The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Rick, I have been taking a break from this radio, it is ticking me off. Ill get back with it soon. Im starting to think it has other problems in addition to the agc. Ill get back on it soon.

just taking a sanity break

Doug

I did a quick look tonight and I need to do the following,
r52 is 6k8 change to 680
r327 remove and jump
change c52 to a 18p ( cant remember what it is right now but Ill dbl check it
c55 remove and jump

it may be a few days before I have time to mess with it again, I will let you know how it goes ...

Ill check that stuff tonight, I know I did not have D21 and D22 removed but I do now. I was wanting to check the driver and final bias current but I cant seem to find test point 7,8 and 9 . I see tp 1 2 and 3 with the big plate type jumper used.

My ps is an astron 35

Thanks

Dj

I found it , thanks.
that is one SMALL diode. heh!
Im also getting reports that it is a little distorted on xmit, maybe not warbling like i had thought. its hard to get a good reliable radio report here lately, Ill have to put my son on the mike and listen to him from the moble.
I have a couple ...

OK I did the mods. my radio didnt have D19 installed . I tried it last night and I would say it has improved some but still nowhere near as good as the 2950 i had here recently. the fairly strong ssb signals are still distorted but maybe not as much. The really strong signals are still bad. When I ...

my r72 is 6k8 from the factory , You didnt by chance mean for me to replace the 6k8 with a 3k9 did you? just though Id ask to be sure.
R73 was 1k so I will put a 2k2 in there if I can find one today.



=========
Change
C53 33p to 4n7
C56 10n to 4n7
R72 3K9 to 6K8
R73 1K to 2K2

Remove
D19 FC54C
R74 ...

what does the n stand for in the capacitor rating
for example would a 4n7 be a 47pf cap in the US ?

thanks Ill dig up the parts and try that.
DJ

Change
C53 33p to 4n7
C56 10n to 4n7
R72 3K9 to 6K8
R73 1K to 2K2

sorry , not enough space between readings let me space them out more

heres the SSB voltages

pin 5 .1 low -- 5 volt high
pin6 .11 low -- 4.1 high
pin7 .2 low -- 4.7 high

pin12 .28 low -- 8.8 high
pin13 .28 low -- 3.1 high
pin 14 .63low -- 5.6 high

Here are the AM voltages


pin 5 .2 low -- 5.0 ...

Rick, that was the ssb voltages in the last post I forgot to post the am, here they are and yes low= no or not much signal and high is a very strong signal
here are the am voltages and Im working on the rest right now

pin 5 .2 low 5.0 high
pin6 .23 4.2
pin7 .6 2.4

pin12 .35 10 volt yes 10 volts ...

Rick it still distorts with r318 one leg up. here are the voltages

pin 5 .1 low 5 volt high
pin6 .11 low 4.1 high
pin7 .2 low 4.7 high

pin12 .28 low 8.8 high
pin13 .28 low 3.1 high
pin 14 .63low 5.6 high

dj

I installed a socket and the new chip, still works the same, distorted on high signal strength.darn it

Whoops, Ok I just did it at the pin14 solder pad ( pin 14 removed)
with no or very low signal its and 0 volts applied it reads 6.9v at pin 14 but as soon as any voltage past .1 or .2 it goes to zero at pin 14 with no signal

with a strong signal pin 14 goes to well over 5 volts and even 7 if I key ...

Yes it was working with the test applied to D16

OK I have isolated pin 14 (lifted it out) and by applying voltage to the anode of D16 like you said and it does clear up the distorted ssb signal as the voltage is increased.

with ZERO volts applied to D16 the voltage at pin 14 is 6.9 with or without ...

OK, I did that and it does clear them up when the voltage gets up near 4 or so volts .

dj

OK this is with the scope probe on 10x
D21 and 22 at anode AND cathode both read the same, about .1 volt at low signal and maybe a little over .1 with a strong signal

on D18 cathode its 0 volt then 2volt with strong signal The anode goes from .1 up to 2.5volt with high signal

D20 cathode reads 1.0 ...

OK, I replaced D21 and D22 just because I had some 4148 diodes and it may have helped just a little bit but not much.

with a dvm on D21 and D22 I get ZERO VOLTAGE on either end of both diodes. I have an Oscilloscope and on D18 cathode I get from 0 to 1.4 with a strong signal and .1 to 2.0 on the ...

I just replaced Q13 with a nte289a npn transistor and voltage at d8 cathode are still .7 to 3 volts or slightly higher

with no signal, switching from AM to LSB or USB it is .7 on ssb and about .18 on am

Rick it goes from .7 to 3.0 volts when I transmit on a radio close by. I have not done anything with q13 yet, is that the culprit?
that is measured with a fluke 76 digital meter with bargraph display I dont have a decent analog meter
thanks
doug

Update:
,Rick
I replaced all the resistors and both caps you suggested and it is still the same. I have not replaced Q13 yet but I have a replacement and will try that tomorrow, is there any good pictures out there that show the copper side of the board with the components labeled?

Could a bad Q13 ...

Thanks Rick, I will change those resistors and report back here with my findings. May take several days to source them but you can bet Ill get them. if the local radio shack has them I will do it tomorrow.

Im not just being picky, this thing is unintelligible on ssb if the signal is strong ( and I ...

so are you saying the early 2970's like mine all had the symptoms I mentioned? This thing you cant hardly understand a strong ssb signal ( like someone a mile away without lowering the rf gain. I dont have all those resistor values here but I can get them. Ill order them up

thanks, I appreciate ...

Rick I just edited my last post I think I measured the wrong pins
ser736640

from the solder side of the board, 12,13 and pin 14 are on the bottom right of the chip with the front of radio facing me. that sound right?

dj

IC1
pin 12 ssb .4.0 volt and am also .4.0
pin 13 ssb 7.2 am -.1
pin 14 ssb -.1 am is 6.56



thanks Rick

DJ

OK lets see here, its an RCI 2970
the board number is EPT295013Z
not sure what the pll is
this looks like a 2950 to me but with an amp added on inside.
I dont see the battery up front on this one like a 2950 I had so Im thinking this is the second series with no battery.

main problem is that on ssb ...

Radio receives ok in AM far as I can tell but on ssb , the stronger the signal is the more distorted it is. If I crank the rf gain all the way down the strong signals come in clearly. Its so bad that I cant hardly understand a really strong signal. I just had a 2950 here and its receiver didnt do ...