Issues after re-cap EPT36001A - Galaxy II

[EI2GGB]

D40 still has 7+v on both sides regardless of USB/LSB being selected. D39 only high the cathode side.

 

[EI2GGB]

Remember you were looking for a tricked cap - now you have a Dead SSB receive.

So in the efforts of all those caps that went in right, Hurray! But - now you have no SSB receive, look back to the "power feed" lines that arrive to specific spots.

Example - TR23, what powers it? A line directly from the S502 switch - the AM line to turn on that transistor.
When you switch in to AM mode - you should see 8 volts on one side of R95, but the other side should be about 0.7 volts - if it is less than that - then there's your short....

So did you check D27? That is a simple diode that is used as an RF switch. It allows some of the RF signal from the 10.695 oscillator - to "gently" mix with - but not drown out - the IF captured off of L14.It mixes in with it at the junction of C72 and C74 - your TP6. It (this TP6) only needs a small mixing "birdie" to sample off of to get enough of the incoming IF Receive to generate the audio being sent to TR16.

If D27 is dead - short - it will kill any signal from TP6 on to the TR15 - because it's PAST the voltage hold back Cap C73, so if a large power carrier surge got into this little area, the Diode is the first to go - any excessive power even from the 10.695 section - will destroy this small signal diode.

Did you try removing TR23 to see if SSB returns in SSB modes. More than likely it won't affect it - but if it does, then the front panel switch may have damaged TR23 - to short out Base to Emitter - sucking down signal and making AM appear all the time - but the radio isn't sending IF to it, because TR23 is a dead short - taking away the SSB signal.

When everything works, TR23 operates only in AM so any signal won't get rectified by D23 / D24 - instead it routes it's IF off of L14 TO TR15 thru C26 - ALSO C24 - SAMPLES this IF and sends it to IC 1 to show on the S/RF meter - which you don't have working in this mode either - so either L14, TR23 or the lines around L14 are faulty.

So to me, everything from L14, D27 - C72, C73, C74 and TR23 are still suspect, because TR15 AND AGC / S/RF meter - need what is there at C72, C74 junction - to even work. D27 needs to have it's Banded end to foil ground - it works as a PIN diode / RF Switch to keep the IF signal (that 10.695MHz) low level - below 0.7 V (may scope to about 1.15 Volts PEP) so it won't drown out the IF trying to get thru to TR15 and IC1

Thanks for all the efforts Andy, I am reading and checking thanks. I posted the piece about D40 D39 just as you posted.

 

[EI2GGB]

Remember you were looking for a tricked cap - now you have a Dead SSB receive.

So in the efforts of all those caps that went in right, Hurray! But - now you have no SSB receive, look back to the "power feed" lines that arrive to specific spots.

Example - TR23, what powers it? A line directly from the S502 switch - the AM line to turn on that transistor.
When you switch in to AM mode - you should see 8 volts on one side of R95, but the other side should be about 0.7 volts - if it is less than that - then there's your short....

So did you check D27? That is a simple diode that is used as an RF switch. It allows some of the RF signal from the 10.695 oscillator - to "gently" mix with - but not drown out - the IF captured off of L14.It mixes in with it at the junction of C72 and C74 - your TP6. It (this TP6) only needs a small mixing "birdie" to sample off of to get enough of the incoming IF Receive to generate the audio being sent to TR16.

If D27 is dead - short - it will kill any signal from TP6 on to the TR15 - because it's PAST the voltage hold back Cap C73, so if a large power carrier surge got into this little area, the Diode is the first to go - any excessive power even from the 10.695 section - will destroy this small signal diode.

Did you try removing TR23 to see if SSB returns in SSB modes. More than likely it won't affect it - but if it does, then the front panel switch may have damaged TR23 - to short out Base to Emitter - sucking down signal and making AM appear all the time - but the radio isn't sending IF to it, because TR23 is a dead short - taking away the SSB signal.

When everything works, TR23 operates only in AM so any signal won't get rectified by D23 / D24 - instead it routes it's IF off of L14 TO TR15 thru C26 - ALSO C24 - SAMPLES this IF and sends it to IC 1 to show on the S/RF meter - which you don't have working in this mode either - so either L14, TR23 or the lines around L14 are faulty.

So to me, everything from L14, D27 - C72, C73, C74 and TR23 are still suspect, because TR15 AND AGC / S/RF meter - need what is there at C72, C74 junction - to even work. D27 needs to have it's Banded end to foil ground - it works as a PIN diode / RF Switch to keep the IF signal (that 10.695MHz) low level - below 0.7 V (may scope to about 1.15 Volts PEP) so it won't drown out the IF trying to get thru to TR15 and IC1

I believe you are spot on with the area of D27 as I neither have voltage on the anode or cathode side.

 

[EI2GGB]

If I am right in my thinking the junction of C72 & C74 is getting fed up through C73? If so I have 2.66v on one side of C73 and nothing on the leg towards C72/C74, I presume i should have?

PS I did swap out D27

 

[Handy Andy]

Yes, scope for RF, the 2.6 volts I presume, is a DC measurement C72,C74 forms the "Tap" or injection point to mix RX IF with Radios internal IF to TR15.

• DC is a tricky thing, that "diode" is supposed to keep RF generated by the 10.695 section, from going too high, then you may have a "birdie" that drowns out your RX IF signal. (The issue of describing this is to keep RX IF and Radio IF from canceling out each other - so work with me as RX IF as RECEIVED SSB signal)
• Too much DC will act as a limiter - quenching out RF simply by swamping it with DC voltage so that it won't appear at the output of C73 - DC makes this signal more of a "static" not kinetic - so the cap itself can't translate the RF off of one plate to even develop it on the other - too much DC current will negate the effect.
• D27's purpose is to keep RF signal that does appear, from spiking or damaging - or even producing the carrier that will drown out your RX IF you're listening for.

The output of L14 - thru C34 then sends some of this into IC 1 - S/RF meter Pins 5, 6, and 7. ONLY from L14 - R96 along with C72 generates a filter of 22K impedance (ohmic attenuation of what is appearing at C72, C73, C74 from backfeeding) to allow L14's signal to enter into IC1's S/RF meter buffer amp. The rest is then allowed to propagate thru C74, PAST the AM Detector. into R103 and C36 and TR15.

R103 and C36 have SSB and AM signal to contend with - but are the next tap point downstream from L14's SSB and AM Detector output from L4 (not L14)

So if SSB RX is dead, you'll need to research L14 and area around it.

It is not beyond the realm of probability that L14 has failed.

Continuity checks here...

 

[EI2GGB]

Yes, scope for RF, the 2.6 volts I presume, is a DC measurement C72,C74 forms the "Tap" or injection point to mix RX IF with Radios internal IF to TR15.

• DC is a tricky thing, that "diode" is supposed to keep RF generated by the 10.695 section, from going too high, then you may have a "birdie" that drowns out your RX IF signal. (The issue of describing this is to keep RX IF and Radio IF from canceling out each other - so work with me as RX IF as RECEIVED SSB signal)
• Too much DC will act as a limiter - quenching out RF simply by swamping it with DC voltage so that it won't appear at the output of C73 - DC makes this signal more of a "static" not kinetic - so the cap itself can't translate the RF off of one plate to even develop it on the other - too much DC current will negate the effect.
• D27's purpose is to keep RF signal that does appear, from spiking or damaging - or even producing the carrier that will drown out your RX IF you're listening for.

The output of L14 - thru C34 then sends some of this into IC 1 - S/RF meter Pins 5, 6, and 7. ONLY from L14 - R96 along with C72 generates a filter of 22K impedance (ohmic attenuation of what is appearing at C72, C73, C74 from backfeeding) to allow L14's signal to enter into IC1's S/RF meter buffer amp. The rest is then allowed to propagate thru C74, PAST the AM Detector. into R103 and C36 and TR15.

R103 and C36 have SSB and AM signal to contend with - but are the next tap point downstream from L14's SSB and AM Detector output from L4 (not L14)

So if SSB RX is dead, you'll need to research L14 and area around it.

It is not beyond the realm of probability that L14 has failed. You are beyond awesome. Yes I was measuring DC. As I am sure you can tell this is really the first time I have tried a project like this and ended our needing to repair. Should I be able to measure the RF signal with my 10x oscilloscope probe. If not I will need to build or buy and RF probe.

Continuity checks here...

Andy,

Thanks so much for this detailed information.

 

[EI2GGB]

Hi Andy, I am back. I think I set us on the wrong course when asked to check TP6 previously. I did not measure the signal there correctly. I am measuring 10.7Mhz there.
I am thinking I have an issue in the RF AMP area, as I am not detecting anything on EBC of TR17. I am not detecting any RF signal in that area.

 

[Handy Andy]

Ok! Whew, thought we would have to trade in the old family car and get a jalopy in return ....

SIGH...

OK, but you said AM and FM is fine - so is SSB RX still out or is all RX affected?

 

[EI2GGB]

Hi Andy, not exactly though AM/FM receive worked only when C35 was removed. With C35 inserted I get the same on AM/FM/SSB. However with a Heathkit IT-12 earlier today I found a number of spot on the radio where I could hear both AM/SSB, just nothing in the RF AMP area.

update : I don't know what's going on, but now i just check TR17 again and its fine. It wasn't earlier today. a possessed radio.

 

[Handy Andy]

When you see it go dead like that - check PLL's Pin 6 too - see it it bounces around - just a thought that maybe it's having lock issues.

Remember the RX has to shift in frequency - from TX frequency - in the PLL section for that 455kHz jump - so if it has issues doing that...

D33 versus D123 - Locate C219 - see if that is good - Don't ask me how I found that...

 

[EI2GGB]

When you see it go dead like that - check PLL's Pin 6 too - see it it bounces around - just a thought that maybe it's having lock issues.

Remember the RX has to shift in frequency - from TX frequency - in the PLL section for that 455kHz jump - so if it has issues doing that...

D33 versus D123 - Locate C219 - see if that is good - Don't ask me how I found that...

Pin 6 of the PLL does seem to be locked with 7.62v.

 

[Handy Andy]

Ok, then also the radio uses two strips, so one strip is for the 455kHz and 10.240 IF to subtract that signal from the 10.695/10.7 MHz IF so that is why I had you go look for signal - but as you have been finding, the radio works just no SSB RX side (from all of this - precipitated out to be this condition - I Hope)

When this condition originally occurred, the caps were suspect...Caps like C24 and C20 - but AM and FM work, and now, the SSB IF section - using a SEPARATE filter and 10.695 has no RX but you do have TX - so then the issues is with the strip from TR19 onto TR22 (the end being L14's output).

Hows' the "secondary" 10.695 strip, including the AN612 doing?

Added:
The reason for this question is...

C35 is a simple filter cap, So why do you hear signal when it out, but it disappears when it's in?

Means it's filtered out something

Then, look at the POWER FEED line to that TR15 - there is something blocking the signal from following the original routes - so it uses the POWER FEED lines instead...

It would explain why; when C35 in, you hear nothing, C35 out - then something can pass into the TR15 amp as signal from a noisy power feeder line....

 

[EI2GGB]

Ok, then also the radio uses two strips, so one strip is for the 455kHz and 10.240 IF to subtract that signal from the 10.695/10.7 MHz IF so that is why I had you go look for signal - but as you have been finding, the radio works just no SSB RX side (from all of this - precipitated out to be this condition - I Hope)

When this condition originally occurred, the caps were suspect...Caps like C24 and C20 - but AM and FM work, and now, the SSB IF section - using a SEPARATE filter and 10.695 has no RX but you do have TX - so then the issues is with the strip from TR19 onto TR22 (the end being L14's output).

Hows' the "secondary" 10.695 strip, including the AN612 doing?

Added:
The reason for this question is...

C35 is a simple filter cap, So why do you hear signal when it out, but it disappears when it's in?

Means it's filtered out something

Then, look at the POWER FEED line to that TR15 - there is something blocking the signal from following the original routes - so it uses the POWER FEED lines instead...

It would explain why; when C35 in, you hear nothing, C35 out - then something can pass into the TR15 amp as signal from a noisy power feeder line....

Thanks Andy, investigating.

 

[EI2GGB]

Thanks Andy, investigating.

Ok, then also the radio uses two strips, so one strip is for the 455kHz and 10.240 IF to subtract that signal from the 10.695/10.7 MHz IF so that is why I had you go look for signal - but as you have been finding, the radio works just no SSB RX side (from all of this - precipitated out to be this condition - I Hope)

When this condition originally occurred, the caps were suspect...Caps like C24 and C20 - but AM and FM work, and now, the SSB IF section - using a SEPARATE filter and 10.695 has no RX but you do have TX - so then the issues is with the strip from TR19 onto TR22 (the end being L14's output).

Hows' the "secondary" 10.695 strip, including the AN612 doing?

Added:
The reason for this question is...

C35 is a simple filter cap, So why do you hear signal when it out, but it disappears when it's in?

Means it's filtered out something

Then, look at the POWER FEED line to that TR15 - there is something blocking the signal from following the original routes - so it uses the POWER FEED lines instead...

It would explain why; when C35 in, you hear nothing, C35 out - then something can pass into the TR15 amp as signal from a noisy power feeder line....

Hi Andy, you're a genius. Power feed was the problem. I had a tiny line break between R56 and R58. Receive is working again. I still don't have signal meter though on SSB receive. Thanks so much for sticking with me.

 

[Handy Andy]

I am not the Genius here, you have been the one doing the work.

I already owe one a dinner...

Wouldn't call that a "genius" - more like I have to remember to step aside and let others that have known this chassis longer than I have - to post a thought or two.

You deserve a Congratulations' and several Accolades - if not a EMMY and OSCAR for putting up with all these antics.

This thread was quite efficient, it didn't turn out to be over 200+posts long with tons of repeating and echoed posts from others asking you questions that were already answered in the first few "pages"

Read thru this thread, lots of places to check.

But I'll try and go over the most impactful ones...

Just so you know, I kept the PC active with the PDF of the schematic you supplied - thank you, many others don't supply a working document of the stuff they are dealing with - you helped us all in this forum, to help you be successful as a repair technician because others came along side to review and help you thru this. It's much harder when you don't have a map to travel these radios' circuit paths these days.

With the S/RF meter - check C34 and those diodes that route to IC 1 - L14 sends it.

R96 and C72/C74 and C73 - The area using C73, remember - "tickles" the IF - RF into the L14 output mixing with it before it gets to TR15. The R96, C72 mess, tends to keep what is on L14, and at C73, from mixing in too much signal at L14 and what goes thru C34 into IC1's S/RF metering.

IF R96/C72 values as well as the others used in this region are too large - one signal will swamp out the other - if C73 is too large in value - it would send too much IF into this area you'd have a bigger problem with No receive because the IF is pounding down the RF input from PIN diode full conduction - from on board birdies that can form.

Don't ask me how I found that out...(PC122 amongst others)

You may find the values per schematic are "approximate" and MAY need to be tweaked.

This also applies to the AN612c section to make IF and Audio mix properly together.

Locate TP 5 and use your scope to help determine if the IF
present on Pin 3 of the AN612 is mixing in proper ratios to the Audio on Pin 1
IF is one thing that can "clip" and distort if it's too much in the input pin.

R159 270K is about Ideal - 220K to 330K work
It's R260 that may be a bit much.
C123 and C124 - supply (RF-Divider) the "strength" of IF signal that Audio mixes with.

A Galaxy 959 - AN612 section . . .
Note the various values used in that same areas...
Only the numbering is different - support is still the same in design.

R172 - compared to R260
C123 and C124 - to C147 and C150...
These values do change because of the Factorys' needing to
make changes to the levels of signal ratios, making sure they are correct.
​

Although the changes here are minor, the suppliers for the chips they now use have different responses to their input signal and levels - some results in mixing levels can be quite critical when it comes to having the right ratios of mixing for inputs to generate the right level of output for TP 5 to review.

So when you're looking at C72/C73/C74 - again, ratios of values to each other plays a role in how the "demodulation conversion" effort works.
​

Above: Your Galaxy
Below? Another - 959 showing similar support
​

There ya' go...

​