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Galaxy saturn low output
- Thread starter BAGEBOY
- Start date
Something we saw over and over in this model was for the bias adjustment on the two final transistors set way too high. This adds a few Watts to the radio's peak power output, but makes the final transistors run way too hot, shortens the service life.
Each transistor is mounted with a tiny bolt through a hole in a metal tab at the top of the transistor. If the metal tab's surface is a flat, almost fuzzy black color/texture, that's a hint. The fuzzy black oxide layer only forms at high temperatures.
And if the metal tabs look shiny and metallic color, this did not happen to your radio.
And if your final transistors are black and fuzzy, this suggest that one or both of them will test bad if you unhook the transistors and test them.
If they look clean and shiny, that doesn't mean they're okay, just means they haven't been slow-cooked.
Do you have a way to test a transistor for failure?
73
Each transistor is mounted with a tiny bolt through a hole in a metal tab at the top of the transistor. If the metal tab's surface is a flat, almost fuzzy black color/texture, that's a hint. The fuzzy black oxide layer only forms at high temperatures.
And if the metal tabs look shiny and metallic color, this did not happen to your radio.
And if your final transistors are black and fuzzy, this suggest that one or both of them will test bad if you unhook the transistors and test them.
If they look clean and shiny, that doesn't mean they're okay, just means they haven't been slow-cooked.
Do you have a way to test a transistor for failure?
73
Next point of focus would be alignment. Four slug-tuned "cans" L40, L42, L43 and L44 should all show a peak with the slug VISIBLY below the rim of the hole in the top of the can.
Best way to see a sharper peak is with a continuous tone into the mike on sideband, with the mike gain turned down to hold the power below 2 Watts. The peak those four slugs will show tends to get flattened at full drive power.
Then again, if adjusting any of those four at full modulated power improves your peak power, that's a result, too.
73
Best way to see a sharper peak is with a continuous tone into the mike on sideband, with the mike gain turned down to hold the power below 2 Watts. The peak those four slugs will show tends to get flattened at full drive power.
Then again, if adjusting any of those four at full modulated power improves your peak power, that's a result, too.
73
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Guys I tried to peak etc..the previous owner got it with hg1969 he said he was talking and the radio remain key and he had. Turn the radio off what he found was the hg1969.was shorted he replace.finals and power is.down more than half..any more ideas finals were.c.checked
A transistor tester won't reveal how much RF power gain a transistor should have. A bogus part may be giving you all the power it has. If so, a transistor tester will tell you that it's good.
Just won't tell you what it's good for. Or isn't good for.
73
Just won't tell you what it's good for. Or isn't good for.
73
Here is a reputable source. He sells the HG brand 2SC1969, about halfway down the page.
https://www.icamanufacturing.com/transistor
They seem to work okay for us. You need to turn the power supply down to 14 Volts or less.
73
https://www.icamanufacturing.com/transistor
They seem to work okay for us. You need to turn the power supply down to 14 Volts or less.
73
I have received my finals I got (2) original 2312 and I bought (6) Hg 1969..
I check 2 hg in my 2950 and the output was(29watts) 2-4 watts more on the Mitsubishi
I placed them in my Saturn I see only 2 watts the finals get barely warm..to confirm. I remove and place back in the 2950 and the power was what I saw when I first checked. So it .means I have a problem with the saturn which causes me to see only 2 watts. I tried the 2312 in the 2950 saw 34 watts in the saturn almost 4 watts Any ideas
I check 2 hg in my 2950 and the output was(29watts) 2-4 watts more on the Mitsubishi
I placed them in my Saturn I see only 2 watts the finals get barely warm..to confirm. I remove and place back in the 2950 and the power was what I saw when I first checked. So it .means I have a problem with the saturn which causes me to see only 2 watts. I tried the 2312 in the 2950 saw 34 watts in the saturn almost 4 watts Any ideas
The Saturn is not unlike the earlier boards that sometimes "doubled up" the output caps.
They also may have installed jumpers to empty spots - meaning they whomever owned it before you (unless you're OEO) Original Equipment Owner - those extra jumpers can "sap energy" from the TX strip - which you confirmed by reinstalling these parts into a known working idealized strip in another radio (good detective work BTW)
You might want to keep holding back a bit and work with SINGLE final until you get power delivery back up. Use a single final - this way to can check one "pocket" for the Final and then check the other by swapping. To make it easier- you can remove the simpler jumpers that connect the Base and Collector - the emitter is ground. The "divided" power was sent thru two caps of similar value thru two jumpers and terminated using another cap at the ends for each Base.
This is where the cap carborundrum comes into play - you have to sort out the caps in the TX strip from the ones that connect RF yet prevent DC from jumping across so each section has it's own DC power but RF flows in and out of it in SPECIFIC ways - freely, while hindering RF loops that would otherwise suck up the RF energy being produced.
You checked for heat good technique on your part,- a hot part usually signaled a leaky section or it's got bad shorted parts in it you have to track down the culprits - sometimes more than one.
Once you see the parts that were bad, and how it responds once those bad parts are taken out - look back on the schematic, for it may result in other path fails - similar to the one you just repaired..
I usually find pairs of parts have to be swapped out. Caps are used like dividers for RF signal - similar to Voltage Dividers used by Resistors.
The way it's put in, and the values used, the caps work as a means to reactively reduce - so they are kinda like resistors in the circuit for RF to flow around them so some RF is allowed to pass at a given level of power while to prevent the part it feeds from getting blown up from too much power, some of that power transfer goes thru another cap to ground to keep both the output of the preceding stage, and the input of the subsequent stage - STABLE to work and not squeal - Welcome to Amps - Build An Oscillator 101.
Then use the ones swapped out in another section to see if it restores or acts the same way
They also may have installed jumpers to empty spots - meaning they whomever owned it before you (unless you're OEO) Original Equipment Owner - those extra jumpers can "sap energy" from the TX strip - which you confirmed by reinstalling these parts into a known working idealized strip in another radio (good detective work BTW)
You might want to keep holding back a bit and work with SINGLE final until you get power delivery back up. Use a single final - this way to can check one "pocket" for the Final and then check the other by swapping. To make it easier- you can remove the simpler jumpers that connect the Base and Collector - the emitter is ground. The "divided" power was sent thru two caps of similar value thru two jumpers and terminated using another cap at the ends for each Base.
- - so jumpers are present you can install one final to check a section of that stage
- They Split (parse) and Combine (merge) is specific ways thru phasing - careful not to mix parts if you don't have to.
- - then work the other side the same way only mode the jumpers to operate the other set of foil pads.
- Keep track of the parts, for each radio output section was slightly tweaked from others - read on
This is where the cap carborundrum comes into play - you have to sort out the caps in the TX strip from the ones that connect RF yet prevent DC from jumping across so each section has it's own DC power but RF flows in and out of it in SPECIFIC ways - freely, while hindering RF loops that would otherwise suck up the RF energy being produced.
- So you know, the board is set up so that one final LEADS the other in the cycle - so as RF builds, they work together but one starts out first with more power in the start of the cycle than the other - them both "snap" and sync together until the cutoff in the Class AB cycle starts over.
- This also may mean that if this power low problem is consistent - then the sections ahead of the Driver and Final may be suspected and have failed parts - remember what @nomadradio talked about with tuning slug position in the cans, near the top - it's going to' need to be checked - including a potential disassembly of the cam to retrieve the cap - remove it, then reassemble the can install and sub a cap in place of that internal cap to make the thing resonate.
You checked for heat good technique on your part,- a hot part usually signaled a leaky section or it's got bad shorted parts in it you have to track down the culprits - sometimes more than one.
Once you see the parts that were bad, and how it responds once those bad parts are taken out - look back on the schematic, for it may result in other path fails - similar to the one you just repaired..
I usually find pairs of parts have to be swapped out. Caps are used like dividers for RF signal - similar to Voltage Dividers used by Resistors.
The way it's put in, and the values used, the caps work as a means to reactively reduce - so they are kinda like resistors in the circuit for RF to flow around them so some RF is allowed to pass at a given level of power while to prevent the part it feeds from getting blown up from too much power, some of that power transfer goes thru another cap to ground to keep both the output of the preceding stage, and the input of the subsequent stage - STABLE to work and not squeal - Welcome to Amps - Build An Oscillator 101.
Then use the ones swapped out in another section to see if it restores or acts the same way
- - it is a path of logic
- - once one section starts working well, the sections ahead (upstream) from it are also suspect
- - you may find a particular value of cap or type (package) of a capacitors to be bad
- - the outline, seems to be the one that failed in more than one stage
- - it was due to an assembler defect
- - not using prime parts in the machine assembly process
- - those can show up as "dead spots" in any section of just one board
- - Quality Control is supposed to catch this but they don't always replace the roll from which the parts get installed from until after the day is complete - you can have up to 10 radios with the same problem of a simple bad cap all going out that same day not getting recalled back to fix because of delays and shipping issues.
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I have 2 Saturn's one has some disc capacitors on the soldered side 3 to be exact. C170 C505 .... however I have seen another which doesn't have them. What is strange the Am power is 10dead key andswings 15-17 rms 40 pep but I am only seeing about 20-25 watts I had one before which had 3 capacitors on the colder side one was 560pf..but the output was 30-35 on ssn..any ideas I adjusted L40, L42, L43 and L44 that's the maximum power .I also adjust I think vr 12 and I saw now increase
I know this was a few years ago, curios if you'll see this and what was your final outcome...
Thanks
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