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Galaxy DX 88HL HELP!!!!
- Thread starter hank
- Start date
hank said:
Repairing any electronics is 60% symptom analysis (recognizing what's not working) and 40% troubleshooting.
So just knowing exactly what's not working is over half the battle.
Below you'll find enough info to repair any Galaxy radio with good receive and no transmit power.
You only need two things for these radios to produce power.
1. Proper voltage
2. Proper drive.
Checking proper voltage is easy with only needing a voltmeter.
Since you are testing the transmit section always make sure your voltage checks are done in TX mode.
Make sure front panel controls are properly set before testing, Mode SW - AM, RF Pwr button to HI, etc...
Key radio and check collectors of TR51 (2SB754), TR44 (2SC2166), TR43&TR56 (2SC2312) all for approx. 6.5 volts.
Checking for proper drive is a bit more involved and requires a good 100Mhz scope with a (x10) scope probe.
Below are the AC/RF voltages peak to peak starting from TR45 out to the antenna.
TR45 collector - 10v peak to peak in TX.
TR44 collector - 15v peak to peak in TX
TR43/56 collectors - 25v peak to peak in TX
Output side of L33 - 80v peak to peak in TX
Output side of C166 - 40v peak to peak in TX
Output to antenna - 60v peak to peak in TX
If you do not have the approx voltages at TR45 then you must troubleshoot the transmit oscillator circuit of X4 (10.695mhz) crystal and TR30.
In transmit check the emitter of TR30 for 10.695mhz.
Next check IC3 pin 7 for 10.695mhz in TX.
Next check IC9 pins 7&8 for 10.695mhz in TX. - very small signal, will only see this with a good scope and switch the probe to x1.
The last troubleshooting aid that can help would be to have a known good DX88 setting on the bench plugged into DC so you can use it
for comparison checks.
8)
-Ray
I agree if you have all voltages where they should be it has to work it rules out everything from bad caps to resisters I am wondering if you have a weak or spuratic final thats dropping off here and there I seen this once and I reheated the legs on the finals and resoldered them which fixed my issue maybe try that mine would almost completely quit.
Try the simple things first. That radio has a frequency band board. Check the connections to and from the band board for starters. Is the band knob rotary switch working correctly.
In regards to tx or rx that could be a completely different issue but could not. Process of elimination
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One thing to look for, is if the counter display is only showing one frequency all the time, I've had to take the covers off and reheat the soldering pins the connector uses to reestablish the connections - these things aren't foolproof - the connecter can come loose.
Other aspects are -
Does the LED display work?
Does the PA work?
No TX or RX is is a strong clue that the 8 volt supply may be damaged.
IT may not be the Regulator that got damaged? It could be the foil traces that take power from that section and distribute it to other locations - every foil trace from the 8V constant regulator is suspect.
In the attached graphic, the biggest Achilles heel for the radio is it's 8V power feed - the main power supply rail is located on the outer skirts of the board and is EXTREMELY vulnerable to shorts because the case and lots of open grounding points are located close by to it.
The Graphic may not reflect your problem, but the highlighted section in RED is what I mean, that outer large foil trace is the 8 volts the radio uses, so if it' (that) has shorted to ground inside the radio - you may have found out why and to fix? Just repair the break and replace the 8V main power transistor 2SA473 they used in it...
Other aspects are -
Does the LED display work?
Does the PA work?
No TX or RX is is a strong clue that the 8 volt supply may be damaged.
IT may not be the Regulator that got damaged? It could be the foil traces that take power from that section and distribute it to other locations - every foil trace from the 8V constant regulator is suspect.
In the attached graphic, the biggest Achilles heel for the radio is it's 8V power feed - the main power supply rail is located on the outer skirts of the board and is EXTREMELY vulnerable to shorts because the case and lots of open grounding points are located close by to it.
The Graphic may not reflect your problem, but the highlighted section in RED is what I mean, that outer large foil trace is the 8 volts the radio uses, so if it' (that) has shorted to ground inside the radio - you may have found out why and to fix? Just repair the break and replace the 8V main power transistor 2SA473 they used in it...
Attachments
="Eldorado828, post: 774306, member: 46753"]Try the simple things first. That radio has a frequency band board. Check the connections to and from the band board for starters. Is the band knob rotary switch working correctly.
In regards to tx or rx that could be a completely different issue but could not. Process of elimination[/QUOTE]
It doesn't matter what band I put it on or what channel it's on, it stays at 10.695. I'm not exactly sure what tests to make. I do have the schematics for it.
In regards to tx or rx that could be a completely different issue but could not. Process of elimination[/QUOTE]
It doesn't matter what band I put it on or what channel it's on, it stays at 10.695. I'm not exactly sure what tests to make. I do have the schematics for it.
The 2SA473 transistor has broken legs. I Will solder it back on and give you an update. I'm also going to resolder and resolder the frequency counter connections and see if that will help. I'm also using a solder with 3% silver. I don't think that will hurt anything will it?
Did I miss something or did he not say this was an intermittent issue. So if I'm right then all those steps Ray listed are valid but only when the unit is in a none working intermittent state. So it's all valid except (Intermittent loss of output power) Soooooo! you first need to be able to follow the procedure laid out while the radio is not functioning right? Now I don't know if that was happening but you can't take measurements while the radio is functioning so if hank was taking readings while the radio was working it means nothing, Just wondering because I don't know! I have tracked down this kind of intermittent issue probably 5 thousand times and for the most part, it has always been a Galaxy a Connex, or Ranger so good luck it's fun. As a footnote, I modified a rock polishing machine with a flat board covered with carpet and 2 straps. I would strap a problem radio and set it at a low-level vibration rate while the radio was turned on and hooked to a signal generator if it was a receiver issue if it was a transmit issue it would be injected with a low-level modulation I would let it run until it quit. I didn't have to do this all the time but for some of the hard dogs it came in handy. Sounds crazy but it did work.