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TEXAS STAR DX 500 won't power up
- Thread starter long night
- Start date
If R18 and R19 are burnt, scorched or otherwise discolored, that means the 2 power transistors associated with them (Q4-Q5) are bad and will need replacing.
This is my 500V after a temper tantrum.... If any of the resistors in the red circles are discolored, the power transistor corresponding with it is most likely blown. Also, take a good look at the resistor in the yellow circle and make sure it's not burnt, that usually only happens when you drive it into nuclear meltdown though.
The 2 resistors at front of the amp in red circles, R18 and R19 I believe are slightly burnt on one end each. It would be much quicker and easier to replace these two and see what happens before replacing all the power transistors. What do you think about trying this first. They would still require replacement if the power transistors need to be replaced also.
If they are indeed burnt, replacing them only, would be a waste of 2 resistors as they would burn out almost immediately. The sole purpose of those 2 resistors is a visual indicator that the power transistors have failed. You would only "need" to replace 2 transistors to get it operational but if you have the disposable income to replace all 4, that would be ideal. Are they DEI transistors or an older box with Toshibas?
Toshibas. So the best thing to do is replace the resistors and put in 4 new matching transistors?
Well, I HATE to hear they are Toshibas, those things are ridiculously high now, $200+ ea. and don't be fooled by the ones on eBay, they're fake. To replace them with HGs requires having the input and output retuned as they are not direct replacements.
For the price of 2 Toshibas you can almost buy a new 500V.
I have HEARD and its been said the HG2879C is closer to the Toshiba part still not a direct replacement though. Again others with more expertise can judge that.
Thank you for all your help. It looks like it will need to sit on a shelf for parts.
R16 and R23 , 1.8 ohm bias resistors, could also be bad, one or both, and not appear to be by looking at them.
I have seen that happen numerous times also.
At this point though, sounds like the keying transistor is bad.
I have seen that happen numerous times also.
At this point though, sounds like the keying transistor is bad.
I live in Vancouver Wa. There no longer any radio shops or technicians around this area to address repairs.
Not the C version, its the regular HG 2879 16D08 that tune wise are the closest to the toshiba 2879's. They aren't a perfect tune match but close enough for government work lol.
As was said DO NOT BUY THE CHINESE FAKES. Lots of fake toshibas out there and no real ones to be found unless you know some one who has a private stash and then good luck getting them to sell some.
You could replace with used toshibas with close matching gains. Used toshibas run about $100/pill. If it were mine and i didnt have any used toshibas to put in it id replace with HG 2879 16D08 pills for $40/pill and run it till it smokes again, wash, rinse, repeat lol.
Before doing any of that id need to know what caused the pills to smoke and fix that also if need be.
How old is this amp? Did you buy it new? The newest Texas Star amplifiers (the ones they are selling now) I am pretty sure come with the Fake Toshiba's already in them. The regular HG 2SC2879 (not the C version) will replace those, however if they've changed the tuning to accommodate the Fake Toshiba transistors in any way, that will have to be put back like original old school DX500 before it will work right.
Sad that there are no shops working on amplifiers anymore, maybe that will change because if HG keeps it up, they will have fair price replacements (they already do, according to some techs, already giving a thumbs up and building/repairing with HG's). I personally recently (like a week or two ago) purchased a pair of HG SD1446's to put into an old 70's era Connex amplifier to replace a bad set of originals (originally MRF455, but I had converted to original SD1446 a while back, that I accidentally threw too much carrier power into and fried, I know, expensive mistake), and the SD1446's were drop in replacement. Slightly less power (like 10%?) but that may be tune/bias issues that need to be changed. The point is that's a minor difference, the HG transistors work great, so far. I have 4 original Toshiba's, non red-dot here, but I am just going to have to sell them because they are simply too rich for my blood to use, I could buy a lot of other parts for the hobby with the money people would pay for those original Toshiba's.
Question for 144inBama, Is that really SMD Chip Capacitors across the output transformers in your 500V? Is that the way it came from Texas Star?
TS used the fake ebay toshibas for about a year before they were caught and exposed. Now they're back to using the may-pop DEI's.