President GRANT Classic SSB power

[cb4ever104]

Hi All .

Got this "Classic" GRANT here . The band mod has been done and AM/FM power is a heathy 10W . However SSB power is max'ing out at around 7W . I've no resistors on the pcb side . The ALC circuit looks to be complete on the component side , although there are a couple of resistors missing . I've attached a photo to see if anyone can see anything suspicious . BTW I'm getting the full 13.8V on the collectors .

Img_0476.jpg

Sammy

[14CS06]

Hello Sammy


On my 2 board the same component are missing
What is the reference of your board

PC-999AE


PC-999AD

@+
Claude

[cb4ever104]

Salut Claude .

PC-999AE . I think yours in an "AD" , no ?

Sammy

[14CS06]

Hello Sammy

I own 2 PC-999AE and PC-999AD
@+
Claude

[Mudslinger]

My one is a PC-999AC, let me know if you need pictures.

I know that when I sent it to Nick he did need to swap components around to get the power output where is should be.

I think it was R263 and R271 which needed to be changed although I have no idea what the values should be unless I take off the lid.

[cb4ever104]

Thanks for that mudslinger . I'll wait and see if Nick replies to the thread .

Cheers !

Sammy

[163TM847]

Check these two resistors, Bottom one should be a 1k5 and top one 100ohm

P1000609.jpg

[cb4ever104]

Thanks Nick . Yeah , they're both OK . I'll keep digging around the ALC circuit and see if I can find anything . I appreciate the help .

Sammy

[163TM847]

Is there a resistor across the ALC VR on the opposite side at all ? Also check too see if the AM/FM power VR adjusts SSB as well as there is a common fault where a track blows so AM/FM dosnt switch over to SSB voltage.

[cb4ever104]

Hi Nick . No , there's nothing on the solder side . I'll check the AM/FM power adjust when I get a chance and get back to you . Cheers !

Sammy

[cb4ever104]

Hi Nick .

No , the AM/FM power setting VR has no affect on the SSB power . One thing I have noticed is that I start to lose 95% AM modulation from 6W onwards . i.e with AM power at 9W I can only achieve 60% modulation . Don't know if it's related or not ? I also did a quick bias check . The 2166 is at 100mA and "both" finals are around 100mA as well . The manual I have says 50mA and 50mA (for both) . Anyway , If I can't find the fault I might send it over to you Nick when I'm in Leeds next month and you can have a look .

Sammy

[zephyr]

Sammy,
I had a blind friend years ago that kept turning the FM power up in his Grant, then wondered why he kept getting complaints that the AM audio was quiet.
Over 8w and it starts to get quieter, you can see this on the RF meter when it goes down when you talk instead of up like it does on side band but not as much.

[cb4ever104]

Hi zephyr . I thought with dual finals you would still get full modulation with 10W deadkey . Saying that I don't use AM so I'm not sure if that's the case or not .

Sammy

[zephyr]

Sammy,
All I can say is it cured the problem for him and he had no more complaints after that.

[bigpimp347]

the more power on AM the less swing you get go for too much power on AM and the AMC cuts out the audio or you start getting a lot of negative swing.
you need around 3/4w of carrier and swing to around 8w will sound good and loud, too much carrier and the audio goes crap.