Good day all, can anybody plse suggest modern replacement trannies for a Pioneer SA 508 amp.
The output trannies are 2SD 883A and 2SB 773A. These were the old gullwing type.
Help much appreciated ! I have thought about MJE15030/ 15032 and MJE15031/ 15033. Or Maybe BD243C/BD244C, These might be the best option.
Regards
Jan
The output trannies are 2SD 883A and 2SB 773A. These were the old gullwing type.
Help much appreciated ! I have thought about MJE15030/ 15032 and MJE15031/ 15033. Or Maybe BD243C/BD244C, These might be the best option.
Regards
Jan
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Any surplus in your area that carry original?
if your willing to change heatsink mounting holes
plenty of options for TO220 package.
NTE might have something with original package.
far as i can see it is a 70 to 80 watt rated
so most 220 are around 40 watt rating
15030 /15032 probably have better gain Ft is higher
for lower Ft even tip3055 /2955 use to be available in 220 package
might be higher wattage than 40 watt. would need to look
if your willing to change heatsink mounting holes
plenty of options for TO220 package.
NTE might have something with original package.
far as i can see it is a 70 to 80 watt rated
so most 220 are around 40 watt rating
15030 /15032 probably have better gain Ft is higher
for lower Ft even tip3055 /2955 use to be available in 220 package
might be higher wattage than 40 watt. would need to look
There is a link that sets the bias via the string of diodes, you can cut the link then the bias will change through the 10R resistor and you can then even replace the resistor with an adjustable pot for fine tuning.
White Dragon, thanks for the reply. I'll search some more. The rail voltage is only +-33VDC and the output is 25W per channel, so should not be a problem to find suitable trannies. I'm searching for drivers as well.
White Dragon, thanks for the reply. I'll search some more. The rail voltage is only +-33VDC and the output is 25W per channel, so should not be a problem to find suitable trannies. I'm searching for drivers as well.
The gull wing types were just a variant of TO-220, usually the same dies were also available in TO-220. But with +/-33V and needing to retrofit anyway, I’d be inclined to use TO-3Ps to ruggedize it a bit. Sanken , Toshiba, Fairchild, take your pick. You don’t need the biggest one on the block. What’s it using for drivers, the old giant TO-92?
wg_ski, Yes the drivers are a 2SA850 and 2sc1735. Those tall TO-92's. My worry is how to get those large pins of a TO-3p through the pcboard. A guy is sending me the amp to fix, seems somebody have worked on it before and the one channel blew within 4 weeks. I think it is bias related but I'll wait see what will be arriving !
I would use TIP41C, TIP42C with strap over top them. A small aluminum bar would be perfect.
Or BD809, BD810. These are maybe as big as TO220 gets at 10A.
However, looking at the manual, I see a +/-32V supply, which is a bit optimistic for TO-220 size transistors, so I would try to fit 2SC5200/2SA1943.
Or BD809, BD810. These are maybe as big as TO220 gets at 10A.
However, looking at the manual, I see a +/-32V supply, which is a bit optimistic for TO-220 size transistors, so I would try to fit 2SC5200/2SA1943.
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Thanks Steveu, I have some spare, will make things easier. I still need replacements for the drivers as I see the 2sa850 have a Pc of 0.8W and Ic max of 0.5A. Vce 100V. I suppose a Ksc1845 and Ksa992 will not suffice. Maybe mje340 or BD139 as drivers
TIP41/2 are probably “as good” as what was in there - but if you’re going to stick with TO-220’s I’d be inclined to use 2N6488/91. They will tolerate 4 ohms loading at that supply, the TIPs will for a while but not day in day out at high volume. MJE3055/2955 would, but are run a bit over rated vceo. That can be checked, then they are ok. Any of those are lower fT than the originals, which is why I suggested TO-3Ps because you can get at least 4 or 5 types that are good for 20+ MHz, and any of them will tolerate 4 ohms on that supply. If they’re out of one type, move on to the next. High fT outputs are not super critical if you can maintain it in the drivers.
MJE1503x are a little thin on SOA, but better than any of the 40 watt Jap types in that regard. If you only run 8 ohm load they would work. The D44/45 will not. Not enough SOA for even 8 ohms. They start rolling off power handling at 12 volts .Fantastic at lower voltage, though. There is no higher fT TO-220 pair and they have no quasi-saturation to deal with.
Giant TO-92’s are for the most part TO-126’s in disguise. Go for any modern TO-126 (or TO-251) which are designed for that service. The higher the fT the better, especially if you use 3 MHz outputs. If there is a 120V and 160-200 volt version, the lower voltage is preferred. The hFE tends to run inversely with vceo, all other things constant. If you can get C2316/A916, the last of the giant TO-92’s made, use ‘em. But I wouldn’t hold my breath….
MJE1503x are a little thin on SOA, but better than any of the 40 watt Jap types in that regard. If you only run 8 ohm load they would work. The D44/45 will not. Not enough SOA for even 8 ohms. They start rolling off power handling at 12 volts .Fantastic at lower voltage, though. There is no higher fT TO-220 pair and they have no quasi-saturation to deal with.
Giant TO-92’s are for the most part TO-126’s in disguise. Go for any modern TO-126 (or TO-251) which are designed for that service. The higher the fT the better, especially if you use 3 MHz outputs. If there is a 120V and 160-200 volt version, the lower voltage is preferred. The hFE tends to run inversely with vceo, all other things constant. If you can get C2316/A916, the last of the giant TO-92’s made, use ‘em. But I wouldn’t hold my breath….