Major M588 no audio on SSB

[Mudslinger]

I have just aquired an "untested" Major M588 and surprise surprise it has issues. (PTBM059COX)

On AM and FM it has audio on TX and RX, but on SSB there is no output and no receive. (There is still noise from speaker)

Is this a common fault? Radio looks to be pretty much untouched inside.

cheers

[Avenger]

Must be quite common as in I've got a major 588 here with exactly the same issue,works a treat on am/ fm but nothing on ssb tx or rx other than a hiss from the speaker

[dt307]

hope some one will chime in as im up to my eyes in it lol.
got an 858 chassis back from the grave today and its getting a vfo and the globe is getting the final bits done as when you turn the s meter up and down by the internal vr the rx gain tracks with it ....ah the joys
off the top of my head ssb common to both rx and tx would be the balanced modulator ic4 check voltages around there would be a starting point for me pull up the service manual and go through the voltage checks

[Otter]

I'd check the 10.692/10.695 MHz oscillator first. Also, is there a "BS" voltage rail in that one. If so, check it.

[Mudslinger]

Thanks for the help.
I think I will send it to Nick as it is above my level of expertise and test equipment.

[dt307]

I'd check the 10.692/10.695 MHz oscillator first. Also, is there a "BS" voltage rail in that one. If so, check it.

what the man says^^^^

if you have no clue what to do ...or where to start better send it to some one that does or

get the block diagram and cross of all the boxes you know are working like the mic preamp,af amp,pa stage ect

you will be left sections you need to put your focus on (no point checking the voltage on the pa trannies as we know they work ect)

pull up the service manual check all voltages as i said for every ic (chip) and every transistor and all power rails.

it will take some time and is boring and take care with your meter probes not to slip (i sneezed a few moths ago while doing something and shorted the damn thing out)

if an oscillator aint working or a rail down or a cap shorted hell could be a dirty mode switch you will find it

this could be a common prob that nick BS or dave CW has seen lots of times and we await input from the gods as what i have asked you to do might be ott for you to do

and some times things turn out to be not what you expect like the old globephone working on yesterday
only thing left to sort was the smeter as when you adjust the vr to set the smeter the rx would go up and down easy fix i thought
some thing not fully shorted as smeter working but dragging it down
removed the diode marked could be shorting to deck ....no
removed the cap marked could be shorting to deck...no
disabled the tx mod,swr ect could be shorting to deck ...no
removed the smeter and rx dropped off ....wtf
put a different smeter in temp mabe the old one shorting to deck ... no
so i shorted the output of the vr to deck and the rx came bouncing in ...bingo i knew the prob instant and was kicking my self
t4 was so out of wack the extra slight loading of the smeter was bringing it into resonance
peeked t4 put everything back and working normal and the vr has no effect on the rx anymore.
now if i would have gone through the service manual and did all the checks and tweaks that i tell people to do i wouldnt have wasted 2 hrs of my life

globe.png