-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
-
Retevis is giving away Radios for the New Year and Every Member is Eligible. Click Here to see the details!
A little help/input here please
- Thread starter TheRealPorkchop
- Start date
Naw , from the description it seems like a DC short somewhere in the RF/IF chain. Although D15/16 "could" be bad or shorted it's unusual for other than a lightening or taser strike. I'm going over notes as this seems familiar .
I have done this already, thanks for the input though. Sadly, I traced it back all the way to the AGC IC and it’s there. I believe maybe the problem is near the transmit & receive switches. Even though it shows a clear switch by the LED between the two, I’m getting a negative voltage reading there during receive.
I’ve been busy and haven’t got to fool with it but I’m gonna try to get back to it tonight. I have really tried the squelch, not that remember anyway. I’ll test that later too.
Evil radio... sometimes I really hate myself.
I've also already been through that voltage chart as well... surprising ya, ain't I?
I've fixed it though...
IC1... checked the voltages and here is what I got :
Pin 1 should be NC, I got 7.30v
Pin 2 should be NC, I got .16v
Pin 3 should be NC, I got .27v
Pin 4 should be 8.40v and I got 8.69v (not terribly bad off)
Pin 5 should be 0.0v and I got .01v
Pin 6 should be 0.0v and I got .50v
Pin 7 should be 0.0v and I got .98v
Pin 8 should be 7.04 with squelch & .68 with none, I got .01v
Pin 9 should be 2.26v, I got 7.48v
Pin 10 should be 1.53 (lowest SQ) 3.32v (highest SQ) I got that right
Pin 11 should be 0.0v and I got .01v
Pin 12 should be .30v and I got 7.27v
Pin 13 should be .30v and I got 3.20v
Pin 14 should be .60v and I got 7.06v
Now, I looked at the schematic and figured the first things to go wrong would be an electrolytic capacitor, so I started hunting the closest ones to IC1. I came across C32 and while not totally bad, instead of 47uF, it read almost 55uF. So I changed it to brand new one, Nichicon for me.
Fired up the service monitor and bam, receive is given and I hear that glorious 1khz tone @ -118dbm. The squelch is working perfect by the way... I'm pretty sure the alignment is a bit off, so that's in order to be performed.
I believe checking more caps at this point would also be a good idea, guess it's possible that more could be faulty or fixing to become faulty. Input? Ideas?
Thank you to every single person in this thread that responded and thank you Kopcicle, you know why.
I've fixed it though...
IC1... checked the voltages and here is what I got :
Pin 1 should be NC, I got 7.30v
Pin 2 should be NC, I got .16v
Pin 3 should be NC, I got .27v
Pin 4 should be 8.40v and I got 8.69v (not terribly bad off)
Pin 5 should be 0.0v and I got .01v
Pin 6 should be 0.0v and I got .50v
Pin 7 should be 0.0v and I got .98v
Pin 8 should be 7.04 with squelch & .68 with none, I got .01v
Pin 9 should be 2.26v, I got 7.48v
Pin 10 should be 1.53 (lowest SQ) 3.32v (highest SQ) I got that right
Pin 11 should be 0.0v and I got .01v
Pin 12 should be .30v and I got 7.27v
Pin 13 should be .30v and I got 3.20v
Pin 14 should be .60v and I got 7.06v
Now, I looked at the schematic and figured the first things to go wrong would be an electrolytic capacitor, so I started hunting the closest ones to IC1. I came across C32 and while not totally bad, instead of 47uF, it read almost 55uF. So I changed it to brand new one, Nichicon for me.
Fired up the service monitor and bam, receive is given and I hear that glorious 1khz tone @ -118dbm. The squelch is working perfect by the way... I'm pretty sure the alignment is a bit off, so that's in order to be performed.
I believe checking more caps at this point would also be a good idea, guess it's possible that more could be faulty or fixing to become faulty. Input? Ideas?
Thank you to every single person in this thread that responded and thank you Kopcicle, you know why.
Oh, I was in a hurry to post this for y'all and forgot to say that I'll be going back and rechecking those voltages. So I'll be back shortly or when the day is new...and I'll have more ideas for you...and you'll have things you want to talk about...I...will...too.
I'm so sorry for that... I just had to do that.
I'm so sorry for that... I just had to do that.
Alright, a recheck and here's what we got :
Pin 1 is the same, Pin 2 is the same and Pin 3 is the same. But the schematic shows there's no connection so I guess those 3 don't mean jack.
Pin 4 is the same. Pin 5 is now .13v, Pin 6 is now .13v, Pin 7 is now .26v and Pin 8 is the same.
Pin 9 is now 2.32v, Pin 10 is 1.45v with no SQ, Pin 11 is the same, Pin 12 is now .29v, Pin 13 is now .29v and Pin 14 is now .62v
I believe that was the issue. A few are slightly off from the chart posted at CB Tricks but for the most part, it seems to be correct now. Maybe the few that's still off will come in line once an alignment is done correctly. I've got to build an 8 ohm load though cause using the speaker for my load and reading the SINAD in the monitor... that damn tone gets to be annoying. But it'll do for now, I guess.
Pin 1 is the same, Pin 2 is the same and Pin 3 is the same. But the schematic shows there's no connection so I guess those 3 don't mean jack.
Pin 4 is the same. Pin 5 is now .13v, Pin 6 is now .13v, Pin 7 is now .26v and Pin 8 is the same.
Pin 9 is now 2.32v, Pin 10 is 1.45v with no SQ, Pin 11 is the same, Pin 12 is now .29v, Pin 13 is now .29v and Pin 14 is now .62v
I believe that was the issue. A few are slightly off from the chart posted at CB Tricks but for the most part, it seems to be correct now. Maybe the few that's still off will come in line once an alignment is done correctly. I've got to build an 8 ohm load though cause using the speaker for my load and reading the SINAD in the monitor... that damn tone gets to be annoying. But it'll do for now, I guess.
It's toasty here in my shop, I just cranked the heat up cause it's kinda chilly outside. I'll probably use my SMD station to warm it up a bit, I thought about that too... stability. I'll report that finding as well, nothing sucks more than a thread that's a dead end with no answer or solution.
Hope this helps!
That's the AGC/SQ and Meter driver...
Below is another area I usualy find a blown cap C44 is the PIN /RF Attenuator that "softens" the response of the otherwise hard-hitting AGC. This is a critical value as it will tend to "distort" the input - in some case of strong overload from another close channel a type of clicking can be heard as the thing tries to "clamp".
C333 tends to help "quiet" the RF gain so it is not so jumpy - but I've added a 223 Disc cap across this near the header that the RF gain uses to enter into the system - to reduce a hum pickup several owners of similar Galaxy front panel designs - heard while adjusting the knobs (any of them) that the board contains - not just this one but on Connex too - any of them that use the vertical or horizontal switch boards.
That's the AGC/SQ and Meter driver...
Below is another area I usualy find a blown cap C44 is the PIN /RF Attenuator that "softens" the response of the otherwise hard-hitting AGC. This is a critical value as it will tend to "distort" the input - in some case of strong overload from another close channel a type of clicking can be heard as the thing tries to "clamp".
C333 tends to help "quiet" the RF gain so it is not so jumpy - but I've added a 223 Disc cap across this near the header that the RF gain uses to enter into the system - to reduce a hum pickup several owners of similar Galaxy front panel designs - heard while adjusting the knobs (any of them) that the board contains - not just this one but on Connex too - any of them that use the vertical or horizontal switch boards.
Last edited:
Thank you Andy, I’ll look at that as well. Might just be a good idea to swap it out with a better quality part while I’m in there. Thanks for sharing that info, appreciate that.
- No one is chatting at the moment.
