I traded for a dx 1600 and it had 4 blown transistors,Question I have removed and checked the gain on the 4 that were good hfe of around 30 on all four,I have 4 new old stock red dot's that have around the same gain at 35-40 hfe..Would there be an issue dropping the red dots in to replace the 4 bad ones?Or would it be better to order 8 new hg's matched to put in it?I have replace all the 10 ohm resistors and there was no damage to the combiners and none to the bias resistors..Just took out 4 of the toshiba's..Thanks
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DX 1600
- Thread starter n4dxx
- Start date
Most likely. That design relies on each one of a pair matching each other. Each pair matching the other four.
My experience is that the red dot parts are not likely to match original type parts well enough.
Eight HG transistors is probably the only choice you can obtain. All the better choices are unobtanium.
I suppose replacing just the four is safe enough to try. You will know if the match is not good enough if the swamping resistor on the output combiner gets hot. When both sets of four balance perfectly, there is no power lost in that resistor. As soon as one side puts more power into the combiner, the resistor absorbs some of the imbalance. If that resistor smokes, the balance is not good enough. Then you'll know you have to install the other four.
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I was going by the numbers on my Atlas DCA55 they were very close in numbers,All of them..I think i will give it a shot at see what happens..I will take a close look at the heat in each area of the 4 boards when i play it.Not sure it's a good plan but we will see.Thanks
Fyi: if you do decide to put in hg transistors, more than likely you are going to have to widen the transistor slots in the board. Hg's are bigger than toshiba's. Also the tune etc is not the same so you are gonna need to change some components and re do the input and output tune as well. The amp gurus will show up soon with more info for ya if needed.
Thanks,I am gonna try the red dot see if she blows..I will update tomm evening when i give it a test run.
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One thing you can do to ensure symmetry between each 2 pill pair is to install one red dot and one non-red dot into each 2 pill pair. That way if there is a small imbalance, it's absorbed by the output transformer core and not the combiner resistors. I've done this successfully a number of times when provided with dissimilar pairs (red dot, non-red dot) from a customer on a budget.
Well i installed the 4 red dots 2 in the back section and 2 in the front section and the 4 non red dots are in the middle 2 sections..i wish i would have thought of that but so far it's running great loafing at 1200 watts not seeing any heat build up on the combiners they seem about equal so far.I think it's gonna work fine.
Way cool! Good to hear the old and new Toshibas play together that well. If they aren't the balance resistor across the output combiner will rat it out.
Every time.
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Every time.
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I have played it all day,All of the resistors are just a bit warm to the touch..I have not driven it hard only around 60-70 watts and so far it's as good as it was before the 4 original final popped.Gonna try and trade it for a decent hf amp such as sb-200 or something like that.
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Hmm. Out of the frying pan and into the fire?
The 572B seems to be a discontinued item, like the 2SC2879. Just nobody like HG stepping in to fill the void.
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