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Pearce Simpson Simba SSB 23 Channel

R

Ranch55

Sr. Member
Jan 18, 2016
820
1,068
153
Texas
I am having a couple of issues with this radio.
1) ... SSB power output has decreased from 14 watts down to 8 ~ 10 watts and I cannot pin point why. Adjusting the ALC pot does not increase SSB above the 8 ~ 10 watts, but it will decrease the output power.
2) ... Occasionally the DC fuse will start blowing constantly when in CB mode, but not PA mode. Then I can unplug the main relay, turn power back on in CB mode and the DC fuse will not blow.
After awhile, I can plug the main relay back in, power on radio in CB mode, and all is fine again for a period of time.

I have been chasing these two issues for a couple of months, off and on.

Any productive help would be appreciated......



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upload_2019-11-15_9-33-36.png

upload_2019-11-15_9-33-36.png upload_2019-11-15_9-34-22.png
 
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Ranch55,
First thought is a final transistor on the fritz drawing excessive current (at times) blowing the fuse and decreased gain responsible for the lower output??
Bias circuit component failure??
The final is probably not "active" in PA mode only the audio circuit??

I'm sure you've already been there but a little "food for thought".

Good Luck

73
David
 
I replaced the driver and final. Didn't really look too much at the bias circuit.
As far as the DC fuse blowing, when it starts blowing, it will continue to do so several times on replacement fuses, without the relay being keyed. Pull the relay, replace the fuse, turn on radio, and the fuse will not blow. But as soon as the relay is plugged in, the fuse will blow again.
I then let the radio sit for awhile .........install relay, install fuse, turn on radio, and all will be back to normal.
This issue may not manifest itself again for 2 or 3 weeks, then all of a sudden it starts doing it again ......
As far as SSB power output decrease, it is only on SSB. AM power output is not affected. Am power output is normal.
 
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How does it act on a DC input to the unit?

I'm thinking AC/DC rectifier(s) are sketchy?? Might answer SSB output issue?? Might answer blown AC fuse issue?? Main transformer shorting??
 
I have considered that.
So I have connected up to DC power supply, bypassing the internal power supply completely. It would just start blowing the DC power fuses at that point.
Acts like a dead short somewhere when the relay is installed. Remove relay and fuses do not blow. Like I said, the issue will manifest itself for awhile, then go away for 2 to 3 weeks, then happen again.

My mistake from the first post. I went back and edited all my posts to correct my error.
IT IS ALWAYS THE DC VOLTAGE FUSE .......

Oh, I forgot to mention that I have installed new relays 3 times, from Ken's Electronics.
 
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Unit 75 said:
It sounds like the power supply is loading down. If you have not installed new electrolytics I would start by replacing the following and see if it fixes the fuse blowing issue.
C228 2200uf 25v
C230 220uf 18v
C212 1000uf 25v
Click to expand...

see my post above.
Thanks.
 
Then I would install all new electrolytic capacitors throughout. Your problem certainly sounds like a cap issue from what you have told us about it sitting awhile and being ok then not. If it was a dead short, the fuse would instantly go all the time.
 
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see if there is a diode and resister right at the side of the relay. years ago I had an olkd radio act like this and found a diode and resister connected in line with the relay . both were bad and would short of the radio and blow the fuse. the one I had there was a 1amp fuse so that helps to find it. not many 1 amp fuses in these radios.
 
Ranch55,
It looks like the CB/PA switch is fed full DC voltage and passes this to the Mode switch(AM,USB,LSB) in CB mode only (not PA mode). Is it possible the mode switch is shorting voltage to ground? May answer low SSB power output?
The schematic is a bit blurry when I enlarge it looking for the relay coil and all associated components but it seems the "short" is related to the current draw through the relay coil??? D44 is a zener diode(1w-9.1v)on the feed to the relay coil through R44(68ohm 1/2w). Are they healthy?

A real head scratcher!!

73
David
 
Last edited:
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Dmans said:
Ranch55,
It looks like the CB/PA switch is fed full DC voltage and passes this to the Mode switch(AM,USB,LSB) in CB mode only (not PA mode). Is it possible the mode switch is shorting voltage to ground? May answer low SSB power output?
The schematic is a bit blurry when I enlarge it looking for the relay coil and all associated components but it seems the "short" is related to the current draw through the relay coil??? D44 is a zener diode(1w-9.1v)on the feed to the relay coil through R44(68ohm 1/2w). Are they healthy?

A real head scratcher!!

73
David
Click to expand...

Open this PDF file and go to the schematic toward the end of the manual and you should be able to zoom in on the schematic.
The Relay coil is shown as "K1" about middle of page on right end of schematic.
You will need rotate clockwise the view.
 

Attachments

  • Pearce Simpson Simba SSB Manual.pdf
    314.2 KB · Views: 13
Ranch55,
Thanks. I downloaded a pdf of the operating manual. The zoom is much better. It's how I was able to find K1.
That zener looks like a good place to start!

73
David
 

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