Issues after re-cap EPT36001A - Galaxy II

[EI2GGB]

While troubleshooting the S-Meter I noticed that I have way to much voltage on T19 Base. Where i should only have 1.7v I have close to 6v.

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.
View attachment 41602
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.
View attachment 41603
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.
​

View attachment 41605
Above: Your Galaxy
Below? Another - 959 showing similar support
View attachment 41606​

There ya' go...

​

Andy,

Thanks again for the comprehensive input, this will give me plenty to look at over the weekend. For now I have closed it back up to get some pleasure in using it.

Thought I would share a pic to let you see what we have been working on.

 

[Handy Andy]

That's in great condition!

May you have - Many Happy QSO's with that

Thank you for letting me work alongside...

TR19 - Hmmm...

Got several diodes that "route thru and around" this section.
6 volts? May need to replace TR19 after fixing the power problem.

​

 

[EI2GGB]

I was in fact too suspecting TR19 as I had a high voltage on the base. I took it out and tested it and it tested fine. But what I did find was that when I was investigating around D19 and R18 that using my signal tracer that it looked like these where shorting above board, as when I separated them the audio signal on my tracer got louder, and the voltage on the base returned to normal.

What I have asking myself though is that if there was an issue in any of the SSB IF AMPS down the line, seeing as next in line is TR14. Wouldn't that hold up the audio signal altogether and I wouldn't be hearing a received SSB signal out the radio speakers.

But what gives me thought is when I do a side by side comparison with an 88HL(very similar board) I can pick up an audio signal on the the collector of TR14, but not on the collector of the Galaxy II. Also on the 88HL on the collector of TR22 with the Heathkit IT-12 I can pick up a nice clean signal, however on the Galaxy II on the same collector I receive a very distorted audio signal, but out of the radio I get a clean audio.

 

[EI2GGB]

This is interesting. Comparing the two radios. When mode is set to AM. TR14 on both radios has voltage (0.7v) on the Collector. When mode is switched to SSB on the 88HL (Reference radio) TR13 has voltage on the Collector. However on the Radio under repair there is no voltage on the collector of TR13.

BTW on both radios the base has 0.7v TR13 when AM is selected, and on TR14 when SSB is selected. This is correct.

 

[Handy Andy]

Look at the schematic above, there is a "Dot" where it shouldn't be,

The D19/D20 act as DC guidance (Steering) so that when in a particular "Mode" the transistor is cutoff from producing any amplified signal - by applying the SAME voltage to both sides of the transistors amp output Collector and Emitter having the same potential no amplification can occur.

I have to run some errands, will return to digest and hopefully post some more thoughts...

THX!

 

[Handy Andy]

There was something you said that made me pause and reflect -

What I have asking myself though is that if there was an issue in any of the SSB IF AMPS down the line, seeing as next in line is TR14. Wouldn't that hold up the audio signal altogether and I wouldn't be hearing a received SSB signal out the radio speakers.

Ok, remember that "SSB" and AM - when they arrive to TR19 (the AM/FM section) it takes in all signal from RF strips IF - and that includes any and all SSB processing too.

TR13, AM/FM "Weighting" the scale of signal for S9 - your RX carrier...

TR14 - SSB Weighting - the scale of Signal for S9 - your SSB signal side.

Both their bases rely of the AM/FM mode (TR13) and SSB mode USB/LSB (CW is included on this MODE (SSB))

L12, separates out AM/FM onto TR8 - single stage IF amp - just to pull out AM/FM from the SSB that is really, really amplified thru TR20-TR22 - Please note the use of 1730L (TR22) in the last stage - AND NO ELECTROLYTIC caps are used, harmed or otherwise left abandoned in the SSB IF strip - so the COMPRESSION level of the SSB signal detection here - is extremely high.

The discriminator parts of IC2 take care of the FM signal - but AM is rampant with SSB and everything else. So it's gets thrown into the 455kHz IF strip to further exacerbates the problem of separating the SSB from the AM - truth is,- once in the AM section, you cant, it's simply the "Received" in the bandwidth (bandpass) of the preceding filter section.

What separates the signal is by the methodology of the diode RF switching and the PLL selecting the right IF "offset" .- and having those same GOSH DARN "diodes" steering power to the right sections and hopefully quenching out the other amplifiers in the combined paths so they don't drown out what you selected.

Since AM has not had any other injected signal to parse down it's frequency - only by image, not by tracking of the PLL done back in the 1St IF stage, the AM received mess, being carrier, heterodyne and SSB combined together - isn't "heterodyned" anymore - it's simply "detected" and sent thru ANL, audio amps and Squelch controls then buffered with a Volume pot and onto the Audio Chip it goes..

FM signal is similar, .but you want to know the SSB side of things...

The effort lies in how the discernment of the last stage IF, being the 10.695 "clarifier" IF - then "Beats" against the L14 output section. That IF is the final "steady state" the SSB signal needs. It is compared with - and no further processing is needed - the audio component is decoded directly from the resulting effort of summation - only you're extracting the Audio - not the IF.

It's why ou heard "audio" without C35, but with it in, you don't - because of that very effect, this section is a lo-pass filter - so C36 is doing the work - the IF present in the line is filtered off because the type of part used, that 945 - isn't able to amplify the IF - it's Hfe is not designed for the effort. So TR15 simply sees audio more strongly than the IF presence - so it processes only the audio - IF is pretty much "canceled out" at TR15.and colorizing of signal is tamed thru C38 a simple smoothing filter - also helps drop off (Hi-cut) any IF that can still be processed in the Squelch circuit.