Ept360014b Saturn LSB USB tone

[Hawkeye351]

I been working on my personal galaxy Saturn lately trying to get my base setup. I've already recapped the entire audio section due to it having a hollow watery sound in all modes in transmit, that's with all the limiters intact. Got great reports on transmit audio, best reports I've gotten on any radio so far after the audio section recap.

Well I've been talking on it a few days on AM and it works great. Receive is phenomenal, transmit from what I'm hearing from others is the best work I've done so far.

But,

I was messing around with USB and LSB last night and noticed the receive isn't quite as strong as AM/FM. I touched up L3 and L4 which brought the SSB receive up some, acceptable. But I noticed the received tone difference between LSB and USB sound different. USB has the normal SSB sound, while LSB has that trebly sound, nasally sound. The carrier oscillators are dead on frequency, PLL oscillators are dead on frequency. None of the IF cans in this radio top out flush, they all end up being 1.5 to 3 full turns down from the top. The only IF can that concerns me is the LSB carrier oscillator, it's almost bottomed out to get on frequency. I'm thinking this could be the reason for the trebly LSB sound. Should I replace the LSB carrier oscillator IF can or would a nearby cap affect it?

Note:
Only the audio section has been recapped. The other sections still have the old original baby blue (light blue) caps in their locations. The radio aligns with no issues other than the LSB carrier oscillator has to be nearly bottomed out to get on frequency.

Thanks guys/gals...

 

[Cable Guy]

If some caps are failing, gotta imagine more to follow. A complete recap may fix your issue.

 

[nomadradio]

The SSB crystal filter will prove to have a shifted "window", or passband as they call it. Ideally, a graph of the sideband filter's frequency response would be a sort of rectangle with rounded corners, and each side slanted a bit. This way you can put your carrier frquency just outside the "window". The audio frequencies that can pass through in one sideband will be the same for upper and lower.

But in the real world, this window won't be perfect. It will bulge either above or below the center frequency of 10.695 MHz. One sideband will now have more treble frequencies in the modulated audio, and the other sideband will have less.

Quick way to judge is with the radio on a dummy load. Turn up the Tone control and click from USB to LSB and back. The audio pitch of the static noise you hear should be the same. In the real world, one sideband will have a lower tone to the hiss than the other sideband.

And this is because the filter's passband window is never perfectly symmetrical. With age, the crystals inside the filter will drift and distort the filter's frequency response.

The older the radio the more likely this becomes. Another good reason to have a junker or three you can rob and see if a used filter is less distorted. Haven't bought one of those new in a while. A new one might work better, might not.

You pays your money and you takes your chance.

73

 

[Hawkeye351]

Recapping the entire radio I think may have resolved that issue. Just got finished recapping it, checked over everything then hooked it up and checked it out. Receive seems better with less hash, haven't realigned it yet, figured I would let it sit for an hour and settle with the new caps. LSB does seem to sound better though.

After an hour I'll give an update on the outcome.

 

[Hawkeye351]

Question though:
For the two 100uf caps in the vco/oscillator section, I had no more 100uf in stock so I used 220uf instead, will this cause issues?

 

[Cable Guy]

C107 and C293? I don't think it will hurt.

Edited to add that C107 may have an effect, but I'm sure c293 would be fine. Either way, I don't think that it would hurt.

 

[Hawkeye351]

After sitting for a while, I realigned the entire radio.

Results:
Receive is awesome, all modes.
Transmit is awesome, all modes.
Transmit and receive sensitivity is great in all modes.
USB now has the trebly sound whereas LSB sounds like it should.
All features work as they should, with the exception of the echo board (switch is broken) which I could care less about cause I don't run echo on my rigs.

Note to self, again, lol:
Recap entire radio if it's old enough before jumping to conclusions of bad parts.

 

[Cable Guy]

Great job! I'd still follow nomads suggestion on the crystal filter, at least sub another if USB won't tone down.

 

[Hawkeye351]

I may have another export SSB parts radio laying around here I could throw in it. Thank you Nomad and Cable.

 

[nomadradio]

I used 220uf instead, will this cause issues?

Not likely.

73

 

[Klondike Mike]

... Recap entire radio if it's old enough before jumping to conclusions of bad parts.

That's what I like to hear. Another radio saved from the scrap heap! For future restorers, I have a electrolytic capacitor kit for this radio. See link below;

https://klondikemikescapkits.com/pr...nklin-w-ept360010a-electrolytic-capacitor-kit