709
903
123
Anchorage, Alaska
Hello everybody, I am looking at a President Grant today for a local operator.
The radio has been modified previously, uppers/lowers, unlocked clarifier, possible clipped amc.

My question is kind of simple, what is involved in getting the clarifier to be center?
I will post some pics later of the uppers/lowers mod (standard MB8719).

If I re-lock the carifier, will he have any issue on SSB (not that he regularly uses ssb)?
I think if the clarifier was locked for TX, and the radio was aligned properly he wouldn't miss this feature.. Opinions?

I changed all the electrolytic caps yesterday, the radio works great minus two things:

If I turn mic gain all the way it will flat top.
The clarifier is unlocked and not centered.

The uppers/lowers mod has two diodes, and uses a spdt switch and the bright/dim switch!
I may re-do the channel mod to simplify it for him, I was going to make a channel chart for the current mod but I don't like the way the wiring was done. (To see if anybody widebanded this radio what should I look for?)

Thank you for any pointers on what to look for or do! (To center the clarifier would be great)
 
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I do not remember seeing a diode used for the channel mod in years. this is the 3 or 4 button silver faced grant radio from what I am thinking. most cases if you have a freq counter and proper alignment equipment you can get the clarifier about centered.do you have all needed to align the radio.

if it is the silver face I think I did the mod with a 3.3k in r174 slot. has been years since I worked on a grant 3 button. here is a link I have used for years that they put about every version of the clarifier mods.

http://www.radioaficion.com/HamNews...en-grant-xl-mods-pll-agc-power-clarifier.html
 
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verify the info I left is for your board. there is like 3 or 4 of the same name with different boards. 999 board, 409 board and 412 board. could be one more. hard to remember all of them.
 
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Yeah, if it won't align to center spot; then the resistors in line with the clarifier control have been bypasses or changed from the original value to increase the slide range. If you compare that radio to the schematic you will easily find them - usually two resistors have been bypassed with a jumper wire IIRC.

Did you make sure that the AM Limiter is on the board and working? Just remember, that with enough mic gain from the front mic gain control AND the AMC control on the board AND a power mic, you can just about get any radio to flat top or have less than a symmetrical wave form.

Nothing wrong with the clarifier unlocked. AS an avid SSBer, I prefer it. But I do not prefer having too much slide, as this condition lends to instability due to temp changes. A stock yet unlocked slide works for me. If you can't lock onto some station because they are more than +/- 600hz; then it is time for them to get back on center freq; not you.
 
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Yeah, if it won't align to center spot; then the resistors in line with the clarifier control have been bypasses or changed from the original value to increase the slide range. If you compare that radio to the schematic you will easily find them - usually two resistors have been bypassed with a jumper wire IIRC.

Did you make sure that the AM Limiter is on the board and working? Just remember, that with enough mic gain from the front mic gain control AND a power mic, you can just about get any radio to flat top or have less than a symmetrical wave form.

Nothing wrong with the clarifier unlocked. AS an avid SSBer, I prefer it. But I do not prefer having too much slide, as this condition lends to instability due to temp changes. A stock yet unlocked slide works for me. If you can't lock onto some station because they are more than +/- 600hz; then it is time for them to get back on center freq; not you.
Someone may have zapped the transistor and then put it back it in, I don't see anything clipped.

edit: (this part relates to channel mod, not the modulation issues)
I will look at the mod posted and see how the diodes involved work, i also spotted a 4.3 kohm resistor added along with a cut trace.
 
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The only diodes I'm aware of in this part of that circuit is the diode that allows the VR control to adjust TX freq and the diode that controls the voltage for TX/RX. If the diode that controls TX freq adjust is clipped, you lose all center freq adjustment. While many modders claim that diode should be clipped, I never mod my radios that way. I keep that diode intact so that I can adjust that VR in order to keep the TX freq the same as RX.

There is - however - the other diode that has to be clipped so that 8v can be fed to the clarifier circuit in both TX/RX modes. That is essential to make the unlock mod work, since doing this allows that diode not to control TX voltage any more. When that is done, the 8v wire from the voltage reg is used to feed that circuit and thus allows clarifier change voltage in both TX and RX.

I cannot recall which diode locations they are. Perhaps someone else can chime in and give the specifics for them.
 
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Robb, the diodes are part of the upper/lowers modification.
Still working on getting pics up having issues with that.

I appreciate your effort and time trying to explain how diodes aren't part of the amc.
I posted a edit to explain how i was talking about something else entirely, my bad brother.
 
the diodes are used for the rotary switch mod. the toggle switch mod does not use diodes. that was why I left you the link earlier in the post. have not seen the diodes used in toggle switches. could be a new way to do it.
 
I will read both links gentlemen thank you, the mod does not work correctly on all channel positions.

I think some one combined the knowledge from the rotary switch mod and used a spdt switch, kind of neat how it is done, you'll see what I mean when I have some pics uploaded!
 

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