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Issues after re-cap EPT36001A - Galaxy II

E

EI2GGB

New Member
Nov 5, 2020
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Hi guys,

I just completed a recap of this radio, for the most part I would replace a cap and test the radio and all was good, however for the last 8 I got a bit cocky and replaced all 8 without testing. When I powered back on I had no receive audio, I am able to transmit be it a bit garbled. I have double checked to make sure all went in in the right polarity. I have also checked for solder bridges and haven't spotted any. Anyone have any suggestions?

Thanks

Gavin
 

Try a LOWER (in uF) value, not everything is 10V these days - this area takes in FM signal thru C28 and R34 - and also any detected RF IF signal from the Am/SSB side of things thru C74 15pF and C36 0.001uF (102) Disc.

TR23 is the AM detector switch, while when in FM mode, the D118 by TR10 acts like an RF switch killing ANY signal if D7 AGC line is high - another problem area you'll need to check for, just look to see if 8 volts is going to the PIN diodes at D7's banded end.

While your in the TR10 area - AM appears a C29 (270pF or thereabouts) and heads down to D23/D24 and TR23 while in FM - passes into IC2 - C19 (IF) and C20(FM) filters/controls this area - this is your 2nd IF section for both AM and FM modes.
 
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Handy Andy said:
Try a LOWER (in uF) value, not everything is 10V these days - this area takes in FM signal thru C28 and R34 - and also any detected RF IF signal from the Am/SSB side of things thru C74 15pF and C36 0.001uF (102) Disc.

TR23 is the AM detector switch, while when in FM mode, the D118 by TR10 acts like an RF switch killing ANY signal if D7 AGC line is high - another problem area you'll need to check for, just look to see if 8 volts is going to the PIN diodes at D7's banded end.

While your in the TR10 area - AM appears a C29 (270pF or thereabouts) and heads down to D23/D24 and TR23 while in FM - passes into IC2 - C19 (IF) and C20(FM) filters/controls this area - this is your 2nd IF section for both AM and FM modes.
Click to expand...
Sorry the delay, and thanks for the great info. I will be continuing troubleshooting this morning.
 
Didn't get much time today, but I think there is an issue around the Product Detector TR15 has nothing on E, B, or C.
 
Last edited:
Handy Andy said:
Try a LOWER (in uF) value, not everything is 10V these days - this area takes in FM signal thru C28 and R34 - and also any detected RF IF signal from the Am/SSB side of things thru C74 15pF and C36 0.001uF (102) Disc.

TR23 is the AM detector switch, while when in FM mode, the D118 by TR10 acts like an RF switch killing ANY signal if D7 AGC line is high - another problem area you'll need to check for, just look to see if 8 volts is going to the PIN diodes at D7's banded end.

While your in the TR10 area - AM appears a C29 (270pF or thereabouts) and heads down to D23/D24 and TR23 while in FM - passes into IC2 - C19 (IF) and C20(FM) filters/controls this area - this is your 2nd IF section for both AM and FM modes.
Click to expand...
Looks like I only have .78v on D7 when on SSB, nothing there when on AM.
 
Ok, good, you don't want 8 volts or even 3.67 volts on it - when it thinks some signal or internal birdies are slamming the RF amp and the AGC is sending a "Wake up" signal to the "front end" PIN diodes. Which are then trying to quench it.

What is nice to know is the MODE switch appears to be working - you have a change in condition when you switch modes. This may be a physical condition issue more than a bad cap - simple wire broken off a potentiometer or even the headers coming loose can cause this.

Onto some simple stuff...did you check the headers, to their respective spots?

  • Thinking you may have moved, disturbed, perturbed or otherwise shifted off one or more pins off their inherited position - making it out to possibly be that age may be taking it's toll on the board connectors as well as the wiring to the Front panel.

You may have "Dead spots" from this, just reheat the soldering pad to the headers respective pins. May help this condition.

Else look for broken wires off the CB/PA switch or even to the rear EXT Speaker PA jacks see if they need some TLC.

I've had radios I've worked on, for days, sit for a week, even two - before I get back to it. Only to find my own advice being thrown at me by the radio saying; pointing out - that your main culprit was a broken wire of the volume control - had to take that one on the chin.
 
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Thanks Andy, So actually Transmit is fine on AM & SSB, Receive is working on FM/AM with C35 Out. Just no receive on SSB. BTW the radio was working before I did the re-cap. I just wanted to get it re-capped before aligning it. With nothing on TR15 I am suspecting something in the Product detector circuitry.
 
Then remember that both AM/FM "share" an IF coil section - so does the SSB mode - shares another separately.

Make sure that the modes you select - signal is getting to IC 1 - for having no meter yet you have transmit and TX light - tells me that the TR23, TR15 - yes, please check to see if the TR15 is working - but also remember...

IC 1 is BEFORE TR15, it sees a signal from AM FM and SSB for Meter and AGC action, so if the meter is dead, this problem is UPSTREAM - back towards the IF sections - for this condition to happen.

SSB seems to show indication - but AM/FM does not... again 455kHz IF back to the RF amp still suspect.
 
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